Abstract: A parallel hybrid power train system is designed based on a 6 t hydraulic excavator, and the specifications are introduced. The power train of a parallel hybrid excavator is a two-input-two-output system with engine torque and integrated starter generator (ISG) torque as inputs while engine speed and state of charge(SOC) of super capacitor as outputs. The model of the powertrain is built in Matlab/Simulink. Three control strategies are designed and simulated. The results show that the “coupling control strategy” is the best of the three. A 32-bit HCU is developed. A prototype hybrid excavator is built. Testing results show that the fluctuation of the engine speed is within ±100 r/min, and the SOC of super capacitor can be kept sustaining during work cycles. Compared with a traditional hydraulic excavator, the engine operates more efficiently, reducing fuel consumption by approximately 15%.

Key words: excavator;parallel hybrid;coupling control;simulation