Smart materials have been widely used for control actuation. A robotic hand canbe equipped with artificial tendons and sensors for the operation of its various jointsmimicking human-hand motions. The motors in the robotic hand could be replaced withnovel electroactive-polymer (EAP) actuators. In the three-finger gripper proposed in thispaper, 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 ispresented. A third-order model was developed based on the system identification of theEAP 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 thedeveloped plant model, a digital PID (proportional-integral-derivative) controller wasdesigned with an integrator anti-windup scheme. Test results on macro (0.8-mm) andmicro (50-????m) step responses of the EAP actuator are provided in this dissertation and itsposition 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 1.79s to 1.61 s. The controller with the anti-windup scheme effectively reduced thedegradation in the system performance due to actuator saturation. EAP microgrippersbased on the control scheme presented in this paper will have significant applicationsincluding picking-and-placing micro-sized objects or as medical instruments.To develop model-based control laws, we introduced an approximated linearmodel that represents the electromechanical behavior of the gripper fingers. Several chirpvoltage 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 samplingfrequency of 250 Hz. The approximated linear Box-Jenkins (BJ) model was well matchedwith the model obtained using a stochastic power-spectral method. With feedback control,the large overshoot, rise time, and settling time associated with the inherent materialproperties were reduced. The motions of the IPMC fingers in the microgripper werecoordinated to pick, move, and release a macro- or micro-part. The precise manipulationof this three-finger gripper was successfully demonstrated with experimental closed-loopresponses.
展开▼
