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This paper presents a new control strategy for Electric Power Steering (EPS) to reduce steering vibration associated with disturbance from road wheels. Disturbance from road wheels may cause undesirable steering vibration if drivers run on an unpaved road or road wheels are not well balanced. For drivers, road information generated by alignment torque is essential to steer a vehicle easily. However drivers are unpleasant for steering vibration associated with disturbance from road wheels. In the steering system, both of them are transmitted to the driver through steering mechanism. We have developed a new EPS control strategy that reduces steering vibration associated with disturbance from road wheels without influencing road information generated by alignment torque considering the difference in frequency. The new EPS controller is constructed based on damping for specified frequency using the motor angular- velocity.

In this paper, an application of variable structure systems (VSS)(1) to electromagnetic-clutch (EMC) control for starting vehicles is studied. Using a conventional open-loop controller, there is the case that changes in EMC dynamics lead to undesirable vehicle vibration though it may be rare. First, to overcome the above problem, we developed a control strategy based on VSS. The VSS control is robust with respect to changes in EMC dynamics. Second, we discussed the chattering problem of this controller in application to actual vehicle control. Finally, we confirmed the validity of the proposed control strategy and the appropriateness of the conditions for reduced chattering derived by simulation. The validity of this control strategy was also confirmed experimentally.

This paper proposes a new Electric Power Steering (EPS) control strategy that enables remarkable progress on steering maneuverability for stationary vehicles. Using a conventional controller, undesirable steering vibration prevented us from reducing steering torque. To eliminate this vibration, we developed a new control strategy based on damping for specified frequency using a motor angular-velocity estimator. We experimented with this proposed control algorithm using a test vehicle and confirmed that it enables reduced steering torque without any perceived vibration for drivers. Concerning the gradient of the assist-map, the proposed control strategy enabled more than three times higher compared with that of the same type vehicles on the market as the test vehicle. This proposed control strategy requires only the torque sensor signal, supply voltage and current to the motor, which are used in the conventional EPS systems, so no supplemental sensors are required.