Download - Velocity_Estimation_w_Nonlinear_Observer
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Longitudinal and Lateral Vehicle Longitudinal and Lateral Vehicle Velocity Estimation with aVelocity Estimation with a
Nonlinear ObserverNonlinear Observer
An Example of Using TruckSim in Developing Vehicle Control Algorithms
Ragnar LedesmaCVS Advanced Engineering
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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
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Overview: Vehicle Velocity / Side Slip Estimation
Variables to estimate:• Longitudinal velocity vx
• Lateral velocity vy
• (Vehicle side slip angle
Secondary variables:• Maximum friction coefficient H
• Road bank angle
Sensors• Lateral/longitudinal acceleration ay/ax
• yaw rate r• wheel speed i and steering angle i
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Vehicle Model for Nonlinear Observer• Simplified vehicle model:
• Measurement variables:• Steering angles
• Wheel speeds
• Yaw rate
• Accelerations
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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
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Example 1: Sinusoidal Steering
vehicle side slip angle
lateral speed
longitudinal speed
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Example 2: Constant Radius Test on Low Friction Surface
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Example 2: Constant Radius Test on Low Friction Surface
vehicle side slip angle
lateral speed
longitudinal speed
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Example 3: Braking in a Turn
vehicle side slip angle
lateral speed
longitudinal speed
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Example 4: Split- Braking (with ABS)
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Example 4: Split- Braking (with ABS)
longitudinal speed
lateral speed
vehicle side slip angle
wheel speeds
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Example 5: Double Lane Change at 80 Km/Hr
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Example 5: Double Lane Change at 80 Km/Hr
longitudinal speed
lateral speed
vehicle side slip angle
yaw rate
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Example 6: Double Lane Change on a Split- Surface
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Example 6: Double Lane Change on a Split- Surface
longitudinal speed
lateral speed
vehicle side slip angle
yaw rate
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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”,
• Difficult to measure ground friction
• Need on-line adaptation model for