Abstract
In view of the safety problems of the single-channel hydraulic steering system which widely used in the multi-axle cooperative steering system of super autonomous rapid transit (SRT), a multi-axle cooperative steering system based on redundant steering-by-wire is developed. Firstly, the real-time task and system status judgment are placed in the master station of the steering controller for processing, fully ensuring the real-time performance of the task. At the same time, the slave station is set to synchronously process the task and judge the status. The two channels of the steering system work simultaneously, and when one channel fails, the other channel can take over the system in real time. This redundancy strategy ensures the safety of the vehicle. Secondly, a multi-axle cooperative steering control algorithm for SRT is proposed. The steering control system consists of a feedforward and an additional feedback control. The feedforward control is subdivided into three steps. In a first step the angle of axle 2 is calculated with dynamic model of first module and the driven path is estimated. This path is used in a second step to calculate the desired kinematics and finally the desired kinematics are transformed into the desired lateral forces by means of the inverse vehicle model. An additional nonlinear feedback controller stabilizes the tracking behavior on vehicle status level. By establishing the kinematics model of SRT and adopting the PID control of yaw angle deviation, the control error of the vehicle is dynamically compensated, and the control accuracy and robustness of the SRT multi-axle cooperative control algorithm are ensured. The steering system has been applied to the three-module & six-axle SRT, with the functions of steering-by-wire and track following, and can achieve the minimum turning radius of 15 m, and its good control accuracy and stability are verified by experiments.
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