| Now steel plants use the exhaust gas produced in production processes to generate power, it is energy-conserving and environment-protective, but there is a technical difficulty that the pressure of control valves cannot be adjusted well. The control valves, as the last control units in industrial process control, are indispensable and widely used in petroleum, chemical engineering, electric power, metallurgical, etc. Since energy saving, emission reduction and environment protection are attracting more and more attention, there are higher and higher requirements on technical properties of the control valves in many industrial occasions. However, the control valves used in our country are mainly traditional types which have slow response speed, high energy consumption, low control accuracy and other drawbacks, so it is very necessary to research the technology of a new kind of high-performance control valve. In this thesis, performance requirements of the control valves used in steel plants or others are analyzed, and new energy-saving technology of hydraulic transmission and control system is concerned. On this basis, research on developing a new control valve is carried out aiming at high efficiency, energy saving, compact structure, rapid response and precise pressure control.Firstly, a new kind of high-performance control valve with the DDVC electro-hydraulic servo system as its actuator (hereinafter called "the direct drive electro-hydraulic control valve") was designed. Hydraulic system principle was drawn up, and main components of it were selected and matched. Then through the contrastive analysis of the direct drive electro-hydraulic control valve and traditional control valve, it is undoubled that the former one’s merits are prominent. After that, a set of compact layout of mechanical structure was finished.Secondly, on the basis of the requirements and characteristics of this system, single-chip microcomputer control mode was choose and a control system in the valve based on PIC16F877MCU was designed. For the hardware, there are keyboard inputs, data collecting and storage, LCD, alarm, servo motor control and other circuits, and the entire control unit could be built into hydraulic unit. For the software, there are three control models which are function setting, servo control and on/off status. Program of the slave computer and the host computer was finished in MPLAB and C++builder, and it has simple algorithm, rapid execution and low power consumption.Thirdly, according to the operation principle, the mechanism model of the direct drive electro-hydraulic control valve was established. Through analyzing the working principle of servo motor and the flow and force characteristics of the pump-cylinder system, together with researching the relationship among flow, pressure, opening and force of the valve body, the dynamic mathematical model of the system was established. Transfer function was deduced afterwards, and the system stability analysis by employing the MATLAB software indicated that the stability margin was satisfactory.Finally, a fuzzy PID switch control strategy optimizing by offline ant colony algorithm was presented, and it was used to control the pressure. By programming in MATLAB to imitate the controller working status, a more accurate simulation was realized. From this, study on the dynamic and static performances of the system controlled by the ant colony fuzzy PID switch or traditional PID was carried out, it indicated that step response performance, square-wave tracking capacity, robustness and resisting disturbance capacity of the system controlled by the former could achieve design requirements and was clearly better than the latter. The simulation result showed that the direct drive electro-hydraulic control valve could meet the operating requirements of high-performance control valve. |
PDF Full Text Request