STRUCTURE AND CONTROL STRATEGY DESIGN OF NOVEL HYDRAULIC HYBRID SWING SYSTEM OF EXCAVATOR

Abstract

This thesis presents a novel energy saving swing system of hydraulic excavator, in which hydraulic hybrid technology is utilized. Two independent hydraulic accumulators are used as the energy storage unit to store the regenerated energy, and several additional control valves are installed in system. The combined control of hydraulic motor displacement and flow control valve, and the variable accumulator control strategy are proposed for the improvement of energy regeneration efficiency. The structure and control strategy of energy reuse are studied to reuse the stored regenerated energy. The test bench is built in lab and experiments of energy regeneration and energy reuse are conducted. As a result, the combined control of hydraulic motor displacement and flow control valve improves 64% of regenerated energy and reduces the swing part oscillation. The variable accumulator control strategy improves 27% of the regenerated energy maximally. The experiment results verify that the energy regeneration efficiency of the proposed system is between 23% and 56% in different conditions. Consequently, the average energy saving efficiency is 26.7% Firstly, the electric hybrid excavators and hydraulic hybrid excavators are discussed. The key components and existed control strategies of energy regeneration and energy reuse are introduced. The advantages and disadvantages of each structure of hybrid hydraulic excavators are analyzed. Secondly, a novel energy saving swing system of excavator is proposed. The design of the system and test bench parameters setting are discussed. In the proposed system, two independent hydraulic accumulators are used as the energy storage unit, and several control valves are set up to regulate the flow in energy regeneration mode and energy reuse mode. Thirdly, the combined control of hydraulic motor displacement and flow control valve, and variable accumulator control strategy are proposed to improve the energy regeneration efficiency. Then the energy reuse control strategy is proposed to reuse the stored regenerated energy. Finally, the experiment of the proposed system is conducted, and the experiment results are analyzed. The energy regeneration efficiency is improved with the proposed control strategy. Consequently, the proposed system could reduce the energy consumption obviously.