Overpressure Compensation for Hydraulic Hybrid Servo Booster Applied to Hydraulic Manipulator

• Published in: IEEE robotics and automation letters 2019-04, Vol.4 (2), p.942-949
• Main Authors: Hyon, Sang-Ho, Taniai, Yuuki, Hiranuma, Kazuyuki, Yasunaga, Kazutoshi, Mizui, Harutsugu
• Format: Article
• Language: English
• Subjects: Actuators; Cartridges; Circuits; Compensation; compliance and impedance control; Cylinders; field robots; Flow mapping; Force; force control; Hydraulic/pneumatic actuators; Hydraulics; industrial robots; Loads (forces); Manipulators; Overpressure; Robot arms; Servocontrol; Servomotors; Torque; Valves
• ISSN: 2377-3766; 2377-3766
• DOI: 10.1109/LRA.2019.2894868

This letter describes our novel hydraulic circuit, referred to as the hydraulic hybrid servo booster, and its application to hydraulic manipulator. The circuit embeds a servomotor controlled pump into a valve bridge so that the high-speed position can be achieved in a hybrid, cost-effective, and precise manner. This letter focuses on the precise manipulation of heavy-load and the compliant joint torque control using the boost mode. The main obstacles includes: first, pressure difference caused by area differences of the single rod cylinder; second, quick changes of the inertial load due to the manipulator and load dynamics; third, limited response and precision of the low-cost cartridge valves; and last, limited output flow of the small servo-pump. All these factors lead to overpressure. We propose a model-based compensation scheme to mitigate the overpressure. This method comprises: first, nonlinear flow map of the valves, and second, relief control based on the estimated flow and pressure of the servo-pump. The effectiveness is validated through the joint position and torque control experiments on our hydraulic manipulator prototype.