Shi Guanglin

Modeling and analysis of the electro-hydraulic proportional valve controlled motor system supplied by variable pressure accumulator

In recent years, the electro-hydraulic control system, which takes accumulator as the energy storage and oil supplying component, has been preliminary applied in hybrid electric vehicles, energy collection and power systems. Different from traditional electro-hydraulic control systems, the imported oil pressure of electro-hydraulic control system which is supplied by accumulator will decline over time. So it is not a constant value. This phenomenon has additional interference with the load control, especially for electro-hydraulic control systems which has a requirement for a constant speed. So firstly an electro-hydraulic valve controlled motor system with variable pressure accumulators for supply hydraulic oil is designed, in which the electro-hydraulic proportional valve control hydraulic motor is needed to drive an AC or DC generator with constant speed rotation and power. Secondly the mathematic model of this system supplied by variable pressure accumulator is built. Then the corresponding system transfer function is deduced. And the static and dynamic characteristics of system are analyzed in theory. Thirdly, based on a combination of Matlab / Simulink and AMESim, the simulation models of the studied system are built, which are focused on the simulation analysis. Fourthly, a method with a combination of real time feedback of output pressure of accumulators and PID control is presented in this paper. Its corresponding control system simulation is completed. Finally, the experiment prototype is made. The theoretical analysis, simulation and the experimental results show that the mathematic model and the transfer function of the system are correct and effective. The performance of the new control method is better than that of the traditional PID control method.

Research on the force compensation control strategy of machine part chamfering robot

As for machine parts with irregular shaped face edges, they are usually chamfered by human labor or chamfering machines which grind along the irregular edges with positon control. Especially some machine parts may have multiple space plane to be chamfered, which also need certain high chamfering quality. To solve this problem, a new machine part chamfering robot is designed, which is based on force compensation control. The chamfering robot mainly consists of vertical axis (Y-Axis), horizontal axis (X-Axis), compensation axis and rotation axis. X-Y table conducts interpolation motion to track the work piece. Meanwhile, the rotation axis, fixing with work piece, can rotate to meet the demand of multiple space contour processing. And the key component is the compensation axis (C-Axis) which has been equipped with a force sensor along the axis. So the compensation axis can receive real time feedback force signal. And according to the preliminary simulation, the friction compensation which is based on the exponential friction model is added to reflect and approximate the real axial cutting force to realize constant force processing while other double axes simultaneously motion to achieve trajectory tracking. Focused on PID control strategy, the control system of the compensation axis and X-Y table, as well as the X-Y-C axes of chamfering robot is analyzed. Furthermore the simulation models are respectively built in this paper. Finally simulation results show that by using force compensation control, the machine part chamfering robot can process with good quality and high efficiency.

Research on the Constant Speed Control System of Hydraulic Motor Under Variable Flow-Rate Input Based on Dual-PID Method

With the development and application of wind power generation and wave power generation, the hydraulic pump-motor control system has a unique effect on power conversion and constant speed driving of power generator. In this situation, the hydraulic pump-motor control system is required that the output speed of the hydraulic motor must be constant when the flow-rate input is randomly varied. Therefore, the power generator driven by the hydraulic motor can maintain constant speed and generate constant frequency electricity power. Considering the particular requirement mentioned above, this paper proposes a stratified-adjustment closed-loop speed control system which is rough-tuned by a variable-displacement motor and fine-tuned by a bypass proportional flow control valve and a control strategy based on dual-PID method. When the flow-rate from the hydraulic pump is randomly varied, the displacement of the variable-displacement motor and the opening of the bypass proportional flow control valve are stratified adjusting by a dual-PID controller, so that the output speed of the variable-displacement motor can maintain constant despite the flow-rate input varying. The simulation and the experiment show that the dual-PID stratified algorithm is effective for constant speed control of hydraulic motor under variable flow-rate input, and it fulfills the requirement of generating constant frequency electricity power.Copyright