Design of soft micro actuator based on dielectric elastomer actuator for micro robots

Abstract

The micro robotics is the key technology in medical and biomimetic robots because micro robots can do tasks in highly confined environments. Micro robots with multi-degree-of-freedoms (DOFs) can produce more complex and delicate motions, which have high potential in the robotic surgery and the micro manipulation. The actuator selection is the main design consideration in micro robots. The actuator suitable for micro robots should have miniaturized structure with the capability of producing a controllable force and displacement. In addition, the micro robots require soft actuators or soft mechanisms to allow safe interaction with the environment. Among various soft mechanisms, dielectric elastomer actuators (DEAs) have high potential to be adopted in micro robotics, due to its large strain, fast response time, high energy density, and small size and lightweight structure. In this thesis, we designed the miniaturized DEA-based soft micro actuator which can produce a large output displacement/force with high bandwidth. The proposed micro actuator mainly consists of an DEA and the spiral flexure spring. The actuator utilize a spiral flexure spring as a biasing element of DEA to convert the area expansion of DEAs to the linear displacement. A spiral flexure spring can display a large stroke with high linearity and low hysteresis error despite its low thickness (~ 0.1 mm). The optimal design of the spiral flexure spring was derived based on the analytical dynamic model of the actuator. Fabricated actuator has a thin, compact and miniaturized structure (thickness = 1.5 mm, diameter = 10 mm), and can produce a high actuation strain (> 40 %) with a high bandwidth. In addition, two actuators can lift a mass of 200 g (approximately 670 times its mass) despite its light mass of 0.15 g. In this thesis, we designed and fabricated compliant micro gripper and 3-DOF micro manipulator using proposed actuators. Fabricated micro robots consist of proposed actuators and linkages. We designed the linkages to convert an actuation of the actuator to a rotary motion of the revolute joint. Fabricated compliant micro gripper has a weight of 0.5 gram, but enables gripping various small objects without a sensory feedback due to its compliance. In addition, we showed that the position of the end effector of the fabricated micro manipulator can be controlled.