CVP Powertrain Analysis - Engine and Vehicle simulation · PDF fileIntegrate high fidelity...

U.S. ARMY TANK AUTOMOTIVE RESEARCH, DEVELOPMENT AND ENGINEERING CENTER

ENERGY ANALYSIS OF A POWERTRAIN AND CHASSIS INTEGRATED SIMULATION ON A MILITARY DUTY CYCLE

GT Suite User’s Conference: 9 November 2015

1

Denise M. Rizzo US Army TARDEC, Warren, MI

Periannan Kumaran Pratt & Miller Engineering, New Hudson, MI

Jonathan Zeman Gamma Technologies, Westmont, IL

UNCLASSIFIED: Distribution Statement A. Approved for public release.

Current Project

• Goal: Integrate high fidelity models of powertrain and vehicle dynamics in a co-simulation environment to understand the influence of chassis dynamics on fuel efficiency and energy losses.

• Background: To date, powertrain and vehicle dynamics models make simplified assumptions about their respective interaction. While this is reasonable under steady state conditions, the transient effects are unknown.

• Applications: Soft soil mobility, obstacle crossing such as step climb, steering loading under a non-straight maneuver such as on a duty cycle course, and fuel economy computation

• Potential Benefits: Understanding of interaction between powertrain and chassis Enables chassis-powertrain system design optimization Framework for chassis-powertrain system optimal control design Delivers an integrated chassis-powertrain system toolset for modeling & simulation

2 UNCLASSIFIED: Distribution Statement A. Approved for public release.

Vehicle Dynamic Simulation Environment

• In vehicle dynamics simulations, vehicle models with detailed subsystems such as engine/powertrain along with detailed chassis are rarely developed to study the integrated behavior of the combined full vehicle systems.

• MSC.Adams is a widely used Multi Body Dynamics Software currently used at TARDEC to model military vehicles and to perform vehicle dynamic simulations.

• The transmission model currently used in these vehicle models are simplified and lacks details in system dynamic behavior. – Typical use of look up tables for torque-speed map – Lacks automatic transmission (version 2012) – No representation of turbo behavior – Compromises the accuracy of transient performance of engine and

transmission


Chassis Vehicle Dynamics Model

• High Mobility Multi-Purpose Wheeled Vehicle (HMMWV) used by US Army

• Fully nonlinear model with rigid

bodies and lumped masses

• Parts are connected through idealized joints and/or force elements

• Linear springs and nonlinear dampers

• Pacejka 2002 tire model

• Manual transmission


Adams HMMWV Model

Powertrain Simulation Environment

• GT-SUITE is a multi physics platform currently used to model and study engine/transmissions/vehicle behavior at TARDEC 1-D simulations Has the ability to model transmission with much more detail than what is available in

MSC.Adams

• The full vehicle model available in GT-SUITE is a simplified reduced order model

Absence of lateral dynamics Absence of detailed tire models Absence of detailed roads and

terrains, which are important for military vehicle development

GT Simulation Environment Example 6 UNCLASSIFIED: Distribution Statement A. Approved for public release.

Powertrain Dynamics Model

• Transient map based system • Engine characterized by torque output map and fuel map • Additional dynamics for turbocharger lag • 4 speed automatic transmission with lock-up clutch • Gear ratio, mechanical efficiency and friction loss included

GT Drive HMMWV Model


Co-Simulation Framework

• Improved hardware and computing power have made this framework a viable solution

• Ability to integrate high fidelity subsystems with detailed full vehicle models

• Common methodology in integrated simulations

• Benefit from the individual strengths of each simulation tool

• Avoid development of duplicate subsystems and components


Integrated Model

GT-SUITE

Co-simulation

• Full vehicle chassis dynamic model developed in MSC.Adams/Car

• Powertrain dynamic subsystem model developed in GT-SUITE

• Use of Simulink as the coupling environment

• Both Adams/Car and GT-SUITE are coupled to Simulink through S-function blocks

• Simulink behaves as the “Master” of both GT-SUITE and Adams/Car

• Communication interval = 1.0 ms

• Subject the integrated vehicle model through various handling maneuvers and terrains of interest


Integration Validation: Acceleration Event

• Perform full load acceleration event to validate the model integration Standalone GT-SUITE Standalone Adams Integrated Model

• Use GT-SUITE full load acceleration results as the baseline. GT-

SUITE is currently used as the simulation tool for automotive performance evaluations

• Update the following parameters in standalone Adams model to match GT-SUITE point mass model Aggregate mass Unloaded tire radius Tire rolling resistance Aerodynamic drag force Gear ratio and shift RPM




• Shift RPM Comparison: Model Comparison – RPM limits for the integrated model are same as GT-SUITE

standalone – Adams/Car standalone model uses single shift RPM for all gears

Integration Validation: Conclusions

• Integrated model speed profile from the co-simulation correlates reasonably well with standalone GT-SUITE model speed profile

• Top speed difference < 1.0mph

• Differences between the standalone GT-SUITE simulation and integrated

simulation results could be attributed to – Tire model differences – Aero dynamic model difference – More details in the integrated vehicle model compared to standalone

GT-SUITE point mass vehicle model

• Standalone Adams simulation speed saturates early due to engine revolution limit in the powertrain subsystem

• Integrated model is well suited to perform additional correlation studies


Additional Simulations

• To demonstrate the advantages of the integrated co-simulation environment over the standalone GT-SUITE and Adams dynamic models

• Events selected – Typical military vehicle requirements 18 inch step climb 60% graded road


18 inch Step Climb

• Determines the required torque to climb a step of specified height

• Performed at WOT

• Starts from standstill position

• Not supported in standalone powertrain dynamic model

• Transfer case at low position for increased torque


18 inch Step Climb: Vehicle Speed and Torque

Simulation Peak Torque (Normalized)

Adams Standalone WOT 1.0

Integrated WOT 0.45


18 inch Step Climb: Conclusions

• Initial speed drop in the standalone Adams model is due to vehicle bouncing off the step before climbing

• The high torques in standalone Adams model results are due to clutch slippage at low engine RPM

• Integrated model speed controller takes longer to settle down to target

speed. This may indicate a need to tune the controller to better follow the target speed at low speeds

• The ability to evaluate a step climb transiently in a simulation environment has now been realized with the integrated model

• The integrated model is more suited to evaluate torque requirements compared to the standalone Adams model for step climb simulations


60% Graded Road

18

• Determines the ability of the vehicle to climb specified inclination at a constant speed

• Performed at low speed

• Starts from a flat road

• Transfer case at low position for increased torque


60% Graded Road: Vehicle Speed


60% Graded Road: Left Front Halfshaft Torque

20


60% Graded Road: Conclusions

21

• The 60% grade maneuver with vehicle dynamics fully

integrated has been shown, however steady state speed control at low speed was elusive and further investigation is required

• Standalone Adams model shows a speed drop when the vehicle was coming off the graded road. This in turn resulted in clutch slippage as seen in the torque results


Fuel Economy and Energy Loss

22

• Current fuel economy studies are performed in standalone powertrain environment with the reduced DOF vehicle model

• Studies are constrained to straight line simulations

• Appropriate for courses with minimal turns and not much influence from lateral dynamics

• Cross country and secondary road have very steep elevation changes and sharp turns

• Need to understand the influence of lateral dynamics on energy loss related to these courses


Influence of Lateral Dynamics on Energy Loss

23

• Perform a straight line simulation for the length of Churchville profile on a flat road

• Repeat the simulation with Churchville profile on a flat road.

Churchville road is considered a cross country terrain



24

• Lateral dynamics does have an impact on the fuel economy mainly due to tire/road interaction.

• Fuel economy for Churchville profile is 30% less than straight line.

• Vehicle speed has an influence on the fuel economy. Higher speeds

resulted in larger difference in fuel economy.

Road Profile Fuel Economy (normalized)

Straight Line 1.00

Churchville 0.70



25

• Noticeable speed drop during turns

• Increased power requirement to maintain required speed



Increased longitudinal tire forces resulting from increased lateral tire forces


Influence of Lateral dynamics on Energy Loss

27

• Tires are subjected to simultaneous lateral and longitudinal slip conditions in a turn

• Application of lateral slip at a given slip ratio tend to reduce the generated longitudinal forces resulting in reduced speed

• More power is required bring the

vehicle back to target speed

Reference : Thomas D. Gillespie “Fundamentals of vehicle dynamics”, 1992


Analysis of Energy Losses

28

• Focus energy loss analysis on following areas – Engine and Accessories – Transmission – Driveline

• Engine and Accessories losses

– Accessories • Alternator and Fan

– Exhaust • Indicates the fuel burned


Analysis of Energy Losses

29

• Transmission losses: – Larger losses in the transmission

and torque converter for the Churchville course.

– Torque converter losses are especially apparent due to the longer time in the inefficient unlocked position.

• Driveline losses:

– Brakes are not applied during the event

– Larger losses are shown in the driveline components for the Churchville course.


Road Test Comparison on Churchville-B

30

• Simulate the integrated model on actual Churchville-B profile

• Churchville-B profile contains steep grades

• Road coordinates were measured by profilometer in order to quantify the road roughness

• Create MSC.Adams road profile from measured data • Model Updates

– Aerodynamic drag coefficient – GVW – Unloaded tire radius – Tire rolling resistance – Power loss

• Event performed at a constant speed


Road Test Comparison on Churchville-B

31

• Fuel economy value compared very well with the road test results

• Integrated model captured all of the energy losses

Model Configuration Fuel Economy(mpg) - normalized

Road Test 1.00

Simulation 0.99


Summary and Conclusions

32

• A transient map based powertrain dynamic model built in GT-SUITE was successfully coupled with a detailed chassis dynamic model in MSC.Adams/Car with MATLAB/Simulink as an intermediate coupler

• Specific simulations pertaining to military vehicles were performed to confirm that the integrated model will be successful in these simulations

• A detailed study was performed to understand the influence of lateral

dynamics on fuel economy and energy loss

• A study comparing the fuel economy in integrated vehicle model to road test on Churchville terrain resulted in good correlation providing high confidence in the integrated vehicle model and co-simulation frame work.

• Simulations such as step climb and soft soil (not presented here) provides an early understanding of power and mobility requirements that was not possible in the past


Future Work

33

• Use FMI framework or direct GT/Adams co-simulation and eliminate the

intermediate Simulink layer

• Replace the constant speed with limit handling which mimics the real world driving scenario


Disclaimer

34

Reference herein to any specific commercial company, product, process, or service by trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or the Department of the Army (DoA). The opinions of the authors expressed herein do not necessarily state or reflect those of the United States Government or the DoA, and shall not be used for advertising or product endorsement purposes.


Churchville-B Animation

35


CVP Powertrain Analysis - Engine and Vehicle simulation · PDF fileIntegrate high fidelity...

Documents

Transcript of CVP Powertrain Analysis - Engine and Vehicle simulation · PDF fileIntegrate high fidelity...