Research On The Intelligent Valve Position Servo System

As computer technology develops and has been used in the industrial automation manufacture process widely, the new intelligent valve positioner based on computer technology, has replaced the common valve positioner and become popular in the current industrial manufacture. Pneumatic control technique has been widely used in manufacture and become an important method of automation due to its unique advantages. Modern product line required the process to be controlled more reliably, exactly and speedily. So it is important that the valve servo position system is researched. The content of this thesis includes six sections:Chapter 1 first describes the background, application and development of the valve positioner and analyzes the deficiency of the common positioner. Then the principle of the intelligent positioner is presented, and the advantages and developing trends are analyzed. In the end this chapter points out the significance and main content of the research work.Chapter 2 describes the construction of the valve servo position system. Design and assemble the experiment system using an Industrial PC, a data acquisition and control card, a potentiometer, a pneumatic Actuator, a ball valve, four high-speed switching valves which controlled by PWM (Pulse-Width Modulation) and etc.Chapter 3 analyzes the modeling of position servo system for pneumatic actuator controlled by high-speed switching valves and deduces the mathematic model of the system. According to the transfer function, we can find the system is a complex 4th-order system, and it can be reduced to a 3rd-order system conditionally. Using Matlab, we establish the model and simulate the real system to obtain the best parameters for the system.Chapter 4 researches on the control algorithms. Based on the mathematic model of the system, several control algorithms are presented, such as PID controller, state feedback controller, and etc. In state feedback controller, state observer are discussed which can observe the real state of the system, such as velocity, and acceleration. To test the static and dynamic performance of the system using control methods, we make experiments on signals-following, such as step signal, square wave, sine wave, and saw tooth wave. Analyzing the control results of different methods with different parameters, we try to find the best control methods for the pneumatic position system to improve its robustness, preciseness, and speediness.