Total Horsepower And Negative Flow Control Analysis

Hydraulic excavator is a very efficient construction machine, has been widely applied in various fields. Hydraulic transmission is its main driving force transmission mode, with big power, high energy consumption characteristics. In order to reduce energy consumption, improve efficiency and machine life and reliability, manufacturers conducted a in-depth research in excavator hydraulic system and developed a variety of controlling machinery and methods. Among them, the total horsepower and negative flow control can be effective in preventing motor overload and improve system efficiency, has become one mainstream of the excavator hydraulic system controlling ways.The two broken pressure-flow lines of Constant power control best approximates to power hyperbolic, approximate realization of constant power control. The pairs of pump outlet pressure acting on loading plunger and constitute the total horsepower control. The control pressure of Negative flow control exported by detection unit of multi-channel valve is applied to the pilot plunger, so that the pump output flow is proportional to the velocity of the load, and inversely proportional to the control pressure. Control system consists of four components:the load piston, planar linkage, the valve-controlled cylinder and swash plate. To work out the calculation method of the structural parameters of the load and the pilot plunger, balance spring and the linkage, deriving the related equations based on the pressure-flow curve. The results show that the equations are under-constrained equations, given different initial conditions are corresponding to different parameters structure. To selection and verify the parametes of the control system to meet the requirements of control system static and dynamic characteristics, establishing the total horsepower and negative flow control simulation model in AMESim. Selecting a different value of the plunger dimension, balance spring elasticity coefficient, the initial amount of compression springs and so on, to get the corresponding parameters of the system step response and comparatively analyse the step response rise time, accommodation time, and overshoot, and the qualitative effect applied to the control system when the parameters changed.so as to select parameters based on the result. Servo piston and valve have a direct impact on overall system performance. So that, first having a analysis of hydraulic torque applied to the swash plate, and deriving the minimum area of the servo plunger selection which meeting the force balance equation. For the analysis of valve output flow, deriving the speed of servo piston with sine integral method to meet the response time. Compared the servo piston velocity with the simulation results. The results show that there is 10%～20% deviations between the speed of integration and the simulation results. Valve spool displacement Deduced from the linkage ideal feedback, compared to the spool displacement derived from simulation of real-time feedback. The results show that the real-time feedback spool displacement is the ideal feedback spool displacement 60 percent. These deviation values are used to amend the calculation results.Then based on maximum flow of valve and the valve spool displacement analysed the structural parameters.