Sumio Sugita

Cancellation of Unnatural Reaction Torque in Variable-Gear-Ratio

Variable-gear-ratio steering, also known as active steering, is an advanced steering technology which enhances the driver’s comfort and vehicle operability. However, one big problem, namely the unnatural reaction torque created by the variable actuator, restricts the further practical-use of the variable-gear-ratio steering. This paper proposes a control method to cancel the unnatural torque using a simple concept called friction relocation. Effectiveness of the method is experimentally confirmed using a hardware-in-the-loop simulator.

Robust fixed-structure controller design of electric power steering systems

This paper presents a two-degree-of-freedom controller structure for electric power steering systems. The controller is synthesized using a hybrid linear matrix inequality and genetic algorithms optimization. Robust stability is studied for both sector-bounded and passive uncertainties resulting in a system of linear matrix inequalities (LMIs) and a linear matrix equality (LME). This system of LMIs/LME defines a guaranteed cost H2 optimization subject to an H∞-norm performance as well as a strict-positive-real constraints. Experimental results involving human-in-the-loop show that the control design did satisfy the criteria for robust control and performance. Furthermore, the ease-of-tuning of the proposed controller structure makes it possible to improve the steering “feel”.

Control Design for Cancellation of Unnatural Reaction Torque and Vibrations in Variable-Gear-Ratio Steering System

Variable-gear-ratio steering is an advanced feature in automotive vehicles. As the name suggest, it changes the steering gear ratio depending on the speed of the vehicle. This feature can simplify steering for the driver, which leads to various advantages, such as improved vehicle comfort, stability, and safety. One serious problem, however, is that the variable-gear-ratio system generates unnatural torque to the driver whenever the variable-gear-ratio control is activated. Such unnatural torque includes both low-frequency and steering-speed-dependent components. This paper proposes a control method to cancel this unnatural torque. We address the problem by using a tire sensor and a set of feedback and feedforward algorithms. Effectiveness of the proposed method is experimentally verified using a hardware-in-the-loop experimental setup. Stability and robustness under model uncertainties are evaluated.Copyright