Real-time non-linear vehicle dynamics preview model

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Real-time non-linear vehicle dynamics preview model

Bernard Linström

5 November 2013

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Introduction

Country Percentage of Total

Accidents

Percentage of Fatal

Accidents

U.S.A. 2.3% 33%

South Africa 24% 25%

• Sport Utility Vehicles (SUVs) are designed for smooth as

well as rough off-road terrains.

• SUVs have a higher ride height and softer suspension to

accommodate for all types of terrains.

• SUVs are more prone to rollover than any other type of

vehicle.

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Control System Delay

Aim: • Develop a real-time non-linear vehicle preview model

• Implement the model to improve the delay of an existing

strategy

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Vehicle Preview Model Assumptions for duration of preview time:

• Constant longitudinal speed

• No aerodynamic forces

• Only lateral load transfer is considered

• Fixed centre of gravity position

• Constant steer rate

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Vehicle Preview Model • Based on the current vehicle state (inputs) the preview model predicts the

future vehicle state (outputs) at a specified preview time

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VPM Explained

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Runge-Kutta Solver

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Differential Equations

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Differential Equations

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Experimental Validation

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• Switches between “handling” and

“ride comfort” mode

• Controlled by running root mean

square (RRMS) strategy

• With a RRMS duration of 1s there is a

switching delay of 300ms

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Model Performance Parameter

Side-Slip Angle

Yaw Rate

Roll Rate

Roll Angle

Lateral Acceleration

Preview Time Solving Time Solving Frequency

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Dynamic Handling Results

Strategy Time in Handling RMS of roll angle Percentage Improvement

RRMS

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DLC Results

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City Results

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Highway Results

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Conclusion

• Preview model successfully developed and validated

• Model solves fast enough with good accuracy

• Used in combination with Running RMS improves handling

• No spurious switching of suspension

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Future Work • Improve the suspension friction estimations

• Create lookup tables for suspension forces to improve solving

time

• Real-time centre of gravity estimation

• Apply the preview model to other vehicle control methods

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Thank you