快速无超调纳米定位

对于“直流电机＋滚珠丝杠”驱动机构，摩擦是实现大行程具有纳米级分辨率点位控制的主要障碍．通过设计高增益PID控制器，可以抑制摩擦的影响并在大范围内实现纳米定位，只是系统的性能受到执行机构饱和的影响．通过将时间优化的Bang—Bang控制器与该PID控制器结合在一起构成变结构控制系统，使用PID闭环控制跟踪Bang—Bang控制下的理论减速轨迹，并实现最终定位，从而消除了饱和所造成的超调．实验和仿真结果显示，该系统可以在较大摩擦力和模型参数变化的情况下获得大范围无超调的纳米定住，并且响应时间最优．

Rapid Nanometer Positioning Without Overshoot

For a DC-motor and ball-screw-driven table system, the friction is a major obstacle to the achievement of point-to-point positioning with nanometer resolution. A high gain PID controller is designed and it is powerful enough to suppress the effect of friction and realize nanometer positioning. However, saturation of the plant affects the system performance. By combining a Bang-Bang type control law with the PID controller, a variable structure control strategy is proposed. The PID control system tracks the theoretic deceleration trajectory calculated with Bang-Bang control law and realizes final positioning. The overshoot caused by the saturation is avoided. Simulated and experimental results indicate that the variable structure control system can realize nanometer positioning over a long stroke without overshoot and the step response is almost time optimal.