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Velocity_Estimation_w_Nonlinear_Observer
1. 1
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Longitudinal and Lateral VehicleLongitudinal and Lateral Vehicle
Velocity Estimation with aVelocity Estimation with a
Nonlinear ObserverNonlinear Observer
An Example of Using TruckSim in Developing
Vehicle Control Algorithms
Ragnar Ledesma
CVS Advanced Engineering
2. 2
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Background
• Current dynamic vehicle control systems include the
following sensors:
• Wheel rotation rates, steering angle, lateral and longitudinal
accelerometers, yaw rate
• Advanced control systems require time-varying
parameters or states that can not be measured directly:
• Vehicle velocity, vehicle slip angle, spindle loads, friction
coefficient, roll angles, etc.
• Need estimators (state observers) to provide reliable
real-time estimates, subject to:
• Model uncertainty, external disturbances, uncertainty in
measurements, changes in operating conditions
3. 3
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Overview: Vehicle Velocity / Side Slip Estimation
Variables to estimate:
• Longitudinal velocity vx
• Lateral velocity vy
• (Vehicle side slip angle β )
Secondary variables:
• Maximum friction coefficient µH
• Road bank angle
Sensors
• Lateral/longitudinal acceleration
ay/ax
• yaw rate r
• wheel speed ωi and steering angle
4. 4
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Vehicle Model for Nonlinear Observer
• Simplified vehicle model:
• Measurement variables:
• Steering angles
• Wheel speeds
• Yaw rate
• Accelerations
5. 5
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Proposed Nonlinear Observer
• Tire-ground friction model required
• Restrictions are imposed on observer gains to assure
convergence of the estimates to the actual states
7. 7
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Example 1: Sinusoidal Steering
vehicle side slip angle
lateral speed
longitudinal speed
8. 8
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Example 2: Constant Radius Test on Low
Friction Surface
9. 9
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Example 2: Constant Radius Test on Low
Friction Surface
vehicle side slip angle
lateral speed
longitudinal speed
11. 11
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Example 3: Braking in a Turn
vehicle side slip angle
lateral speed
longitudinal speed
12. 12
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Example 4: Split-µ Braking (with ABS)
13. 13
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Example 4: Split-µ Braking (with ABS)
longitudinal speed
lateral speed
vehicle side slip angle
wheel speeds
14. 14
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Example 5: Double Lane Change at 80 Km/Hr
15. 15
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Example 5: Double Lane Change at 80 Km/Hr
longitudinal speed
lateral speed
vehicle side slip angle
yaw rate
16. 16
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Example 6: Double Lane Change on a Split-µ
Surface
17. 17
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Example 6: Double Lane Change on a Split-µ
Surface
longitudinal speed
lateral speed
vehicle side slip angle
yaw rate
18. 18
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Next Step: Adaptive Nonlinear Observer
• Nonlinear observer relies on tire-ground friction model
• Friction model is characterized by “maximum friction
coefficient”, µΗ
• Difficult to measure ground friction
• Need on-line adaptation model for µΗ