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Velocity_Estimation_w_Nonlinear_Observer
This document presents a nonlinear observer approach for estimating vehicle longitudinal and lateral velocity. It describes sensors used and a simplified vehicle model. A nonlinear observer is proposed using a tire-ground friction model. Examples are shown applying the observer to different vehicle maneuvers, like sinusoidal steering, braking in a turn, and lane changes. The next step is to develop an adaptive nonlinear observer that can estimate the maximum friction coefficient online without prior knowledge of road conditions.
Velocity_Estimation_w_Nonlinear_Observer
- 1. 1 Edit Presentation Titleon Slide Master Edit Date on Slide Master 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 Edit Presentation Titleon Slide Master Edit Date on Slide Master 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 Edit Presentation Titleon Slide Master Edit Date on Slide Master 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 Edit Presentation Titleon Slide Master Edit Date on Slide Master Vehicle Model for Nonlinear Observer • Simplified vehicle model: • Measurement variables: • Steering angles • Wheel speeds • Yaw rate • Accelerations
- 5. 5 Edit Presentation Titleon Slide Master Edit Date on Slide Master Proposed Nonlinear Observer • Tire-ground friction model required • Restrictions are imposed on observer gains to assure convergence of the estimates to the actual states
- 6. 6 Edit Presentation Titleon Slide Master Edit Date on Slide Master Example 1: Sinusoidal Steering
- 7. 7 Edit Presentation Titleon Slide Master Edit Date on Slide Master Example 1: Sinusoidal Steering vehicle side slip angle lateral speed longitudinal speed
- 8. 8 Edit Presentation Titleon Slide Master Edit Date on Slide Master Example 2: Constant Radius Test on Low Friction Surface
- 9. 9 Edit Presentation Titleon Slide Master Edit Date on Slide Master Example 2: Constant Radius Test on Low Friction Surface vehicle side slip angle lateral speed longitudinal speed
- 10. 10 Edit Presentation Titleon Slide Master Edit Date on Slide Master Example 3: Braking in a Turn
- 11. 11 Edit Presentation Titleon Slide Master Edit Date on Slide Master Example 3: Braking in a Turn vehicle side slip angle lateral speed longitudinal speed
- 12. 12 Edit Presentation Titleon Slide Master Edit Date on Slide Master Example 4: Split-µ Braking (with ABS)
- 13. 13 Edit Presentation Titleon Slide Master Edit Date on Slide Master Example 4: Split-µ Braking (with ABS) longitudinal speed lateral speed vehicle side slip angle wheel speeds
- 14. 14 Edit Presentation Titleon Slide Master Edit Date on Slide Master Example 5: Double Lane Change at 80 Km/Hr
- 15. 15 Edit Presentation Titleon Slide Master Edit Date on Slide Master Example 5: Double Lane Change at 80 Km/Hr longitudinal speed lateral speed vehicle side slip angle yaw rate
- 16. 16 Edit Presentation Titleon Slide Master Edit Date on Slide Master Example 6: Double Lane Change on a Split-µ Surface
- 17. 17 Edit Presentation Titleon Slide Master Edit Date on Slide Master Example 6: Double Lane Change on a Split-µ Surface longitudinal speed lateral speed vehicle side slip angle yaw rate
- 18. 18 Edit Presentation Titleon Slide Master Edit Date on Slide Master 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