Design and Control of an Electrohydraulic Soft Actuator System for Robotic Grippers

摘要

Electrohydraulic actuators are widely used in industrial applications due to high efficiency and easy of control. This paper proposes the concept of electrohydraulic soft actuator (EHSA) system for robotic grippers. The system consists of one or multiple bending soft actuators, a piston hydraulic pump, and an electrical motor with ball screw mechanism. Each soft actuator has two hydraulic chambers which enable bidirectional bending deformation. The two ports of the hydraulic pump are connected to the two chambers of the soft actuators so as to form closed circuits. The characteristics of the fluidic soft actuators are modeled and identified at two different load conditions, one of which is that the actuators are operated in free space, and the other is that the actuators touch objects. The effectiveness of the model is verified by experimental results with the assumption that the bending angle of the fluidic soft actuators is relatively small. Based on the model, an estimator is designed to obtain the contact force between the actuators and the objects. Finally, closed-loop force control for the actuators is realized by taking the estimate as feedback information. It is shown that the force control has good dynamical response and acceptable steady error.