A Nonlinear Tracking Controller for Haptic Interface Steer-by-Wire Systems

Problem Motivation

In recent years, due to scarcity in fossil fuel and growing environmental awareness research focus in the automotive industry has been shifting towards hybrid or electric vehicles and steer-by-wire systems. Power limitations in the hybrid vehicles mandate efficient technologies, the engine may be cycled on or off, making hydraulic steering systems unfeasible. Hence the need for steer-by-wire systems in vehicles has gained importance.

Force feedback is one of the highest rated inputs to the driver after vision. While force feedback provides the driver with an invaluable input, excessive feedback results in the need for larger driver forces to steer the system. Hence, it is essential for the control strategy to ensure that the "road feel" provided by the force feedback can be adjusted to provide a comfortable driving environment.

Steer-by-wire systems provide improved vehicle response, and the ability to use additional driver input devices, improving the flexibility in vehicle design.

Haptic Interface Goals

  Ensure accurate reproduction of driver steering angle commands at the wheel.

  Use drive motor.

  Provide force feedback to the driver.

  Use feedback motor.

  Displacement of the driver input device should be governed by a set of target dynamics.

  Tunable dynamics that permit various choices of “road feel”.
  Ability to scale inputs.

  Adaptive techniques to compensate for unknown system parameters.

  Elimination of force measurement.

  Identification of tire/road interface forces.

System Description

Simulation Results

Fig. 1 Target system response, Standard steering system response

Fig. 2 Tracking errors

Fig. 3 Torque observation errors

Experimental Setup

References
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