Bilateral control of vehicle Steer-by-Wire system with variable gear-ratio

For the Steer-by-Wire system, it is necessary to develop advanced control systems and to design advanced architectures. In this paper, a new SBW control system with the consideration of the variable gear-ratio is presented. This SBW system includes two control loops, which are called upper control loop and lower control loop, respectively, 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.