Simulation for Function Developement - gtisoft.com · the risks: wrong initial assumptions have...

SIMULATION FOR FUNCTION DEVELOPMENTGT POWER

“IN THE LOOP”

GT Power "in the loop"

Bosch Engineering | BEG France | 17/05/2017

© Robert Bosch GmbH 2017. All rights reserved, also regarding any disposal, exploitation, reproduction, editing, distribution, as well as in the event of applications for industrial property rights.2

Usage of GT Power during the SW development process

Content

1. Introduction

1. What are the reasons to use GT Power ?

2. How was GT Power used ?

2. Proceeding

1. System investigation

2. Concept development

3. SW validation with co-simulation

4. Engine calibration (Three Pressure Analysis - TPA)

3. Conclusion and perspectives



Introduction




Introduction

Benefits:

development time: decoupling of engine and software development cycles

using GT Power for the first phases before “final confirmation” on engine.

development cost: GT Power less expensive than testbench …

the risks: wrong initial assumptions have less impact on project schedule

In the other hand: time and cost to build up the GT model !

SW development cycle

Engine development cycle

Engine ready

for testing

Engine ready

for testing




Introduction

Simulation with GT Power can be used instead of engine testbench for:

1. System investigation: analyze the system behaviour and physical tendencies

2. SW development:

- Concept phase: evaluate the system modelling / tools: MAPFIT or MOCA

- Implementation phase: SW validation via co-simulation / tools: Ascet and INTECRIO

3. SW calibration:

- Get unmeasurable data at the testbench (residual gas fraction, air speed ...) / TPA

- Reduce the testbench measurement points (DoE – Design Of Experiment)

Tradeoff GT model development cost / benefits

• From investigation phase to SW calibration, the use of simulation tools depends

on the model accuracy !

• For one single project, expensive / For many projects (reuse), high potential



Proceeding

VCR : Variable

Compression Ratio




Step 1: System investigation

System: Air Path

Topic: Charge determination

Bosch develops a model based engine

charge determination. This model covers

the usual range of engine operation.

However, with new technologies, the air

path variability increases, and the model

implemented in ECU software has to be

extended to these new degrees of freedom

and operation area.


How does the system behave ?

GT Power is used to get a better feeling of

the charge behaviour and give some input

for the concept development phase.

VVT : Variable Valve Timing

Variable Intake

Geometry : flaps,

trumpets, etc.

VVL : Variable Valve Lift





What is a charge determination model ?

Bosch ECU software implements a charge determination physical model

• Calculation of the fuel quantity to be injected

• Estimation of the engine torque

• Control of the charge and the boost pressure

• Transitions between injection modes, and to CDA (Cylinder DeActivation)

Question: How do new technologies impact the engine charge ?

Intake VVT position

Intake manifold pressure (Throttle and Wastegate)

VVL, VCR, swirl flaps, etc.

Exhaust VVT position

Exhaust manifold pressure

Modelled

engine

charge

Charge

determination





Analysis of the

valves behaviour

Variation of the

cylinder air filling

The GT Power simulations help to understand the system behaviour.

This knowledge is necessary to define a new concept, a new model.

GT Power simulations with variation of the

intake valve timing and other parameters




Step 2: Concept validation

Objective: to check whether the new SW model of

the charge determination is good or not, a Design of

Experiments (DoE) has been simulated on GT Power

to collect some points.

DoE: >2000 operating points, >4 degrees of freedom

• Engine speed

• Intake manifold pressure

• Intake and exhaust valve timing

• Valve lift, variable compression ratio, swirl flaps, etc.

Question: How to compare the charge model from the

ECU software to the measured one in GT simulations ?




Step 2: Concept validation

Simulation of different

engine operation points

Model design

Engine Model

GT Power

Calibration tool

MAPFIT(Bosch internal tool)

Charge Model

Ascet(ETAS tool)

Optimization tool, used to

calibrate the maps and curves

SW design and

code generation

Simulation data

A first design of the charge determination model is made in Ascet.

The model algorithm is used by an optimization tool to calibrate the maps

and curves based on the simulation results from GT Power.

The correlation results, and the analysis of the shape of curves and maps,

inform whether the concept is representative enough of the system or not.

After some recursion, the model is improved, ready for implementation.




Step 3: SW validation

After the concept validation, the SW functions are implemented in Ascet

to generate embedded code.

In order to save some time at the testbench, it is suitable to test the

generated code and detect implementation bugs GT Power can be

coupled to the SW functions in a co-simulation environment.

Step by step validation of model physical values.

SensorsEstimated charge

Desired charge

Measured charge

Ascet

ECU SW functionsGT Power

System model

Charge model

Charge

controller

Engine model

Validation of the

charge model

Validation of the

charge controller

Actuators

setpoints




Step 3: SW validation

With co-simulation, stationary and transient phases are analyzed

Interface (signals)

GT Power / Ascet Environment that synchronizes the SW functions

simulation and GT Power (via Simulink)SW functions

SIMULINK

Engine

model

INTECRIOASCET

Combination of two co-simulation environments

• Coupling Ascet / Simulink via Intecrio (master)

• Coupling Simulink / GT Power (slave)

Simulink used as interface between the ECU

functions (Ascet) and the engine (GT Power)

Intake manifold pressure(testbench measure)




Step 4: Three Pressure Analysis (TPA)

Target: Use testbench measurements to validate the simulation model

and calculate unmeasurable values with the GT Power engine model.

Cylinder pressure(testbench measure)

Exhaust manifold pressure(testbench measure)




Step 4: TPA Results

Valv

e L

ift

[mm

]

0

2

4

6

8

10

12

14Inlet

Exhaust

Fitted_Measured

Simulated

Valv

e L

ift

[mm

]

02468101214

Cylin

der

Pre

ssure

Cylin

der-

01

[bar]

010203040506070

Cyl1LHV 0.98

CA [deg]

-100-90 -80 -70 -60 -50 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80 90 100

Cylin

der

Pre

ssure

Cylin

der-

04

[bar]

010203040506070

Cyl4LHV 0.92

Valv

e L

ift

[mm

]

02468101214

Cylin

der

Pre

ssure

Cylin

der-

01

[bar]

0

10

20

30

40

50

60

70

CA [deg]

-400 -300 -200 -100 0 100 200 300 400

Cyl1LHV 0.98

Cylinder 1

Cylinder 4

TPA has been done for

over 2000 operating points

Accuracy of most points

has been good enough to

use the results

New data like residual gas

portion, better cylinder

pressure indication, etc.,

are used for the engine

calibration



Conclusion and Perspectives




Conclusion

GT Power can be used all along the software development cycle.

This proceeding allows to decouple the software development milestones

from the hardware (engine) development ones.

The two questions helping to decide to use GT Power or not:

• How accurate does the GT model need to be ?

• What is the related development cost compared to the benefits ?

In the perspective of the study, GT Power helped to work on different

topics, improving the SW maturity before the testbench sessions:

• The charge determination model

• The charge control using innovative technologies like VVL, VCR, etc.




Perspectives

Enhanced ECU software maximizes the potential of new engine

technologies: CO2 reduction, performance, dynamic

• GT Power is a relevant tool to develop such enhanced features

Reducing project cost by investing in system modelling

• Hardware test facilities are expensive

• No engine failure risks in simulation

• The more accurate the model is, the more development steps it could support

o For the ECU charge determination evaluation, the engine geometry is enough

o For BSFC optimization, a good combustion model is necessary

• In the end, the real system is the final judge… but could be less and less

necessary for the software development purposes !

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