The engine, motor and pump are connected with the shaft to drive the rotary motor, the walking motor and the arm, bucket rod and bucket hydraulic cylinder together. Its power source part of the working mode has the following:
1) The engine alone drive mode, the system can run in this mode when the optimized torque of the engine output can match the external load and the battery charge state (SOC) value is high. This mode is the same as the traditional hydraulic excavator.
2) The combined driving mode of engine and motor, it can work in this mode when the external load is driven by motor power. The engine outputs a certain optimized torque, the battery outputs a certain energy to drive the motor, and the motor uses the extra torque to match the external load. The battery SOC decreases at this time, and the driving ability of the motor will be restricted by the battery SOC.
3) The engine drives the external load and the motor, the optimal torque of the engine output in this mode is greater than the demand of the external load, so some of the output energy of the engine is converted into the internal energy of the battery through the motor generation. And the power generation capacity of the motor is limited by battery capacity.
4) The dynamic arm potential energy recovery mode, when the excavator is in the falling stage of the moving arm, the external load is small, the potential energy recovery of the moving arm can be realized by the power generation function of the motor, and the recovered potential energy can be stored in the battery.