21054-6001-RO-OO
COST AND EMISSION STUDIES OF A
HEAT ENGINE/BATTERY HYBRID
FAMILY CAR
G.H. Gelb
B. Berman
E. Koutsoukos
Prepared for
Division of Advanced Automotive Power Systems Development
Office of Air Programs
Environmental Protection Agency
Contract Number 68-04-0058
April 1972
TRW
SYSTEMS GROUP
SPACE PARK . aCDONDO Bf/ICH. CALIFORNIA 90278
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21054-6001-RO-OO
COST AND EMISSION STUDIES OF A
HEAT ENGINE/BATTERY HYBRID
FAMILY CAR
G.H. Gelb
B. Berman
E. Koutsoukos
Prepared for
Division of Advanced Automotive Power Systems Development
Office of Air Programs
Environmental Protection Agency
Contract Number 68-04-0058
April 1972
TRW
SYSTEMS GROUP
ONE SPACE PAflX • REOONDO B£ACH. CALIFORNIA 90?7B
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FOREWARD
This report presents the results of analytical and experimental work
performed during the period from July 1971 through February 1972 under
contract number 68-04-0058 for the Environmental Protection Agency. The
overall program direction and report preparation was the responsibility
of Dr. George H. Gelb of Power Conversion and Applications, Advanced
Technology Division, TRW Systems Group. Mr. Baruch Berman of the same
organization led the analytical studies of the electrical systems of the
hybrid power train. He was assisted by Dr. T.C. Wang in the power train
... r
modeling phases and Mrs. Roselyn Lipkis who performed the computer pro-
gramming and simulations. Dr. Elias Kputsoukos of the Chemical Engineer-
ing Department of the Applied Technology Division supervised the emission-
related experimental portions of the program.
The authors would also like to express thanks to Mr. Harry Gehm who
aided in instrument engineering and engine modifications and Messrs Ernie
Hoover and Thomas Hurst for their technical support in the laboratory
activities.
Dr. Jalal Salihi managed the project for the Division of Advanced
Automotive Power Systems Development, Office of Air Programs, Environmental
Protection Agency. Dr. Salihi was assisted by Mr. Edward Beyma and Dr.
Joseph Sommers of the Office of Air Programs.
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NOMENCLATURE
a,, - vehicle acceleration, mph/sec
g, - gear ratio at gear 1 (differential)
g^ -.gear-ratio at gear 2
I. - alternator current, amps
In - battery current, amps
IM - motor current, amps
*PCU " P^ current, amps (series configuration)
IpnjA - alternator PCU current, amps (parallel configuration)
*PCUM " motor PCU current, amps (parallel configuration)
P.. - power into alternator, watts
P. - power out of alternator, watts
PB - battery power, watts
P. . - probability of occurrence of the i velocity with the y accel-
J eration in the LA-4 matric
PJP - power out of engine, watts
PCU - power control unit
PM- - power into motor, watts
PM - power out of motor, watts or hp
PO - power transmitted out of planetary gear to propeller shaft, hp
PPCU " P^U P°wer» watts (series configuration)
PPCUA " a^ternator P^u power, watts (parallel configuration)
PPCUM " motor p^^ P°wer» watts (parallel configuration)
PR - vehicle road power requirement, hp
r - driving wheel radius, 1 foot
RB - battery resistance, ohms
V. - alternator voltage, volts
n
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VR - battery voltage, volts
VD- - battery open circuit voltage, volts
D I
VM - motor terminal voltage, volts
VR - vehicle velocity, mph
WM - motor speed, rpm
WR - road velocity, rpm
a - chopper duty cycle, defined as the ratio of time that the power
silicon controlled rectifier is conducting to the total period of
the chopper
APPCUA ~ a^ternator PCU power loss, watts
n« - alternator efficiency
n Q - planetary gear efficiency
n-j - gear 1 efficiency
n o ~ 9ear 2 efficiency
n M - variable gear efficiency
nM - motor efficiency
nPCU ~ P^ efficiency (series configuration)
nPCUA " a^ternator PCU efficiency (parallel configuration)
nPCUM " motor P^ efficiency (parallel configuration)
nRr - rectifier efficiency
ns - overall efficiency from engine to rectifier
nSYS " overa^ efficiency for entire configuration
TM - motor torque, ft-lb
TD - road torque, ft-lb
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TABLE OF CONTENTS
Page
ABSTRACT 1
SUMMARY AND CONCLUSIONS . 7
1.0 INTRODUCTION 17
2.0 SELECTION OF CANDIDATE SERIES-CONNECTED HYBRID POWER TRAINS . . 18
2.1 General Specifications and Assumptions 18
2.2 Candidate Series Systems 20
2.2.1 Full Voltage Series System 20
2.2.2 Two Alternator Series System 22
2.2.3 Series System with Alternator PCIJ 25
2.3 Evaluation of Candidate Series Systems 25
2.3.1 Preliminary Selection - Criteria 32
3.0 CHARACTERIZATION OF PARALLEL HYBRID SYSTEM 34
3.1 Description of EMT . 34
3.2 Specification of Parallel System Components 37
4.0 CHARACTERIZATION OF HYBRID VEHICLE BATTERIES 41
5.0 MODELING AND SIMULATION OF HYBRID VEHICLES 42
5.1 Instantaneous Values of Component Performance of Series
and Parallel Hybrid Power Trains 42
5.2 LA-4 Performance of Series and Parallel Hybrid Power
Trains 42
5.3 Effect of Series and Parallel System Parameters on
Overall System Efficiency . 43
5.3.1 Effect of System Parameters on Full Voltage
Series System Performance 54
5.3.2 Effect of System Parameters on Parallel (EMT)
System Performance 61
5.4 Ratings of the Electrical Portions of the Hybrid
Power Trains 62
6.0 ESTIMATES OF THE COST AND WEIGHT OF HYBRID FAMILY VEHICLES . . 67
6.1 Comparison of Series and Parallel Hybrid Systems 67
6.2 Costs of Hybrid Vehicle Ownership . . 70
7.0 HYDROCARBON ACCUMULATOR MATERIALS SCREENING .......... 74
7.1 Test Equipment and Procedures . . . . . 74
7.2 Selection of Candidate Materials 78
7.2.1 Discussion of Results .- 79
1v
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TABLE OF CONTENTS (Cont'd)
Page
8.0 CHARACTERIZATION OF TRW-HARSHAW THREE-COMPONENT CATALYST .... 87
8.1 Background of Three-Component Catalysts 87
8.2 Catalyst Preparation and Bench Scale Tests 89
8.3 Evaluation of TRW-Harshaw Catalyst on Engine Exhausts ... 91
8.3.1 Single Cylinder Catalyst Characterization Tests . . 91
8.3.2 TRW-Harshaw Characterization Tests on Vega
Engine 106
9.0 CHARACTERISTICS OF UNIVERSAL OIL PRODUCTS CATALYTIC
CONVERTER. . 119
9.1 Converter Description and Test Procedure 119
9.2 Test Results 119
10.0 HYBRID SYSTEM FULL SCALE EMISSION TESTS 124
1C.1 Introduction .124
10.2 Experimental Equipment 124
10.3 Experimental Procedure for Performing Emission Tests . . . 126
10.4 Full Scale System Emission Results 127
APPENDIX A - EPA Vehicle Design Goals 130
APPENDIX B - Engine Sizing and Selection 138
APPENDIX C - Comparison of Series Systems 143
APPENDIX D - Rotating Machinery Characterization 149
APPENDIX E - PCU Efficiency Model . 166
APPENDIX F - Computer Modeling and Simulation 171
APPENDIX 6 - Computer Simulation Results .188
APPENDIX H - Size and Cost Estimate Data Base 229
APPENDIX I - Hydrocarbon Accumulator Materials Screeing Data .... 233
APPENDIX J - Determination of Stoichiometric Mixture Ratio 243
APPENDIX K - Engine Modifications, Instrumentation and Test Fuel . .249
REFERENCES 254
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LIST OF FIGURES
Page
FIGURE 2.1 - WHEEL POWER DEMANDS FOR A 4000 LB CAR 19
FIGURE 2.2 - FULL VOLTAGE SERIES-CONNECTED HYBRID SYSTEM ........ 21
FIGURE 2.3 - TWO ALTERNATOR SERIES CONNECTED HYBRID SYSTEM 23
FIGURE 2.4 - SERIES HYBRID SYSTEM WITH ALTERNATOR PCU 26
FIGURE 2.5 - PER UNIT TORQUE REQUIREMENTS OF THE TRACTION MOTOR
FOR SERIES CONNECTED HYBRID SYSTEMS 28
FIGURE 3.1 - EMT HYBRID SYSTEM IN URBAN TRAFFIC MODE . . . . 35
FIGURE 3.2 - EMT HYBRID SYSTEM IN HIGHWAY TRAFFIC MODE 36
FIGURE 3.3 - POWER LEVELS OF EMT HYBRID SYSTEMS MOTOR AND ENGINE ... 38
FIGURE 5.1 - FULL VOLTAGE SERIES SYSTEM ON LA-4 MISSION WITH
VARIABLE GEARING AND REGENERATION (RUN IA) 44
FIGURE 5.2 - FULL VOLTAGE SERIES SYSTEM ON LA-4 MISSION WITH
VARIABLE GEARING AND REGENERATION (RUN GA) 45
FIGURE 5.3 - FULL VOLTAGE SERIES SYSTEM ON LA-4 MISSION WITHOUT
VARIABLE GEARING, WITH REGENERATION (RUN CA) 46
FIGURE 5.4 - FULL VOLTAGE SERIES SYSTEM ON LA-4 MISSION WITH
VARIABLE GEARING, WITHOUT REGENERATION (RUN BBA). 47
FIGURE 5.5 - FULL VOLTAGE SERIES SYSTEM ON LA-4 MISSION WITHOUT
VARIABLE GEARING OR REGENERATION 48
FIGURE 5.6 - EMT SYSTEM ON LA-4 MISSION WITH VARIABLE GEARING AND
REGENERATION (RUN TTA), 49
FIGURE 5.7 - EMT SYSTEM ON LA-4 MISSION WITH VARIABLE GEARING AND
REGENERATION (RUN XA) v . .. 50
FIGURE 5.8 - EMT SYSTEM ON LA-4 MISSION WITHOUT VARIABLE GEARING,
WITH REGENERATION (RUN RA) 51
FIGURE 5.9 - EMT SYSTEM ON LA-4 MISSION WITH VARIABLE GEARING,
WITHOUT REGENERATION (RUNl-LA)... .......... . . 52
FIGURE 5.10 - EMT SYSTEM ON LA-4 MISSION WITHOUT VARIABLE GEARING
OR REGENERATION (RUN JJA). ... 53
FIGURE 7.1 - TEST CANISTER USED IN HYDROCARBON ACCUMULATOR
, SCREENING, SINGLE CYLINDER CHARACTERIZATION OF TRW-
HARSHAW CATALYST AND FULL SCALE HYDROCARBON
ACCUMULATOR 75
FIGURE 7.2 - HYDROCARBON ACCUMULATOR 77
FIGURE 7.3 - TYPICAL TIME VARYING CHARACTERISTICS OF HYDROCARBON
ACCUMULATOR MATERIAL SCREENING TESTS 80
FIGURE 8.1 - EXPERIMENTAL SET UP FOR SINGLE CYLINDER
CHARACTERIZATION OF TRW-HARSHAW CATALYST 92
FIGURE 8.2 - TRW-HARSHAW CATALYST CONVERSION EFFICIENCY 99
VI
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LIST OF FIGURES (Copt'd)
FIGURE 8.3 - TRW-HARSHAW CATALYST CONVERSION EFFICIENCY 32,000 V/V/Hr 100
FIGURE 8.4 - TRW-HARSHAW CATALYST CONVERSION EFFICIENCY 37,000 V/V/Hr 101
FIGURE 8.5 - TRW-HARSHAW CATALYST CONVERSION EFFICIENCY 33,000 V/V/Hr 102
FIGURE 8.6 - TRANSIENT NO CONVERSION BEHAVIOR OF TRWrHARSHAW CATALYST 105
FIGURE 8.7 - FULL SCALE TRW-HARSHAW CATALYTIC CONVERTER 107
FIGURE 8.8 - FULL SCALE TRW-HARSHAW CATALYTIC CONVERTER . . 108
FIGURE 8.9 - PERFORMANCE OF FULL SCALE TRW-HARSHAW CATALYTIC
CONVERTER 23,000 V/V/Hr 109
FIGURE 8.10 - PERFORMANCE OF FULL SCALE TRW-HARSHAW CATALYTIC
CONVERTER 40,000 V/V/Hr ... 110
FIGURE 8.11 - HYDROGEN CONCENTRATIONS IN THE EXHAUST STREAM OF
THE VEGA ENGINE 112
FIGURE 8.12 - AMMONIA PRODUCTION OF THE TRW-HARSHAW THREE-
COMPONENT CATALYST 115
FIGURE 8.13 - WARM-UP CONVERSION CHARACTERISTICS OF FULL SCALE
CONVERTER 116
FIGURE 8.14 - FULL SCALE CONVERTER THERMAL WARM-UP CHARACTERISTICS . 117
FIGURE 9.1 - UOP CATALYTIC CONVERTER MOUNTED ON VEGA EXHAUST
MANIFOLD 120
FIGURE 9.2 - UOP CATALYTIC CONVERTER PERFORMANCE 38 SCFM 121
FIGURE 9.3 - UOP CATALYTIC CONVERTER PERFORMANCE 20 SCFM 122
FIGURE 9.4 - UOP CATALYTIC CONVERTER PERFORMANCE 27 SCFM 123
FIGURE 10.1 - MAJOR HARDWARE COMPONENTS OF FULL SCALE EMISSION TESTS 125
FIGURE B-l - CHARACTERISTICS OF A TYPICAL MEDIUM DISPLACEMENT
INTERNAL COMBUSTION ENGINE 139
FIGURE B-2 - CHARACTERISTICS OF 1971 CHEVROLET VEGA ENGINE AT
1800 RPM 141
FIGURE D-l - CHARACTERISTICS OF MOTOR FOR SERIES SYSTEM 151
FIGURE D-2 - SERIES SYSTEM MOTOR EFFICIENCY 152
FIGURE D-3 - SERIES SYSTEM MOTOR EFFICIENCY 153
FIGURE D-4 - TORQUE OF THE PARALLEL SYSTEM MOTOR 156
FIGURE D-5 - CHARACTERISTICS OF MOTOR FOR EMT SYSTEM 157
FIGURE D-6 - EFFICIENCY OF MOTOR FOR EMT SYSTEM 158
FIGURE D-7 - EFFICIENCY CURVE FOR FORCE AID COOLED ALTERNATOR OF FULL
VOLTAGE SERIES SYSTEM 160
FIGURE D-8 - EFFICIENCY CURVE FOR 10 KW, 12,000/1200 RPM FORCED
COOLED, 40 LB ALTERNATOR 165
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OF FIGURES (Cont'd)
FIGURE E-i - 'MOTORTCU USED IN SERIES AND PARALLEL MODELS , ...... 167
FIGURE F-l - FULL VOLTAGE SERIES HYBRID POWER TRAIN . . .' ....... . .173
FIGURk F-2 2 PARALLEL (EMT) "HYBRID POWER TRAIN. .'..". , . .. . . . ,.. . . 180
FIGURE j-r- DETERMINATION OF STOICHIOMETRY USING EXHAUST CO FROM .,
#4 CYLINDER OF VW 1600 . . ....'. ... ... . . .'. 244
FIGURE J-2 - DETERMINATION -OF STOICHIOMETRY FROM REDUCTANT-OXIDANT
BALANCE IN VEGA EXHAUST .........;.... . . 246
FIGURE K-l - VEGA CARBURETION MODIFICATIONS ........ ..... 250
FIGURE K-2 - VEGA INSTALLATION ...... ..... ........ 251
viri
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LIST OF TABLES
Page
TABLE I - COMPARISON OF THREE CANDIDATE SERIES-CONNECTED
HYBRID POWER TRAINS ..'.... 8
TABLE II - SUMMARY OF HYBRID SYSTEMS EFFICIENCY ON LA-4 DRIVING
CYCLE .. , , 12
TABLE 2.1 - PRELIMINARY SPECIFICATIONS OF FULL VOLTAGE SYSTEM
USING FORCED COOLED ALTERNATOR 29
TABLE 2.2 - PRELIMINARY SPECIFICATIONS OF FULL VOLTAGE SYSTEM
USING OIL SPRAY COOLED ALTERNATOR ............. 29
TABLE 2.3 - PRELIMINARY SPECIFICATIONS OF TWO GENERATOR SYSTEM ;
USING FORCED COOLED ALTERNATOR 30
TABLE 2.4 - PRELIMINARY SPECIFICATIONS OF TWO GENERATOR SYSTEM
USING OIL SPRAY COOLED ALTERNATOR ... . .'. ... . . . 30
TABLE 2.5 - PRELIMINARY SPECIFICATION OF SERIES SYSTEM WITH
ALTERNATOR PCU USING FORCED COOLED ALTERNATOR .... . .; . 31
TABLE 2.6 - PRELIMINARY SPECIFICATION OF SERIES SYSTEM WITH
: ALTERNATOR PCU USING OIL SPRAY COOLED ALTERNATOR .... 31
TABLE 2;7 - COMPARISON OF NON-HYBRID SYSTEM PERFORMANCE WITH
; OIL SPRAY COOLED ALTERNATORS ........; 33
TABLE 3.1 - EFFECT OF GEAR SHIFTING ON EMT TRACTION MOTOR ...... 39
TABLE 5.1 - LIST OF INPUT PARAMETER VARIATIONS FOR THE SERIES
SYSTEM COMPUTATIONS . ... . . . . . ... . . .'. . . . 55
TABLE 5.2 - LIST OF INPUT PARAMETER VARIATIONS FOR THE PARALLEL
SYSTEM COMPUTATIONS ............. 56.
TABLE 5.3 - PERFORMANCE OF FULL VOLTAGE SERIES SYSTEM COMPONENTS
ON LA-4 MISSION 5.7
TABLE 5.4 - PERFORMANCE OF FULL VOLTAGE SERIES SYSTEM COMPONENTS
ON LA-4 MISSION 58
TABLE 5.5 - PERFORMANCE OF PARALLEL (EMT) SYSTEM COMPONENTS ON
LA-4 MISSION 59
TABLE 5.6 - PERFORMANCE OF PARALLEL (EMT) SYSTEM COMPONENTS ON
LA-4 MISSION 60
TABLE 5.7 - SUMMARY OF THE EFFECT OF PARAMETRIC CHANGES ON SERIES
AND PARALLEL HYBRID SYSTEMS EFFICIENCY 62
TABLE 5.8 - COMPARISON OF DESIGN RATINGS AND LA-4 SIMULATION RESULTS
FOR SERIES SYSTEM TRACTION MOTORS 64
TABLE 5.9 - COMPARISON OF DESIGN RATINGS AND LA-4 SIMULATION RESULTS
FOR PARALLEL SYSTEM TRACTION MOTORS 64
TABLE 5.10 - COMPARISON OF DESIGN RATINGS AND LA-4 SIMULATION RESULTS
FOR SERIES SYSTEM MOTOR PCU 65
TABLE 5.11 - COMPARISON OF DESIGN RATINGS AND LA-4 SIMULATION RESULTS
FOR PARALLEL SYSTEM MOTOR PCU 65
ix
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LIST OF TABLES (Cont'd)
Page
TABLE 5.12 - COMPARISON OF DESIGN RATINGS AND LA-4 SIMULATION
RESULTS FOR SERIES SYSTEM ALTERNATOR 66
TABLE 5.13 - COMPARISON OF DESIGN RATINGS AND LA-4 SIMULATION
RESULTS FOR PARALLEL SYSTEM ALTERNATOR 66
TABLE 5.14 - COMPARISON OF DESIGN RATINGS AND LA-4 SIMULATION
RESULTS FOR PARALLEL SYSTEM ALTERNATOR PCU 66
TABLE 6.1 - SUMMARY OF OEM COSTS AND WEIGHT COMPARISON OF PARALLEL
AND SERIES POWER TRAINS 68
TABLE 6.2 - HYBRID VEHICLE POWER TRAIN WEIGHT , 71
TABLE 6.3 - HYBRID VEHICLE FUEL AND BATTERY COSTS 72
TABLE 7.1 - PERFORMANCE COMPARISON OF ACCUMULATOR MATERIALS 83
TABLE 8.1 - BENCH SCALE TESTS ON TRW-HARSHAW CATALYST 90
TABLE 8.2 - TRW-HARSHAW COPPER CATALYST DATA 95
TABLE 10.1 - FULL SCALE HYBRID SYSTEM EMISSION TEST RESULTS 129
TABLE D-l - SERIES HYBRID TRACTION MOTOR 149
TABLE D-2 - PARALLEL HYBRID TRACTION MOTOR. . 154
TABLE D-3 - FULL VOLTAGE SERIES SYSTEM ALTERNATOR-RECTIFIER
CHARACTERISTICS 161
TABLE D-4 - TYPICAL ALTERNATOR-RECTIFIER OUTPUT POWER SCHEDULE
VS. SPEED FOR EMT 163
TABLE D-5 - PARALLEL SYSTEM ALTERNATOR-RECTIFIER CHARACTERISTICS. . . 164
TABLE E-l - SUMMARY OF PCU LOSSES BY LOSS CATEGORY 169
TABLE 1-1 - HYDROCARBON ACCUMULATOR MATERIALS SCREENING DATA 233
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ABSTRACT
TRW Systems has conducted a combined analytical and experimental
study, "Cost and Emission Studies of a Heat Engine/Battery Hybrid Family
Car," for the Division of Advanced Automotive Power Systems Development,
Office of Air Programs, Environmental Protection Agency under contract
number 68-04-0058.
The broad objectives of the studies were to:
• Select and analyze the performance of series and parallel
configured heat engine/battery hybrid family cars.
• Define the relative efficiencies, weight and costs of hybrid
power trains.
• Generate data characteristics of selected three-component
catalysts.
t Perform preliminary materials screening and development of a
hydrocarbon emission trap (hydrocarbon accumulator).
t Demonstrate that a hybrid car with an internal combustion
engine could meet the 1975/76 emission goals.
\
Analytical Studies of Heat Engine/Battery Hybrid Power Trains
Selection of a candidate series system for analysis was made on the
basis of; ability to meet the EPA vehicle design goals, total system weight
and volume, overall efficiency at selected speeds and accelerations and pre-
liminary cost appraisals. From a field of several series systems, one system,
the full voltage series hybrid was selected. The parallel system selected
for analysis was that using the Electromechanical Transmission (EMT)
developed by TRW Systems.
Extensive computer modeling of both systems was performed. Detailed
mathematical models of alternators, traction motors, power control units
(PCUs), gearing and batteries were developed by a combined approach of
analysis and utilization of equipment manufacturers' data. Computations
were made to determine the. performance of each of the major subsystems in
terms of power level, current, voltage, speed, torque and efficiency for
a matrix of vehicle velocity-acceleration points. The matrix was broad
enough to cover the complete velocity range of vehicle operation at all
reasonable acceleration and deceleration rates.
1
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The matrix performance quantities and their probability of occurrence
in the LA-4 driving mission were combined to establish the average and RMS
values for a realistic driving cycle. Engine powers, battery impedances,
gear efficiencies and operation without regeneration and transmission gear
ratios were adjusted to develop sensitivity trends of system performance
to these variables. The effectiveness of regenerative braking was inves-
tigated.
In the absence of any accessory loads, the efficiency of the parallel
system between the engine output shaft and the driving wheels could be as
high as 77%. (All overall efficiency values are based on maintaining the
battery's impedance increases and gearing losses increase, system efficiency
may fall to about 68%. With a steady accessory load of 5 horsepower, the
engine shaft output must increase and the engine-to-wheel efficiency would
fall to 54.3% and 49.8%, respectively.
The series hybrid system exhibits a somewhat lower efficiency on the
LA-4 cycle. Without accessory load but with an advanced battery and low
loss gearing its efficiency is near 55%. As battery and gearing degrade,
system efficiency may fall closer to 48%. If the 5 horsepower accessory
load is added, these values will decrease to 43.3% and 38.8%, respectively.
Since the series system's generator and traction motor must be rated for
continuous power at top vehicle speed, larger machines are required. On
the other hand, the series system offers a greater flexibility of opera-
tion—full engine output can be utilized at any road speed.
Multiple gear ratios between the traction motor and rear wheels was
shown to be important to the overall system efficiency. Its impact was
slightly greater in the parallel system (about 8 percentage points) since
the traction motor's torque rating is lower than that of the series
system and without step down gearing, the RMS current placed a heavier
burden on the machines.
Regenerative braking was shown to improve the overall efficiency in
both systems. In the series system, regenerative braking improved the
system efficiency by approximately 10%. The parallel system, the EMT,
uses the traction motor as a generator as part of its normal mode of
driving wheel torque control and thus regenerative is inherent in the
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system. However, computations showed that utilizing the kinetic energy
of the car for battery charge during decelerations could affect the system
efficiency by a larger amount that in the series system.
Planetary gear efficiency was shown to dominate the overall system
efficiency of the parallel system, with all other parameters held constant.
A change in the planetary system's efficiency from 90 to 80% decreased the
overall efficiency by ll%--almost equal in magnitude to the efficiency gain
resulting from the use of a variable gear ratio.
It is important to note that these results are dependent on the de-
tailed models which are chosen to represent the characteristics of the
power trains components as well as the specific driving profiles over
which the evaluations are made. Thus, while the results are arrived at
using valid techniques of modeling and computations, the absolute values
of efficiency, etc. should only be used in terms of trend and comparison.
The weight of the complete parallel system including engine, gearing
and batteries is approximately 87-89% of the series system. The OEM cost
of the series power train, excluding batteries and engine is nearly 25%
higher than the parallel system; however, the impact on a comparison of
both systems' total cost would be far less when the added costs of the
engine and battery are factored in.
Estimates of the new car costs for hybrid vehicles are difficult to
establish without a detailed knowledge of the OEM to consumer makeup
structure. Rather than project a first cost based on arbitrary costs,
models, cost comparison between hybrids and conventional cars was made
on fuel consumption and battery replacement estimates. It is estimated
that the fuel economy savings of hybrid operation can pay for battery re-
placement costs.
Experimental Studies of Emission Control of ICE/Battery Hybrid Power Trains
Steady state data on the conversion efficiency of a three-component
catalyst was taken. The catalyst, composed of copper oxide on alumina, is
manufactured by Harshaw Chemical Company and activated by TRW Systems.
Initial tests were carried out on the exhaust flow from one cylinder of a
VW 1600 cc engine. The test catalytic converter was sized for single
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3 3
cylinder exhaust flow rates ranging from 20,000 to 35,000 ft /ft hour.
Catalyst bed temperatures ranged from 1200 to near 1600°F.
The data exhibited characteristics which were expected on the bases
of chemistry and selectivity of nitric oxide (NO) reduction. The NO con-
version efficiency of the catalyst (defined as the ratio of the concentra-
tion of a specie at the converter outlet to the inlet concentration) was
in excess of 90% for air-fuel ratios having a reductant to oxidant ratio
in excess of one; that is, for all rich mixtures. The hydrocarbon (HC)
and carbon monoxide (CO) efficiencies increased as the air-fuel ratio be-
came leaner. At stoichiometry where the total reductants and oxidants
were equal, the simultaneous conversion of all three pollutants was over
90%. Beyond stoichiometry, the NO conversion fell rapidly with the addi-
tion of excess oxygen. HC and CO conversions remained close to 100% with
increased mixture leaness. The overall effect of low HC, CO conversion on
the rich side of stoichiometry and low NO conversion on the lean side
restricts the air-fuel range over which the catalyst can operate effectively.
For example, the air-fuel ratio at 1390°F bed temperature must be maintained
within +0.2 of stoichiometry to insure the simultaneous conversion exceed
80%.
Space velocity appeared to play a smaller role on conversion than
temperature—at least over the ranges investigated in these experiments.
With increasing temperature the bed of effective catalyst performance
broadens. In addition as the temperature is increased, the relative con-
version efficiencies of HC and CO reverse—at low temperature, (^1200°F)
CO conversion is favored, at higher temperatures (M500°F), CO conversion
is favored.
Various materials were screened as candidates for use in hydrocarbon,
accumulator. The materials included activated carbon and charcoal, silica
gel, molecular sieve and alumina. Tests were conducted by exposing a con-
stant volume of material to the exhaust of a single cylinder of the VW
engine. The engine and accumulator were started cold; the mixture ratio
and flow rates were controlled to produce as reproducible starting condi-
tions as possible.
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Tests indicated that activated carbons are the most efficient material
for trapping hydrocarbons in the exhaust stream during cold starts. They
have the highest mass capacity at any given temperature and are still able
to adsorb hydrocarbons at nearly twice the temperature that its nearest
competitor loses its adsorption capability.
In order of decreasing effectiveness were molecular sieve, silica gel
and alumina. While the molecular sieves showed promise as a secondary
choice Pittsburgh Activated Carbon of the BPL series was chosen for use in
a full scale hydrocarbon accumulator. This material exhibited no chemical
or physical deterioration after several adsorption-desorption cycles in
which it was exposed to temperatures near 600°F and space velocities greater
than 80,000 V/V/Hr.
A 1971 Chevrolet Vega engine was selected for use in full scale system
emission tests. The engine was modified for hybrid operation; the major
modification was replacement of the carburetor with an intake manifold fuel
injection system adapted from the VW fuel injection equipment.
A test converter containing approximately 400 cubic inches of the
TRW-Harshaw catalyst was constructed to treat the total exhaust of the
Vega. Tests, were run to characterize the steady state conversion and the
production of ammonia. The conversion efficiencies of this converter were
similar to the single cylinder data; however, better geometry caused the
bed to operate at higher temperatures than the single cylinder tests at
equal space velocities.
The composition of the exhaust of the engine showed that on the rich
side of stoichiometry, sizable corrections of the reductant-oxidant ratio
had to be made to account for hydrogen. Measurements of ammonia produced
in the catalyst indicated that the ammonia concentration at rich mixtures
(about 2 points from stoichiometry) could be almost 50% of the NO concen-
trations. However, at stoichiometry, the ammonia was only 1% of the NO
concentration. Ammonia production at a given air-fuel ratio increased as
the catalyst bed temperature decreased--a result predicted by thermodynamics,
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. Two cajbalytjc .converters supplied by. Universal•• ,0.11.: Products (UOP) were
tested on, the. Vega.., These devices, containing a light loading of pTatinuni'
on., alumina were o.per.a.ted at similar exhaust velocities-as.'in the> TRW- :
Harshaw characterization tests. The converters had good-HC;and1GO^oxida-'
tion properties for lean mixture ratios; however, the peak NO conversions
were much less than that exhibited by the copper oxide catalyst.
The hydrocarbon accumulator and full scale TRW-Harshaw catalytic con-
verter were combined with the Vega-EMT power train. Emission measurements
of the hybrid system were made according to the latest Federal procedures—
i.e., cold start transient bag, stabilized hot bag and hot start transient
bag. Chemiluminescent measurement of NOV was used. The engine was run on
: ' ' ' /\
a power schedule which simulated operation on the Federal driving cycle.
The 1975-;76 emission standards were achieved in several tests. The
hydrocarbon accumulator was shown to have a dramatic impact in total HC
emissions. The, catalytic converter was able to light off rapidly and con-
trol NO emissions well enough to provide a margin of NO control under the
' ' /\
1976 standards. CO was found to be the most difficult specie to control.
CO problems were directly attributable to cold start emissions during the
period when considerable engine choking was required.
Physical changes in the catalyst were small, if any, over the testing
period which amounted to approximately 100 hours. The most noticeable
change appeared to be a decrease in the total bed volume; however, this
may have been do to the bed being shaken on the test stand and settling.
-------
SUMMARY AND CONCLUSIONS
Candidate Series-Connected Hybrid Power Trains
Three series-connected hybrid configurations were studied in detail:
a full voltage system in which the alternator voltage is maintained at the
battery bus voltage, a two-generator scheme in which one alternator feeds
the battery while the other machine feeds the traction motor, and an alter-
nator PCU system in which the alternator voltage is boosted by power pro-
cessing to battery bus voltage. Details of preliminary comparative anal-
yses, block diagrams and description of operation are found in Section 2.0.
Table I summarizes the results of the analyses. The alternator PCU
system suffers from the inefficiency of two tandem power processors as well
as additional expense and volume associated with a boost PCU capable of
controlling the full engine output power.
Of-"the other two systems, the two-generator scheme offers slightly
higher efficiency. However, it appears to have some potential control
complexity problems, such as the need for specific alternator control
sequencing to insure proper sharing of engine power. The full voltage
series system was therefore selected for further analyses.
The parallel hybrid power train selected for study was the Electro-
mechanical Transmission developed by TRW Systems.
Selection and Characterization of Power Train Components
The following comprise the major power train components which had to
be selected and characterized for computer simulation:
• traction motors
t power control units, (PCU)
• rectifiers
t alternators
• batteries J.
• mechanical gearing
• internal combustion engine (heat engine)
-------
TABLE I '
COMPARISON OF THREE CANDIDATE SERIES-CONNECTED HYBRID POWER TRAINS
System
Full Voltage
Series
Two Generator
System
AT ternator
PCU System
Total
Weight
(lb)
705
691
697
System Efficiency
No Power Transfer from Battery
Efficiency
at 21 mph
(*)
28.0
38.5 •
30.0
Efficiency
at 42 mph
(*)
56.4
60.5
49.0
Efficiency
at 60 mph
(X)
66.0
7.1.5
60.0
Efficiency
at 85 mph
(X)
75.5
77.0
71.0
Battery Impact
Power to*
Battery at
22 mph '
Cruise, kw
+1.82
+2.81
+1.1
**
Power from
Battery at
Mean MaxPwr
23 kw
-26.10
-26.80
-26.9
Power
PCUs
one
one
two
Control
Complexity
dual loop
multi loop
dual loop
00
*Refers to the power available to the battery due to excess of engine power over road cruise power.
:The larger the number, the more efficient is the path from engine through generator to battery
terminals (see section 2.3.1).
**Refers to the peak burden placed on battery during an average urban acceleration. The lower the
peak, the more efficient ;the traction system and the higher the utilization of engine power con-
verted in the generator (see section 2.3.1).
-------
Internal combustion engine requirements are briefly discussed in
Appendix B. Estimates of power train efficiency suggested a peak horse-
power output of about 85 hp. An examination of internal combustion engine
fuel economy and emissions suggested a 3:1 speed variation over the full
range of vehicle speeds.
The characteristics of lead-acid batteries were reviewed. Based on
data supplied from work conducted, the contract "Development of High Rate
Lead-Acid Batteries for Hybrid Vehicles," EPA contract no. 68-04-0028,
-3
86x10 n was chosen as a reasonable total impedance for advanced, high
power density batteries. Impedances two and three times greater were also
selected to reflect changes in battery charge state and aging. An open
circuit voltage of 240 VDC was assumed to be required.
The continuous high speed cruise traction power required of a 4000 pound
family car provides the nominal rating for the series hybrid motor specif-
ication. The motor for the parallel system was rated on the basis of
average power and torque demands from analysis and previous experience with
EMT dynamometer tests. Contacts were established with a variety of motor
manufacturers including H.K. Porter, Westinghouse, GE and Lear Siegler.
These contacts established a preliminary motor configuration and machine
characteristics which are to be found in Appendix D.
Power control units specifications were developed from analyses of
PCUs which were designed for the EMT and could be used 1n either series or
parallel hybrid power trains. Two motor PCU units were specified and rated
according to peak current capability. The ratings reflected the possible
use of variable gear ratios between the motor and wheels to lower the peak
motor torque and current below the levels which would be encountered with
a single gear ratio. Detailed specifications and efficiency computations
of the PCUs can be found in Appendix E. :
Three alternator designs were investigated, one using forced air cool-
ing, another using an integral fan and the third using oil spray cooling
with external heat transfer equipment. Oil cooling was rejected as it is
usually associated with machines- designed for extremely high power densities
where efficiency is of secondary concern. One of the study guidelines was
to use machinery possessing high efficiency and oil .cooled designs did
not appear to fulfill this requirement.
-------
the series system alternator suggested the use of an integral fan. Over
a narrow speed range an integral fan can be designed to provide the cool-
ing air flow without low speed inefficiency. In the parallel system, the
alternator operates over a 10:1 speed range at constant armature current.
An external, constant air flow cooling system is preferred.
The gear efficiencies for the various systems were estimated from data
published in standard engineering handbooks. Wherever necessary the effi-
ciencies were slightly degraded as functions of increasing mesh speed to
reflect possible higher viscous losses with speed. The planetary gearing
of the parallel system was more difficult to analyze in that it is not
clear what specific design or means of lubrication would be chosen. For
these reasons, planetary gear efficiency was treated as a variable which
could take on values thought to bracket planetary performance.
Extensive computer models and analysis techniques were developed. The
bounds of possible vehicle operation were defined in terms of peak accel-
eration/deceleration rates from zero to 80% of the vehicle's top speed of
85 mph. A matrix of velocity-acceleration-road power demand points was
computed within these bounds. In addition, the probability of each
specific matrix point (a point represented the midpoint of a small velocity
and acceleration increment about the matrix point) for driving the LA-4
cycle was computed.
The series and parallel systems were mathematically modeled and com-
puter programs were developed. The models and programs are fully explained
in Appendix F.
Evaluation of Instantaneous and Average LA-4 Performance of the Series
and Parallel Hybrid Power Trains
The state of important performance measures of each of the major com-
ponents of the selected parallel and series systems were calculated for each
matrix point. The above-mentioned component characteristics were used in
the computations. Engine power levels, gearing and battery characteristics
were selected on the basis of preliminary analyses and experience.
Complete sets of instantaneous component efficiencies for typical
series and parallel input parameters can be found in Appendix G.
10
-------
System and component average and RMS performances were computed by
using matrix point performance measures and matrix point probabilities
and making appropriate averaging and root-mean-square computations. A
description of the techniques are found in Appendix F.
Overall system efficiencies for LA-4 operation are summarized in
Table II. System efficiencies are indicated as functions of the major
input parameters of battery impedance, gear train efficiency and degree
of gear ratio variation between the traction motors and wheels. In each
case, the state of. charge of the battery remained constant over the driv-
ing cycle.
Figures 5.1, 5.2, 5.3, 5.4 and 5.5 show block diagrams of the full
voltage series system along with average efficiency and input/output
power levels generated from the LA-4 cycle. Figures 5.6, 5.7, 5.8, 5.9
and 5.10 present similar information for the parallel system.
A variable gear ratio between the traction motor and the differential
was shown to substantially increase the overall system efficiency of both
configurations. The improvement was as much as 15% for the series and
13% for the parallel.
Regeneration was also important in raising the overall system effi-
ciency; by as much as 10% in the series system and 13.5% in the parallel.
Battery impedance variation has little effect on the parallel system;
doubling the impedance decreases the series system efficiency by about 7%.
The planetary gear efficiency of the parallel system is important to
the performance of that type of power train. An 11% change in efficiency
decreases the overall system efficiency by a similar amount.
The design ratings of all the rotating machines and PCUs were con-
servative for LA-4 operation as long as a variable gear ratio was used
for the parallel system. The series system motor and motor PCU are
designed for higher continuous power than those of the parallel and
thus the impact of variable gearing on their rating is lessened.
n
-------
TABLE II
SUMMARY OF HYBRID SYSTEMS EFFICIENCY ON LA-4 DRIVING CYCLE
ro
• . Battery
;.; Impedance
n
Full Voltage :
Series System
Parallel (EMT)
System
86 x 10~3
86 x 10~3
86 x 10"3
172 x 10"3 ;
172 x 10"3
86 x 10"3
86 x 10"3
86 x 10"3
172 x 10"3
172 x 10"3
•Motor to Wheel
. Gear Ratio
constant
variable
constant
.variable
;. va ri ab'l e
; constant
constant
variable
variable
variable
Planetary Gear
Nominal
Efficiency
—
. —
. —
80% .
80%
90%
80%
80%
Regenerative
Braking
yes
yes
no
yes
no
yes
no*
yes
yes
no*
Overall
Efficiency
47.9
55.1
42.9
52.0
46.4
61.7
53.6
76.7
66.6
54.0
*Regenerative braking capability in the EMT is a normal part of its control system.
-------
Weight and Cost Estimates of Hybrid Power Trains
The OEM cost of the series system is estimated to be $768; the
parallel system will cost $600, both exclusive of battery and engine.
Assuming 500 pounds of lead-acid batteries and a 350 pound engine, the
parallel system will weigh between 1451 and 1501 pounds. The series
system will weigh 1649 to 1699 pounds. In each case, the heavier value
includes the incorporation of a variable gear ratio transmission.
While new car customer costs of hybrids cannot be estimated at this
time, it appears that the fuel savings would be able to pay for battery
replacement costs. Furthermore, the durability and modular packaging of
the electrical equipment may lead to novel power train marketing and re-
cycling such as "portable" PCUs where the control electronics is owned by
the customer and he transfers it from one vehicle to another as he changes
ears.
EXPERIMENTAL ACTIVITIES
Experimental studies were conducted on the effectiveness of selected
internal combustion engine emission control concepts used within the con-
text of hybrid vehicle operation. The usefulness of the devices depended
on controlled engine operation during start-up and hot operation and
therefore, could not be applied to a first approximation to conventional
1C powered vehicles where driveability demands would interfere with engine-
control system operation.
Hydrocarbon Accumulator Materials Screening
The first device studied was a hydrocarbon accumulator which operates
on an adsorption-desorption cycle. It is based on well-developed chromato-
graphic principles of organic compound separation. The accumulator
material adsorbs engine exhaust hydrocarbons from the relatively cool
exhaust stream during engine start-up and retains them as the exhaust
temperature rises and the engine choke is relieved. When the exhaust or
bed temperature reaches a predetermined point, a large portion (^99%) of
the exhaust is diverted through a jacket around the accumulator; the re-
maining exhaust flows through the accumulator, picking up hydrocarbons
and returning them to the engine intake or catalytic converter for com-
bustion. 13
-------
The selection of the most promising hydrocarbon accumulator material
was carried out by a material screening process. The materials tested were,
in order of decreasing effectiveness, activated carbons, activated char-
coals, molecular sieves, silica gels and, aluminas. Test materials were
placed within a canister.downstream of the exhaust port of one single
cylinder of a 160Q cc VW engine. Cold start tests were carried out to
assess the retention and desorption properties of each of the materials.
The materials were also investigated for chemical and mechanical degrada-
tion.
Tests indicated that activated carbons are the most efficient class of
materials within the range tested. They exhibit the highest capacity for
exhaust hydrocarbons at a given temperature and are capable of continued
adsorbing nearly twice the hydrocarbons of the next best material. Even at
space velocities in excess of 80,000 V/V/Hr and exhaust temperatures as high
as 600°F, one material, Pittsburgh Activated Carbon, BPL series, did not
show chemical or mechanical deterioration after several absorption-desorp-
tion cycles as long as care was exercised when the accumulator was being
filled. ;
Characterization of TRW-Harshaw Three-Component Catalyst
A copper oxide-on-alurm'na catalyst was evaluated for use as a three-
component .catalyst, that is one which simultaneously controls hydrocarbons
(HC), carbon monoxide (CO) and nitric oxide (NO). The catalyst is manufact-
ured by Harshaw Chemical Co. and is activated by a TRW process.
Bench scale tests on the catalyst showed that:
• it could convert about 90% CH4 and NO and 100% CO in a synthetic
•• , exhaust gas mixture .
t the CO oxidation process started around 300°F, NO reduction
around 500-650°F and methane oxidation around 1000°F.
Catalyst conversion tests were conducted using,a canister containing about
3 ' '••'•' ''" ••
100 in of catalyst. The bed was exposed to the flow from the same cylinder
as in the hydrocarbon accumulator tests. The tests showed that, in steady
state:
• The catalyst is generally non-selective in promoting the re-
action of exhaust components. At temperatures around 1200°F
CO oxidation is favored over HC; the opposite is true
14
-------
above 1500°F. However, other reactions are presumed to
cause these effects rather than catalyst selectivity.
• The catalyst can reduce the levels of all three pollutants
simultaneously by 75% for bed temperatures in excess of
'1350°F and in an air-fuel ratio band of 0.7.
t Relative conversion of HC and CO are temperature dependent.
t Space velocity effects the conversion efficiencies on an
individual basis. At stoichiometry NO conversion decreases
from 90% to 70% as the space velocity increases from 32,000
to 37,000 V/V/Hr. While HC and CO conversions were unaffected
by space velocity at that air-fuel ratio, they become
, space* velocity sensitive for richer mixtures.' '
•. Chemical effects and non-selectivity work to limit the
catalyst effectiveness. It appears that the air-fuel ,ratio
point of maximum simultaneous conversion moves to leaner
mixtures with increasing temperature.
The catalyst will tend to suffer reduced NO conversion efficiency
with time when exposed to lean mixtures. However, the time constant of
the loss is on the order of minutes. Also the catalyst recovers its
f -,•'*''.' '. • " ' ' • " ' ' ' • ' '
initial capability almost immediately when exposed to a slightly rich, ,
mixture. Thus the catalyst will provide effective control to short dura-
tion swings in the mixture ratio. .
Steady state tests on the full exhaust stream of a Vega ICE were
conducted using a scaled-up version of the single cylinder converter.
Scaling up the converter by a factor of four slightly increased the band
of effective CO conversion; the other conversions were unaffected.
Data comparing engine hydrogen generation and catalyst ammonia pro-
duction suggested there was no direct link between them. There is a
strong dependence of ammonia generation on temperature and air-fuel ratio.
At A/F levels below 13, NH3 approaches 100% of the total reacted NO,
thus all the NO goes into producing NH-. However, in the A/F and tempera-
ture band where the catalyst must function for good three-component con-
trol, NH« production is always less than 10% of the reduced NO.
Physical changes in the catalyst were small, if any, oyer the period
of testing. The cost and catalyst bed size for a full size converter
are well within practical limits. The estimated catalyst cost for a full
size passenger vehicle is around $10 to $15; the estimated catalyst volume
is 0.2 cubic feet.
15
-------
Two catalytic converters supplied by Universal Oil Products were
tested. While the converters showed good CO and HC oxidation character-
istics at lean air-fuel ratios, the peak NO conversion did not exceed
40%. It is possible that the converters were too small for this applica-
tion.
Full Scale Hybrid Power Train Emissions
The emissions of a hybrid power train were measured for the system
operating over the 1972 Federal driving cycle and using the cold start,
constant volume sampling "bag" technique. The engine ran over a power
schedule simulating the load demand which would be required in a real
hybrid vehicle.
An emission control system using a fast relief choke schedule,
hydrocarbon accumulator and three-component catalyst was able to bring
the system emissions below the 1975-76 standards. Hydrocarbons ranged
from 34% to 73% of the 1975 standards; NOV was 15% to 80% of the 1976
J\ - •
levels. CO proved to be the most troublesome component. While the 1975
standard for CO was met, it is felt that improved carburetion during cold
start would have increased the margin by which the CO standards would be
satisfied.
While long term testing has not been performed to demonstrate the
ability of the control approach to meet the standards for 50,000 miles,
short-term evaluation involving about 100 hours of testing has shown good
chemical and physical stability of the materials used in both control
devices.
16
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1.0 INTRODUCTION
Heat engine/battery hybrid automotive power systems have been under
investigation by TRW Systems.since 1967. As part of a company-funded
effort a parallel hybrid configuration termed the Electromechanical
Transmission (EMT) was conceived and a full-scale power dynamometer
proof-of-principle breadboard system was constructed and demonstrated.
ts
A description of the EMT as well as experimental data taken on the system
was previously reported in the EPA-sponsored contract, "Analysis and
Advanced Design Study of an Electromechanical Transmission," No. EHSH-71-
002, April 1972 (reference 1).
Hybrid power systems appear attractive for low emission, high fuel
economy vehicles. However, several questions 'related to the selection of
the best hybrid system, cost of such systems and the emission levels of
such vehicles remain.
In order to resolve many of these questions, TRW Systems has been
under contract (No. 68-04-0058)to the Division of Advanced Automotive Power
Systems Development, Office of Air Programs, Environmental Protection
Agency to perform "Cost and Emission Studies of a Heat Engine Battery
Hybrid Family Car." The period of performance was June 30, 1971 to
February 29, 1972. The latter date was extended approximately one month
to cover additional experimental measurements not originally called for
in the contract.
Among the objectives of the contract were the development of detailed
models of candidate heat engine-battery hybrid power trains for full size
family cars, analysis of the efficiency of the candidates and an estima-
tion of the size, first cost and cost of ownership of such vehicles. A
second phase of the work was a laboratory investigation of the character-
istics and suitability of three-component catalytic devices and hydro-
carbon traps as means for controlling internal combustion engine emissions
within the context of a hybrid environment. The goal of the experimental
work was to demonstrate that a full-sized hybrid system could meet the
1975-76 emission standards.
17
-------
This report is organized into two basically different sections, re-
flecting the extensive analytic and computer simulation work as well as
laboratory effort. It will be necessary to utilize data from one section
in the other in some cases; whenever this occurs, the reader will be
alerted.
The report contains a large number of appendices in which the back-
ground and supporting calculations which are necessary for a full under-
standing of the report results are to be found.
2.0 SELECTION OF CANDIDATE SERIES-CONNECTED HYBRID POWER TRAINS
2.1 General Specifications and Assumptions
The initial phase of vehicle power train selection must start
with a definition of the loads and modes of operation which a power
train will encounter in service. The Office of Air Programs has prepared
a complete set of vehicle design goals for a passenger car which will
have the performance, safety, convenience and ease of operation which may
be necessary to satisfy the requirements of the average motorist. These
design goals also specify that the vehicle be capable of meeting the
Federal emission standards for 1975-76 established by the 1970 Clean Air
Act. The design goals may be found in Appendix A.
The interpretation of the performance goals into wheel power loads
depends on the detailed vehicle velocity-time schedule of the specified
maneuver, say the high speed pass maneuver. Using some assumptions as to
the nature of the schedule, the wheel power demands for a 4000 pound
family car having the drag characteristics stated in the Design Goals can
be computed. Figure 2.1 shows the level-road and peak cruise requirements
as a function of vehicle velocity along with some grade requirements. To
cruise at 85 mph, approximately 65 road horsepower is needed and the power
train must be capable of providing short duration wheel power bursts in
excess of 100 horsepower. If it is assumed that the power train elements
between the engine and wheels have an overall efficiency of approximately
75% and with allowance for passenger comfort and convenience features, the
engine must be capable of continuously supplying about 85 shaft horsepower
at 85 mph cruise.
18
-------
ROAD
HORSEPOWER
25 -
FIGURE 2.1
WHEEL POWER DEMANDS FOR A 4000 LB CAR
20 30
40 50
VEHICLE SPEED (MPH)
60 70 80 90
-------
The selection and specifications of an engine for a hybrid system
are reviewed in Appendix B. Economy and emission characteristics combine
to set the range of engine displacement and its speed range. The series
system's generator speed range is directly proportional to the engine
speed range; for this study a 3:1 generator (engine) speed range is assumed.
Several other general criteria for operation must be specified before
starting analyses of the power trains. These refer to the modes of power
train operation and in particular the demarkation between urban and high-
way operation. We shall assume that at one-half the vehicle's top speed,
42.5 mph, there is a departure point between urban and highway operation.
In urban traffic below 42.5 mph the'engine will operate at constant power
and speed. When the vehicle speed increases above 42.5 mph, it is assumed
that the engine speed will linearly increase up to its maximum value cor-
responding to the vehicle's top speed. At the same time, the engine's
throttle will be adjusted so that the engine's output times the power train
inefficiency between engine and wheels equals the road cruise power at that
speed.
Finally,, performance analyses of a hybrid power train must consider
the possibility of battery charge state change. A power train which causes
a net discharge of the battery does not fulfill all the design criteria;
one that ;tends to overcharge the battery will be inefficient and might cause
battery damage in the field. It is difficult to establish the engine power
level a priori which will keep the battery near constant charge and one
must use a trial and error approach in evaluating various parameters and
their effect on performance.
2.2 Candidate Series Systems
. Three candidate series-connected hybrid power trains were selected
for study'. Block diagram representations of the system are shown in Figures
2.2, 2.3:and'.2.4.
2.2.1 Full Voltage Series System
This system (Figure 2.2) contains an alternator directly
coupled through fixed gearing to the engine. The rectified voltage and
power of the machine is delivered to the battery bus where the power can be
used to either charge the battery or power the traction motor. The
20
-------
FIGURE 2.2
FULL VOLTAGE SERIES-CONNECTED HYBRID SYSTEM
REFERENCE
HIGHWAY
ENGINE
SPEED
REFERENCE -
URBAN
ENGINE
SPEED
r
PO
ENGINE
rINE
D
•
FIELD
PCU
O O
V->vA-/
ALTERNATOR
BATTERY
R
E
C
T
1
• F
1
E
R
r<
)
• .
MOTOR
PCU
c\
s
r
DC
SERIES
MOTOR
VEHI
WHE
r
^-
THROTTLE
SERVO
^ BATTERY CURRENT INTEGRAL I
u I O •—I
O . O —URBAN THROTTLE LEVEL
I g\4 WHEEL SPEED
MODE CROSSOVER SPEED
DRIVE
LOGIC
-'- t
MOTOR CURRENT
FEEDBACK
_J
TORQUE
COMPARATOR
TORQUE
COMMAND
-------
alternator runs at one-third its rated speed in urban traffic reflecting
the 3:1 maximum speed range of the engine. During highway operation its
speed varies proportionally to road speed. The output voltage of the
alternator, however, must remain at the battery voltage so that alternator
power can be delivered to the battery bus. Thus, a field control system
is required to maintain a proper alternator voTtage. Feedback engine speed
control is accomplished by the field PCU;, as the engine speed rises above
the reference urban or highway value the alternator field and voltage in-
crease, increasing the load on the engine which in turn tends to slow the
engine down.
Traction motor power is processed by a regenerative chopper motor
PClr '. Duty cycle control of the chopper is accomplished through a drive
logic which compares the driver's torque command with the motor's developed
torque (armature current) and adjusts the duty cycle appropriately. The
motor PCU is capable of operating as a regenerative system, taking motor
(generator) power and processing it back to the battery.
Engine torque output is controlled by moving the engine throttle. In
the urban mode, the throttle position is pre-set to give some assigned
power output at the reference speed. At 42.5 mph, the throttle position
reference shifts to a signal proportional to the integral of the battery
current. When the^battery begins to discharge, the throttle opens very
slowly. During regeneration or dynamic braking it closes slowly. All the
systems described in this report have this form of engine power control
incorporated in their design.
2.2.2 Two Alternator Series System*
Figure 2.3:shows the block diagram of the two alternator
system. Alternator #1 is rated at a lower power level than alternator
#2 equal to the urban engine power output. Alternator #2 is rated for a
continuous power output equal to the load requirement of the traction motor
at top vehicle speed. i
*_ • • •
When the vehicle is at rest, the total output of the engine is pro-
cessed by alternator #1 and delivered to the battery. ,As the operator
accelerates the car, the field of alternator #2 increases and the field
*The Two Alternator configuration was suggested for study by Dr. Jalal
Sallhi of EPA.
22
-------
FIGURE 2.3
TWO ALTERNATOR SERIES CONNECTED HYBRID SYSTEM
BATTERY CURRENT INTEGRAL
ro
BATTERY
V.
)
ENGINE
THROTTLE' '
ERVO
NO. i
URBAN THROTTLE LEVEL O
REFERENCE HIGHWAY
ENGINE SPEED
REFERENCE URBAN-
ENGINE SPEED
WHEEL
SPEED
MODE
CROSSOVER
MOTOR
PCU
A
L
E
R
N
A
T
o
R
NO. 2
FIELD NO. 2
* *
1^-
— T
R
C
T
I
F
1
c
R
NO. 2
CHOKE
-£"*&-
c
\
D!C
j • v.
^\
j
DC
C FD 1 PC
MOTOR
VEHICLE
WHEELS
ft
} CURRENT
LIMITS
-
DRIVE
LOGIC
MOTOR CURRENT
FEEDBACK
TORQUE
TORQUE COMPARATOR
COMMAND
-------
of alternator #1 decreases, shifting engine power from the first machine
to the second. When the output of #2 reaches the engine power, field #1
is essentially off and field #2 is prohibited by a threshold detector
from further increase. At very low vehicle speeds, a current detector on
alternator #2 protects that machine against overloading.
The voltage of alternator #2 is controlled through the drive logic
such that the alternator can deliver power to the traction motor at any
speed. However, when the alternator's current limit is reached the logic
turns on the motor PCU and allows battery power to flow to the traction
motor. The PCU is similar to that of the full voltage system—it is a
regenerative chopper drvice. Increasing the chopper duty cycle draws
more power from the battery/alternator #1 power sources. A choke, L,
must be included in the circuit for continuity of alternator #2 current.
The engine throttle control system and motor torque feedback controls
are similar to the full voltage system. However, the engine speed control
is somewhat more complex in that the fields must be adjusted in a manner
that maintains stability and restricts speed excursions of the engine.
While the single alternator of the full voltage system must be capable
of producing battery voltage at one-third its top speed, alternator #2 is
uncoupled from the battery bus voltage and therefore need be capable of
only producing one-half battery voltage at one-third rated speed. (At
42.5 mph the motor terminal voltage"is approximately one-half its voltage
at top speed and alternator #2 need only produce power at half battery
voltage to supply power to the motor.) Machine #2 therefore can be some-
what smaller than the full voltage alternator as its field is better
utilized and can be run closer to saturation during urban operation.
Alternator #1 still must produce battery voltage at one-third rated speed;
however, it is inherently a smaller machine handling less power and the
poor field utilization impact is lessened.
24
-------
2.2.3 Series System with Alternator PCU
The series system with alternator PCU is an attempt to reduce
alternator size requirements by running the alternator field around satur-
ation independent of the machine's speed. The alternator is coupled to a
voltage boost type PCU as shown in Figure 2.4. In almost all other
respects its operation and control is the same as the full voltage system.
The boost PCU incorporates an inductive energy storage element which
is first charged from the alternator and then discharged in series with
the alternator into the battery bus. This technique of alternator control
has been successfully employed on the EMT dynamometer demonstration and is
utilized for regenerative power control on all the three series traction
motor systems. A further description of the boost PCU technique can be '
found in reference 1. :
Duty cycle input control of the boost PCU is accomplished through an
alternator PCU controller. It processes engine speed error signals sim-
ilarly as the other systems but instead of changing the alternator's field,
it adjusts the PCU duty cycle.
2.3 Evaluation of Candidate Series Systems
Preliminary specifications for the major rotating machines and
power processors were developed in terms of the required vehicle perfor-
mance of Figure 2.1. Each component is specified in terms of the para-
meters which impact the greatest on the final selection.
The parameters which were used are:
• equipment rating on a per unit (p.u.) basis
• equipment rating on a kw and/or hp basis
• equipment rating in KVA
• equipment weight in Ib
t equipment size in cubic feet
t equipment efficiency under selected driving conditions
• equipment projected cost
• equipment control simplicity and reliability.
25
-------
FIGURE 2.4
SERIES HYBRID SYSTEM WITH ALTERNATOR PCU
ro
cr>
BOOST PCU
LOGIC
FIELD (SATURATED) ,
ALTERNATOR
THROTTLE
SERVO
MOTOR CURRENT
FEEDBACK
URBAN THROTTLE LEVEL
REFERENCE HIGHWAY
ENGINE SPEED
REFERENCE URBAN
ENGINE SPEED
TORQUE
COMPARATOR
NOTE: ENGINE SPEED RANGE 3 :1
MODE CROSSOVER
TORQUE
COMMAND
-------
Power rating of equipment on a per unit (p.u.) basis allows a first
order qualative comparison between a multitude of systems which would
operate at different rated power levels.
Unity per unit is defined as the inherent rated physical capability
designed into the equipment. For quantitative evaluation, the ratings
are determined in absolute units of kilowatts or horsepower. For example,
in this study the full load motor rating is 65 hp at 85 mph.
Thus, 1 p.u. power for the traction motor is 65 hp, 1 p.u. voltage
is the battery open circuit voltage and motor current at 65 hp and battery
voltage is 1 p.u. machine current. The power ratings are pivotal for the
efficiency computations.
The nature of the load transients, out of phase current, voltages
and rectification are such as to impact the equipment rating in a manner
analogous to that derived from power factor loads. The ratings which
reflect the capability of units operating under non-ideal conditions are
given in KVA and are very important for computations of component size,
weight and cost.
Figure 2.5 repeats the vehicle performance requirements of Figure 2.1;
however, superimposed are the current requirements for a motor rated at
65 hp, 360 VDC, 194 amperes, at 5000 rpm with an efficiency of about 90%.
This machine,initially chosen for preliminary system comparison,would
represent advanced state-of-the-art machinery and would be of a light-
weight design so that it could produce about 0.2 hp/lb. The specification
for the alternators depend on the specific system under consideration.
Appendix C treats these specifications along with PCU requirements.
Tables 2.1, 2.2, 2.3, 2.4, 2.5, and 2.6 summarize the specifications
of the major units. In all three systems, the use of an oil spray cooled
alternator was investigated as a means for increasing the power density
of that component.
27
-------
ro
CO
10
FIGURE 2.5
PER UNIT TORQUE REQUIREMENTS OF THE TRACTION MOTOR
FOR SERIES-CONNECTED HYBRID SYSTEMS
20 30
40 50
VEHICLE SPEED (MPH)
60 70
-------
TABLE 2.1
PRELIMINARY SPECIFICATIONS OF FULL VOLTAGE SYSTEM USING FORCED COOLED ALTERNATOR
Rating at Base
Speed (p.u.)
Rated Power Level
Efficiency at Top
Vehicle Speed
Approximate KVA at
Top Speed
Weight (Ib)
Size (cu. ft.)
Input
1
64.5 kw
---
.__
30
—
Alternator
3
58x3 kw
90
61x3=183
230
Rectifier
1
57.5:kw
99.2
57.5
- —
, n(. Included within
'•ua Alternator
PCU
1
54 kw
94
272
120
2.0
Motor
1
65 hp
90
—
325
1.27
Total
Total Series
Efficiency
75.5*
; . _---••
705 Ibs.
4.32
TABLE 2.2
PRELIMINARY SPECIFICATIONS OF FULL VOLTAGE SYSTEM USING OIL SPRAY COOLED ALTERNATOR
Rating at Base
Speed (p.u. )
Rated Power Level
Efficiency at Top
Vehicle Speed
Approximate KVA at
Top Speed
Weight (Ib)
Size (cu. ft.)
Input
1 '•
71.0 kw
—
30
—
Alternator
3
58x3 kw
82
61x3=183
165
.92
Rectifier
1
57.5 kw
99.2
57.5
---
within
aUprnatnr
PCU
1
54 kw
94*
272
120
2.0
Motor
1
65 hp
90%
---
325
1.27
Total
Total Series
Efficiency
68.6%
_._
640 Ibs.
4.19 :
29
-------
TABLE 2.3
PRELIMINARY SPECIFICATIONS OF TWO GENERATOR SYSTEM USING FORCED COOLED ALTERNATOR
Rating at Base
Speed (p.u.)
Rated Power Level
Efficiency at Top
Vehicle Speed
Approximate KVA at
top Speed
Weight (Ib)
Size (cu. ft.)
Input
... 1.
63.0 kw
..
30
Alternator #1
.3 -
3x10.2 kw
80
'"^-^if
32.3
70.0
0.55
Alternator #2
1 .5
,,1.5x54.8 kw
-—J2-
86.0
116
0.75
Choke
---
—
9? .. ',
29.8
80
.2
Rectifier #1
- -1
10 kw
. ... 99.2 .
10
--
w/alternator
Rectifier #2
1
54 kw
99.2
54
—
w/alternator
PCD
1
20 kw
94
272
70
1.7
Motor
1
65 hp
90
--
325
1.27
Total
—
—
77.0
—
691 Ib.
4.47
00
o
TABLE 2.4
PRELIMINARY SPECIFICATIONS OF TWO GENERATOR SYSTEM USING OIL SPRAY COOLED ALTERNATOR
Rating at Base
Speed (p.u.)
Rated Power Level
Efficiency at Top
Vehicle Speed
Approximate KVA at
Top Speed
Weight (Ib)
Input
62.5
65.6
30
Alternator #1
3
3x10.2 kw
Alternator #2
1.5
1.5x54.8 kw
^73 83^.
80
32.3
40.0
86.0
83
Choke
—
—
99
29.8
80
Rectifier #1
1
10 kw
99.2
10
--
Rectifier #2
1
54 kw
99.2
54
---
PCU
~T~
20 kw
94
272
70
Motor
1
65 hp
90
325
Total
71.0
641 Ib.
-------
TABLE 2.5
PRELIMINARY SPECIFICATION OF SERIES SYSTEM WITH ALTERNATOR PCU USING FORCED COOLED ALTERNATOR
Rating at Base
Speed (p.u. )
Rated Power Level
Efficiency at Top
Vehicle Speed
Approximate KVA at
Top Speed
Weight (Ib)
Size (cu. ft.)
Input
1
68.5 kw
—
--
30
—
Alternator
1
61.6 kw
90
64.6
102
0.7
Rectifier & Boost PCU
with Storage Inductor
1
57.5 kw
99.2x94=93.3
57.5
120
2.0
PCU
1
54 kw
94%
272
120
2.0
Motor
i
65 hp
90%
)
325
1.27
Total
—
71. OX
—
697
5.97
TABLE 2.6
PRELIMINARY SPECIFICATION OF SERIES SYSTEM WITH ALTERNATOR PCU USING OIL SPRAY COOLED ALTERNATOR
Rating at Base
Speed (p.u.)
Rated Power Level
Efficiency at Top
Vehicle Speed
Approximate KVA at
Top Speed
Weight (Ib)
Size (cu. ft.)
Input
1
75.5 kw
, —
~
30
" .
Alternator
1
61.6 kw
82
64.6
60
0.55
Rectifier »
Boost PCU
1
57.5
99.2x94=93.3
57.5
120
2.0
PCU
nr
54 kw
94X
272
120
2.0
Motor
65 hp
90%
—
325
1.27
Total
—
65. 5X
—
655
5.82
31
-------
2.3.1 Preliminary Selection - Criteria
The assessment of the three candidates is based on computing power
train weights, volumes and efficiencies at selected operating conditions.
The first set of conditions termed "non-hybrid conditions" character-
izes power train efficiency at selected speeds assuming there is no battery.
Under these circumstances, the engine power must be computed so it can
supply the vehicle's cruise power at the wheels taking into account power
train losses. The road power demand at various vehicle cruise speeds is:
21 mph - 3.75 hp or 2.8 kw
42.50 mph - 15.00 hp or 11.2 kw
60.00 mph - 28.75 hp or 21.4 kw
85.00 mph - 65.00 hp or 48.5 kw
The second set of operating conditions which are analyzed involves
using typical urban road power requirements to calculate battery charge
and discharge power. The engine power is either held at a constant level
in the urban mode or is allowed to throttle up to the road cruise demand
of the highway mode. During the LA-4 runs (reference 1) a 4000 pound car
required about 23 kw mean maximum road power for acceleration events. That
is, if one computes the peak power required for each acceleration from
rest, the average of the peaks is 23 kw. The average speed on LA-4 is about
21 mph and as shown above, the road demand at that speed is 3.75 hp. The
system which draws minimum power from the battery during acceleration or
is able to deliver largest charge power to the battery during cruise .con-
ditions would be preferred. For these preliminary calculations, a constant
engine power level of 15 hp is assumed for vehicle speeds below 42.5 mph.
The computations for non-hybrid and hybrid conditions are found in •
Appendix C and are summarized in Table I of the summary section. Of the
three systems, the series system with alternator PCU has the lowest over-
all efficiency. The two generator scheme offers slightly higher efficiency
of the two other systems, however, its control is potentially more difficult.
For example, the need to control both alternator fields in order to control
engine power may cause stability problems in the electrical and mechanical
loops.
32
-------
TABLE 2.7
COMPARISON OF NON-HYBRID SYSTEM PERFORMANCE
WITH OIL SPRAY-COOLED ALTERNATORS
CO
GO
System
Full Voltage
Series
Two Generator
Series w/alter-
nator PCU
Efficiency
21 mph (%)
21.0
24.6
23.4
Efficiency
42 mph (%)
51.5
57.0
44.5
Efficiency
60 mph (%)
60.4
65.0
49.5
Efficiency at
top vehicle
speed
68.6
71.0.
65.5
Weight
Ob)
640
641
655
Size
(cu ft)
4.19
4.22
5.82
-------
Oil spray cooled alternators were also examined as a part of the
system selection process. Table 2.7 summarizes the non-hybrid cruise
efficiency of power trains using this type of machine. The alternator
PCU system has the lowest efficiency at higher vehicle speeds and was
rejected. The efficiency comparison between the other two systems again
favors the two generator system; however, there is a substantial loss
in overall efficiency in both systems due to the use of the higher power
density-lower efficiency alternator.
The full voltage series system with a forced air cooled alternator
was therefore chosen as the candidate series system.
3.0 CHARACTERIZATION OF PARALLEL HYBRID SYSTEM
The parallel hybrid system selected for this study is the Electro-
mechanical Transmission (EMT) system developed by TRW Systems. This
power train has been described in reference 1 and therefore its
modes of operation will be discussed only briefly.
3.1 Description of EMT
The EMT system consists of a planetary gear, alternator, alter-
nator PCU, traction motor and motor PCU as shown in Figures 3.1 and 3.2.
The engine input power drives the sun gear of the planetary set; the ring
gear drives the power train propeller shaft and the planet carrier drives
the alternator. The planetary gear algebraically divides the input power
of the engine between the ring gear and planet carrier in direct proportion
to the speeds of the respective elements. Thus, when the propeller shaft
is stopped (car at rest), the planet carrier and alternator turn at maxi-
mum speed and all engine power goes into the alternator. As the car ac-
celerates and the propeller shaft speeds up, the planet carrier slows down
and less engine-produced energy is absorbed by the generator.
. i
In urban operation the engine runs at constant speed and power. Its
throttle is preset and its speed is controlled by increasing or decreasing
the alternator's load to reflect a balancing torque back on the engine
shaft.
34
-------
INTERNAL
COMBUSTION
ENGINE
en
URBAN
REFERENCE
SPEED
FIGURE 3.1
EMT HYBRID SYSTEM IN URBAN TRAFFIC MODE
PLANETARY
GEAR TRAIN
ALTERNATOR
,ALTERNATOR
PCU
DIFFERENTIAL
PROPELLER SHAFT
MOTOR
TRACTION OR
REGENERATION
POWER
DRIVING
WHEELS
MOTOR
PCU
— — OPERATOR
TORQUE
COMMAND
BATTERY
-------
FIGURE 3.2
EMT HYBRID SYSTEM IN HIGHWAY TRAFFIC MODE
INTERNAL
COMBUSTION
ENGINE
co
PLANETARY
TRAIN
PROPELLER SHAFT
BRAKE APPLIED
TO ALTENATOR
SHAFT
I ALTERNATOR j
L___T___J
MOTOR
I
I
/\ THROTTLE
*T-* SERVO
I
I ALTERNATOR |
I PCU |
I „._ J
DRIVING
MOTOR
PCU
J-.T
DIFFERENTIAL
OPERATOR
TORQUE
COMMAND
BATTERY
BATTERY
CURRENT
INTEGRAL
-------
The torque on the propeller shaft is directly related to the engine's
torque and planetary gear ratio. Since they are both constant in urban
operation, the propeller shaft torque is essentially constant in that mode.
The driving wheel torque is therefore must be controlled by a traction motor
which is capable of adding torque to (motor operation) or subtracting
torque from (generator operation) the propeller shaft.
PCUs are provided between the alternator and battery bus in order
that the alternator's output voltage can be boosted to battery voltage at
constant armature current. (Alternator field flux is maintained constant
at saturation.) A bi-directional PCU between battery bus and motor receives
operator commands in terms of desired motor torque magnitude and sign. For
motoring, the PCU acts as a chopper as in the PCU for the full voltage
series system. For generation, it acts as a boost .PCU as in the series
system with an alternator PCU.
During highway operation, the planet carrier and the alternator are
locked out and the engine speed increases linearly with road speed. The
propeller shaft feels an engine torque proportional to the developed
torque of the throttled engine. The motor/PCU continues to operate the
same as in the urban mode. Engine throttle levels are slowly changed by
a battery feedback loop as described in the full voltage system.
3.2 Specification of Parallel System Components
Previous studies showed that the continuous power rating of the
traction motor for the EMT could be less than one-half required for 85 mph
cruise. Figure 3.3 shows how the EMT's peak motor power varies with vehicle
speed. In contrast with the series system, peak motor power of the
parallel system reaches a maximum around 42.5 mph and then falls rapidly
to zero at 85 mph. On the other hand, since the motor must deliver the
power for vehicle-acceleration, the motor will have to operate at per-
haps two to three times rated torque at one-fourth its rated speed.
»- ^ . .•
: One'method suggested for reducing the motor torque and improving
motor efficiency at lower speeds is to use a multi-step gear ratio
between the motor and the wheels. Thus, at any road speed and power the
37
-------
FIGURE 3.3 .
POWER LEVELS OF EMT HYBRID SYSTEMS MOTOR AND ENGINE
CO
00
40 50
VEHICLE SPEED (MPH)
-------
motor will be able to turn at a higher rpm and lower torque and reduce
ohmic losses and PCU current requirements.
Table 3.1 presents a comparison of efficiencies of the motor at
various peak load conditions with and without gearing. The gear ratio
schedule between the motor and differential is assumed to be:
2:1 from 0 to 42.5 mph
1.5:1 from 42.5 to 55 mph
1:1 from 55 to 85 mph
The characteristics of the motor on which these calculations are based
can be found in Appendix D.
TABLE, 3.1 ,
EFFECT OF GEAR SHIFTING ON EMT TRACTION MOTOR
Road
Speed
(mph)
30
42.5*
42.5
50
55.0*,
55.0
70.0
85.0
Road
Power
(hp)
95
114
114
125
120 .
120
103
27
Torque
P..U.
10
7.9
4.8
: 1
Current
[amperes)
900
720
455
130
Motor
Voltage
Motor
RPM
113 12500
166
200
172
4250
5950
7200
Motor
Eff.
70
78
84
89
. With Gear Shift
Torque
P.U.
5
4,2
5.6
4.5
6.75
4.8
1
Current
amperes )
500
435
530
460
625
455
130
Motor
Voltage
174
224
197
223
182
200
172
Motor
RPM
5100
7200
5400
7000
4650
5950
7200
Motor
Eff.
81
87
82
87
79
.84
89
*Values immediately before gear shift
39
-------
The greatest improvement in motor efficiency takes place at low
vehicle speeds where gearing affects motor torque requirement the most.
While the series system's motor efficiency is also improved by using a
variable ratio gear train, low speed improvement is not as great as in
the EMT system since the series machine is rated at a higher nominal
torque level and thus can operate more efficiently at low speeds.
A secondary benefit of gearing is that is may allow some relaxation
of battery requirements in terms of power density. Improved machine effi-
ciency means less power demand on the battery for acceleration and for
similar motor loads a lighter weight or low power density battery could
be used.
The alternator for the EMT system operates under unique circumstances.
The alternator's speed varies over a 10:1 speed range between vehicle speeds
of 0 to 42.5 mph. Since its shaft torque is essentially constant over that
range, its input power varies by a factor of ten. In order to utilize the
machine's field as fully as possible, the machine must be run with a satur-
ated field under all cases. The resulting 10:1 variation in alternator
voltage is handled by boost power conditioning between the alternator and
battery. The preliminary rating of the alternator was based on it being
capable of absorbing the full output of the engine for extended periods
(car at rest). Thus, assuming a nominal 15 hp engine output in urban
operation and a 90% efficiency planetary gear system, the alternator was
rated at 10 kw input/12,000 rpm.
The planetary gear efficiency is dependent on the detailed design of
the gear system and its lubrication. The planetary gear box designed for
the EMT dynamometer demonstration combined planetary elements of a conven-
tional automatic transmission with spur gears within a completely oil-
flooded housing. With the addition of extra gears to adjust the planetary
ratios to the various input/output shafts, the average efficiency of the
gear box computed as the sum of the alternator and propeller shaft outputs
divided by the engine input was around 75%. Various mechanical design
handbooks indicate gear efficiencies typically >95%. In order to
40
-------
reflect the variability of design, two planetary gear system efficiencies
were chosen, 80 and 90%, and the effect of gear efficiency on overall
system efficiency was treated parametrically.
Other gearing efficiencies were estimated from handbook values.
Generally, gear efficiencies were taken as a decreasing function gear or
shaft speeds to account for windage and lubrication losses which would
tend to increase non-linearity with speed.
The power conditioning units were characterized in terms of their
current and KVA capabilities. Detailed designs were made to identify:
• appropriate SCR and rectifier elements
• commutation capacitors, inductors and reactors
• fusing
t relays
• electronic logic elements
Two designs for the motor PCU were developed. One had a current
handling capacity of 900 amperes, the other 600 amperes. The lower current
design was used where variable gearing was assumed; in these cases, the
gearing would reduce motor and hence PCU current and commutation require-
ments. Complete descriptions of the PCUs are to be found in Appendix E.
4.0 CHARACTERIZATION OF HYBRID VEHICLE BATTERIES
The lead-acid batteries were characterized in terms of their internal
impedance. A review of battery charge/discharge characteristics ' as well as
studies from the hybrid vehicle lead-acid development program ' indicated
battery impedance was a function of battery design and charge state.
Experience with the EMT and previous computer analyses * ' showed that
the variation of the battery charge state during LA-4 operation was so
small that charge state effects on impedance could be neglected and
full charge impedance was taken as the battery variable. Measurements
taken during the lead-acid development program showed that a 240 VDC
battery (120 cells) having a 75-second power density of over 150 watts/
pound would have an impedance of 86x10-3 ohms. Degraded battery conditions
were modeled by assuming impedances of 170xlO~3 and 240xlO"3 ohms, reflect-
ing 50% and 67% losses in active material area.
41
-------
A charge model for the battery was not incorporated as part of the
program. Previous analyses had shown that the energy associated with gas-
ing during charge would be very small relative to the charge or discharge
power-levels. Experiments on the EMT showed the water losses from standard
SLI batteries operating on the LA-4 driving cycle have typically been very
small, also suggesting a low energy loss due to gasing.
5.0 MODELING AND SIMULATION OF HYBRID VEHICLES
5.1 Instantaneous Values of Component Performance of Series and
Parallel Hybrid Power Trains
Appendix F presents the detailed computer program models and
simulation procedures for analyzing both the instantaneous and LA-4 per-
formance of the full voltage series and parallel hybrid systems. The
instantaneous values, i.e., the values of power train component operation
at matrix values of vehicle acceleration and speed are to be found in
Appendix G.
The computer print-out is divided into those quantities which are
velocity and acceleration dependent—motor power levels, battery voltages
and currents, PCU efficiencies, etc., and those quantities which are
vehicle speed dependent only,such as engine power level.
Those places in the computer listing where the motor PCU chopper
duty cycle, ct, equals 1.0, are points where, for the particular vehicle
parameters of that computation, the battery voltage either sank too low
to provide the motor's terminal voltage requirement or the voltage of the
motor was too low relative to the battery voltage for the motor PCU acting
as a boost PCU to charge the battery.
5.2 LA-4 Performance of Series and Parallel Hybrid Power Trains
The performance of series and parallel hybrids was evaluated for
urban operation as defined by the LA-4 route. The velocity-time profiles
used as inputs were gathered from fifth wheel data of actual cars driving a
specific route in Los Angeles traffic during morning hours. The route is
such that it combines congested, freeway & boulevard traffic in a manner
representative of L.A. driving. A composite of LA-4 velocity-time data forms
42
-------
basis for the 1972 Federal driving cycle; however, the LA-4 route is
longer, requiring about 30 minutes and covering about 10 miles. A total
of 14 hours of vehicle operation, representing about 52,000, one-second
events had been previously reduced for computer input.
The performance of simulated vehicles operating on the LA-4 driving
profile was computed by multiplying the instantaneous component operating
values by the probability of occurrence in the LA-4 velocity-acceleration
matrix. Appendix F describes the procedure more fully and also indicates
how coiiiponent driving cycle averages and RMS values were computed.
Figures 5.1, 5.2, 5.3, 5.4, and 5.5 show block diagrams of the full
voltage series system along with the average efficiencies and input/out-
put levels which result from operation on the LA-4 cycle. Figures 5.6,
5.7, 5.8, 5.9, and 5.10 present similar information for the parallel system.
The numbers associated with each block in the diagrams represent the
average efficiency of the component during LA-4 operation. The battery
losses are shown as a separate item; in each of the runs the battery charge
state did not change from run start to finish. The arrows and power levels
show the power flow direction and average values at selected points of the
system. Average power levels at other points can be found by multiplica-
tion of the efficiencies within the blocks. In all the calculations
vehicle accessory loads were neglected.
5.3 Effect of Series and Parallel System Parameters on Overall
System Efficiency
The important operating parameters of the two hybrid systems
were varied to determine their effect on system performance. The para-
meters which were varied were the engine input power in the urban mode,
battery impedance, the efficiencies of gear 1, gear 2 and the planetary
gearing. The effects of the introduction of a variable transmission ratio
between the motor output shaft and the differential, and the possible
benefits of vehicle kinetic energy regeneration were also studied. A
single test run was also made on the series system model operating without
the engine to simulate the performance of an all-electric vehicle.
43
-------
FIGURE 5.1
FULL VOLTAGE SERIES SYSTEM ON LA-4 MISSION WITH
VARIABLE GEARING AND REGENERATION
RUN IA
Tlryc = 55.2%
ENGINE
18. 3 HP
GEAR 2
97.5%
ALTERNATOR
67.6%
RECTIFIER
99%
8.9KW
10.2 KW
1.74KW
MOTOR
PCU
92 59f>
88.4%
MOTOR
83.5%
82.3%
GEAR 1
95 6%
96%
10.1 HP
3.34 HP
WHEELS
BATTERY
DISSIPATED POWER
288 WATTS
-------
FIGURE 5.2
FULL VOLTAGE SERIES SYSTEM ON LA-4 MISSION WITH
VARIABLE GEARING AND REGENERATION
RUN GA
= 52.0%
ENGINE
19.1 HP
GEAR 2
97.5%
ALTERNATOR
68.2%
RECTIFIER
99%
9.42 KW
10. 1 KW
1.75 KW
.
MOTOR
PCU
92.1%
88.7%"
MOTOR
83.4%
82.4%
GEAR 1
OC "JOT
96%
9.92 HP
3. 34 HP
WHEELS
BATTERY
DISSIPATED POWER
577 WATTS
-------
FIGURE 5.3
FULL VOLTAGE SERIES SYSTEM ON LA-4 MISSION WITHOUT
VARIABLE GEARING, UITH REGENERATION
RUN CA
nsys = 47.9%
ENGINE
21.3 HP
GEAR 2
98%
ALTERNATOR
69.7%
RECTIFIER
99%
10.75 KW
11.5 KW
'1.48 KW
BATTERY
DISSIPATED POWER
358 WATTS
MOTOR
PCU
90%
82.5%
MOTOR
75. 3%^
74.4%
GEAR 1
97.3%^
97.3%
10.2 HP
3. 34 HP
WHEELS
-------
FIGURE 5.4
FULL VOLTAGE SERIES SYSTEM ON LA-4 MISSION WITH
VARIABLE GEARING, WITHOUT REGENERATION
RUN BBA
SYS
21.4HP
ENGINE
GEAR 2
97.5%
ALTERNATOR
69.7%
RECTIFIER
99%
10.8KW 10.1 KW
MOTOR
PCU
92.1%
BATTERY
DISSIPATED POWER
414 WATTS
9.92 HP
GEAR 1
95.3%
WHEELS
-------
FIGURE 5.5
FULL VOLTAGE SERIES SYSTEM ON LA-4 MISSION WITHOUT
VARIABLE GEARING OR REGENERATION
RUN AAA
SYS
23.8 HP
ENGINE
GEAR 2
97.8%
ALTERNATOR
71.2%
RECTIFIER
99%
12.3 KW 11.5KW
MOTOR
PCU
90.2%
MOTOR
75.3%
10.2 HP
GEAR 1
96.2%
WHEELS
BATTERY
DISSIPATED POWER
289 WATTS
-------
FIGURE 5.6
EMT SYSTEM ON LA-4 MISSION WITH VARIABLE BEARING AND REGENERATION
RUN TAA
=75.7%
VD
ENGINE
13.3 HP
PLANETARY
GEAR
90%
6.45 HP
5.36 HP
4.58 KW
ALTERNATOR
81%
6.11 HP
VARIABLE
GEAR
98%
RECTIFIER PCU
ALTERNATOR
95%
GEAR1
95%
10.2 HP
3.33 HP
WHEELS
3.52 KW
BATTERY
DISSIPATED
POWER
277 WATTS
MOTOR '
86.3% 86.3%
MOTOR PCU '
89% 92%
3.02 KW
5.84 KW
-------
FIGURE 5.7
EMT SYSTEM ON LA-4 MISSION WITH VARIABLE GEARING AND REGENERATION
RUN XA
Tlcyc = 66.6%
s
ENGINE
15.3 HP
PLANETARY
GEAR
80%
6.54 HP
5.41 HP
4.72 KW
ALTERNATOR
81.2%
5.84 HP
VARIABLE
GEAR
RECTIFIER PCD
ALTERNATOR
95%
3.64 KW
GEAR 1
95%
10 HP
3.34 HP
WHEELS
BATTERY
DISSIPATED
POWER
556 WATTS
MOTOR
86.2% 86.2%
MOTOR PCU
89.6% 91.1%
3.07 KW
5.66 KW
-------
FIGURE 5.8
EMT SYSTEM ON LA-4 MISSION WITHOUT VARIABLE GEARING, WITH REGENERATION
RUN RA
~ 6 I . 7%
en
ENGINE
16,5 HP
PLANETARY
GEAR
80%
5,17 KW
ALTERNATOR
82.2%
RECTIFIER PCU
ALTERNATOR
95%
4.03 KW
BATTERY
DISSIPATED
POWER
298 WATTS
MOTOR
82.2% 81.3%
MOTOR PCU
85% 88.5%
2.85 KW
6.16 KW
-------
FIGURE 5.9
EMT SYSTEM ON LA-4 MISSION WITH VARIABLE GEARING, WITHOUT REGENERATION
RUN LLA
nSYS = ^'^
tn
ro
ENGINE
18.6 HP
PLANETARY
GEAR
80%
7.64 HP
2.67 HP
5.98 KW
ALTERNATOR
83.5%
5.20 HP
VARIABLE
GEAR
98%
RECITFIER PCU
ALTERNATOR
95%
4.75 KW
GEAR 1
95%
10.1 HP
MOTOR i
82.6% 82.6%
MOTOR PCU '
78.7% 91.8%
1.26 KW
5.1 KW
BATTERY
DISSIPATED
POWER
388 WATTS
WHEELS
-------
FIGURE 5.10
EMT SYSTEM ON LA-4 MISSION WITHOUT VARIABLE GEARING OR REGENERATION
RUN JJA
nSY3 = 53.6%
U)
ENGINE
19.0 HP
PLANETARY
GEAR
80%
7.83 HP
2.75 HP
6.17 KW
ALTERNATOR
83.7%
5.39 HP
VARIABLE
GEAR
98%
RECTIFIER PCU
ALTERNATOR
95%
GEAR 1
95%
10.? HP
MOTOR
81.5% 81.2%
MOTOR PCU '
72.2% 89.0%
4.9 KW
I.48KWJ
WHEELS
5.66 KW
BATTERY
DISSIPATED
POWER
216 WATTS
-------
Tables 5.1 and 5.2 present listings of the combinations of parameters
and operating modes of the more meaningful simulation runs. In the initial
runs it was impossible to assign appropriate parameter values such that
during LA-4 driving the battery charge state would be constant. Thus, many
of the runs shown here are part of a learning procedure by which we were
able to define the conditions for constant charge state.
Tables 5.3 through 5.6 present the average and selected RMS values of
the hybrid systems and major components for the LA-4 mission. Definitions
of the symbols can be found in the nomenclature.
5.3.1 Effect of System Parameters on Full Voltage Series System
Performance -
/ '. - '
The effect of inserting a variable gear ratio between the
motor output shaft and the differential is to increase the series system's
efficiency by about 15%. Comparing runs CA and IA shows that system
effi ci ency.i ncreases from 47.9% to 55.0%.
The effect of doubling battery impedance from 86 to 172 mi Hi ohms in
a fixed gear ratio series system is to decrease system efficiency as1 shown
in runs K and CA. System efficiency falls from 47.9% to 44.0%. In a
geared system the effect is similar as indicated in runs IA and GA where
the respective efficiency decrease is from 55% to 52%.
The effect of degrading the efficiency of the gearing between the
engine and the alternator (^ is in direct proportion to the efficiency
change. Comparing runs Z, CA and K shows that a decrease of ng2 from .98-
.95 to .90-.87 reduces the system efficiency from 47.9% to 44.2%, nearly
a 10% reduction in efficiency. The effect of changing the differential
gear efficiency (g-|) is similar.
Comparison of runs CA, AAA, GA and BBA shows that regeneration affects
overall efficiency. Without regeneration, the series hybrid system effi-
ciency loses about 10 percentage points.
54
-------
TABLE 5.1
LIST OF INPUT PARAMETER VARIATIONS FOR THE
SERIES SYSTEM COMPUTATIONS
Battery
Resistance
Run PIC (xl°3a'
Designation (hp) B ngl
C
D
F
G
H
I
J
K
Z
CA
GA
AA
AAA
BB
BBA
IA
20.0
17.5
17.5
20.0
20.0
17.5
17.5
20.0
20.0
19.4
17
20
22.2 ,
20
19.5
16
86
86
86
172
240
86
86
172
86
86
172
86
86
172
172
86
98-95
97-94
98-95
97-94
97-94
97-94
90-87
98-95
98-95
98-95
97-94
98-95
98-95
97-94
97-94
97-94
V
98-95
98-95.
98-95
98-95
98-95
98-95
98-95
98-95
90-87
98-95
98-95
98-95
98-95
98-95
98-95
98-95
Variable
Gearing
no
yes
no
yes
yes
yes
yes
no
no
no .
yes
no
no
yes
yes
yes
Regeneration
yes
yes
yes
yes
yes
yes
yes
yes
yes
yes
yes
no
no
no
no
yes
55
-------
TABLE 5.2
LIST OF INPUT PARAMETER VARIATIONS FOR
PARALLEL SYSTEM COMPUTATIONS
THE
Run
Designation
R
RA
X
P
Q
S
T
TA
TAA
U
V
W
Y
CC
CCA
EE
EEA
XA
JJ
JJA
KK
KKA
LLA
Battery
Resistance
PIC (x!03n)
(hp) RB ngo
15
14.9
15
15
13
15
13
11
11.75
15
13
13
13
15
19.7
15
18.6
13.6
15
17.8
15
17
17.25
86
86
172
86
86
172
86
86
86
86
86
172
86
86
86
172
172
172
86
86
172
172
172
80
80
80
90
90
90
90
90
90
80
80
80
90
80
80
80
80
80
80
80
80
80
80
ngl
97-94
97-94
97-94
97-94
97-94
97-94
97-94
97-94
97-94
97-94
97-94
97-94
98-87
97-94
97-94
97-94
97-94
97-94
97-94
97-94
97-94
97-94
97-94
Step
Down
Gearing
no
no
yes
no
no
no
yes
yes
yes
yes
yes
yes
yes
no
no
yes
yes
yes
no
no
yes
yes
yes
Regeneration
yes
yes
yes
yes
yes
yes
yes
yes
yes
yes
yes
yes
yes
no*
no*
no*
no*
yes
engine power only**
engine nower only**
engine power only**
engine power only**
engine power only**
* Traction motor not operated as generator
** Traction motor operated as generator but absorbs
engine power contribution to propeller shaft only
56
-------
TABLE 5.3
PERFORMANCE OF FULL VOLTAGE SERIES SYSTEM
COMPONENTS ON LA-4 MISSION
Run
— ^_ u
Urban Engine Power, hp 17.5
Battery Resistance, 103n 86
Motor-Wheel Gear Ratio variable
ngl .97-. 94
ng2 .98-. 95
in drive
in regen
PM<->
TnO .
Mm hp
nu ' . r .
in drive
in regen
MI ' . . .
in drive
in regen
/JM"
PPCU
in drive
in regen
~n
B u
charge
discharge
LlC> hp
p.
HI
I
in drive
. in regen
*PCU
in drive
in regen
~TD
B .
charge
discharge
TA
drive probability
regen probability
6
1
-1
2
1
1
-1
1
1
-6
4
1
1
-5
-9
.9123+00
.4537+01
.1324+01
.0192+01
.3097+01
.5166+01
.0894+01
.1515+01
.3531+01
.6917+00
. 6843+01
.2177+01
.486 +01
. 7594+00
.583 -01
-9-. 848 +00
9.9857+00
1
1
9
1
1
1
-1
7
5
6
-2
-1
-4
4
3
0,
0,
. 9634+01
.4325+01
.8379+00
. 5767+02
.3763+02
.394 +02
. 3339+02
.3875+01
.1595+01
.3479+01
.3173+01
. 6845+00
.0103+01-
.5663+01
.8174+01
,70516
,29483
17.5
86
1:1
.98-. 95
.98-. 95
6.
1.
-1.
2.
1.
1.
-1.
1.
1.
-6.
8.
1.
1.
-5.
3.
-8.
1.
1.
1.
9.
2.
2.
2.
-2.
8.
5.
7.
-2.
4.
-3.
5.
3.
0.
0.
9119+00
4536+01
1324+01
0066+01
3829+01
5008+01
1007+01
2277+01
4855+01
1128+00
9723+01
3089+01
6451+01
0481+00
7428-01
6108+00
2832+01
9633+01
4324+01
8373+00
5506+02
0691+02
0676+02
0727+02
1607+01
587 +01
0715+01
0362+01
161 +00
5097+01
8597+01
9615+01
70518
29481
20
240
variable
.97-. 94
.98-. 95
6.
1.
-1.
2.
1.
1.
-1.
1.
1.
9408+00
4622+01
1324+01
0234+01
3964+01
5255+01
0894+01
,1562+01
,3611+01
-6.6917+00
4,
1,
.6939+01
.2181+01
1.48 +01
-5
-2
-1
9
2
1
1
1
1
1
-1
7
.952 +00
.4571+00
,0361+01
.4908+00
.1966+01
.6029+01
.1226+01
. 58 +02
.3819+02
.4021+02
. 3339+02
.5375+01
5.1721+01
6.3983+01
-2
-6
-4
4
4.
0.
0.
.2566+01
.3354+00
.0573+01
.7795+01
4695+01
70394
29605H
20
172
1:1
.98-. 95
.98-. 95
6.
1.
~T.'
1.
1.
-1.
1.
1.
-6.
9.
1.
1.
-5.
-7.
-9.
1.
2.
1.
1.
2.
2.
2.
-2.
8.
9127+00
4538+01
1324+01
01 93+01
39Q7+01
51 67+01
0894+01
2379+01
5024+01
054 +00
009 +01
3343+01
6812+01
0494+00
0269-01
6202+00
2451+01
1877+01
5964+01
118 +01
5592+02
0757+02
0832+02
0576+02
8721+01
5.8591+01
7.4847+01
-1.
1.
-3.
6.
4.
0.
0.
9715+01
,8099+00
8385+01
,1224+01
5109+01
70514
29485
20
86
1:1
.98-. 95
.90-, 87
6
1
-1
2
1
1
-1
1
1
-6
8
1
1
-5
1
-9
1
2
1
1
2
2
2
-2
8
.9119+00
.4536+01
.1324+01
.0066+01
.3829+01
. 5008+01
.1007+01
.2277+01
.4855+01
. 1 1 28+00
.9723+01
. 3089+01
.6451+01
.0481+00
.4607-01
.5777+00
.1655+01
.1875+01
.4657+01
.0067+01
. 5506+02
.0691+02
.0676+02
.0727+02
.167 +OT
5.59 +01
7.0757+01
-2
3
-3
5
3
0
.0363+01
.2632+00
.906 +01
.3361+01
.8932+01
. 7flRlfi
0.29481
57
-------
Run
Urban Engine Power
Battery Resistance, 103n
Motor-Wheel Gear Ratio
nal
:> '
102
PR. hp
in drive
in regen
^Mo- "P
pMo- hD
in drive
in regen
TMi. k*
in drive
in regen
~n^, drive
~u, regen
$
PPCU
in drive
in regen
"npcu. drive
~fOJ> re9en
*S
charge
discharge
TIC
lAi
PAD
DA
$
^M
in drive
in regen
Ip. max
-D>CU
'pcy
in drive
in regen
IB
charge
discharoe
fB loss, watts
IA
drive probability
regen probability
charge probability
a set equal to one
in drive
Remarks
C
20
86
1:1
.98-. 95
.98-. 95
6.9034+00
1.4525+01
-1.1324+01
2.0039+01
1.382 +01
1.4997+01
-1.1007+01
1.2271+01
1.4845+01
-6.1127+00
7.5328-01
7.4468-01
8.9713+01
1.3083+01
1.6443+01
-5.047 +00
9.0283-01
8.2566-01
-9.585 -01
-9.0848+00
1.3202+01
2.1872+01
1.596 +01
1.1177+01
7.0032-01
2.5504+02
2.0689+02
2.0673+02
-2.0727+02
1.1475+03
8.1428+01
5.5788+01
7.0611+01
-2.0337+01
-1.2342+00
-3.7035+01
6.1152+01
3.5878+02
4.2329+01
0.70495
0.29476
0.63519
0.10584
0.00007
CA
19.4
86
1:1
.98-. 95
.98-. 95
6.9034+00
1.4525+01
-1.1324+01
2.0039+01
1.382 +01
1.4997+01
rl. 1007+01
1.2271+01
1.4845+01
-6.1127+00
7.5328-01
7.4468-01
8.9713+01
1.3084+01
1.6444+01
-5.0465+00
9.0277-01
8.2556-01
-6.3562-01
-9.5453+00
1.1871+01
2.1335+01
1.5567+01
1.0852+01
6.971 -01
2.5504+02
2.0689+02
2.0673+02
-2.07?7+0?
1.1475+03
8.1385+01
5.5759+01
7.0575+01
-2.0324+01
6.4593-02
-3.8886+01
5.4741+11
3.5846+02
4.3859+01
0.07495
0.29476
0.58381
0.10584
0.00007
G
20
172
variable
.97-. 94
.98-. 95
6.6128+00
1.4156+01
-1.1324+01
1.9493+01
1.362 +01
1.4766+01
-1.0894+01
1.1278+01
1 . 3207+01
-6.6917+00
8.3371-01
8.2369-01
4.6323+01
1.1853+01
1.4342+01
-5.9365+00
9.2086-01
8.8714-01
r2. 7011+00
-1.025 +01
9.6094+00
2.1833+01
1 . 5932+01
1.1151+01
6.9991-01
1 . 5653+02
1 . 3683+02
1.3828+02
-1.3339+02
1.1589+03
7.2861+01
5.0764+01
6.2419+01
-2.3051+01
-7.5855+00
-4.079 +01
4.6561+01
5.7691+02
4.4649+01
0.70090
0.29476
0.61718
0.10177
0.00407
GA
17
172
variable
.97-. 94
.98-. 95
6.6128+00
1.4156+01
-1.1324+01
1 . 9493+01
1.362 +01
1.4766+01
-1.0894+01
1.1278+01
1.3207+01
-6.6917+00
8.3371-01
8.2360-01
4.6323+01
1.1S5 +01
1.4336+01
-5.9397+00
9.2123-01
8.8762-01
-1.1019+00
-9.6383+00
9.8358+00
1.9137+01
1 . 3962+01
9.5311+00
6.8265-01
1 . 5653+02
1 . 3683+02
1 . 3828+02
-1.3339+n?
1.1589+03
7.3217+01
5.1002+01
6.2709+01
-2.3163+01
-1.1245+00
-3.8417+01
4.6657+01
5.774 +02
3.8141+01
0.70090
0.29476
0.55921
0.10177
0.00407
' -
AA
20.
86
1:1
.98-. 95
.98-. 95
6.9034+00
.4525+01
- .1324+01
.7872+01
.0575+01
.4997+01
0. +00
1.0468+01
1.4845+01
0. +00
7.5328-01
0. +00
7.4507+01
1.1595+01
1.6443+01
0. +00
9.0283-01
0. +00
5.2959-01
-6.7427+00
1.3202+01
2.1872+01
1.596 +01
1.1177+01
7.0032-01
2.1255+02
1.4578+02
2.0673+02
n +OQ
1.1475+13
7.9339+01
4.9792+01
7.0611+01
0. +00
4.6824+00
-2.7723+01
6.1152+01
2.8768+02
4.241 +01
0.70495
0.29476
0.63519
0.29484
0.00007
AAA
22.2
86
:1
.98-. 95
.98-. 95
6.9034+00
1.4525+01
-1.1324+01
1 . 7872+01
1.0575+01
1.4997+01
0. +00
1.0468+01
1 . 4845+01
0. +00
7.5328-01
0. +00
7.4507+01
1 . 1 598+01
1.6448+01
0. +00
9.0257-01
0. +00
-6.7492-01
-7.9065+00
1.2053+01
2.3845+01
1 . 7402+01
1.2397+01
7.1242-01
2.1255+02
1.4578+02
2.0673+02
0. +00
1.1475+03
7.9135+01
4.9667+01
7.0435+01
0. +00
-2.1748-01
-3.246 +01
5.6533+01
-------
TABLE 5.5 !
PERFORMANCE OF PARALLEL (EMT)iSYSTEM
COMPONENTS ON LA-4 MISSION
Run
Urban Engine Power, hp
Battery Resistance, 10
Motor-Wheel Gear Ratio
Planetary Gear Efficiency
Differential Gear Efficiency
PR.
_
PIC.
J .
in drive
in drive
in regen+
in regen-
PM, h
in drive
_
pMi
.
in drive
in regen
.
in
in regen
TpCUM
!PCUM . .
. in drive
_ in regen
_
IB
h
charge -
discharge
PPCUM
in drive
^ in regen
F-Ai
TA
IPCUA
-P-PCUA
PB
charge
drive probability
.regen+ probability
regen- probability
'charge probability
a set equal to one
in drive
in regen
Battery state change
P
15
/ 86
-' 1:1
• -'. 90
, 97-94
6.9119+00
2.2747+01
-2.0446+00
1.6217+01
7.5556+00
7.9586+00
8.3436+00
6 14£5+00
6.0197+00
-1 .0894+01
1.723 +01
1 . 1 384+01
1.5586+01
-9 0082+00
1.165 +01
1.9171+01
-7.3963+00
5.5273+01 '
'?.3501+02
1.8401+02
2.2738+02
-L 5948+02
5.8983+01
3.7049+01
6.9008+01
-1.8972+01
-4.4152+00
-3.8045+01
5.3322+01
' 2.7952+00' "
1.6006+01
-4.677 +00
6.3755+00
5.8536+00
5.3933+00
4.8754+00
4-. 091 2+0 1.
1.921 +01
' 4.628 +00
-1.3551+00
-9.3176+00
1.2315+01
. 0.36119
0.63859
:0. 29476
0.63179
0.32231
0.00000 .
0.32231
charged
q
13
86
1:1
90
97-94
6.9119+00
2.0063+01
-3.5357+00
1.4423+01
6.88 +00
7.228 +00
7.9167+00
5.4345+00
5.3258+00
-1.0894+01
1.7261+01
1.1431+01
1.3535+01
-9.7593+00
"T.'TS35+DT~
1.6641+01
-8.0237+00
5.527 +01
2.347 +02
1.8274+02
2.0143+02
-1.679 +02
6.01 +01
3.8284+01
6.0495+01
-2.064 +01
' 5.4935-01
-3.6725+01
5.0676+01
— 3~:375T+ou:
1.4023+01 .
-5.0839+00
5.5255+00
5.0731+00
4.6227+On
4.16?. +00
3.4698^01
• 1.6425+01
3.9496+00
-1.6684-01
-8.9915+00'
1.17 +01
0.44261
0.55717
0.29476
0.57340
0.24089
0.00000
0.24089
discharged
S
15
172
1:1
90
97-94
6.8797+00
2.2671+01
-2.0446+00
1.6212+01
7.549 +00
7.9407+00
8.3436+00
6.1425+00
"570T97+TTrr
-1.0894+01
1.716 +01
1.1361+01
1.5524+01
-9.0082+00
Tri624+-0t-'
1.9105+01
-7.3963+00
5.5254+01
2.3493+02
1.8394+02
2.2723+02
-1.5948+02
6.2048+Ul
3.8163+01
7.2622+01
-1.8688+01
-2.9197+00
-3.7496+01
5.6492+01
— Z7812B+DO' —
1.6143+01
-4.7208+00
6.3755+00
5.8536+00
5.3933+00
4.8754+00
4.0912+01
T. 91 75+01 "
4.628 +00
-1.3389+00
-9.3572+00
- 1.2438+01
0.36089
0.63859
0.29476
0.63179
0.32255
0.00023
0.32231
charged
T
13
86
variable
90
97-94 ;
6.8721+00
1.9986+01
-3.5357+00
1.442 +01,
6.8753+00
7.2187+00
7. 91 67+00
5.4345+00
5.3258+00.
1.0894+01
1.7173+01
1.1399+01
1.3465+01
-9.7593+00
1.1597+01
1.5597+01
-8.4226+00
2.8047+01,
1.4444+02
1.1963+02
1.2999+02
-1.1142+02
5.6697+01'
3.6824+01
5.4594+OV
-2.2721+01
-3.224 +00
-3.8346+01
4.6298+01
2.4936+00
1.27 +01'
-5.6067+00'
5.526 +00;
5.0738+00; '
4.6231+00'
4.1626+00
3.47 +0t
1.6401 +01 ••
3.9502+00: '
-1. 0497+00;
-9.4023+00' -
1.0727+01! •
OY44217 ,'
0.55717 j-
0.29476 !
0.58468 !-'
0.22554 .
0.00044 .
0.22510 '
charged .
U
15
86
variable
80
97-94
6. 8721 +00
1.9986+01
-3.5357+00
1.6559+01
6.988 +00
7.3618+00
7.9703+00
5.4414+00
-1.0894+01
1. '71 65+01
1.1382+01
1.3318+01
-9.8453+00
1.1561+01
1.5424+01
-8.4963+00
2.8045+01
1.4445+02
1.1969+02
1.2919+02
.__-.].....! 2.1 6+.Q2....
5.6546+01
3.6679+01
5.4022+01
-2.2916+01
-4.0053+00
-3.6211+01
. 5.1261+01
2.4083+00
1.2569+01
-5.6556+00
5.6677+00
' 5.2039+00
4.7519+00
4.2817+00
_ 3.5736+01
1.6868+01
4.0636+00-
-1.2367+00
•-8.879 +00
..•.1,1877+jQl _
0.44217
•'• 0.55717
0.29476
0.63140
..0.22554
0.00044
0.22510
charged
V
13
86
variable
80
97-94
6.8721+00
1.9448+01
-3.8028+00
1.4765+01
6.3874+00
6.5345+00
7.869 +00
4.9231+00
4.8247+00
-1.0894+01
1.722 +01
1.1482+01
1.36 +01
-9.6844+00
1.1756+01"
1.5758+01
-8.3595+00
2.8073+01
1.4443+02
1.1941+02
1.3014+02
_.-.]. LQ3-1.+.Q2...
5.7391+01
3.7516+01
5.5144+01
-2.2552+01
2.2748-01 '
-3.5311+01
.,.-1^9-464+01
2.8782+00
1.282 +01
-5.5617+00
4.912 +00
4.51 +00
4.0651+00
3.6453+00
3.0189+01
1.4373+01
3.4574+00
-2.2308-01
-8.6558+00
._ .1,146 _±Q1_..
0.45882
0.54052
0.29476
0.58041
0.20889
0.00044
0.20845
discharged
W
13
172 ; .-
variable
80: , •- •;•
•97-94 /';
' 6.6883+00
1.9121+01
-3.8028+00
1.4747+01
6.3615+00
6.4788+00
7.869 +00
4.9P31+00
4.8247+00
-1.0894+01
1.6931+01
1.1345+01
1.3314+01
-q. 6844+00
--'Trl 604+01
1.5449+01
-8.3595+00
2.7959+01
1.4398+02
1.1905+02
1 . 2939+02
-1. 103.1 ±02.
5.8065+01
3.7726+01
5.6254+01
-2.2092+01
8.5209-01
-3.4703+01
5.0433+01
2.7531+00
1.2632+01
-5.5833+00
4.9151+00
4.514 +00
4.0679+00
- 3-. 649 +00-
3.0199+01
1.4375+01
3.461 +00
-3.5008-01
-8.6742+00
1.1243+.O.L
0.45610
0.54052
0.29476
0.58041
0.21155
0.00310
0.-20845 .--.
discharged
-'"'•'" Y
13
...•"• •: ; -86
, . , variable-. ,
'-,-i ;i.99 , .,-
.•^•••;'; sofsyjv; ;
'" 6.8675+00 '
1.9438+01 -
-3...8028+00 _
1,..4639+01
7:"07T 5+00-,-:"
7.2783+00,J •••-
&.-5697+00
-^fifvonR+oo
. ...5V3905+.QO
-1.0101+O.lrV
1.771-+01.-cp
1.186Wl>La.'
1.4426*01 or
-'qV6R-?q+00
-- '1^1-73^01 ,,o-
JV^/I^OT'"'-
-a.,,3,5.61,+00
2",'869,4,+Al .,-
1.4688-+02 'X
1. 2 167+02 '!?>
1.3502+02 '^V
-1.1033+02 MI
"" 6vO"038+0,r'
3".'8,9.5( +01
5.8'281+01, M|
-2.2542+0'l " t
-1.6418-0«y-'H
-3s-75^+Ol':;;;iii
.... 51M83+D1 ,
3.2017+00 a?
1.3:5^18+01
-:5r5-553-+r(DO
r -5^52 6 ;:+:(i)0 a^
5.0738+flO-; |