基于Smith预估器的积分切换增益滑模控制

Smith predictor based sliding mode control with integral type switching gain

许多化工过程的传递函数往往包含积分环节和一阶惯性加纯时延环节。由于纯时延的存在,一般的控制方法很难使之稳定,即使能,也需要很长的调节时间且会出现振荡,因此在过程控制中这类系统被公认是一挑战性课题。Smith预估控制能克服纯时延,然而对模型非常依赖,当建模出现误差何不确定时,就会出现较大的振荡,甚至发散。特别是系统有常值干扰时,使用Smith预估控制方法,含积分环节的一阶惯性加纯时延系统则会出现余差。因此,本文提出1种基于Smith预估器的积分切换增益滑模控制,该方法使用1种超前一滞后网络前馈补偿常值干扰,利用滑模控制的鲁棒性以克服系统模型的不确定,系统能够实现渐趋稳定。积分型切换增益减小了系统抖动。仿真研究表明本文提出的方法能够控制好包含积分环节的一阶惯性加纯时延系统,是1种有应用潜力的控制方法。

It is well known that many of chemical process can be described by integrating first-order plus time delay model.Due to time delay,general approaches encounter great difficulties to stabilize them.Even if some of general approaches can stabilize them,it will take long setting time and oscillation will take place in transient process.Therefore,such systems are recognized as a challenging problem in process control.System time delay can be eliminated by Smith predictor.However,conventional Smith predictor depends on the model heavily.The performance will decrease in the presence of modeling uncertainty,for example,great oscillation or even instability will occur.Especially,conventional Smith predictor can not reject constant disturbance for processes with integration.For these existing issues,a new Smith predictor based sliding mode control approach with integral type switching gain is developed in this paper.By using a lead-lag networked,the constant disturbance can be eliminated.Sliding mode control is a robust control method,which can cope with system uncertainty effectively.The proposed control approach can achieve asymptotical stability.Due to employing the integral type switching gain,the system chattering is reduced significantly.Simulation studies show that the proposed approach has good performance,which is a potential control method in application.