Year

2013

Degree Name

Master of Engineering - Research

Department

School of Electrical, Computer and Telecommunications Engineering

Abstract

Recent research shows that the Steer-by-Wire (SBW) technology has been applied in the flight area, and it could be used in motor vehicles in the near future. The vehicle SBW system has been recently proposed to replace the traditional vehicle steering system by moving the mechanical linkage between the steering wheel and the front wheel. It has many advantages, including providing vehicle design freedom and improving vehicle handling. Two of the most challenging problems faced by the vehicle SBW system are 1) how to establish the effective force feedback between driver and the wheel so that the driver’s steering signal can be accurately followed by the wheels so the road condition can be felt by the driver, and 2) how to design and choose the available hardware so that a reliable transmission with high speed can guarantee the reliability and stability of the SBW system. It is therefore necessary to develop advanced SBW control systems and to design advanced architectures for the SBW system. In this thesis, a new SBW control system with the consideration of the variable gear-ratio is presented and the hardware in-the-loop is designed. This SBW system includes two control loops, which are called upper control loop and lower control loop, to achieve bilateral control. The force feedback motor, which is installed with the steering wheel, and the steering motor, which is installed in the front wheel, are adopted in these two loops, and two PID controllers are designed for them, respectively, so that steering signal and road feeling can be tracked. To improve vehicle handling performance in terms of the change of velocity, the reactive torque map and variable gear-ratio are further considered in the two loops. The practical constraints on the angles of the steering wheel and the front wheel are also considered in the design of the SBW system. A simulation model is established to validate the effectiveness of the developed control system. The simulation results show that the system is stable and both the desired steering wheel angle and the tyre-road contact can be well reflected. The experimental platform has also been established in this thesis, which uses the HILINK board from Zeltom Company as the Electronic Control Unit (ECU). The experiment shows that the front wheel can track the steering wheel’s position accurately and the force feedback can be achieved for the operator. The Hall- Effect current sensors are also used experimentally to detect the currents from the steering motor and the force feedback motor. Then the force feedback can be controlled with the PID controller.

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Unless otherwise indicated, the views expressed in this thesis are those of the author and do not necessarily represent the views of the University of Wollongong.