Abstract: Aiming at the rotary speed fluctuation of the excavator upper platform caused by the large and variable swing inertia and the large disturbance torque, the speed control of electric drive swing system of a 20ton excavator upper platform was investigated. The mathematic model of the swing system was built and analyzed. The PI plus disturbance observer control scheme was presented and the disturbance observer was designed. The simulation was performed at the condition of the maximum, minimum swing inertia and the step disturbance torque. The simulation results indicate that the scheme of disturbance observer makes the impact of inertia variation of platform on rotary speed fluctuation drop from 3.1% to 1%, and the impact of external disturbance on rotary speed fluctuation drop from 1.3% to 0.1%. Therefore, the impact of inertia variation of platform on rotary speed is decreased, the ability of antidisturbance is enhanced and the operability of the swing system is improved through the disturbance observer.
Key words: hybrid power excavator; electric drive swing system; speed control; disturbance observer(DOB)