Study On Control Of Straight Travel Electric Actuator

Valve is widely used in the control of the pipeline system in petrochemical, electricity, metallurgy, urban heating, textile, construction,etc. With the acceleration of China’s modernization and automation of industrial processes, the status of the valve industry in the equipment manufacturing industry has become increasingly prominent, which has brought challenges to the valve industry. The valve actuator, as the key component to drive the valve, higher requirements have been put forward in its response speed, control accuracy, security, etc.In which,the electric actuator constantly enjoying the achievements of technological development has already met the needs of the control towards valve,because of its outstanding performance. However, the high-end market of electric actuators are mostly monopolized by the foreign giants, so it is imperative to develop the high level electric actuators with independent intellectual property rights. Based on the above thinking, the study on the control of straight travel electric actuator is carried out.Firstly, according to the specific working conditions of the electric actuator, the overall design of the control system was completed and a controller based on LPC1768 chip was designed. For the hardware, there are keyboard inputs, LCD display, serial communication, data storage and acquisition, alarm, servo motor drive and other circuits. For the software, the parameters setting, servo control, serial communication and other functions of the actuator were achieved. The algorithm is simple and the program has high execution speed.Secondly, according to the demand of remote control to the electric actuator, based on RS-232 serial communication protocols, a PC monitoring system was designed by using VB language. The PC monitoring system can communicate datas with the lower machine controller, complete the control of control system, be able to establish a database and complete more advanced database operations.Thirdly, a method which can quickly and accurately identify the electromagnetic torque of AC induction motor was introduced, aiming to apply to the electronic torque protection systems of electric actuator. A detailed derivation of the torque identification algorithm was given, which was begun with the mathematical model of AC induction motor, through coordinate transformation, the rotor field orientation, the rotor flux observer and finally achieved. The accurate simulation was carried out by modeling in Matlab/Simulink, and with the study on the identification of the step load torque of the system, the superiority of the proposed identification algorithm was verified.Finally, the electric actuator system was analyzed, based on the mathematical model of the individual part of the system, the transfer function of electric actuator was deduced, and verified that the system had good stability.Then, the control strategy of the electric actuator control system was studied, based on the conventional PID, the "teaching and learning" (TLBO) algorithm optimized PID control strategy was proposed.By programming in MATLAB, the performances of the actuator control system with the new control strategy in step response and tracking sine, square wave, random signal were obtained.The superiority of applying the new control strategy was verified, and the electric actuator can meet the design requirements.