Experimental comparison of antagonistic hydraulic muscle actuation under single/dual and zero/overlapped servovalve configurations

Abstract

There are many studies on the antagonistic actuation of pneumatic artificial muscles; however, hydraulic artificial muscles have been rarely studied. The purpose of this study is to compare the characteristics of the antagonistic actuation of hydraulic muscles under different servovalve configurations. A dual-servovalve configuration can independently control the muscles on both sides, whereas a single-servovalve configuration cannot although it has a cost advantage. A zerolapped-servovalve has better response performance, whereas an overlapped-servovalve can use a higher gain in the controller. We use a single-zerolapped-servovalve as a reference, and compare it with a dual-zerolapped-servovalve, a single-overlapped-servovalve, and a dual-overlapped-servovalve configuration under position control and torque control for antagonistic actuation. Experimental results show that only the dual-servovalve configuration can adjust the range of the average pressure under position control or directly control the average pressure under torque control, thereby adjusting the compliance of the joint. Zerolapped servovalve shows better tracking performance; however, the overlapped servovalve shows better stability under higher proportional gain.