Research Of Self-sensing Piezoelectric Gripper Based On Space-sharing

In order to install and test micro system component by higher precision and reliability, it is very necessary to research a kind of gripper having sensing function. The gripper could be implemented using piezoelectric ceramic for its bilateral electromechanical property, the gripper is named self-sensing(SSA) gripper. SSA gripper has advantages in decreasing system volume and weight, saving space, true collocation and increasing stability. The point in realizing SSA is to find a good approach which could separate sensing signal from actuating signal. This paper uses space-sharing approach to separate sensing signal from actuating signa n. This paper introduces structure design of gripper in detail, sets forth the feasibility of self-sensing grasp force, makes sure the proper work status, develops a measure and control system to validate self-sensing effect.Space-sharing SSA approach implements the self-sensing actuator by dividing the electrode of one piezoelectric ceramic into sensing and actuating sections. The electrode on piezoceramics is divided into two parts using lithography, one for actuation, another for sensing. This paper realizes self-sensing gripper with the aluminum material and the steel material separately.Based on the theory of bilateral electromechanical transducer, piezoelectric transducer is modeled by transfer matrixes of bilateral transducers that give a perfect explanation of space-sharing based SSA approach. This paper derives structure equation according to gripper's structure. Because piezoelectric ceramics have inner resistor, it can not keep static charge, so it can not sense static force. Therefore this paper brings a kind of new work pattern for gripper, let gripper keep a micro vibration in the course of operation. The micro vibration has no influence on static grasp force, but it can let piezoelectric ceramic sense static force.In order to make certain appropriate micro vibration, this paper developes a virtual swept machine combining LabVIEW with NI-DAQ to analyze gripper, the proper vibration status was found according to experiment.The sensitivity of gripper is the ratio between grasping force and AC amplitude variety obtained by sensor electrode. The sensitivity was calibrated as 3.6mN/V through experiment. This paper develops a set of measurement and control system with LabVIEW. Seting a desired grasp force 1.62mN, the gripper automatically worked to grasp object, finally the practical force was maintained on 1.62mN. Experimental results prove the microgripper can sense its own actuating effect without any extra sensor element.