Design And Control Of A Novel Dual-axis Microgripper For Micro Manipulation With An Asymmetric Compliant Structure

As the end effector of the micro manipulation system,the performance of the microgripper has a crucial impact on the manipulation accuracy and efficiency of the micro manipulation system.A novel dual-axis microgripper with asymmetric structure was proposed and the kinematic and static characteristic were analyzed.Finite element analysis(FEA)was conducted to investigate the performance of the microgripper.Finally,the experimental platform was built and the microgripper performance tests were carried out.The main work of the thesis is as follows:A novel PZT actuated dual-axis microgripper with asymmetric structure was designed,which can be divided into right and left parts.Two stage amplification mechanism was adopted in each part.Parallelogram mechanism was employed to reduce the parasitic displacement to achieve the parallel motion of left jaw.Double parallel plate guide mechanism was adopted to ensure right jaw move along Y direction.Two leaf type flexure hinges were constructed under left jaw to measure the grasping force.Pseudo-rigid-body(PRB)method and matrix-based compliance modeling(MCM)method were adopted to established the PRB model and the MCM model of the microgripper.Based on the theoretical models,the kinematic and static characteristics,including displacement amplification ratio,position error of the jaw,input stiffness,output coupling,input coupling and strain stress distribution were analyzed.Based on finite element method,commercial software ABAQUS was used to investigate the static and dynamic characteristics.The displacement amplification ratio,stress distribution and natural frequency of the microgripper were analyzed,respectively.The experimental platform was built to investigate the actual performance of the microgripper.The experimental results show that the microgripper can operate objects with different sizes and rotate the tiny object to a certain angle.Through the displacement characteristic experiment,the actual displacement amplification for left part and right part are 11.12 and 4.64,respectively.At the same time,the hysteresis characteristics between the input voltage and output displacement were explored.The first two natural frequencies of the microgripper are obtained by sweeping experiments,which are 358 Hz and 655 Hz,respectively.In order to reduce the hysteresis between the output displacement and the driving voltage and improve the operation precision of the micro operating system,PI displacement controller was employed.The PI grasping force closed-loop controller was adopted to ensure that the grasping force were controllable.Finally,the PI grasping force/PI displacement switching controller was designed to make precise closed-loop control of the entire gripping-holding-rotating-releasing operation.