Modeling And Control Based On The Stick-slip Driving Precision Positioning Stage

In the field of micro-nano manipulator，since SEM nano manipulator has a good vsualfeedback real-time observation，provides a nano resolution, and has a high caccuumworking environment, it has drawn a widely attention in many reaching fields. But mostSEM nano manipulators are based on open-loop control, resulting in a steady state errorand poor anti-interference ability. Base on the above situation, this paper develops anano precision positioning stage with feedback control which meets the requirements ofSEM.The precision positioning stage of this paper is based on the stick-slip drivingprinciple. By analyzing the features of the existing friction model, this paper proposes anew friction model——LS model. LS model contains only7parameters, and it is verysuitable for the simulation and calculation on friction. The simulation results show thatLS model can describe the Stribeck effect, the hysteresis, rate independent and nonlocalmemory phenomenon. Based on the LS model, a dynamic model of the precisionpositioning system is established. The simulation results indicate that the kinetic modelcan correctly describe the motion characteristics of the positioning system. And it alsoproves that the LS model can accurately describes the stick-slip motion.In order to accomplish the close-loop control of the precision positioning system, adynamic model of the piezoelectric ceramic-flexible hinge system is established. Thedynamic model with simple structure can reflect the hysteresis of the piezoelectricceramic and the flexible hinge. According the feedforward control principle, this paperproposes a feedforward-PID control scheme to accomplish piezoelectric displacementclosed loop control. The simulation results show that the feedforward-PID controlscheme can significantly improve the response speed of the system, and make thesystem obtain better dynamic characteristics. As the work space of SEM is limited, thispaper presents a predictive-switching-control method. The simulation results show thatthis method can achieve an accurate positioning control. By applying a PID control onthe control signal, system shock and the steady-state error are decreased obviously.Based on the theoretical analysis, complete the nano precision positioning platformtest system and make a testing on the performance of nano precision positioning.Through the feedforward–PID control on the piezoelectric ceramics, the piezoelectricceramic obtains a good positioning uniformity and a high positioning resolution. Thedynamic performance of the piezoelectric ceramic is significantly improved. Theexperimental results show that, the nano positioning system with closed-loop controlalso has a good positioning uniformity. The experimental results above show that the positioning system with closed loop control has the ability to meet any requirementof SEM.