Design Of Torque Coupling Excavator Hydraulic Hybrid System And Control Method Research

Since the oil crisis of the 1970s, many research efforts have been made to improve the energy efficiency of power system on automobile and construction machinery. The parallel hybrid excavator hydraulic system which utilizes hydraulic accumulator exclusively as energy storage device is one of the most advanced subjects in research area of construction machinery energy conservation home and abroad. Parallel oil-hydraulic hybrid system not only has the ability to stabilize the working points of engine, but also has the ability to recover the wasted hydraulic energy at the throttle of control valve on traditional excavator. Besides, taking the advantage of hydraulic accumulator, this kind of system can make up the disadvantages of oil-electricity hybrid system, so to provide new possibilities for progress of hybrid technique.In hydraulic excavator, in order to improve the low energy efficiency caused by complex working conditions and load fluctuation, a scheme of torque coupling oil-hydraulic parallel hybrid system is proposed. This hydraulic hybrid system utilizes hydraulic accumulator exclusively as the energy storage device and the combination of accumulator and hydraulic secondary component as the assist power source to real-time compensate the power difference between target engine working point and fluctuated load of working hydraulic system. Based on this new kind of system, selection of hydraulic elements of assist power source and parameters matching method researches are arranged. Meanwhile, a kind of power system composite control method combined with PI control and load prediction control based on the characteristic of system, states of working load and energy storage states of accumulator is introduced to reduce the deviation of engine working point from the high fuel efficiency range. According to the system and control strategy, researches of simulation by Amesim and experiments are arranged. The research results show that, compared with traditional hydraulic excavator, the range of engine speed fluctuation decrease 40% and the range engine torque fluctuation decrease 30% under common working condition.