Medium-sized Hydraulic Excavator Slewing System Performance

Slew system is an important sub-system of hydraulic excavator, the performance of slew system directly affects property improvement of the whole machine. For medium-sized hydraulic excavator, because the quality of the entire machine and its load is high, the slew system has typical characteristics of large inertia load system:its starting and braking characteristics, coordination of compound action on slewing and boom lifting are not very ideal. In order to optimize the performance of hydraulic excavator's slew system, this paper made a deep study on slew system of medium-sized hydraulic excavator from the following three aspects:overflow when starting, reverse when braking, poor coordination of compound action on slewing and boom lifting.The general law of slew platform's motion is generalized, Formula of slew platform's inertia moment is deduced by D-H coordinate method. Aim at the typical double-pump double-loop medium-sized hydraulic excavator, the non-full open valve controlled slew motor system's block diagram and transfer function are derived. Then the slewing and boom lifting hydraulic circuit is theoretically analyzed, and the reason of poor coordination on slewing and boom lifting compound action is concluded: the slew system and the boom system are coupled.The co-simulation model is build by hydraulic analysis software AMESim and dynamic analysis software ADAMS, and then verifid through experiments. The co-simulation model is used to analyze the slew system's characteristics:how slew platform's moment of inertia, motor's displacement, gear ratio affect overflow characteristics when starting and reverse characteristics when braking; dynamic characteristics of platform and hydraulic boom cylinder; how the diameter of hydraulic boom cylinder, equivalent orifice diameter of priority valve affect the coordination on slewing and boom lifting compound action. Based on this, the coupling between slew system and boom system is optimized, and the performance optimazation of the slew system is realized by parameters amendment.