线控转向系统的自适应高阶滑模控制

车辆线控转向(steer-by-wire,SbW)系统存在摩擦力矩及回正力矩等不确定动态特性,难以实现精确建模与有效控制.为此,提出一种基于自适应模糊逻辑系统的自适应高阶滑模(adaptive higher-order sliding mode, AHOSM)方法,实现SbW系统的有效控制.首先,通过自适应模糊逻辑系统逼近SbW系统的未知动态,使控制器的设计不再需要摩擦力矩及回正力矩的动力学模型;其次,采用高阶滑模和自适应增益技术削弱传统滑模控制器存在的抖振现象;再次,通过构造Lyapunov函数设计增益自适应律补偿逼近误差和系统不确定项对控制精度的影响,该方案不需要系统不确定项的界已知,且能够避免增益过估计现象;最后,通过稳定性分析证明该控制器可以在有限时间内建立实际滑动模态,数字仿真和硬件在环实验进一步验证了该控制方法的有效性和优越性.

Adaptive higher-order sliding mode control for SbW system

The uncertain dynamic model of friction torque and self-aligning torque in the steer-by-wire(SbW) system makes it difficult to achieve accurate modeling and effective control. Therefore, an adaptive higher-order sliding mode (AHOSM) control method based on the adaptive fuzzy logic system(FLS) is proposed to control the SbW system effectively. Firstly, the adaptive FLS is employed to approximate the unknown dynamics of the SbW system, so that the dynamic models of the friction torque and self-aligning torque are no longer needed in the design of the controller. Then, the higher-order sliding mode and dynamical gain technique are introduced to reduce chattering in traditional sliding mode controllers. In addition, the gain adaptive law obtained from the Lyapunov function is adopted to compensate the influence of approximation error and system uncertainties on the control precision, which does not require priori knowledge of the bounds of the uncertainties and can avoid the gain-overestimation phenomenon. Finally, the stability analysis shows that the real sliding mode can be established in finite time. Simulation results and hardware-in-the-loop(HIL) experiments further demonstrate the effectiveness and superiority of the proposed control strategy.