The Study For Dynamic Properties And Optimization Design For Dig Force In Hydraulic Excavator Working Device

Hydraulic excavator is a multi-functional engineering machinery doing earthwork operations, it plays a decisive role in national economic construction. The working device is an important part of excavator, it is also the executive device in the earthwork operations. The equipment operation performance largely reflects the performance of the mining excavator. In the real mining process, because of the bad working condition, variable mining object and complex work load, the movement of working parts and the law of force is very complex, the short of digging force may be existed. Based on these phenomena, this paper takes hydraulic excavator as the research object, the dynamic characteristics of working are simulated and analyzed and the digging force of bucket is optimized, the main research contents are as follows:(1) The kinematic and dynamic mathematical model of working device has been established by using the Denavit-Hartenberg coordinate transformation in odd order and the method of Lagrange respectively, the function relationship between displacement [ ],,TX Y Z, velocity v and acceleration a in the key position of the hinge point and its dynamic equation function are obtained.(2) By using the classical method of bottom-up design in the software PROE, three-dimensional model of working device is established. It is put into the virtual prototype assembly of working device which is established by software ADAMS. The kinematics and dynamics simulation of the multi rigid body system in virtual prototype is done, the main operation parameters of working device and the curve of force and torque regulation in key hinge point are obtained.(3) Based on the finite element software ANSYS, the flexible components of swing arm are established. The constraint modal studies of two mechanisms are done and the first six order of natural frequency in mechanism and corresponding graphs of their vibration mode are obtained. After the flexible replacement in software ADAMS, the rigid flexible coupling virtual prototype model of working device is obtained and its dynamics analysis is done. The results show that: the trend of stress points curve in the rigid flexible coupling model is basically consistent with the curve in the multi rigid body system, there are some different fluctuation based on curve of multi rigid body system and the volatility of curve under external loads is obvious. The maximum stress location of swing arm mechanism and bucket rod mechanism is near the rotary hinge point in moving arm and the bearing of bucket cylinder the in one cycle operation respectively.(4) A simplified prototype parametric model of bucket mechanism is established in software ADAMS, the digging force that is transmission ratio is the objective function of optimization design. The results show that: the four longitudinal coordinate of sensitivity parametrical point’s value in linkage mechanism is large, thus have large influence in transmission ratio of mechanism, the range of transmission ratio in bucket mechanism after optimization design changes from the previous maximum of 0.2991 to 0.3788 within a small stroke of oil cylinder, increased by 30.1%, the optimization effect is obvious.