非线性系统的线性定常扰动观测器前馈控制

Linear Time- invariant Disturbance Observer Feedforward Control for Nonlinear System

针对非线性系统控制的复杂性,提出了一种基于扰动观测器的非线性系统的前馈控制方法。首先选择一个具有期望特性的线性定常目标模型;然后将系统中的非线性特性等效为目标模型的一个输入扰动,并将其扩充为目标模型的状态变量,以得到线性定常替代模型;再对该替代模型设计扰动观测器以得到扰动估值;最后由前馈控制抵消等效扰动对被控对象的影响。该方法的设计过程完全在线性理论框架下完成,且不依赖被控对象的模型,只要求被控对象的线性替代模型存在即可。证明被控对象可逆时其线性替代模型的存在性定理;针对同一离散时间被控对象,与基于支持向量机α阶逆系统方法的非线性内模控制方法进行了对比仿真研究。仿真结果表明该方法在线性化、抗扰动、及系统鲁棒性3个方面都表现出更好的性能。

It presents a feedforward control strategy based on linear time invariant disturbance observer for nonlinear controlled ob jects. At first, choose a linear time invariant model as target model which have a desired dynamics. And then describe the non line ar properties of the controlled object as an equivalent input disturbance variable of the target model, which can be extended as state vari ables, so that the target model with the disturbance becomes the substituting model of the controlled object. Thirdly, design an observer of the substitute model to get the estimated value of the disturbance variables. Finally, a feedforward control can counteract the influence of the disturbance on the controlled object. The design theories of this method are confined within the architecture of linear system theo ry, and independent of the mathematical model of the controlled objects. Particularly, the controller is without any nonlinear part. In circumstances of reversible controlled object, the existence theorem of the substituting model is proved. At last, for the identical dis crete time controlled object, comparative simulation research is performed between this control method and a nonlinear internal model control based on support vector machine a th order inverse system method. The simulation results indicate that the method proposed in this paper is better in linearization, anti disturbance capability and system robustness.