针对四辊卷板机侧辊位移跟踪控制存在负载变化、参数摄动和未建模动态等不确定性问题，提出一种基于非线性扰动观测器的自适应滑模控制策略。采用非线性扰动观测器在线获取并补偿等效扰动；针对引入非线性扰动观测器后的系统，采用反步法设计自适应滑模控制器，利用自适应律动态补偿扰动观测误差，以降低滑模控制器的切换增益。该设计方法放宽了滑模切换增益对系统不确定性上界的先验性要求，降低了外界干扰和系统不确定性对侧辊位移跟踪性能的影响。同时，采用李雅普洛夫方法证明了侧辊位移跟踪闭环控制系统的稳定性。根据工程实际参数进行仿真，结果表明，该控制策略对系统的不确定性，特别是负载变化具有较强的鲁棒性，可以满足侧辊位移快速、精确跟踪的要求。
An adaptive sliding mode control strategy based on nonlinear disturbance observer (NDO) is proposed for the displacement tracking control of the side roller of four roller bending machine, according to the uncertain problems such as varying load, parameter perturbation and un-modeled dynamics. The nonlinear disturbance observer is introduced to obtain and compensate the equivalent disturbance online. Subsequently, the backstepping design method is adopted to design an adaptive sliding mode controller (ASMC) for the system with nonlinear disturbance observer. The disturbance observation error is dynamically compensated with the adaptive law to reduce the switch gain of the sliding mode controller. This design method relaxes the prior requirement of the sliding mode switch gain to the upper bound of the system uncertainties, and reduces the influence of external disturbances and system uncertainties on the displacement tracking control performance of the side roller. Simultaneously, the stability of the closed-loop system is verified using the Lyapunov method. Numerical simulation is carried out according to actual engineering parameters, simulation results show that the proposed control strategy has strong robustness to the system uncertainty, especially to the variable load, and the requirement for precision and rapid tracking of the side roller displacement of the four roll bending machine can be satisfied.
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