不确定离散时间系统的变结构控制

Uncertain Discrete Time Variable Structure Control Systems

常规变结构控制用于不确定系统 ,须利用不确定性界确保系统的鲁棒性 ,控制器过于保守且抖振变大 .本文把未知干扰和参数不确定性的影响等效为名义系统的外界干扰 ,利用时延技术对干扰进行在线估计 ,并将估计值引入到变结构控制中 ,从而抵消掉系统中的慢变不确定性 ,利用离散趋近律法 ,推出了准滑动模态的存在条件及其带宽 .该方法克服了以往控制方法中须已知不确定性界的限制 ,且不必满足匹配条件 ,用较低的控制增益保证了系统的鲁棒性 ,降低了准滑动模态带即削弱了抖振 .

The conventional variable structure control technique for uncertain system requires that the uncertainty bound is known as a premise to assure robustness.The requirement creates an over conservative controller and enlarges chattering.The proposed controller regards the influence of unknown disturbances and parameter uncertainties as an equivalent disturbance and generates an on line estimation used in SMC to cancel the slowly varying uncertainties by the mechanism of time delay.The reaching law approach is used to get the conditions and band of quasi sliding mode.The new methodology offers a robust feedback control with much lower gains and reduces chattering without a prior knowledge of the uncertainty bounds or matched conditions.