Bernard Linstrom, Vehicle Dynamics Group, University of Pretoria. Paper 79742_0

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Real-time non-linear vehicle dynamics
preview model
Bernard Linström
5 November 2013
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Introduction
• 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.
Country
Percentage of Total
Accidents
Percentage of Fatal
Accidents
U.S.A.
2.3%
33%
South Africa
24%
25%
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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
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