Improving an electric power assisted steering stability controller for ripple compensation

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Supervisor:
Dr. Kiss Bálint
Department of Control Engineering and Information Technology

Ripple is a harmonic oscillation at high motor torque in EPAS (Electric Power Assisted Steering) system. If the electronical motor rotates, because of several reasons, felharmonic torques appear in the accomplished motor torque, that are felt by the driver as torque oscillations during the process of driving. These disturbing torque oscillations have to be rejected as much as possible in the control loop in order to improve the steering feel, felt by the driver. My project is incorporating the ripple waves in the EPAS system model, and tuning the controller to reject the ripple torque as much as possible without disturbing the behavior of the original coloumn torque controller. In my thesis, first, I introduce the EPAS system, and the control theory of the original coloumn torque controller. Then, I present the phenomenon of ripple, and some related works. Next, I present the extension of the EPAS 2-dof model, the Simlunk modell used for simulations,

and the implemented ripple compensation. Finally, I test the implemented compensation with simulations and measurements, evaluate the measurements and make suggestions for possible further developments.

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