Pneumatic-Electric Hybrid Drive Robot Hand for Both Powerful Grasping and Dexterous Manipulation Using Passive Clutch Mechanism

Abstract

In this paper, we propose a novel pneumatic-electric hybrid drive robot hand for both powerful grasping and dexterous manipulation. The concept is to use both pneumatic actuators to exert a large grasping force and electric motors to precisely control fingers. However, this concept has been difficult to apply to a robot hand that needs to be lightweight and compact because pneumatic actuators are generally too large for the stroke requirement. We solved this problem by using lightweight pneumatic artificial muscles (PAMs) and a passive clutch mechanism that shuts off the drive of the PAMs to the fingers when the hand did not grasp, which reduces the stroke requirement of the PAM. We developed a 3-degrees-of-freedom (DoFs) and 3-fingered robot hand that was 220 × 220 × 160 mm and 1.45 kg. It achieved a grasping force of 110 N and speed of 1300 mm/s at its fingertips. We also attempted manipulation with the three fingers driven independently by electric motors. As an example, the hand achieved peg-in-hole operation by hand manipulation, with a tolerance of a few tens of micrometers. The hand can potentially perform hybrid control, where the PAMs are used to generate force while the electric motors are used for fine adjustment. Finally, we demonstrated heavy rail installation in which the robot hand brought an 8.5-kg rail with power grasping, adjusted its position using the hand with a hybrid control, and inserted screws with hand manipulation.