Masahiko Kurishige

A New Control Strategy to Reduce Steering Torque Without Perceptible Vibration for Vehicles Equipped With Electric Power Steering

This paper proposes a new electric, power steering control strategy, which significantly reduces the effort needed to change the steering direction of stationary vehicles. Previous attempts to reduce undesirable steering vibration have failed to reduce the steering torque because high-assist gains tend to produce oscillation or increase noise sensitivity Herein, to eliminate this vibration, a new control strategy was developed based on pinion angular velocity control using a newly developed observer based on a simplified steering model. Tests yielded excellent estimations of the pinion angular velocity, and this made it possible to eliminate vibration at all steering wheel rotation speeds. Experiments with a test vehicle confirmed significant steering torque reduction, over a wide range of steering wheel speeds, without vibration transmission to the driver The proposed control strategy allowed use of an assist gain more than three times higher than is conventional. Additionally, the proposed control strategy does not require supplemental sensors. [DOI: 10.1115/1.4001838]

Evaluation of EPS Control Strategy Using Driving Simulator for EPS

We have developed a driving simulator for Electric Power Steering (EPS), which can be used to evaluate steering maneuverability on low μ roads. The simulator calculates an 11 DOF (degrees of freedom) vehicle motion based on the steering wheel angle, the accelerator pedal position and the brake pedal position which are operated by the driver. A reaction torque corresponding to the alignment torque is applied to the steering shaft using motors. A 3D CG reproducing the view from the cockpit is displayed on a forward screen. The simulator also includes column type EPS, which generates the assist torque. Consequently, the driver feels the steering torque with good reality. The tire model we used is non-linear and it enables us to simulate the vehicle dynamics also on slippery roads. We compared driver behavior in vehicle and simulator tests and found the simulator could evaluate the relationship between steering maneuverability and EPS control strategy even when the road was slippery.