Design,Analysis And Experiment Of A Compliant Micro-Gripper With Multi-stage Amplifier

The development of micro-devices,intelligent systems and advanced materials has been expanding rapidly in recent year,with the proposed applications including biological manipulation,drug delivery,micro-surgery and micro-assembly.Micro-manipulation technology gradually breaks through the traditional mechanical and electrical framework.Micro-gripper is one of the core technologies as a typical end-effector for exploration of micro world,which can execute complex manipulations efficiently and accurately.The demand for accuracy and minimum in manipulations has stimulated extensive research on micro-gripper with large-stroke,high precision and high efficiency that plays a significant role.To address above issues and challenges,this dissertation presents a novel large-stroke compliant micro-gripper based on the piezoelectric actuator and compliant transmission mechanism.In particular,the dissertation studies the structure design,flexible modeling approach,experimental study for manipulation of various gripping objects,which showed as follow:Firstly,we design a novel three-stage compliance-based displacement amplification that incorporates the merit of compactness of the bridge-type mechanism and the cumulative magnification of the lever-type mechanism such that delivers and enlarges the operation range of micro-gripper.Meanwhile,the compliant parallelogram mechanism is employed to ensure the parallel gripping behavior and uniform stress distribution.Accordingly,a compliant micro-gripper driven by piezo with integrated position and force sensors is designed and developed.Secondly,we present a static modeling method for proposed micro-gripper based on elastic beam theory by analyzing the deformation of each flexure hinge and the relationship between decomposed amplifiers and hinges.On this basis,we further derive the stiffness and displacement amplification ratio of micro-gripper.Finite element approach is adopted to effectively demonstrate the static modeling method,as well as the performance of the proposed micro-gripper.Thirdly,Considering the dynamic impacts of gripping objects by regarding the gripping objects as a spring-damper system with a characteristic radius,a position kinematic and dynamic modeling method that unifies the free motion and gripping motion is proposed.Further,we investigate the force dynamic modeling for accurately predicting the dynamic behaviors of the micro-gripper during the whole gripping manipulations.Lastly,in the line with the mechanical structure designed above,a micro-gripper is fabricated monolithically and the whole experimental system is established for performance testing.In the free motion state,the static characteristics of micro-gripper are investigated to evaluate the grasping capacity by free motion experiments.In the gripping motion state,the dynamic performance experiments with the rigid and soft objects of different sizes are grasped respectively,which demonstrate the accuracy of the developed position/force modeling method by distinguishing the dynamic performance in different manipulation states.Based on the manipulation states of micro-gripper,we design a position/force switch controller and achieve the accurate manipulation of objects from free motion to gripping motion.