并联机器人模型参考变结构控制研究

Research on model reference variable structure control for parallel robots

为了抑制并联机器人建模中不确定性因素对系统性能的影响,采取了基于参考模型的变结构控制策略。以系统状态误差始终指向滑动模态且具有李雅普诺夫意义下渐近稳定的动态品质为目标设计控制量,抑制不确定性因素对系统性能的影响。通过对参考模型和滑动模态运动进行极点配置,使系统状态误差在状态空间中更快速地收敛于原点。实例将球面三自由度并联机器人用作跟踪飞行器姿态定位平台的执行机构,设计出跟踪偏差的检测方案。仿真结果表明,基于参考模型的变结构控制方法对系统的不确定性因素引起的参数变化及外界扰动具有较好的控制效果,在变结构不确定性控制量作用下,系统在0.6s后,姿态角跟踪误差控制到0.0001°的范围内。

To restrain the influence of uncertainties on system performance in parallel robot modeling, a variable structure control strategy based on reference model is adopted. Aiming at the dynamic quality that the system state error always points to the sliding mode and is asymptotically stable in the sense of Lyapunov, the control variables are designed to suppress the influence of uncertainties on the system performance. By pole assignment of reference model and sliding mode motion, the system state error tends to the origin of state space more quickly. As an example, a spherical 3-DOF parallel robot is used as an actuator of a positioning platform for tracking aircraftattitude, and the detection scheme of tracking deviation is designed. Simulation results show that the variable structure control method based on the reference model has better control effect on the parameter changes and external disturbances caused by the uncertainties of the system. Under the action of variable structure uncertainty the attitude tracking error is controlled to 0.0001° after 0.6 s.