Active tracking controller of steerbywire system by rack force estimation
                                                               ZHANG Mingming, WU Xiaodong, XU Min
                                (School of Mechanical Engineering, Shanghai Jiaotong University, Shanghai 200240, China)

Abstract: Aiming at the precise tracking control of steerbywire (SBW) system in intelligent vehicles, dynamic modelling of SBW system, external disturbance analysis and estimated compensation and tracking motion controller design were researched. An active tracking controller specified for SBW system was proposed, and a rack force estimator based on an extended disturbance observer was utilized for estimation and compensation, and finally combined with a robust sliding mode controller to obtain the whole design of the active tracking controller of the SBW system. Meanwhile, based on ISO standards for vehicle steering performance test, experiments with different road conditions were done to validate the proposed algorithms. The results indicate that the rack force can be estimated online effectively, and the tracking performance of the steerbywire system equipped by the active tracking controller is improved a lot, and the effects stand out especially in large velocity and large load working condition.

Key words: steer by wire (SBW); tracking controller; rack force estimation; feedforward compensation