3-UPS/PU并联机构动力学建模及自适应滑模控制

摘要

为减少动力学模型不确定性(包括参数不确定和未知的负载干扰)对3-UPS/PU并联机构控制精度的影响,提出一种自适应滑模控制.首先在运动学反解基础上采用虚功原理建立该机构关于动平台工作空间的动力学模型.控制器结合了动力学名义模型和滑模控制理论,利用滑模面设计的自适应律可以对不确定性进行在线估计并补偿,从而提高系统鲁棒性.通过Lyapunov函数分析了系统稳定性.该控制器优点是:无需依赖不确定性上界,结构简单,易于工程应用,适用于并联机构这类复杂不确定系统.仿真结果显示,所采取的控制器能有效克服时变的模型不确定性,使动平台各自由度的平均跟踪误差相比传统滑模控制明显减少.%In order to reduce the impact caused by dynamic model uncertainty (including parameter uncertainty and unknown load disturbance) on control precision of 3-UPS/PU parallel mechanism,an adaptive sliding mode controller is proposed.Firstly,dynamic model for mechanism with respect to platform workspace is constructed based on the inverse kinematics and virtual work principle.The controller incorporates the nominal dynamic model and sliding mode control theory;an adaptive law is designed by means of the sliding mode surface,which can estimate and compensate the uncertainty online,thus the system robustness is improved;and the system stability is analyzed via Lyapunov function.The present controller has some advantages and which doesn't need to rely on the upper bound of uncertainty,and it is easy to implement due to its simple structure and suitable for complicated uncertain systems such as parallel mechanism.The simulation results show that the present controller can overcome the time-varying uncertainty efficiently and make the average tracking errors of platform freedoms obviously decreased comparing with traditional sliding mode control.