§
`"E
`
`iversity
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`5 Q
`
`Un
` §§
`
`Durham E—Ti1eses
`
`Some drive tra/in control problems in hybrid re
`en_gme/fbattery electric vehicles
`
`Masding, Philip Wilson
`
`How to cite:
`
`hybrid i.c engine/battery electric
`Masding, Philip Wilson (1988) Some drive train control problems
`velzicles, Durham theses, Durham University. Available at Durham E—Theses Online:
`littp:,3fetlieses.d11r.ac.11k,-‘B408,’
`
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`
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`Please consult the full Durham E—These5 policy for furtl1er details.
`
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`e—1'nai1: e—theses.admin@d11r.a.c.11l{ Tel: +44 U191 334 610'?’
`htfp: ;",/ellleses 4dLI1‘.zLL'.U lc
`
`2
`
`

`
`Some Drive ’i[‘rau73n Comtrofi Problems In
`
`Hybrid i.c Engine/Battery Electric Vehicies
`
`The copyright of this thesis rests with the author.
`
`No quotation from it should be published without
`
`his prior written consent and information derived
`
`from it should be ackuowiedgcd.
`
`by Philip Wilson Masding B.Sc.
`
`A Thesis Submitted for the Degree -of Doctor of Philosophy
`
`Schooi of Engineering and Applied Science
`
`University of Durham
`
`1988
`
`"'2
`
`DU‘ . 5
`
`E§’.E» 33
`x
`=. 2-,.
`‘I-Lu:
`3‘; xi? “it:
`
`"*
`
`NW ‘I989
`
`3
`
`

`
`Declaration
`
`None of the work contained in this thesis has been previously submitted
`
`for a. degree in this or any other university.
`
`It is not part of a joint research
`
`project.
`
`Copyright
`
`The copyright of this thesis rests with the author. No quotation
`
`from it should be published without his prior written consent and information
`
`derived from it should be acknowledged.
`
`4
`
`

`
`Acknowledgements
`
`I would like to acknowledge the tremendous support and encouragement I
`
`have had from my supervisor, Dr.
`
`IR. Bumby, throughout this research.
`
`I
`
`am also grateful to Mr N. Herron and Mr K. McGee for their assistance in
`
`maintaining and building the rig and to Mr N. Herron in particular who designed
`
`the mechanical system for the gearbox. Finally I would like to thank Mr C. Dart
`
`for his help with electrical work on the rig.
`
`I am also grateful to the Ford Motor Company, Lucas Chloride E.V. Systems
`
`Ltd., and Shell Research Ltd. for the provision of equipment.
`
`5
`
`

`
`Abstract
`
`This thesis describes the development of a microprocessor based control
`
`system for
`
`a. parallel hybrid petrolf electric vehicle.
`
`All
`
`the fundamental‘
`
`systems needed to produce an operational vehicle have been developed and
`
`tested using a full sized experimental rig in the laboratory.
`
`The work begins with a review of the history of hybrid vehicles,
`
`placing emphasis on the ability of the petrol electric design to considerably
`
`reduce the consumption of oil based fuels, by transferring some of the load
`
`to the broad base of fuels used to generate electricity.
`
`Efficient operation of a hybrid depends on the correct scheduling of
`
`load between engine and motor, and correctgchoice of gear ratio. To make
`
`this possible torque control systems using indirect measurements provided
`
`by cheap sensors, have been developed. Design of the control systems is
`
`based on a theoretical analysis of both the engine and the motor. Prior to
`
`final controller design, using the pole placement method, the transfer functions
`
`arising from the theory are identified using a digital model reference technique.
`
`The resulting closed loop systems exhibit well tuned behaviour which agrees
`
`well with simulation.
`
`To complete the component control structure, a pneumatic actuation
`
`system was added to a ‘manual gearbox’ bringing it under complete computer
`
`control. All aspects of component control have been brought
`
`together so
`
`that an operator can drive the system through simulated cycles. Transitions
`
`between modes of operation during 3. cycle are presently based on speed, but
`
`the software is structured so that efficiency based strategies may be readily
`
`incorporated in future.
`
`Consistent control over cycles has been ensured by the development
`
`of a. computer speed controller, which takes the -place of an operator. This
`
`system denionstrates satisfactory transition between all operating modes.
`
`6
`
`

`
`CONTENTS
`
`Page
`
`List of Symbols
`[list of F‘igx1:'es
`
`CHAPTER 1:
`
`INTRODUCTION
`
`_
`
`1.}. Possible Improvements or Alternatives to LC. Engine Vehicles
`1.1.1 Novel Engines
`
`1.1.2 The Electric Vehicle
`
`1.2 The History of Hybrid I.C. Engine/Electric Passenger Cars
`
`1.3 The Context of the Present Work
`
`CHAPTER 2: THE LABORATORY TEST SYSTEM
`
`2.1 Loan Emulation
`
`2.2 The Hybrid Drive System
`
`2.3 Computer Control and Signal Monitoring
`
`2.3.1 Motorola. M68000 System
`
`2.3.2 Duet 16 Personal Computer
`
`2.4 Instrumentation
`
`2.5 Software System
`
`2.5.1 System lnitialisation
`
`2.5.2 Active Rig Control
`
`2.5.3 Data Logging
`
`2.5.4 Data Transfer
`
`-
`
`2.5.5 Data Analysis
`
`.
`
`2.5 Discussion
`
`2.7 Soitweu-e Dr)m.11nem.al.io11
`
`vii
`x
`
`1
`
`5
`6
`
`7
`
`9
`
`17
`
`32
`
`32
`
`34
`
`36
`
`36
`
`38
`
`38
`
`40
`
`40
`
`43
`
`44
`
`45
`
`46
`
`47
`
`:31;
`
`CHAPTER 3: PHYSICAL ANALYSIS OF THE ENGINE AND MOTOR 57
`
`3.1 Analysis of the Electric Traction System
`
`3.1.1 D.C. Machine Analysis
`
`3.1.2 Motor Torque Equation
`
`3.1.3 The Eifects of the Power Electronic Controller
`
`59
`
`59
`
`61
`
`62
`
`iii
`
`7
`
`

`
`3.2 Physical Analysis of the I.C. Engine
`
`3.2.1 Inlet Manifold Pressure Variations
`
`3.2.2 Transfer Function for Engine Torque
`
`3.2.3 Throttle Servo-System
`
`3.2.4 Engine Speed on No—Load
`
`3.3.5 Transfer Function for Engine No—Load Speed
`
`CHAPTER 4: EXPERIMENTAL IDENTIFICATION RESULTS
`
`4.1 Calibration of Indirect Torque Measurements
`
`4.1.1 Engine Torque Model Calibration
`
`4.1.2 Engine Torque Model Testing
`
`4.1.3 Motor Torque Model Calibration and Testing
`
`4.2 Gain Functions for the Three Operating Modes of the Motor
`
`4.2.1 Field Boost Mode
`
`4.2.2 Full Field Mode
`
`4.2.3 Field Weakening Mode
`
`4.3 Transfer Function Identification
`
`4.4 Transfer Function Identification for the Motor
`
`4.4.1 The Closed Loop Transfer Functions for Current
`
`__4.4.2 Direct Identification of the Motor Torque
`
`Transfer Function
`
`4.5 Manifold filling Delay and Engine Torque Variations
`
`4.6 Engine No~Load Speed Transfer Function
`
`4. 7 Discussion
`
`CHAPTER 5: CONTROLLER DESIGN
`
`5.1 Controller Design Method
`
`5.2 Control Algorithm
`
`5.3 Design of Individual Controllers
`
`. 5.3.]. Engine Torque
`
`5.3.2 Electric Motor Torque Control
`
`5.3.3 Motor Torque Control Test Results
`
`5.3.4 Mode Determination
`
`iv
`
`66
`
`66
`
`69
`
`71
`
`T2
`
`79
`
`80
`
`80
`
`82
`
`83
`
`84
`
`85
`
`86
`
`88
`
`92
`
`92
`
`93
`
`97
`
`99
`
`100
`
`118
`
`118
`
`121
`
`123
`
`123
`
`126
`
`127
`
`128
`
`8
`
`

`
`5.3.5 Engine Speed Synchronisation
`
`5.3.6 Engine Starting and Load Transfer
`
`5.4 Quantisation Errors and Noise
`
`5.5 Model Reference Controller Design
`
`5.5.1 Application of the Model Reference Technique
`
`to the Motor
`
`5.6 Discussion
`
`CHAPTER 6: THE AUTOMATED GEAR CHANGING SYSTEM
`
`6.1 The Case for a Variable Transmission in Road Vehicles
`
`6.2 Variable Transmission Systems
`
`H
`
`6.3 Transmission System Hardware on the Hybrid Vehicle Rig
`
`6.4 Interface Circuitry
`
`6.5 Software Control
`
`6.5.1 Stage 1: Shift into Neutral
`
`6.5.2 Stage 2: Speed Matching
`
`6.5.3 Stage 3: Engaging the New Gear
`
`6.5.4 Error Handling
`
`6.5.5 Location on Power Up
`
`6.6 Resnlts
`
`6. '3 Discussion
`
`CHAPTER 7:
`
`INTEGRATED DRIVE TRAIN CONTROL AND
`
`DRIVE CYCLE TESTING
`
`7.1 Component Sequencing Control
`
`7.2 A Speed Based Mode Controller
`
`7.3 Drive Cycle Testing
`
`7.3.1 Speed Conversions
`
`7.4 Complete Computer Control
`
`7.4.1 The Speed Control Loop
`
`7.5 Automated Cycle Control Using the
`
`Speed Based Mode Controller
`
`7.5.1 Preliminary All Electric Performance
`
`130
`
`131
`
`133
`
`136
`
`139
`
`140
`
`159
`
`159
`
`166
`
`168
`
`168
`
`169
`
`171
`
`172
`
`172
`
`174
`
`174
`
`175
`
`186
`
`187 '
`
`189
`
`190
`
`192 .
`
`193
`
`194
`
`197
`
`197
`
`9
`
`

`
`7.5.2 Calibration of the Expert System
`
`7.5.3 All Electric Performance with Expert Control
`
`7.5.4 Effect of Mode Transitions and Gear Changes
`
`7.6 Discussion
`
`CHAPTER 8: CONCLUSIONS AND PROPOSALS
`
`FOR FUTURE WORK
`
`8.1 General Conclusions
`
`8.2 Proposals for Future Work
`
`REFERENCES
`
`199
`
`200
`
`200
`
`202
`
`216
`
`216
`
`222
`
`226
`
`vi
`
`10
`
`10
`
`

`
`Liet of Symbols
`
`0.
`
`Cd
`
`C,
`
`ea
`
`fc
`
`ft
`
`g
`
`G'a(s)
`
`gc(w’)
`
`gc(z)
`
`gf
`
`Zero of gc(w’).
`
`Coefiicient of drag
`
`Coefficient of rolling resistance
`
`Back e.rn.f. voltage, V
`
`Counter Value from flywheel speed probe
`
`Number of teeth on the flywheel speed probe gear
`
`Gain Di 9'c(w').
`
`Armature closed loop transfer function
`
`P-i—I Controller in w’-plane forrn.
`
`Bilinear discretisation of _gc(w’
`
`Final drive ratio
`
`Gf(s)
`
`Field closed loop transfer function
`
`id
`
`if
`
`if
`
`J
`
`Jag
`
`K
`
`KC
`
`K3
`
`kg
`
`K;
`
`KP
`
`Kg;
`
`KT
`
`Kg
`
`Armature current, A
`
`Field current, A
`
`Mean field current during a transient, A
`
`Flywheel inertia,
`
`lrgmz
`
`Equivalent inertia of vehicle mass M, kgmz
`
`Constant relating dynarnorneter speed to load
`
`Scaling factor, flywheel count
`
`to roaclspeed
`
`Back e.n1.f. constant (= 37%)
`
`gaT,/2
`
`Manifold filling delay gain
`
`Gain of armature controller
`
`Power stroke delay gain
`
`Motor torque constant
`
`Gain of engine torque/speed transfer function
`
`k,,(E9,pm)
`
`Manifold pressure/throttle gain
`
`vii
`
`11
`
`11
`
`

`
`Armature inductance, H
`
`Field inductance, H
`
`Mass air fiow into inlet manifold,
`
`lcg/s
`
`Mass charge flowing out of inlet manifold, kg/s
`
`Vehicle mass, kg
`
`Mass of gaseous mixture in the inlet manifold, kg
`
`Engine or motor speed, r.p.1n.
`
`Speed at which linearisation takes place, r.p.1n.
`
`Adaptive gain matrix
`
`Engine power, kW
`
`Inlet manifold depression, Inbar _
`
`Manifold depression at no load and N r.p.rn., mbar
`
`Armature resistance, 51
`
`Field resistance, 9
`
`Vehicle wheel radius,
`
`in
`
`Motor torque, Nm
`
`Torque in gearbox output shaft, Nin
`Engine torque, Nm
`
`Vehicle aerodynamic and rolling resistance loss torque, Nrn
`
`Controller design criteria:
`
`rise time, sec
`
`Control system sampling period, see
`
`Armature voltage, V
`
`Field voltage, V
`
`Adaptive error at jih sampling point
`
`Field current set—point function
`
`Plant model coeflicient vector
`
`Armature current set-point function
`
`Signifies small change in variable
`
`viii
`
`12
`
`12
`
`

`
`Controller design criteria damping factor
`
`Engine throttle position, 0.9” steps
`
`Demand throttle position, 0.9° steps
`
`Electric motor a.cce1erator/ brake demand
`
`Mean demand Value during transient
`
`Inlet manifold fifling time constant, sec
`
`Engine inertia. time constant, sec
`
`Field flux, Wb
`
`Plant model input/output vector
`
`C*ont.rol!er
`
`torque de1nzmcI
`
`ix
`
`13
`
`13
`
`

`
`List of Figures
`
`Fig.
`
`1.1 Series Hybrid Electric Vehicle Drive Train
`
`Fig.
`Fig.
`
`1.2 Peirallel H}-'l)l‘l(l Elecirir Veliiclc l)ri\'e Trsiiii
`1.3 Typical Engine Eiiicieiicy ivleip for a 5UliV\’ LC. Engine
`
`Page
`
`23
`
`28
`29
`
`Fig.
`
`1.4 liiilueiice of
`
`\/Veiglitirig Faicior on the Perloriiiaiice of
`
`the Hybrid
`
`Vehicle
`
`30
`
`Fig.
`
`1.5 Use of the Engine Over an Urban Driving Cycle for an Optimally
`
`Coiitrolled Hylirid Vehicle
`
`Fig.
`
`1.6 Possible Hybrid Vehicle Control System
`
`Fig. 2.1 Test. Bed La}-‘D111.
`
`Fig. 2.2 Power Loading Provided by the Dyiiamoiiieter
`
`Fig. 2.3 Test Bed C‘-oiiipiiting and Interface Eqiiipiiieiit
`
`Fig.
`
`2.4 S-zsftwaire Structure
`
`I
`
`Fig. 3.]
`
`Elt3111E‘}1i—S of the Electric. Traction Drive
`
`Fig. 3.? Block Diagram of Electric Motor Equations
`
`,
`
`Fig. 3.3 Variat.ioii OfiFlE’l(l
`
`(..'u1‘renl. Witli O[J€l‘al«lIlg Mode
`
`Fig.
`
`3.4]
`
`"Block Diagraiii for Motor Current Control
`
`Fig. 3.5 Engine Physical Processes
`
`Fig.
`3_{3 Block Diagreini for the T111-ottle Servo—System
`Fig. 4.1 l.(‘. Engine Power (‘lmrac1.erist.ics
`
`-I
`
`30
`
`31
`
`.33
`
`54
`
`55
`
`56
`
`T2’.
`
`T41
`
`75
`
`76
`
`77
`
`78
`103
`
`Fig.
`
`4.17..
`
`I.C. Engine Power l'_‘liaracteristics: Vai'ia.tior1 of Regression Con-
`
`s1.e.iit.s $\‘it.ii Speed
`
`7
`
`103
`
`Fig.
`4.3 Coiiiparisoii of Torque TI‘(1I1S(ll!(‘E‘l”
`Torque Prediciioii
`‘
`
`ii.-‘Ie2isiii‘e1rie1it.s with I.C. Engine
`104
`
`I
`
`Fig. 4.4 The Effect. of the Engine Cooling Fan on Torque. Mea.suremeiit.s 104
`
`Fig. 4.5 Yuriaiioii of l\’loLor Torque Cori-;<t.a.:1t. with Field Gurreiii.
`
`10.5
`
`14
`
`14
`
`

`
`Fig.
`
`51.5 VeI‘iiica.ti0n 01'
`
`1.1113 1n<.lirect- Torque -1\\‘lt:‘&!.5l1I‘€11]L’[11.5
`
`For the I‘./101.01‘
`
`11.15
`
`Fig.
`
`~‘1.?(a.) Vz—u‘i;i.1.ir3ii uli Field C‘-uri'ei11. witli Input D€'D.1E1.11Cl
`
`in the Field Boost.
`
`M a acl <-‘
`
`1116
`
`Fig.
`
`=1-.T{1))
`
`\fei1‘ia.1.i01i
`
`01‘ Ai'mei1.L1i‘r* Current. with Input De-n1a.i1d in the Field
`
`130<‘Js1.
`
`1\"lO(.1€'
`
`1116
`
`Fig.
`
`4.8 Va1‘iei1.i-311 of Current. with Input Den‘ia.n(1 in the Full Field Mode
`
`107
`
`Fig.
`
`t1.9(a_1 V:-i.ria.1i0n of Field C—nn'e11l1 with Input Demand in the Field
`
`Weakening Mode
`
`10?
`
`Fig.
`
`4.523(1))
`
`'Va_~iri2il.io11 of Armai-ure Current. witli
`
`lnput. De-n1a.nd in the Field
`
`V1-’eakening 1\~’1«3de
`
`Fig. 4.10 Adaptive Irieiitificmion System
`
`108
`
`109
`
`Fig. 4.11 l\‘1oc1e1 Ide1il.ifii:a.tion for the Closed Loop Ariiiaiure Current. Control
`
`Response G,(:)
`
`110
`
`Fig.
`
`4.12 (‘onipamison of Torque Transfer F'nncti0ns with. Experimental Da.1.aL
`
`for the Field Bm:ns1.. Mocle
`
`1][)
`
`Fig.
`
`=l.13 Comparisons of Gains for the 1\’1a.nifo1cl Filling Delay and Steady
`
`S1.en‘.e Data R.c1et1.i11g Manifold Depression to Th1'0f.t.le Opening
`
`Fig. 4.14 Block Diagram of the Linearised Engine Mujdel
`
`' Fig. 4.15 Engine Bella-ivionl‘
`
`all
`
`1001} :'.p.111.
`
`Fig. 4.16 Engine Beliewiom at. 31100 r.p.m.
`
`11]
`
`112
`
`113
`
`113
`
`Fig. 4.17 \'erificeLt-ion of Transfer Functions for Engine Speed on N0—L0e.cl 114
`
`Fig.‘
`
`4.16 Preclictecl and Mea.s111'ec| Torque and Current Responses for a
`
`T1‘&I1S1El11—i in the Field Boost Mode
`
`7
`
`__
`
`114
`
`Fig.
`
`4.121 P1*edic:t.ed and Mea.su1‘ed Torque and (iurreni. Responses for
`
`a
`
`Trzmsient.
`
`in the Full Fielci
`
`lvlode
`
`7
`
`I
`
`115
`
`Fig.
`
`4.20 Preclictecl and [V1ea.sured ‘Torque ei.nr1 C-ui'1‘en1. Responses for
`
`3.
`
`Transient
`
`in the Field 1/‘iiealceiiiiig 1\loc1e
`
`115
`
`xi
`
`15
`
`15
`
`

`
`Fig. 4.2l M01201‘ TO}‘q11(“ Model‘: Test. for the Direct.
`
`Icle11tifi(‘a.tio11 in the Fielcl
`
`Boost Mode
`
`[15
`
`Fig. 4.23 l\IIoi.0;‘ TOI‘([l1f-‘
`
`lvloelelz Te-sl
`
`for the Direrl.
`
`l<.lr=:1tificai.ion in the Full
`
`Field 1\/Icicle
`
`J
`
`115
`
`Fig.
`4.23’: M010? To1'qm== l\/lnrlol:
`We-a,kening Mode
`
`"F931 for the Direci.
`
`lu;len’iiFira.t.ion in the Field
`l
`L1?
`
`Fig. 5.i(a) Ul](‘O]1]pE‘]1S?Ll’-€’Cl Lorna for (7onf.rol of Engine Torque at. 2000 r.p_ii1.
`
`145
`
`Fig. 5_l{b) Coiiip-3nsa.t.c=d Locus for Control of Engine Torque at 2000 r.p.m.
`
`145
`
`Fig.
`
`.5.2(a) Simulate-cl and Experiineiiteil Perforiiiemce of the Engine Torque
`
`Control S1.-'sf.e111 at. ZOEIU r.1).m.
`
`146
`
`Fig.
`
`532(1)) Sinililated a.ncl E}\'p€:‘fiI1'l€13l.itl
`
`P€]'{0I‘i]1ELl]('E
`
`of the Engine Torque
`
`(7ou1.rol S_\-‘stein at .‘3f_|0(l r.p.m.
`
`146
`
`Fig.
`
`5.3 Engine Torque Coiitrol S}-‘steal: Comparison of_Inclire::t. and Dire.<:t
`
`Torque 1\-leasuremeiits During El. Large Step DlSl.l11'l)EL1](‘.E‘
`
`'
`
`Fig.
`
`5.4 I\Io1.or Torque C'—ont.rol System
`
`1
`
`147
`
`148
`
`Fig.
`
`5..5(a)
`
`l.l11C0l]11)E51]S£<}.l-Etl Locus for Motor Torque Control
`
`in the Field
`
`Boost
`
`I\-lode
`
`149
`
`Fig.
`5.-5{l)) _C0mpe11sal.ecl Locus for M0101‘ Torque CO1'll-]'Ol
`Mode _
`V
`
`in the Field Boost
`149
`
`5.6(a) Mot-or Torque Coiitrol Tesit
`Fig.
`C?o11dition.~*.
`
`in the Field Boost Motle at Design
`'
`i
`-
`150
`
`Fig. 5.6(b) Motor Torque Clontrol Test.
`
`in the Field Boost Mode _Away From
`
`Design (‘c-ndit.ions
`Fig. 5.7 l\i0l-OI’ Torque Control Tt.=sl_.
`
`in llio l3‘ull Field Mode
`
`150
`151
`
`Fig.
`
`5.S(a) N_lO'l-O1‘ Torque Control Test
`
`in the Field VVea.keni1ig Mode at
`
`Design C'onclit.ions
`
`1.52
`
`xii
`
`16
`
`16
`
`

`
`Fig,
`
`5.8(l3) Motor Torque Control Test
`
`lll
`
`the Field Vtlealreiiiiig l\-“lode Away
`
`From Design Conditions
`
`352
`
`Fig.
`
`-5.9 l\-‘lot-or Torque C5o1itrol De111onsl.ra.ting Sa.lvisl}:.rtr_i1‘3-' Transition Between
`
`Operaiiiig l\a'lodr~s
`
`153
`
`Fig. 5.10 l\rloto1' Tf)l‘(]1_](‘ Control:
`the Field Boost Mode
`
`lfllfr--ct of llsiiig Field Wealiening Gains in
`-
`1.53
`
`Fig. 5.11 Engine Speed Control Block Diagram
`
`1.54
`
`Fig. 5.12(a) Uiicoinpeiisatecl Locus for (‘oiitrol of Engine Speed on NO~LOEL(l
`
`Fig.
`
`512(1)) Co1n]3e11sal.iecl Locus for Control of Engine Speed on No-Load
`
`Fig. 5.13 Step Test for
`
`the Engine Speed Control Systeln
`
`Fig. 5.14 Aiizdysis of the Engine Starting and Load Transfer Process
`
`Fig.
`
`5.1-5 Hill Climbing Control Design Process
`
`156
`
`1336
`
`133?
`
`Fig. 5.16 Locirzi of Control Paraineters During a. Hill Clixnla Design Procedure
`
`158
`
`Fig.
`
`5.17 Coniparison of Reference Model Perforniemce a.nd_._ C.‘-ontrol System
`
`Designed by the Hill Climb Method
`
`1.58
`
`Fig.
`
`6.1 Road Load and Motor Operating CltII'V€S
`
`for All Electric Vehicles
`
`17 00
`
`Tractive Effort and Road Loacl Curves for All Electric Vehicles
`Fig.
`Showiiig the Ellect of Gear Ratio
`'
`A
`179
`Fig. 6.3 The Clearclizmge I‘v'1ecl1a.:-lism
`180
`
`'
`
`-
`
`Fig. 6.4 The Pneun1atic’Circuit
`
`Fig, 6.5 Regions Coverecl by the Position Sensors
`Fig. 6.6 Gear Cliaiige Algoritl1m Flfll-‘-'Cl1l’rLl”l»
`V
`
`7
`
`181
`
`182
`183
`
`Fig. 6.T(a) Torque and Speed Profiles During er Down Clianige from Third to
`
`Second
`
`184
`
`XIII
`
`17
`
`17
`
`

`
`Fig. 67(1)} Torque and ."3'pr_=e-d Profiles 'Di_1t‘i11g an Up C5ha.nge- from Secoiicl
`
`to
`
`Third
`
`‘
`
`Fig 6_8(a.)
`
`5§f.a.gc~‘ Tiniiiigs lor a. Down Cliaiigt-7 {min Tliirrl
`
`(.0 Seccmzl
`
`Fig.
`
`f3.S(l)) Stage Timings li-31‘ an Up Cliaiige froiii S(.‘L"OJ1(,l
`
`to Third
`
`Fig.
`
`7.1 (f‘omplc1.e Vt'"‘l}(‘l(‘l(‘ COlii})C}I1Ei1l'- Coiitrol Sy.s'1'.e111
`
`Fig, 7.2 Fl0W(,‘l1E-LI‘li
`
`for Coiiiiioiieiit Seqiiencing Logic:
`
`Fig. 7.3 EC'E'1-5 C_vcle with Mammal Accel(*|:a.f.or and B1‘a.l{e C3011‘r.rol
`
`Fig.
`
`7.4- Block Diagrain for
`
`:‘\ut.o11iz:f.ic Cfycrle Speed C-‘ontrol
`
`184
`
`[85
`
`185
`
`2(]='L
`
`205
`
`206
`
`20?
`
`Fig.
`
`7.5 Identifir:a.l.i011 Expeitiment for the Fl},-'wl1ee] anti Dyuaiiiomet-6.1‘
`
`208
`
`Fig. 7.6 (70n1pensa.1.ed Locus for the Flyvvhecl and Dynaiiiometer
`
`Fig. 7.7 Step Tetjt for the Cycle Speed C011?-rol System
`
`Fig.
`
`7.8[a.} ECEl5 C.'._vc]e Using the Ulllllflfliliietl Speed Coiltroller
`
`Fig.
`
`7.8{l))
`
`\a’aria.’r.ion in Motor Torque
`
`Fig.
`
`7.9 Flywheel Inertia C'a.lil)ralii011
`
`Fig.
`
`7’.lf}(a) EC‘»El5 Cycle Using the Expert. C?o11t.:'0I S_g=s1.£-in
`
`209
`
`"209
`
`210
`
`210
`
`211
`
`1212
`
`Fig. T.]0(b) Va1'ia.l.i011 in Mcitor T01-we Showing Iiiiiiiecliate Drop at Break
`
`Points
`
`_
`
`__.
`
`212
`
`Fig.
`
`T.11(a) EC-E15 (‘._vcle Using Speed Based Ix»-lode and Gear Shifting
`
`Strategy
`
`Fig. T_11(li) Variation in Motor Torque
`
`Fig. T.11(r) Variaf-i011 in Eiigine Torque
`
`Fig. 7.12(a) ECE1-5 Cycle Using Ba?-t.eIy Recliarge Motle
`
`M
`
`Fig T_1‘2(l_\) Variaiioii
`
`in Engine and Motor Torqm?
`
`213
`
`213
`
`214'
`
`2]?)
`
`21-3
`
`Kit.’
`
`18
`
`18
`
`

`
`CHAPTER 1
`
`INTRODUCTION
`
`Conventional internal combustion (i.c.) engine vehicles, based on the
`
`Otto and Diesel cycles, have dominated road vehicle transport for the greater
`
`part of this century. Among their many advantages are unlirnited range, ease
`
`of refuelling, good power characteristics and the low cost materials required for
`
`their construction [JPL, 1975 pp 3-‘2][Unnewehr and Nasar, 1982 pp 214-217]
`
`Despite these facts conventional vehicles bring with them problems of air
`
`pollution and inefficient use of dwindling fuel resources, which at the present
`
`rates may be depleted early in the twenty-first century ]Foley, 1976]. Although
`
`diminishing energy resources, and in particular depletion of fossil fuels, poses
`
`8. problem to many areas of technology it
`
`is particularly pronounced in the
`
`transport sector where the choice of fuels is most restricted. This dependence
`
`on one type of fuel
`
`is
`
`illustrated by examining figures
`
`for
`
`total energy
`
`consumption in Britain over
`
`recent years. Energy consumption in Britain
`
`peaked in about 1973 ]Bumby and Clarke, 1982] subsequently falling by 11%
`
`in the years up _to 1981 as a. result of price rises, conservation measures and
`
`recession.
`
`Price rises were particularly great
`
`for oil based fuels and many
`
`non transport users switched to gas or coal overithis time period. As a
`
`result of this switch over amongst more flexible users, the transport sector has
`
`become responsible for using a progressively greater proportion of the total
`
`amount of oil used in the UK. Over
`
`the period 1973-1981 this proportion
`
`rose dramatically from 29% to 47%. Further analysis of the transport sector
`
`itself shows that most fuel is used by passenger cars.
`
`In 1978 such vehicles
`
`accounted for 63% of all
`
`fuel used in vehicles, whilst
`
`the public transport
`
`sector for example, including taxis, coaches and buses used only 4.4% of the
`
`total
`
`]Dept.
`
`of Energy, 1978].
`
`Faced with this heavy dependence on oil,
`
`inspite of its likely exhaustion in the relatively near term,
`
`there has been
`
`19
`
`19
`
`19
`
`

`
`increasing interest
`
`in possible alternative vehicle propulsion systems over the
`
`last twenty years. Amongst
`
`the many possible alternative power plants are
`
`the Stirling engine,
`
`the Brayton engine (gas turbine) the all electric vehicle
`
`and the hybrid vehicle [JPL, 1975]. Of these alternatives the hybrid power
`
`plant is the subject of the present study. A hybrid power plant maybe defined
`
`as one that is powered by two or more energy sources and as such there are
`
`a multitude of possible combinations. Examples of some which have been
`
`investigated are:
`
`Heat engine/battery electric
`
`Flywheel] battery electric
`
`Heat engine/flywheel/battery electric _
`
`Pneumaticf battery electric
`
`Battery/ battery
`
`The purpose of this study is to consider the control problems relating to the
`
`heat engine/battery electric power train in particular. As many authors have
`
`pointed out
`
`[Mitcham and Bumby, 19"r'7][UnneWehr and Nassar, 1982] using
`
`two power plants adds considerably to the complexity and cost of the whole
`
`vehicle and hence the power
`
`train must offer other compensating factors
`
`such as lower running costs,
`
`reduced pollution and less noise in sensitive
`
`areas. Of the alternatives to conventional
`
`i.c.
`
`vehicles mentioned earlier,
`
`the electric vehicle would seem to offer all
`
`these advantages without
`
`the
`
`added complexity of a duel power source. Unfortunately, due to current
`
`battery technology, electric vehicles are basically ‘energy deficient’ [Unnewehr
`
`and Nassar, 1982]. Despite the fact that many types of advanced batteries
`
`have been the subject of much research and development, many people still
`
`feel
`
`that
`
`for
`
`the present, at
`
`least,
`
`the only practical storage battery for
`
`use in electric vehicles is the lead/acid type [van Niekerk et al, 198D][Dell,
`
`1984], which has an energy density of 40 Wh/kg as opposed to the energy
`
`20
`
`20
`
`

`
`density of petroleum which is 12300 Wh/kg [Unnewehr and Nassar, 1982].
`
`In addition the energy density of lead/acid batteries falls at high discharge
`
`rates which always occur in vehicle applications during acceleration. As a
`
`consequence of these factors even advanced electric ‘vehicles such as the ETV—
`
`1, developed for the U.S. Department of Energy by Chrysler and General
`
`Eiectric, suffer from severe range limitations varying in this case from 160 km
`
`at 60 km/h down to 95 km at 90 km/h even under
`
`favourable steady
`
`cruise conditions [Knrtz et al, 1981]. One way of reducing the severe range
`
`restrictions of the straightforward all electric vehicle is to combine it with
`
`some secondary energy source in a hybrid design. As can be seen in the
`
`list of hybrid drives above, all
`
`incorporate an electrical system. Of these
`
`systems the flywheel/battery electric,
`
`the pneumatic battery/electric and the
`
`battery/battery can be considered as primarily electric since the secondary
`
`energy storage device has very limited capacity. Nevertheless this secondary
`
`device can make a substantial
`
`improvement
`
`to the vehicle range simply by
`
`providing energy for short bursts of acceleration.
`
`For example flywheel
`
`systems, despite their modest energy storage capacity, can easily provide
`
`enough energy to accelerate a. vehicle up to 30 mph Once,
`
`thus protecting
`
`the batteries from the damaging high discharge rates which normally occur
`
`during such operation.
`
`In one such study simulations showed that electric
`
`vehicle range could be extended by 80% by using a flywheel of about 0.5 kWh
`
`capacity [Burrows et al, 1980].
`
`On the other hand the hybrid heat engine/' battery electric is by no
`
`means primarily electric, with the power and stored energy capacity of the
`
`engine typically exceeding that of the electrical system.
`
`In this case the motor
`
`takes on a secondary role in shielding the engine from operating conditions
`
`which are particularly unfavourable to it. Typically this means that such
`
`a vehicle will operate electrically when the total power requirement
`
`is low.
`
`21
`
`21
`
`

`
`Since low loading is typical of urban driving this vehicle has the potential to
`
`reduce pollution and noise in the urban environment whilst at the same time
`
`still ofiering the extended range capability characteristic of the engine.
`
`ln
`
`general this system seeks to emphasise the particular strengths of each power
`
`source whilst playing down the disadvantages.
`
`When considering any type of hybrid electric vehicle two basic me-
`
`chanical configurations form the basis of nearly all designs. These are the
`
`series and parallel configurations, which are illustrated by figures 1.1 and
`
`1.2 respectively.
`In the parallel hybrid both the engine and the motor are
`connected directly to the roadwheels.
`Provision is usually made for them
`
`to operate either independently or jointly in powering the vehicle.
`
`In the
`
`series hybrid however, only the motor is connected to the road Wheels and
`
`must therefore be sized to meet all vehicle acceleration and top speed power
`
`requirements.
`
`In this case the engine supplies power indirectly via. the gen-
`
`erator battery combination. Although the series system has been considered
`for large bus applications [l3rusaglino, 1982][l3ader, 1981}[Roan, 1976], on the
`
`grounds that
`
`it gives greater flexibilty in positioning components and ease
`
`of controlling the i.c. engine,
`
`the multiple energy conversions invariably lead
`
`to a low overall efficiency. Consequently almost all designs for passenger car
`
`applications have tended to favour the parallel configuration. As seen previ-
`
`ously this latter application is most important because passenger cars offer the
`
`greatest potential fuel savings in the country as a Whole. Clearly if hybrid
`
`vehicles could otter significant fuel savings in this transport sector, the benefit
`
`to society would be substantial. Before considering what potential the hybrid
`
`heat engine/electric has for making fuel savings in this sector it is important
`
`to consider what it is competing against in terms of likely improvements to
`
`conventional Vehicles and other alternative vehicle power systems.
`
`22
`
`22
`
`

`
`1.1 Possible llmprovements or Alternatives to JLC. Engine Vehicles
`
`It is important to recognise that any alternative to i.c. engine vehicles
`
`is competing against a mature, established technology backed up by a large
`
`industrial
`
`research base.
`
`As a result conventional vehicles have shown a
`
`steady improvement over the years and seem likely to continue to do so.
`
`It is
`
`therefore pointless to compare possible economic and environmental advantages
`
`of a new vehicle technology against the i.c.
`
`engine vehicles which are being
`
`built
`
`today. A more realistic comparison is to judge the new technology
`
`against an estimate of what conventional vehicles will achieve 10-15 years
`
`from now. This 10-15 year period will then allow a reasonable time span for
`
`the new technology to be put
`
`into production on a worthwhile scale. Some
`
`of the likely improvements in i.c.
`
`engine design which might be made over
`
`the next few years are discussed by Blackmore and Thomas [Blaclrmore and
`
`Thomas, 1979]. This review suggests that major economy improvements could
`
`be achieved by using higher compression ratios coupled with leaner mixtures
`
`thus saving 20% of fuel use over all operating conditions.
`
`Lean mixtures
`
`must be used in conjunction with the higher compression ratios to avoid
`
`problems with knocking. Other savings can be achieved by improvements to
`
`cold starting ( saving 25% on short
`
`trips ), power modulation by variable
`
`mixture strength as opposed to the inefficient throttling method ( saving 20%
`
`on average ) and finally up to 10% can be saved by improving fuel and
`
`lubricants. Apart
`
`from changes to the engine itself further improvements
`
`can be made by altering vehicle aerodynamics and designing better tyres and
`
`gearboxes.
`
`Electronic engine control systems also offer substantial improvements
`
`in fuel economy.
`
`One major application for electronics is
`
`in optimising
`
`ignition timing. Standard mechanical distributors produce a crude variation
`
`in spark timing on the basis of engine speed, as sensed by a centrifugal weight
`
`23
`
`23
`
`

`
`system, and engine load, as determined indirectly by a vacuum diaphragm
`
`lever system connected to the inlet manifold. Load and speed are in fact
`
`the correct indicators needed to optimise ignition timing, but the mechanical
`
`system can never re-produce the complex function relating them to optimum
`
`spark advance.
`
`In contrast,
`
`in an electronic system,
`
`it
`
`is possible to store
`
`the best spark advance as a function of manifold depression and speed in a
`
`two dimensional loolr—up table. As described by Main [l\/lain, 1986] Ford have
`
`produced a microprocessor system which not only controls spark timing but
`
`also controls a. continuously variable transmission system (CVT).
`
`Unlike some proposed vehicle systems the hybrid heat engine/battery
`
`electric can incorporate all
`
`the changes rnentioned above in its own engine
`
`and so its potential advantages remain undiminished.
`
`1.1 .1 Novel Engines
`
`Apart
`
`from all electric and hybrid vehicles which may generally be
`
`considered as the electric alternative, Whether partial or complete,
`
`there are
`
`two other major possibilities; alternative fuels and novel engines. Leading
`
`examples of alternative fuels are those based on agricultural products such as
`
`alcohol made from sugar. This has been successfully applied in Brazil with 95%
`
`alcohol by volume being used in cars with modified carburetters. According
`
`to the Jet Propulsion Laboratory (JPL) [JPL, 1975] lesser concentrations, up
`
`to 28%, maybe used in ordinary cars without any Such modifications. A
`
`second alternative is to produce synthetic petroleum from coal as has already
`
`been done in S. Africa. Neither of these alternatives are without drawbacks
`
`though, alcohol for example is particularly prone to absorb water in storage
`
`and the petrol from coal process is undesirable on both environmental and
`
`efficiency grounds [Mitcham and Bumby, 1977].
`
`Amongst the most
`
`likely novel engines are the gas turbine, based on
`
`24
`
`24
`
`

`
`the Joule Brayton cycle, and the Stirling engine. Gas turbines are already
`
`highly successful as aero-engines but need much development for small scale
`
`use in cars.
`
`in addition they use more expensive materials in order
`
`to
`
`withstand the high temperatures associated with a continuous combustion
`
`process [Burnby and Clarke, 1982]. External combustion engines such as the
`
`Stirling design promise a broader choice of fuels and the ability to optimise
`
`combustion conditions for better efficiency and reduced emissions. Despite
`
`improvements to heat exchangers however the Stirling engine still suffers from
`
`large thermal inertia.
`
`In their study of alternative vehicle power systems, JPL concluded
`
`that the Stirling engine and the gas turbine might achieve gains of 20% and
`
`30% respectively when compared with the conventional vehicles of the time
`
`(1975). When such improvements are viewed in the light of the predicted
`
`improvements to the conventional car itself, these figures are not outstanding,
`
`particularly when it is considered that in all cases the alternative engine costs
`
`more to produce.
`
`1.1.2 The Electric Vehicle
`
`Although of somewhat
`
`limited range the ‘all electric vehicle must
`
`not be dismissed prematurely as a likely replacement means of transport,
`
`particularly in certain applications. Fleet trials of electric vehicles have shown
`
`them to be very useful
`
`in applications with a well defined use pattern and
`
`limited range requirement, such as the small delivery vehicle. Volkswagen
`
`[Altendorf et al, 1982] undertook one such trial with 40 electric vehicles
`
`beginning in 1978 and found them to be reliable and acceptable to their
`
`operators. Unfortunately this success will not beirepeated in the car market
`
`until improved battery technology is w