A 6-Speed Automatic Transmission Plant Dynamics Model for HIL Test Bench

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SAE TECHNICALPAPER SERIES 2008-01-0630

A 6-Speed Automatic Transmission PlantDynamics Model for HIL Test Bench

Quan Zheng, Asif Habeebullah, Woowon Chung and Andrew HermanDelphi Corporation

Reprinted From: Transmission and Driveline, 2008(SP-2147)

2008 World CongressDetroit, MichiganApril 14-17, 2008


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Figure 2 HIL Bench Architecture

6-SPEED AUTOMATIC TRANSMISSION PLANTDYNAMICS MODEL

Powertrain dynamics modeling has been an activeresearch and development field for many years. Ingeneral, a complete powertrain model hasrepresentations of engine, torque converter,transmission, and driveline/ vehicle dynamics.Depending on the application, the powertrain model mayhave different levels of complexity for a certain part ofthe powertrain model. For example, if the emphasis is onengine applications, then the engine model may be ofhigh-fidelity. Similarly, for chassis applications, thevehicle dynamics model is very detailed.

In our case, the motivation for the development ofautomatic transmission plant model is to enable thealgorithm/test engineer(s) to check the controllerperformance with a representative transmission plantmodel in the absence of the real transmission hardware.The powertrain plant dynamics model is a key element ofthe Virtual Car Test Bench as shown in Figure 1, whichrequires a powertrain model with high-fidelity

representation of the transmission dynamics. SuchVirtual Car Test Bench is used for controller andsoftware testing, control algorithm development andtesting.

The initial model is developed by starting with anexample SimDriveline model from the MathWorks. Thismodel represents the major components of the drive-train (engine, torque converter, transmission, and vehicleload) by specialized blocks from the SimDriveline block-set of the Simulink library.

The 6-speed AT mechanical model is then configuredusing SimDriveline toolbox building blocks. Unlike theconventional modeling approach of deriving thetransmission dynamics state equations and transitions,SimDriveline toolbox offers components with built in stateequations and transition conditions. Therefore, the statetransitions and boundary conditions are taken care of bythe physical model.

Table 1 shows the clutch state table for the 6-speedautomatic transmission of interest. Figure 3 shows thepowertrain model developed using SimDriveline toolbox.

The model parameters of various blocks are updated toreflect the vehicle design parameters. The engine speed-torque map, the torque converter parameters (speed andtorque ratios, capacity factor), transmission gear ratios,clutch design parameters, transmission inertias, the finaldrive gear ratio, the vehicle inertia and the road-loadvalues. The model also uses certain parameters that arenot readily available due to the lack of proprietary designinformation. These parameters are tuned in an iterativefashion and this is found to be an arduous process. The

key transmission dynamics model parameters are tunedby inputting the actual vehicle engine speed in the model.The modeled transmission input speed and output speedare then compared with vehicle data.

The powertrain model is developed with the followingstages to deliver different levels of model fidelity at eachstage:

Stage 1: Develop and validate 6-speed AT mechanicalmodel.

TestDrive

Host PCwith

TestDriveConsole

M-Node

TCM

Laptop withINCA

PRNDL

Throttle

Brake

TFT

Outputs

Inputs Sensors

T h r o

t t l e

B r ak

e

G e ar

T F T

T I S

S

T O S S

V K P H

CAN bus

Solenoid currents

C C P

Actuators

Gear PWM

S ol en

oi d

c ur r en

t s


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Stage 2: Develop and validate the hydraulic pressuregeneration model

Stage 3: Validate vehicle dynamics model

Stage 4: Develop and validate engine model to haveproper torque generation.

This staged development process enables us to focus onthe key modules needed for controller and softwaretesting purpose, and at the same time, the modeldevelopment is continued to improve the model fidelity ofother modules.

D6

1 Used for engine braking when on.

D5

D4

D3

D2

1

D1

R

F1CBLR

LR/BC26C35R

C456

OD

C1234

UD

D6

1 Used for engine braking when on.

D5

D4

D3

D2

1

D1

R

F1CBLR

LR/BC26C35R

C456

OD

C1234

UD

Table 1 Clutch state table of 6-Speed AT

Figure 3 Drive-train Plant Model

6-SPEED AT MODEL VALIDATION

The automatic transmission model is validated by vehicledata.

One challenge of the model development is the tuning ofthe model parameters. The original design parametersare limited, and are sometime proprietary. Therefore,model parameter identification and tuning becomes animportant task. Another challenge of the modeldevelopment is that a detailed engine dynamics model isnecessary to fine tune the transmission dynamicsresponse.

The focus of the model is on the transmission dynamics.Therefore, actual measured vehicle data is used to tunethe transmission model parameters. In this case,

measure engine speed is used as input to the powertrainmodel. The modeled transmission input speed iscompared with the measure transmission input speed.

Another source of variation is the vehicle loading on theoutput shaft of the transmission. There are several stepsto develop a set of representative parameters for vehicleloading. After the load model is derived, the simulatedoutput speed is compared with the measured outputspeed.

Figure 4 - Figure 6 show the model validation results.These results are organized by recording signals from atypical test vehicle driven under selected drivingconditions (this constitutes the test-data), running themodel with its inputs being driven from the test-data andcomparing the model outputs against the test-dataoutputs.

Figure 4 shows the vehicle data of throttle, brake andgear requests, which are inputs to the model. Figure 5shows the engine speed and engine torque traces. Theengine torque graph shows the comparison enginetorque calculated by model and the data taken fromvehicle. It is obvious that engine model needs additionalimprovements. For our model validation purpose, enginespeed is fed into the powertrain model usingSimDriveline speed input block. This allows us to focuson transmission dynamics directly without focusingheavily on the fidelity of engine model. Figure 6 showsthe comparison of transmission input speed (TISS),transmission output speed (TOSS) and vehicle speedcalculated by the model and measured from vehicle. Asshown in Figure 6, the model and vehicle data show aclose correspondence for the most part with thetransmission up-shifts and down-shifts. However, there

are a few areas that the speed levels of modeled andmeasured data do not line up. This is due to the vehicleloading part of the model being not accurate. This is partof our future work to improve the vehicle dynamics modelin order to add proper loading to the transmission.

0 50 100 150 200 250 3000

20

40

T h r o

t t l e

ModelVehicle data

0 50 100 150 200 250 300-2

0

2x 10

4

B r a

k e

ModelVehicle data

0 50 100 150 200 250 3000

5

10

G e a r r e q u e s

t

Time (secs)

ModelVehicle data

Figure 4 Model (User) Inputs


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Command Current Control Pressure

Closed Loop Plant Model

Clutch Braking Force= uFF=P*A

Generate TOSS,TISS and VRPMrelation

Figure 8 Current, Pressure and Closed Loopstructure

As pointed out earlier, engine RPM signal needs to befed to the plant model because a validated high fidelityengine plant dynamics model is not yet available at thisstage of development. Engine torque is estimated byusing measured engine speeds.

CONTROL ALGORITHM TESTING

The new generation of Delphi's transmission controlmethodology is to provide the customer with the bestcalibration authority. This means that transmissioncontrol can be achieved by very general calibrationsetting. For those familiar with the art of transmissioncontrols, a key point of the art is to properly controltransmission actuators at each phase of shifting process.

In order to test this new generation of transmissioncontrol strategy, closed loop test bench is a necessity.An example of the testing needs is given below.

One important aspect of transmission shift control is toproperly determine the shift progress, i.e. shift phases.For the apply and release clutch phase transitions, phaseduration time is used as well as certain event triggers,such as Shift Begin, Shift Finish, etc. As shown in Figure9, during 1->2 power off shifting, Apply1 Clutch SYRpoint can be set to true by model the HIL bench.Therefore, the phase transition algorithm can be verified.

Figure 9 Example Power off 1->2 shift

PLAY BACK MODE

Play Back Mode is an important function of the HILVirtual Car bench. Play Back enables test engineers toplayback test data repeatedly to test certain areas ofcontroller functionality. This functionality also allows datacollected in a test vehicle or dyno to be repeated, whichis important to reproduce errors that are difficult,damaging or maybe even dangerous in a test vehicle(Zheng, et al., 2007).

The concept of Play Back Mode is to make HIL testbench re-produce the recorded (vehicle) signalsrepeatedly, i.e. to re-create the vehicle test scenario onthe test bench.

In this section, we will detail the data capture methodusing production vehicle calibration tools to re-createconditions in the HIL environment similar to vehicleconditions.

Since the bench model is running in Matlab environment,it is necessary to convert all data file to this Matlab .matdata format. Figure 10 shows the process of data formatconversion, which can be summarized at the followingsteps:

Collect input signals to TCM using productionvehicle calibration tool;

Convert .dat file to Matlab .mat format(mdfimport developed by Mathworks, Figure 12);

Convert data to the right format (loop rate, row,column, etc.)


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Vehicle test data(*.dat) mat file

mdfimport

Time align as 5ms andRow ,column changeSave as mat file

Run model 5 ms step By conversion m fileDeveloped by Delphi

Figure 10 Data format conversion

Figure 11 Input signals to the TCM

Figure 11 shows input signals to the TCM that arenecessary for the proper transmission control. In thiscase, TCM uses CAN for Eng related signal sharing,which are the necessary input to the model as well.

Figure 12 shows MDFIMPORT program used to convertthe recorded vehicle data (*.dat) to Matlab data format.

Figure 12 MDFIMPORT program developed byMathworks

Figure 13 shows data comparison between input andoutput data. Here the compared data are TISS, TOSSand VRPM. B* represents bench generated signal. Asshown, the Play Back Mode data matches the vehicledata very well.

Figure 14 shows the comparison of solenoid currentgenerated on the bench and vehicle compared result,where variables AUTCURA (26Brake), AUTCURB(UD),AUTCURD(35R) and AUTCURE(OD) represent solenoidcontrol current (from 0 to 850mA), and B* representbench test result with mat conversion. As shown in thefigure, the two sets of data match very well, which meansthat same outputs from TCM can be expected via PlayBack Model.

In summary, Play Back Mode feature allows testengineers to replay vehicle test data on the HIL benchrepeatedly, which is not possible by human driving a car.Therefore, Play Back Mode makes it easier to find theroot cause of a problem and eventually fix the problem.


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0

500

1000

1500

2000

2500

3000

0 50 100 150

BVTINSPDF

VTINSPDF

0

500

1000

1500

2000

2500

3000

0 50 100 150

BVOUTSPDF

VOUTSPDF

0

500

1000

1500

2000

2500

3000

0 50 100 150

BVRPMVRPM

Figure 13 VTINSPDF (TISS), VOUTSPDF (TOSS) andVRPM

-100

0

100200

300

400500

600

700

800

900

106 111

BAUTCURA

BAUTCURB

BAUTCURD

BAUTCURE

AUTCURA

AUTCURB

AUTCURD

AUTCURE

Figure 14 Compared result

FUTURE DEVELOPMENT

The above described 6 Speed HIL environment offersthe ability to evaluate real-world data against previouslydiscussed model. The extensions of this capability willfollow primary paths. Below are the areas of focus forfuture development:

1. Increased model fidelity, addressing the following:

Add vehicle dynamics to the model by modelinga differential, longitudinal car dynamics and tires.

Exercise the current to pressure generationportion (already available in the model) so that itproduces the clutch pressures for thetransmission clutches.

Add a hydraulic plant to model the transmissionhydraulics; SimHydraulics physical modelingblock-set could be utilized for this purpose.

Use Simulink Parameter Estimation todynamically tune the model parameters tofurther refine performance.

Improved Engine model

2. Increased TCM HW and SW Test Coverage (itemsdescribed in the INTRODUCTION not addressed inthis paper):

Increased test coverage for current TCMsoftware applications.

Automation of existing and newly-developed testcases.

Development of more sophisticated pass/faildetermination of test cases.

CONCLUSION

In this paper, we presented the development of the 6-speed automatic transmission plant dynamics model forthe Delphis HIL Virtual Car Test Bench and how the HILbench is used in the verification and validation ofproduction controller and software. System architecture,

plant model, bench capabilities and example test casesare presented. Finally, future development is given.

REFERENCES

1. Q. Zheng, W. Chung, K. Defore and A. Herman, AHardware-in-the-loop Test Bench for ProductionTransmission Controls Software Quality Validation,SAE Technical Paper, No. 2007-01-0502, 2007.


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CONTACT

Quan Zheng, Ph.D.Staff Research Engineer -Forward TransmissionControlsDelphi Powertrain SystemsTechnical Center Brighton12501 E. Grand River , Brighton, MI 48116 Phone: 810-494-4546Email: [email protected]

Asif HabeebullahSystems EngineerDelphi Powertrain SystemsTechnical Center Brighton12501 E. Grand River , Brighton, MI 48116 Email: [email protected]

Woowon ChungSenior Project Engineer - Forward TransmissionAlgorithmsDelphi Powertrain SystemsTechnical Center Brighton12501 E. Grand River , Brighton, MI 48116Phone: 810-494-4539Email: [email protected]

Andrew HermanStaff Engineer- Forward Transmission AlgorithmsDelphi Powertrain SystemsTechnical Center Brighton12501 E. Grand River , Brighton, MI 48116Phone: 810-494-4483Email: [email protected]

DEFINITIONS, ACRONYMS, ABBREVIATIONS

ECM : Engine Control Module

TCM: Transmission Control Module

PCM : Powertrain Control Module

AutoBOB : Automated Break-Out-Box

HAL: Hardware Abstraction Layer

HWIO: Hardware Input Output Layer

HIL: Hardware In the Loop

Matlab, Simulink, Stateflow, SimDriveline are RegisteredTrademarks of MathWorks, Inc.

TestDrive is a Registered Trademark of Opal-RTTechnologies.

INCA is a Registered Trademark of ETAS Inc.

A 6-Speed Automatic Transmission Plant Dynamics Model for HIL Test Bench

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