Abstract:The position of conventional hydraulic swing system with large inertia is controlled with driver-in-loop. According to the observation, the driver adjusts the handle to control the multiway valve with single degree of freedom. Because the human reaction is slow, the production efficiency and repetitive positioning precision is low, and it is difficult to meet the requirements of engineering operations with high rotary positioning accuracy. Furthermore, the energy consumption is high. To solve the above mentioned problems, based on the separate meter-in and meter-out hydraulic swing system, a velocity and position combined control method was proposed. In this method, a precisely desired position was given as the input signal for the position closed-loop control, and the desired velocity and displacement were S-curves. In addition, the velocity feedforward control and position closed-loop control were used to reduce the tracking error, and the pressure and velocity feedback control were also applied to the swing system to improve smoothness of the working process. Firstly, a three-dimensional co-simulation simulation model was developed, which integrated the multi-body dynamics system and electro-hydraulic system for analyzing the feasibility of this swing system, and the control parameters of the hydraulic components were determined according to hardware and the control strategy developed. Then the system principle and the control strategy were verified and debugged by making a simulation. Besides, an experiment was carried out on a 6-ton hydraulic excavator. The simulation and experiment results demonstrated that high positioning accuracy can be achieved in both forward and reverse moving directions with different desired speeds. The positioning error was about 0.5°~1.5°, and the velocity and pressure fluctuation were all reduced. The maximum fluctuation pressure was decreased by 41.6%.
