`Measurement and Control
`
`http://tim.sagepub.com/
`
`
`A microprocessor controlled gearbox for use in electric and hybrid-electric vehicles
`P.W. Masding, J.R. Bumby and N. Herron
` 1988 10: 177Transactions of the Institute of Measurement and Control
`
`DOI: 10.1177/014233128801000402
`
`The online version of this article can be found at:
`
` http://tim.sagepub.com/content/10/4/177
`
`Published by:
`
`
`http://www.sagepublications.com
`
`On behalf of:
`
`
`The Institute of Measurement and Control
`
`
`
`Additional services and information for can be found at:Transactions of the Institute of Measurement and Control
`
`
`
`(cid:160)(cid:160)
`(cid:160)(cid:160)(cid:160)(cid:160)(cid:160)
`
`Email Alerts:
`
`
`http://tim.sagepub.com/cgi/alerts
`
`
`
`
`http://tim.sagepub.com/subscriptionsSubscriptions:
`
`
`
`
`http://www.sagepub.com/journalsReprints.navReprints:
`
`Permissions:
`
`
`http://www.sagepub.com/journalsPermissions.nav
`
`
`
`
`http://tim.sagepub.com/content/10/4/177.refs.htmlCitations:
`
`>>
`
`
`
`- Sep 1, 1988Version of Record
`
`What is This?
`
`
`
`Page 1 of 11
`
`
`
`Downloaded from at WAYNE STATE UNIVERSITY on May 23, 2012tim.sagepub.com
`
`
`
`FORD EXHIBIT 1028
`
`(cid:160)
`(cid:160)(cid:160)
`(cid:160)
`(cid:160)
`(cid:160)
`(cid:160)
`(cid:160)
`(cid:160)
`
`
`A microprocessor controlled
`gearbox for use in electric and
`hybrid—electric vehicles
`
`by P. W. Masding. Bsc, J. R. Bumby, Bsc, PhD, CEng, MIEE and N. Herron
`
`This paper describes the automation and control of a
`‘manual’ synchromesh gearbox in a form suitable for use in
`an electric or hybrid-electric vehicle. Such a computer
`controlled transmission system allows full integration and
`control of the drive train leading to improved vehicle
`performance. The automation process is described, and a
`fill! description given, of the computer control algorithms
`necessary to ensure smooth and reliable operation of the
`transmission system. It is shown that an up-change can be
`achieved in 1.4 seconds and a down-change in 1.2 seconds.
`These times are shown to represent maximum gear change
`times and details of how they can be reduced substantially
`are discussed.
`
`Keywords: Microprocessor control, vehicle gearbox auto-
`mation. computer control algorithms
`
`1. Introduction
`
`Automating the operation of a vehicle transmission
`allows the control of the engine and transmission system
`to be integrated, giving substantial benefits in terms of
`vehicle performance, energy efficiency and clriveability.
`Although such a statement
`is applicable to internal
`combustion (ic) engine vehicles, electric vehicles and
`hybrid-electric vehicles. the details relating to how the
`engine/transmission should be controlled are quite differ-
`ent. The main thrust of this paper is to consider the auto-
`mation and control of a discrete ratio, synchromesh
`transmission for use in an electric or a hybrid-electric
`vehicle. As a hybrid—electric vehicle includes both an
`electric traction motor and an ic engine in its drive system
`it is relevant to outline briefly the benefits to be gained by
`automating the transmission system in both an ic engine
`and an electric vehicle.
`
`Fig 1 shows a typical efficiency map for a 50 kW ic
`engine. Also shown on this diagram is a line corre-
`sponding to the road load seen by the engine when
`operating in a fixed gear. lt is only at high loads that the
`engine operates at all efficiently. At low loads the oper-
`ating point is well removed from the high-efficiency (low-
`specific-fuel-consumption) area. At a road load of 10 kW,
`the engine operates at about 3000 rev/min and is rela-
`tively inefficient. By reducing engine speed relative to the
`vehicle speed, through a suitable change in gear ratio, the
`engine operating point can be moved up, along the
`constant power line, towards the high-efficiency region.
`As the operating point moves up this constant power line
`
`school of Engineering and Applied science, University of Durham.
`South Road, Durham, England DH1 3l.E.
`
`Trans Inst MC Vol 10, No 4, July-September 1988
`
`it would, ultimately, reach the optimum engine operating
`line,
`the locus of which links the maximum engine-
`efficiency points at each speed.
`Such an optimum engine-operating schedule can be
`followed if a continuous variable transmission (CVT ) is
`used (Stubbs, 1981; Stubbs and lronside, 1981; Steig and
`Spencer Worley, 1982; Srinivasan et al, 1982; and Chan
`et al, 1984). Unfortunately, current CVT's have an effi-
`ciency which is lower than comparable discrete ratio
`units, and there is a danger that any efficiency benefits
`accruing from improved engine utilisation can be lost in
`the transmission itself. With this in mind Thring (1981)
`has suggested that a discrete ratio transmission with a
`number of ratios spanning a relatively large range may be
`a more efficient solution, even though the engine does not
`quite follow the optimum engine schedule. With this in
`mind, a number of workers have investigated the micro-
`processor control of automatic transmissions (Trummel
`and Burke, 1983; Richardson et al, 1983), while others
`seeking greater efficiency and lower costs have investi-
`gated the automation of spur gear transmissions (Busca
`et al, 1979; Main et al, 1987).
`Whereas the ic engine vehicle meets a variety of
`operating requirements, the electric vehicle is generally
`designed for an urban or sub-urban operating environ-
`ment where, for the advanced electric vehicle,
`traffic
`compatibility over a speed range of typically 0-100 km/h
`may be required. Such a requirement can be met by an
`electric-traction system with a single gear
`ratio of
`between 5:1 and 6:1,
`thereby simplifying the trans-
`mission system and reducing weight and cost. Generally,
`such vehicles employ power electronics to give con-
`tinuous control of the motor torque over the full speed
`range of the motor.
`A typical torque/speed characteristic for a DC separ-
`ately excited traction motor is shown in Fig 2 and should
`be compared with the similar diagram, Fig 1, for the ic
`engine. The difference in the diagrams, and in particular
`the area of maximum efficiency, is immediately apparent.
`The area of maximum efficiency now tends to be at rela-
`tively high specd, low torque, in contrast to the low-speed
`high-torque requirement of the ic engine. This demands a
`different gear change logic if motor efficiency is to be
`maximised.
`
`To operate the motor over its complete speed range,
`two distinct operating schemes are necessary. At about
`2000 rev/min the torque is seen to fall with speed. This
`transition point is tenned the ‘break speed’ and is the
`speed at which the motor will operate with full field
`current and full armature voltage. Below the break speed
`it is necessary to control the armature voltage at full field,
`
`177
`
`Page 2 of 11
`
`FORD EXHIBIT 1 028
`
`
`
`Masding, Burnby and llerrort
`
`100
`
`W
`
`3*O
`
`
`
`Engnetorque.Nm
`
`to kw
`
`2°"‘”
`
`
`
`0
`
`1000
`
`2000
`
`3000
`
`4000
`
`5000
`
`6000
`
`Fig 1 Road-load and engine-operating curves for an ic engine vehicle
`
`Engine speed. r:p.rn
`
`Motor
`
`torque.Nrn
`
`
`
`
`
`TractivcelfortltN
`
`Fig2 Road-load and motor-operating curves for
`electric vehicle
`
`all-
`
`while speeds above the break speed are achieved by
`reducing the field current but at full armature voltage: so-
`called field weakening.
`Fig 2 shows that the area of maximum efficiency tends
`to be at speeds just above the break speed in the field
`weakening region. To capitalise on this a number of
`electric vehicle designs have incorporated a ‘transmission
`system with a number of discrete ratios (Bindin, 1986;
`Burba et ul, 1986). The use of such a transmission allows
`the motor break speed to appear at a relatively low
`road-wheel speed. therefore extending the range of road
`speeds over which field weakening control can be used.
`By arranging a battery switching system which halves the
`applied armature voltage,
`this range can be extended
`further, down to below 10 km/h. Armature control
`
`178
`
`20
`
`£0
`
`80
`60
`Flood speed, ltmlh
`
`100
`
`‘I20
`
`11.0
`
`150
`
`Fig 3 Tractive-effort and road-load curves for all—electric
`vehicle showing the affect of gear ratio
`
`electronics can now be dispensed with. Vehicle movement
`from rest is achieved by the use of starting resistors in the
`annature circuit.
`
`Apart from a potentially improved drive system effi-
`ciency.
`the use of a stepped transmission can also
`improve the performance of the electric vehicle. This will
`become an even greater requirement in the future when
`electric vehicle range is extended by the use of high-
`energy—density battery systems. such as the sodium]
`
`Trans inst MC Vol 10. No 4. July-September 1988
`
`Page 3 of 11
`
`FORD EXHIBIT 1 028
`
`
`
`sulphur cell (Bindin, 1986). Fig 3 shows the motor
`maximum torque profile of Fig 2 converted to an equiva-
`lent traction force at the vehicle wheels for three different
`
`transmission ratios. Also shown is a typical road load
`requirement at different gradients. With a fixed ratio of
`5.65:1,
`the vehicle can cover the‘ speed range 0-100
`km/h but is incapable of starting on gradients greater than
`15% and travelling at speeds much above 100 km/h. A
`typical perfonnance specification for an ic engine vehicle
`is a start from rest on a 20% gradient and the ability to
`sustain 120 km/h on a 2% gradient. Obviously, the elec-
`tric vehicle with fixed gear ratio is a compromise and, for
`a more general-purpose vehicle, it has difficulty meeting
`either requirement. By adding two more gear ratios, both
`low— and high-speed performance is improved, while with
`an integrated motor/transmission control system, drive
`system efficiency can also be maximised.
`As the hybrid ic engine/battery-electric vehicle can
`operate in an ic engine mode, an electric mode or with
`both power sources together providing the propulsion
`power, integrated control of the engine. traction motor
`and transmission is of prime importance (Trummel and
`Burke, 1983; Bumby and Forster. 1987; Forster and
`Bumby, 1988). With these benefits in mind, this paper
`examines the feasibility of automating and controlling a
`four-speed discrete-ratio transmission in a form suitable
`for use in an electric or hybrid-electric vehicle.
`
`2. The hybrid ic engine/battery-electric test
`system
`
`2.1 The test facility
`
`The arrangement of the laboratory test system in which
`the automated transmission is installed is shown in Fig 4
`and is used to examine the control and driveability prob-
`lems relating to a parallel hybrid drive (Fig 5). in this
`drive arrangement a 32 kW ic engine, and a 37 kW separ-
`
`Masding. Bumby and Herron
`
`ately excited DC traction motor. are connected mech-
`anically in parallel at
`the input
`to the standard,
`four-speed, synchromesh transmission by a 1:1 toothed
`belt drive. Both the ic engine and the electric traction
`motor power electronics have been modified for com-
`puter control. In the case of the ic engine, the main butter-
`fly valve is controlled by a stepper motor and is capable
`of moving this valve from a fully closed to fully open
`position in 425 ms. The control system for the DC
`motor incorporates both an armature and field chopper
`so that smooth control of the motor over its complete
`speed range, in both motoring and regenerative braking
`modes, is possible.
`Incorporated between the ic engine and the belt drive
`is a one-way clutch, or frcewheel, which allows the drive
`system to be operated in a pure electric mode with the ic
`engine remaining stationary. When necessary the engine
`can be started, run up to speed and synchronised with the
`rest of the drive train ready to pick up load. All drive
`train control is carried out by a Motorola M68000-based
`computer system This computer system also gathers test
`data, stores it in memory, and, at the end of a test, passes
`this information to the test-bed control computer for
`analysis and graph plotting. Data are also passed during a
`test to generate on-line displays. A fuller description of
`the test facility and its computer control can be found in
`Bumby and Masding (1988).
`
`2.2 Requirements of an automated transmission
`
`In examining the feasibility of a computer controlled
`gearbox it is important to recognise that if good drive-
`ability is to be achieved without a ‘hot shift’, then gear
`change times must be as short as possible. in addition
`when a gear change is completed, drive torque should be
`reapplied quickly and smoothly.
`With the drive arrangement described in section 2.1.
`the permanent connection of the electric motor to the
`
`d.c. traction motor
`
`Power electronics
`
`‘T’ slotted bed plate
`
`Test had control eolnputor
`DUET-16 (P.c. )
`
`surety trbe.
`lmtrumontntlon 5
`test-and control
`
`Toothod belt drive
`
`Transmission
`
`
`
`M68000
`
`onvo train control a
`Data acquisition
`°°'""“"'
`
`Torque transducers
`
`Drlve shalt
`
`F'°°*""°°‘ W‘
`
`Lc. engine
`
`Fig 4 Test-bad layout
`
`Trans Inst MC Vol 10, No 4, July——September 1988
`
`Flywheel
`
`Dynarnornotor
`
`_Dynal-nomoter
`control unit
`
`179
`
`Page 4 of 11
`
`FORD EXHIBIT 1 028
`
`
`
`Masding, Bumby and Herron
`
`AGCOIOIIIOI’
`
`Broke
`
`Motor
`controiler
`
`Transmission
`
`Fig 5
`
`Parallel hybrid configuration
`
`shaft provides a means of precisely
`gearbox input
`controlling_ the speed of this shaft. This allows a gear
`change to be completed without
`the need for a slip-
`ping clutch. In addition, the electric traction system is
`used to move the vehicle away from rest, with the ic
`engine being automatically started and synchronised with
`the moving drive train at speeds above 1000 rev/min. a
`control sequence again not requiring the use of a slipping
`clutch.
`
`3. Transrnission-system hardware
`
`The function of the gear-change mechanism is to move
`the gear lever to any point on the H gate in a similar
`manner to a human operator. As the laboratory test
`system is used extensively to study control problems in
`hybrid electric drives it is advantageous to retain manual
`movement of the transmission lever. Such freedom of
`
`is provided by two pneumatic cylinders
`movement
`attached to the gear selector as shown in Fig 6. Activating
`the
`longitudinal cylinder causes a plate
`to move
`backwards and forwards. thus shifting the gear change
`lever between I /3 and 2/4 ends of the H gate. This plate
`is mounted between two sets of bearings rotating in the
`horizontal plane. Each bearing wheel has a grooved edge
`which locates with a bevel on the edge of the plate.
`A second cylinder is mounted on the plate and moves
`with it. This cylinder provides the necessary sideways
`movement of the gear selector. between 1/2 and 3/4 sides
`of the H gate.
`The circuit diagram for the pneumatic system is shown
`in Fig 7. Compressed air is supplied to the system from a
`reservoir which is recharged as necessary by an electric
`pump. During normal operation a regulator valve main-
`tains the working pressure in the system at about 2 bar.
`Each of the two working cylinders is controlled by a
`piston valve. There are five ports on each piston valve,
`180
`
` L
`
`‘tudinal pneumatic
`c,°§.;‘°..‘..
`
`Fig 6 The gsanchange mechanism
`
`the flow path between them being controlled by activating
`the appropriate solenoid.
`In the case of the longitudinal cylinder. two additional
`components are used to help stop the piston in the
`central. neutral, position. The first is a fast-acting valve
`which cuts the air supply to the cylinder 12 ms after its
`solenoid has been energised. Second, flow regulators are
`fitted to both supply lines feeding the cylinder. These
`allow air to flow freely into the cylinder but, when air is
`
`Trans inst MC Vol 10, No 4. July-September 1988
`
`Page 5 of 11
`
`FORD EXHIBIT 1 028
`
`
`
`Masding. Bumby and Herran
`
`Solenoid
`(isolates port 1)\
`10
`
`
`
` I
`Transverse cylinder
`
`Port numbering system
`
`Valve ports:
`
`1aMciin inlet port
`2I4=0UIl¢’( DOHS
`3I5=Erhaust ports
`1!. Connects ports land I. when on
`12 Comccts ports land 2 when on
`
`Fig 7 The pneumatic circuit
`
`returning to the exhaust ports, the flow is restricted. As a
`result, the speed of the piston’s movement is decreased.
`which reduces the tendency of the piston to overshoot the
`neutral position before the air-cut-off valve can be
`activated.
`
`Both cylinders have magnetic pistons which operate
`sensor switches attached to the outside of the casing (see
`Fig 6). A system of two switches on the transverse
`cylinder and four on the longitudinal cylinder completely
`define the position of the gear selector. The area of the H
`gate covered by each position sensor is shown diagram-
`matically in Fig 8. Each of the position sensors is inter-
`faced to the M68000 through appropriate filter and
`isolation circuitry.
`The six sensors alone are sufficient to confirm when a
`
`particular gear is engaged and when the gearbox is in
`neutral. Logical OR of the two centre sensors on the
`longitudinal cylinder gives a single signal which covers the
`whole of the central, neutral, region. However, ambiguous
`positions exist;
`for example,
`the reading obtained
`between first and neutral is the same as that between
`neutral and second. This ambiguity is removed by con-
`necting the centre two sensors on the longitudinal cylin-
`der to a positive edge triggered D-type flip-flop decoder
`circuit.
`
`4. Software control
`
`The gear change control software has been designed to
`be readily incorporated into the existing hybrid drive
`control software. The structure adopted for this control
`software, described in Bumby and Masding( 1988), is that
`of a background program concerned in receiving, and
`transmitting, data to the operator and a level-3 (lowest
`level used) interrupt routine, activated every 20 ms, in
`which all time-sensitive control algorithms run. In the
`gear change software, gear change requests from the
`
`Trans inst MC Vol 10, No 4, July-September 1988
`
`0
`
`9
`
`Transverse cylinder
`sensors
`
`13“ —>
`
`Right
`
`cylir?der sensors
`
`signals
`
`Decoder circuit
`
`Fig 8 Regions covered by the position sensors
`
`operator can be made in the background routine. but
`during automatic operation the decision as to when to
`change gear, and what gear to change to. is made in the
`devel-3
`interrupt. The main gear change
`control
`algorithms also run at this interrupt level. All control
`181
`
`Page 6 of 11
`
`FORD EXHIBIT 1 028
`
`
`
`Masding, Bumby and Herron
`
`‘rot
`
`No
`
`Aflfvutu wpraprklc Idcwlds to rnwu to n-amal
`Forward or Bad: dopundhg an pvcnnl your
`pin:
`
`Lon or right dQcndng Ill hall your
`
`
`
`
`Q-Inga 09: Fruit motor eontacterc M acultuu
`
`Oamgo awn: Frau! new counselor: to brake
`( Ramon: gearbox loading from my Motor )
`
`
`
`
`
`Englnc P61 Spud Canlrul
`Upivm: Sclaolnta Flyuhsol-qcnrutlo-68 rpm
`Dovmshllk: Stiadnh molorsgoud-BB rpm
`( Rcmovcu goorbox Iocdhg item use Engino ]
`
`
`
`
`
`Nuulrd
`
`
`
`amen Sc-an var earn: ncutrd modlng
`If to entrust funding: on abtchnd thu-
`lum ulr oil and In nulrd lug-TRUE
`
`Syndxrenluo Hater Spud
`BONGO-IANGE
`Initially apvly bruit: untl
`sndl uvurpood Irror
`‘lhcn preut centacton to
`cooderuh unll are
`
`I: am.
`finer! an Pol uacderator dqorllhrn
`
`UPQIANGE
`the PM uulorntnr
`dgu-Ham only
`
`
`
`
`
`
`Sc! ayneh M9
`-1306
`
`
`
`
`Duck anon for can require:
`engages may amwaorlau
`far no new gear
`It 10 tuna! roodnqo an
`antenna man not engage-TRLIE
`
`
` mun:
`
`mu ....'”,;‘§‘.‘£.‘1‘.”,".'.."?.‘.......
`
`Fig 9 Gear-change algorithm
`flowchart
`
`182
`
`Trans Inst MC Vol 10, No 4, July-September 1988
`
`Page 7 of 1 1
`
`FORD EXHIBIT 1 028
`
`
`
`algorithms are written in ‘C’ with small assembler
`routines being used to interface with input/output
`devices.
`
`The flowchart of the ‘C’ interrupt routine which pro-
`vides the gear change logic is shown in Fig 9.
`
`4.1 Stage 1 - Gear change
`
`At the start of any gear change, the loading on the gear-
`box input shaft is removed and the gear selector moved
`into neutral. On its first pass,
`the control software
`activates the necessary solenoids to move the gear selec-
`tor out of gear and into neutral by sending a bit pattern to
`the output register of the appropriate versatile interface
`adaptor (VIA). A two—dimensional array provides the
`program with all the bit patterns necessary, based on the
`current and next gear. These codes activate the longi-
`tudinal cylinder as appropriate to move out of the current
`gear and, at
`the same time, activate the transverse
`cylinder to move left or right, ready for the next gear.
`When the gear selector moves into the region covered by
`the centre sensor - ie, the neutral zone, a high-level inter-
`rupt signal
`(level 4)
`is generated to ensure prompt
`removal of the air supply to the longitudinal valve. Con-
`trol now passes back to the level-3 interrupt routine
`which waits until the correct neutral position has been
`reached (ie, left or right centre on the ‘H’ gate) before
`cutting off the air supply to the transverse cylinder.
`Checking the position consists of reading the VIA input
`register ten times and only accepting that the gear selector
`is in neutral if all ten give the. same correct reading.
`immediately after setting the appropriate VIA output
`to activate the cylinders, the loading on the gearbox is
`removed. Unfortunately,
`if the ic engine is producing
`power, it is not simply a matter of setting the throttle
`demand to zero and closing the butterfly valve. Compli-
`cations in reducing the engine loading arise from the fact
`that the engine must pick up load smoothly once a gear
`change is completed. if the engine throttle is simply set to
`zero, its speed will fall rapidly behind the rest of the drive
`train during the gear change. Consequently, when the
`throttle is returned to its previous setting, the engine will
`accelerate rapidly until it ‘hits’ the rest of the drive train,
`causing an unacceptable jolt. To overcome this problem
`either a controlled synchronisation procedure can be
`used or. as is the case here, closed-loop speed control of
`the engine is provided to maintain the engine speed about
`88 rev/min behind the motor during the gear change.
`With such a small speed difference the engine does not
`‘hit‘
`the drive train with any significant force when it
`comes back on load, with the result that drive train power
`can be restored quickly and smoothly.
`Setpoints for the engine speed controller depend on
`whether the gear change is up or down. With an up-
`change, because of the presence of the one-way clutch.
`the engine can immediately start
`to slow towards the
`speed it will need when the new gear is engaged.
`in
`contrast it
`is not physically possible to accelerate the
`engine to the speed that will be necessary after a down-
`change until the gearbox is in neutral. Two setpoints are
`used to overcome this problem. For a down-change the
`engine follows 88 rev/min behind the motor as it acceler-
`ates, and for an up-change the engine is sent immediately
`towards the speed for the next gear.
`When the electric motor has been supplying the power
`particular attention must be paid to the accelerator and
`
`Trans inst MC Vol 10. No 4, July~September 1988
`
`Masding, Bumby and Herron
`
`is simply
`brake signals in any situation in which it
`required to rotate the motor without loading the drive
`shaft. if both brake and accelerator sigrtals are set to zero,
`then the logic within the power electronic controller is
`undefined. Application of a small signal to either over-
`comes this problem and the controller switches positively
`into one or other mode. Accordingly, the gear-change
`routine applies a small signal
`to the accelerator
`in
`preparation for a downvchange and a brake signal for an
`up-change.
`
`4.2 Stage 2 ~ Speed matching
`
`the speed of the
`Once neutral has been obtained,
`gearbox input shaft is synchronised to that of the output
`by sensing the speed of the flywheel (road-wheel speed)
`and controlling the speed of the electric motor to a set-
`point based on the flywheel speed times the new gear
`ratio. The action of
`the synchronisation algorithm
`depends on the size and sign of the error so that the time
`taken to match speeds is minimised. intuitively mixed use
`of the motoring and regenerative braking modes, depend-
`ing on the sign of the demand from, say, a P+l algorithm,
`would seem an obvious form of control. However,
`because of the delays that arise due to the way in which
`the power electronics switch between motoring and
`regenerative braking, this is not possible. These delays,
`caused by contactors closing and the field current
`reversing, would introduce an unacceptable 500 ms
`delay. To avoid this problem, and to achieve synchronisa-
`tion in about 700 ms, the controller takes a different
`course of action depending on whether an up-change or a
`down-change is requested. On a down—changc, having
`preset the contactors to accelerate prior to making the
`neutral move, speed control
`is achieved by a P+l
`algorithm using the accelerator alone. if the system over-
`shoots, natural slowing of the motor is adequate without
`recourse to regenerative braking. On an up—change the
`system has been primed for braking and a constant brake
`value is applied for as long as the overspeed error is
`greater
`than 200 rev/min. Below this error natural
`slowing of the motor is used to achieve synchronisation.
`Simultaneously, the controller outputs a small accelerator
`signal to switch the power electronic controller into the
`motoring mode ready for subsequent use. Once speed
`matching to within 100 rev/min has been achieved. a P+l
`control algorithm takes over to maintain this speed until
`the gear is successfully engaged.
`
`4.3 Stage 3 - Engaging the new gear
`
`When the speed error is less than 100 rev/min. the
`longitudinal solenoid is activated to engage the new gear.
`Any residual speed errors are partly corrected by the
`synchromesh in the gearbox and partly by the control
`algorithm described above. Once the engage move has
`been made. the program waits for the sensors to confirm
`that the position for the new gear has been reached. The
`program now returns ‘false’ to the calling routine, signify-
`ing that the gear change has been successfully completed.
`thereby allowing power to be restored on the drive shaft.
`
`4.4 Location on power up
`
`On initial power up. a gear change initialisation routine
`is activated that locates the gear selector in the neutral left
`position ready for the first gear change. This is clone
`183
`
`Page 8 of 11
`
`FORD EXHIBIT 1 028
`
`
`
`Masding, Bumby and Herron
`
`without use of the decoder circuit since the output from
`the flip-flop might be erroneous until the neutral position
`is crossed for the first time. A simple series of logical
`movements based on the sensor "readings make up the
`stmcture of the location routine.
`
`5. Results
`
`Typical results for both a down-change and an up-
`change are shown in Figs 10a and 10b. respectively, for
`the drive operating in a hybrid mode. Before the gear
`change, the ic engine is providing all the traction power. A
`controlled gear change then takes place, with power being
`quickly and smoothly re-applied by the engine once the
`gear change is complete. Figs Ila and 11b show the
`speed synchronisation phase in more detail and also show
`how the motor-speed setpoint varies during the gear
`change. In Fig 10, the response of the torque transducer
`monitoring the it: engine torque is also recorded as this
`
`gives some indication as to the smoothness of the gear
`change.
`speed
`the gear change the flywheel
`Throughout
`(vehicle road speed) remains substantially constant. Once
`neutral has been reached, speed synchronisation takes
`place using the electric traction motor to control the gear-
`box input shaft speed. The motor setpoint is now defined
`and depends on the gear being selected. At all times it is
`related to the flywheel speed through the appropriate
`gear ratio. Clearly shown in Fig 10 is the way in which the
`engine speed is immediately allowed to ‘drop away‘ in an
`up-change towards the final engine speed while during a
`down-change it is tightly linked to motor speed as soon as
`neutral has been achieved.
`
`6. Discussion
`
`The requirements of the gear change system as
`described in section 2 were to minimise gear change time
`
`Electric motor speed
`
`....... ..
`
`ic engine speed
`
`--. -—-.
`
`ic engine torque
`
`Fig 10a Torque and speed profiles
`during down-change from third to
`second
`
`ic engine speed
`....... .. electric motor speed
`-—.--. ic engine torque
`
`electric motor speed
`i1:.cngin¢ speed
`
`i.c. engine torque
`
`0.5
`
`10
`
`1.5
`
`20
`
`25
`
`3.0
`
`40
`'
`
`Time (secs)
`
`
`
`l'°'°"9l“° 59"‘
`
`-20
`
`-30
`
`-40
`
`éc
`
`a‘.
`l—'
`
`15u
`
`3_
`U) 1000
`
`S00
`
`0.5
`
`1.0
`
`1.5
`
`2.0
`
`2.5
`
`3.0
`
`3.5
`
`1.0
`
`Time (secs)
`
`“*9 ‘°b Twine W speed vr°*“°s
`during an up-change from second
`to third
`
`184
`
`Trans Inst MC Vol 10, No 4, July—Septernber 1988
`
`Page 9 of 11
`
`FORD EXHIBIT 1 028
`
`
`
`electric motor set point
`1
`electric motor speed
`2--..—-_._... .
`-
`a-.~a—.—._.._.,
`_
`I
`u...-
`
`u
`
`..-.--
`
`,.
`
`,
`
`u_.
`
` —.-_......_..-. _.
` motor moturoi decoy
`
`-
`
`—~
`
`.
`
`.
`
`-—
`
`Masding, Bumby and Herron
`
`I
`
`.
`
`.
`
`o
`
`_
`
`-
`
`..n- "‘
`u
`
`speed synchronisation
`
`i.c. engine
`rc- connected
`
`.20
`
`.40
`
`.60
`
`.80
`
`1.0
`
`1.2
`
`1.4
`
`1.6
`
`1.8
`
`Time (secs)
`Fig 11a Diagram showing ‘stage’ timings during a down~change from third to second
`
`electric motor speed
`
`motorzbroking
`
`-
`electric motor
`set point —->!
`L....-._._.....-._._.."..t«...,._._ __ _____._____
`
`.
`‘ ' "° :.v-. I ~---~.._.—
`
`speed synchronisation
`
`.20
`
`.40
`
`.60
`
`.80
`
`1.0
`
`1.2
`
`1.4
`
`1.6
`
`1.8
`
`Fig 11b Diagram showing ‘stage’ timings during an up~change from second to third
`
`Time (secs)
`
`and, when drive power is restored, to do this quickly and
`smoothly to give good dziveability. With the gear change
`system described here the time taken to gear engagement
`for an up-change is, typically, 1.4 s and 1.2 s for a down-
`change. Smaller adjustments in speed are necessary if the
`gear change is between sequential gears. and typically this
`reduces the total gear change time by 200 ms.
`The way in which the gear change time is distributed
`between the three distinct stages of a gear change is
`shown in Fig 11. Typically 300-400 ms are used engag-
`ing neutral. If the H gate does not have to be crossed, the
`lower time is appropriate. Speed matching then takes
`place in. typically, 600-800 ms. During a down-change,
`when an increase in motor speed is demanded, the P+l
`controller has been designed so as to give a good, fast
`
`Trans Inst MC Vol 10, No 4, July-September 1988
`
`C
`
`‘response with little or no overshoot. This control is
`clearly demonstrated in Fig lib. The third stage of the
`gear change, that of gear engagement, takes, typically.
`100-300 ms depending on the accuracy of speed match-
`ing in the synchronisation phase.
`Analysis of the time breakdowm described above
`suggests that, with modifications to the system hardware,
`gear change times can be cut by up to 50%. For example,
`modification of the electric-motor controller to allow fast,
`and easy. movement between motoring and regenerative
`braking modes, coupled with modifications to the speed-
`synchronisation algorithms, could reduce the time
`required for speed matching to under 500 ms. Further, if
`modifications were made to the shift mechanism, so that
`it acted more directly on the gear selector inside the gear-
`
`185
`
`Page 10 of 11
`
`FORD EXHIBIT 1 028
`
`
`
`Masding, Bumby and I-Ierron
`
`box, then gear movements (ie, gear to neutral, neutral to
`gear) could be reduced to 100-200 ms. With such modi-
`fications a complete gear change could be achieved in
`500-700 ms.
`"-
`
`Perlmps one of the greatest benefits of the transmission
`control system described is the smooth way in which
`torque is re-applied to the drive system following a gear
`change (see Fig 10). This smooth response is due entirely
`to the speed-synchronisation approach adopted in the
`gear change strategy and gives some indication of the
`driveability to be expected in an actual vehicle. An alter-
`native to using speed-matching algorithms in the control
`is to incorporate a slipping clutch at the input to the trans-
`mission and control the re-engagement of this clutch
`following a gear change (Main, 1987; Whlzer and
`Miersch, 198 7). However, it is difficult with such systems
`to avoid torque oscillations in the propshaft following re-
`engagement. In addition, the clutch-control system must
`be able to account for clutch wear. Both of these prob-
`lems are avoided if speed synchronisation is used, as the
`need for clutch control during a gear change can be dis-
`pensed with.
`
`7. Conclusion
`
`This paper has demonstrated the feasibility of auto-
`mating a manual transmission in a form suitable for use in
`an electric or hybrid-electric road vehicle. In particular,
`the use of slipping clutches are eliminated from the
`system with gear changing being achieved by ‘speed-
`synchronisation’ control algorithms. Elimination of the
`slipping clutch has allowed torque to be re-applied after a
`gear change in a smooth, controlled manner such that
`good driveability can be anticipated.
`
`8. Acknowledgments
`
`The authors would like to acknowledge the financial
`support of
`the Science and Engineering Research
`Council. We are also grateful to the Ford Motor Co. and
`Lucas Chloride EV Systems Ltd for the provision of
`equipment.
`
`9. References
`
`Bindin, P. 1