Energy storage and reutilization for a single-rod electro-hydrostatic actuator system

Abstract

Single-rod electro-hydrostatic actuator (EHA) systems have higher efficiencies when compared to conventional valve-controlled systems. However, increasing demands for energy resources, declining fossil fuels and increasing greenhouse gas emissions require the development of technologies that can further improve the system efficiency. Studies have been conducted to investigate the energy consumption in EHA systems and possible ways of decreasing the waste of otherwise useful input power; for instance, the possibility of reusing gravitational potential energy from the load. In this thesis, a recently developed EHA in the Fluid Power and the Tele-Robotics research lab at the University of Manitoba is built upon to improve the energetic efficiency. The existing test rig consists of a single-rod cylinder, with a swinging mass attached to the tip of its rod, in a way that four quadrants of operation are duly covered. It is identified that at motoring operations, the inertial load, driven by the cylinder, is decelerated by the pump. As a result, potential energy stored at the moving mass is simply wasted, in the form of heat. To overcome this, a novel Energy Storage and Reutilization (ESR) system is designed and prototyped to capture and reuse the potential energy of the load. This new ESR system employs a hydraulic accumulator as the energy storage component. The stored energy is later used to help the pump drive the cylinder. The proposed design is cost-effective, easy to implement, and requires a simple algorithm to be matched to the existing EHA. The effectiveness of the ESR system has been experimentally demonstrated, where a 20% improvement in the energetic efficiency has been obtained, when compared to the existing EHA. The new design is promising and as will be shown in this thesis, there is considerable room for further developments.