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Closed-Loop Self-Sensing Multilayer Microhydraulic Actuators for Dexterous Microrobotic Grippers: Design, Modeling, and Numerical Validation

Hyman Norman Abramson1, Phillip Harris Paul2
1Retired Executive Vice President Southwest Research Institute
2Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, California 94550

Abstract

Multilayer microhydraulic actuators present a miniaturized electrowetting-enabled method of enabling microrobotic mobility, however, its applicability for dexterous grasping hinges on whether motion, touch, and grip can be achieved without requiring external displacement or force transducers. In this paper, we address this research question via the development of a closed-loop two-finger microrobotic gripper, wherein two sets of multilayer microhydraulic actuators are used as actuators and self-sensors. Our approach integrates a reduced-order electromechanical model, capacitive displacement observer, contact residual, hybrid position–force controller, and slip-adaptive supervisor for a five-layer, 40~μm-pitch microrobot powered by four-phase, 50~V excitation. The new analysis interprets each of the model equations as pertaining to the physical gripper, relates numerical constants to the resultant performance characteristics, and separates each figure panel into an independent image asset. The proposed design results in 1.8~μm root-mean-square static displacement error over a range of 400~μm stroke. Dynamic response yields 2.6~μm error at small phase lag between control input and output displacement. The controller reacts to a command of 200~μm displacement in 17.6~ms when operating in force control and 9.4~ms when controlled by velocity command. Force control maintains error in grasp force smaller than 1~mN when the target is between 2 and 12 mN. Slip detection occurs with mean latency of 1.4~ms. Finally, even with coupled variations of parameters, grasping success rate exceeds 96%. We conclude that the answer to the research question is affirmative: the same electrode layers can power and monitor a microrobot as well.

Keywords: microhydraulic actuator; electrowetting; self-sensing; microrobotics; closed-loop control; microgripper; surgical robotics; capacitive proprioception
Citation
Hyman Norman Abramson, Phillip Harris Paul. Closed-Loop Self-Sensing Multilayer Microhydraulic Actuators for Dexterous Microrobotic Grippers: Design, Modeling, and Numerical Validation[J], TK Techforum Journal (ThyssenKrupp Techforum), Volume 2021 (3). 50-63.

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