Control Strategy for Hybrid Excavator Swing System Driven by Electric Motor

Hybrid power technology is adopted to raise the efficiency and lower the emission of construction machinery. The efficiency can be improved better if the swing system is driven by electric motor in hybrid construction machinery due to its better efficiency than the hydraulic motors used in conventional hydraulic excavators and the regeneration of kinetic energy of upper structure. The purpose of this paper is to investigate the control strategy for hybrid excavator swing system driven by electric motor. At first, the configuration and working principle are introduced of swing system driven by electric motor and the working condition is also analyzed; then the model of the swing system is built and analyzed. The range of swing inertia of the upper structure is tested for controller design by site experiments. Based on the working requirement, the control flow chart of the swing system is given and a dual-mode (torque and speed) control strategy is presented. In speed control mode and torque control mode, a robust speed controller based on simplified mixed sensitivity algorithm and a P torque controller are designed respectively. Simulations and actual tests verify the feasibility and effectiveness of the proposed control method.