Evaluation of Tracking Control for Hydraulic Direct-drive System

Abstract

Biped humanoid robots, whose size and output are equivalent to humans, have been developed. However, it is difficult to mount high-power large electrical motors with a mechanical transmission due to spatial limitations. Generally, hydraulic systems have a high energy density and excellent layout characteristics. This study proposes a hydraulic direct-drive (HDD) system using a single-rod cylinder for biped humanoid robots. The HDD system is based on meter-in control using pump-derived output flow and a meter-out control using a proportional valve. In this study, a bench was developed to evaluate the proposed HDD system, which can control the cylinder based on the pump flow rate. The proposed system was compared with a valve-based control system and an electro-hydrostatic actuator in terms of its responsiveness to step the velocity input and the sinusoidal position input. The results of this comparison demonstrate that the proposed system exhibits good velocity and position following capability.