A study on a flow distribution control algorithm of a tandem pump for efficient electric excavators

This paper presents a flow distribution control algorithm for a tandem pump and an electric motor in an electric excavator system. Efficiency is the main issue for electric excavators since the main energy comes from the battery unlike the conventional hydraulic excavators. Better efficiency and longer working hours can be achieved if the main motor operates where the integrated efficiency of the motor and the pump is the maximum under the same hydraulic pump output power and the desired pressure condition. Moreover, a flow distribution control should be considered for better efficiency of the hydraulic tandem pump as the pump efficiency tends to be affected by displacement In this paper, a flow distribution control is added to the previous optimal operation point control by considering a swash plate angle for each operation case. The control algorithm is derived from each efficiency map of the motor and the hydraulic pump. Optimal operation points are produced where the integrated efficiency is the maximum under the same power, pressure, and the swash plate angle. The proposed algorithm is simulated through the MILS (Model-In-the-Loop Simulator). Electric energy consumption in the controlled electric excavator system is decreased compared to that in the uncontrolled electric excavator system.