The Performance Analysis Of Constant Power Variable-Displacement Pumps

For an excavator, it has to rotate, shake the arm, move the arm, shovel, and walk. What' s more, the working environment is complex and usually bad. The excavator consumes great amount of power when being working. In order to performance excellently and use the power of the engine effectively, constant power variable-displacement pump is widely used in the hydraulic system of excavator. The characteristic of variable-displacement pump is an important reference of control system's quality. In order to optimize variable-displacement pump, it is necessary to analyze the influence of the components on the characteristic.Then we setup the mathematical model of variable-displacement pump and the model is simulated with MATLAB/SIMULINK. It is a direct method to study the characteristic of variable-displacement pump. It can give guidance to the designer and save a lot of time and sources, which will be widely used in the development of hydraulic component.The variable-displacement pump integrated several control methods which is widely used in construction machinery is regarded as the studying object in this thesis. Firstly, the principle of total power control,variable power control and negative flow control are introduced. The formulas of flow are given and the influence of spring on the static characteristic is analyzed. Secondly, the total power control model and negative flow control model are setup after the simplification of the variable-displacement mechanism. System simulation diagram is described and runs in the MATLAB/SIMULINK. Simulation results are analyzed, getting advantage and disadvantage of the system response. The influence of the components on the dynamic response is analyzed by changing the parameters. At last, the spring of constant power control mechanism and the main size of servo piston are optimized based on mathematics and hydraulic theory by the optimization toolbox of MATLAB.The influence of the components on the characteristic are generalized and the design basis of variable-displacement mechanism is discussed based on the analysis of the variable-displacement pump, which offers reference of constant power variable-displacement pump's design.