A novel three-finger IPMC gripper for microscale applications

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Title: A novel three-finger IPMC gripper for microscale applications
Author: Yun, Kwan Soo
Abstract: Smart materials have been widely used for control actuation . A robotic hand can be equipped with artificial tendons and sensors for the operation of its various joints mimicking human -hand motions . The motors in the robotic hand could be replaced with novel electroactive -polymer (EAP ) actuators . In the three -finger gripper proposed in this paper , each finger can be actuated individually so that dexterous handling is possible , allowing precise manipulation . In this dissertation , a microscale position -control system using a novel EAP is presented . A third -order model was developed based on the system identification of the EAP actuator with an AutoRegresive Moving Average with eXogenous input (ARMAX ) method using a chirp signal input from 0 .01 Hz to 1 Hz limited to 7 ? ? ? ? V . With the developed plant model , a digital PID (proportional -integral -derivative ) controller was designed with an integrator anti -windup scheme . Test results on macro (0 .8 -mm ) and micro (50 - ? ? ? ?m ) step responses of the EAP actuator are provided in this dissertation and its position tracking capability is demonstrated . The overshoot decreased from 79 .7 % to 37 .1 % , and the control effort decreased by 16 .3 % . The settling time decreased from 1 .79 s to 1 .61 s . The controller with the anti -windup scheme effectively reduced the degradation in the system performance due to actuator saturation . EAP microgrippers based on the control scheme presented in this paper will have significant applications including picking -and -placing micro -sized objects or as medical instruments . To develop model -based control laws , we introduced an approximated linear model that represents the electromechanical behavior of the gripper fingers . Several chirp voltage signal inputs were applied to excite the IPMC (ionic polymer metal composite ) fingers in the interesting frequency range of [0 .01 Hz , 5 Hz] for 40 s at a sampling frequency of 250 Hz . The approximated linear Box -Jenkins (BJ ) model was well matched with the model obtained using a stochastic power -spectral method . With feedback control , the large overshoot , rise time , and settling time associated with the inherent material properties were reduced . The motions of the IPMC fingers in the microgripper were coordinated to pick , move , and release a macro - or micro -part . The precise manipulation of this three -finger gripper was successfully demonstrated with experimental closed -loop responses .
URI: http : / /hdl .handle .net /1969 .1 /5792
Date: 2007-09-17


A novel three-finger IPMC gripper for microscale applications. Available electronically from http : / /hdl .handle .net /1969 .1 /5792 .

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