Control Strategy for Macro-Micro Composite Actuator on the Basis of PSO-LQR and by Switching Non-Singular Terminal Sliding Mode

Macro-micro composite actuator is the core component of precision positioning platform, and its control accuracy directly affects the performance of the platform. In order to improve the control accuracy of macro-micro composite actuator, this paper proposes a master-slave dual-loop composite control strategy. In the design of macro control loop, a dynamic model is established based on the principle of electromagnetic force driving, and the linear quadratic regulator tuned by particle swarm optimization algorithm (pso-lqr) and the traditional LQR are respectively used to construct the controller. Through the comparative analysis of numerical simulation and experimental test, it is verified that the pso-lqr controller is of higher displacement positioning accuracy in the outer loop control. In the design of micro motion control loop, a dynamic model is established based on linear piezomagnetic equation, and a non-singular terminal sliding mode controller is designed as the inner loop by combining exponential reaching law with hyperbolic tangent function, which effectively suppresses the chattering of the system. Moreover, in order to verify the effectiveness of the proposed control strategy, a macro-micro composite positioning experimental platform is built with a laser interferometer, and positioning performance experiments are carried out. The results show that, under the same conditions, pso-lqr controller is superior to the traditional LQR controller in terms of step positioning and displacement tracking, its micro motion part can achieve 1 μm step without displacement overshoot. For a positioning target of 15 μm, the displacement error under the control of non-singular terminal sliding mode controller is about 0.24 μm, thus effectively suppressing the chattering of the system. Finally, a laser interferometer is used to calibrate the grating displacement sensor during the macro-micro composite positioning, and repeatability experiments are carried out, with the final positioning accuracy being controlled at 370 nm.