Hydraulic Excavator Hybrid System Modeling And Control Strategies

Hydraulic excavators(HE) have been paid much attention in the field of energy saving and environment protection, for the reasons of their widespread usage, high oil-consumption and bad emission. Improving the global power match of the drive chain of the EHA (Engine-Hydraulic system-Actuator) is one of the main orientation for developing energy saving research of the excavator. The researches of the conventional power match play an important roles in the energy saving of the excavator. However, because of the acutely variational load, the problems about the poor efficiency and bad emission of engine are not able to be solved radically by the existing technology. A new way of thinking about the researches of the energy saving is proposed for the conventional hydraulic excavator power match due to the successful applications of hybrid automobiles. The control stratege of power match based on the hybrid system of the hydraulic excavators is studied primarily in this paper.Firstly, a hybrid system structure based on the analyses and researches of the existing hybrid drive and energy recovery system structure is established, and it is suitable for the features of the excavator work condition. On the basis of this system, the hybrid excavator system simulation models are established, besides, the coupling characteristics and power element parameters are analyzed. The effectiveness and feasibility of the proposed hybrid excavator system are proved by the simulations.Subsequently, the control strategies which have been applied for hybrid excavators are analyzed comprehensively. Aiming at the current shortcomings of these strategies, a quasi-stable work point control strategy basing on the prediction of work condition and a global variable instantaneous optimal control strategy are proposed in according to the features of excavator working condition. The former, which is the same as many control strategies proposed in the literatures, is based on the rules of experience; the latter is the idea of taking advantage of the global instantaneous optimization, which is the first time in the control strategies of the hybrid excavators. The simulation results show that there is a certain advantage in terms of stabilizing the engine operating point, maintaining a reasonable charge state for a super capacitor and obtaining better fuel economy. Some theoretical and empirical theories are put forward for the further study of hybrid power system structure and excavator control strategy in this paper.At last, some experiences is adapted in order to gain some data which is required in the simulation and validate some hypothesizes which are put forward in model.