Research On The Calibration Method And Control System Of Planar 3-RRR Parallel Mechanism

With the German industry 4.0 strategy putting forward and the development of micro-nano operation,a new requirement for positioning accuracy,movement range and response speed of parallel robots,large movement range and high positioning accuracy.For parallel robots,high positioning accuracy and large movement range are contradictory.At present,combination of macro and micro is usually taken into account.The object of this thesis is the macro part of the micro-micro-precision positioning mechanism,3-RRR parallel mechanism.As the absolute positioning accuracy of the mechanism is generally improved by kinematic calibration and the improvement of control algorithm,this thesis focuses on the two areas.(1)Research on kinematic calibration method.The inverse kinematic model of planar 3-RRR parallel mechanism is established,and on this basis,the traditional error model is deduced,after that,the error sensitivity analysis was carried out.The result shows that the positioning error of the 3-RRR parallel mechanism is mainly from the input angle error of the mechanism.Therefore,the traditional error model is improved,and an error model considering the backlash of the reducer is proposed.(2)Improvement of control algorithm.The semi-closed-loop control system of planar 3-RRR parallel mechanism is susceptible to external interference,thus the absolute positioning accuracy is low,with the serious of the friction and wear,the absolute positioning accuracy gradually lost.In this situation,an external sensor is installed on the moving platform of the planar 3-RRR parallel mechanism,the position of the platform is feedback real-time,and this constitutes a fully-closed-loop control system.Considering the non-linearity and strong coupling of the planar 3-RRR parallel mechanism and the time-varying nature of its motion control model,combined a fuzzy controller and a traditional PID controller,a fuzzy PI full-closed-loop control algorithm is designed.(3)Experimental research.First,carried out the homing and repeatability experiments,and then the kinematic calibration experiments were carried out based on two different error models;finally,conduct the full-closed-loop control experiment...