A Planar 3-DOF Micro-positioning System Based On Compliant Mechanisms

Micro-positionering systems,driven by piezoelectric ceramic actuators,have been widely employed in sample scanners of the scanning probe microscopy(SPM),nanoimprint lithography,micro/nano manipulation,precision electronic manufacturing,precision machining,and precision metrology.That is the background of this dissertation in which the focus is on presenting mechanical performance evaluation model and optimal design approach for planar 3-RRR(3-revolute-revolute-revolute)micropositioning platforms.Prototypes test results of three planar 3-RRR micro-positioning platforms verify the whole performance indexes.Then three corresponding planar3-DOF(degree of freedom)micro-positioning systems are built to conduct the experimental research on overall performance indexes.Firstly,mechanical performance evaluation indexes of micro-positioning platforms are discussed.The configuration of planar 3-RRR is selected as an example.A performance evaluation model of micro-positioning platforms is built.High precision models of seven performance indexes and four constraints are involved.Based on the presented performance model,an optimal design approach of planar 3-RRR micro-positioning platforms is proposed.Using multiple-objective particle-swarmoptimization(MOPSO)algorithm and Pareto strategy,a preferred noninferior solution can be obtained quickly with a proper decision-making method.Two prototypes of planar 3-RRR micro-positioning platforms are design and fabricated.Prototype test results on seven performance indexes validate the precision of proposed performance indexes modeling and the efficiency of proposed optimal design approach.Secondly,in order to increase the usable workspace of the macro-positioner,a planar 3-RRR micro-positioning platform with a large range is developed.After experimental or simulated comparison of several micro-displacement magnifying mechanisms,a two-level lever amplifier is selected to expand the workspace.Theoretical models on three displacement losses,involving preload ports,input ports,and the transferring mechanism,are built to improve the modeling accuracy with the increase of magnification.Prototype test results using micro-vision measuring system,laser interferometer and capacitive sensors verify three presented displacement loss models.A 1-DOF micro-positioning platform is design and fabricated to further quantify the displacement loss.Then test results on basic performance indexes of the planar 3-RRR micro-positioning platform show the large workspace and high resolution.Thirdly,after the performance evaluation modeling,optimal design approach and displacement loss of planar 3-RRR micro-positioning platforms,three corresponding planar 3-DOF micro-positioning systems are built.For the micro-positioning system based on first design example,different simulated load are designed.The servo controller parameters in both three input ports and the terminal end-effector are optimized using an iterative learning controller.Experimental results show the high tracking precision and accuracy.The micro-positioning system based second design example is embedded into a macro-micro positioning system.The repeat positioning accuracy of macro-positioning system along a line during a finite workspace is measured.The precision meets the desired demand.Measurement and compensation on the actual prototype sizes of the micro-positioning system with a large workspace is conducted.High trajectory tracking precision and accuracy are obtained using proper servo controller.Finally,conclusions and future works are put forward.This work will provide the theoretical support and practical methods on designing planar 3-RRR micro-positioning platforms with high performance indexes and developing planar 3-DOF micro-positioning systems.