Study On Control System And Electronic Torque Protection Of Electric Actuator

The control valve is an important execution unit in the industrial automation and process control. With the development of modern science and technology, people have higher standard on the accuracy requirements of the regulating valve and the market demand of control valve is also growing increasingly especially for high-performance control valve. In order to meet the domestic needs on the production of industrial automation and reduce the cost of industrial production, at the same time in order to break down foreign monopoly for China’s high-performance control valve technology, we need to develop the high-performance control valve with independent intellectual property rights. The performance of the control valve depends primarily on the actuator. As one of them, the electric actuator widely used because of the character of convenient drive energy and small size.In order to improve response speed,control accuracy and security, this paper does some research work on control system and electronic torque protection of the electric control valve based on development status and development tendency of control valve.Firstly, according to the requirements and characteristics during the production process, a controller of regulating valve based on ATmega128 microcontroller is developed. It can perform many functions such as keyboard input, data acquisition, liquid crystal display, data storage, infrared control, temperature detection, hazard warning function and other functions. The hardware circuit is drawn in Protel while the main program and subroutine programming is finished in AVR Studio software.Secondly, on the basic research of the mathematical model of the three-phase ac motor and the motor vector control principle, we can make the three-phase ac motor to be equivalent for dc motor through some mathematical methods, such as coordinate change, flux linkage, and then we can deduce the identification algorithm of the electromagnetic torque. Through the algorithm the function of the torque automatic and real-time measuring can be realized, And it only needs two data that the three-phase voltage and three-phase current of the motor.Finally, based on the identification algorithm of the electromagnetic torque, we can built a simulation model in the Matlab/Simulink environment, and then we load this simulation system with different kind of types load, such as step load,lope load and so on. Then we can get the measuring accuracy of identification algorithm in the simulation environment, the data from which can be the preliminary data reference for the next experiments which can finally validate the precision of the identification algorithm. Then we have design the control system containing the software and hardware with the STM32F103 as the control chip, to realize the function of the real-time measuring. This control system is equipped with three main functions, that the detection of the three phase current and three-phase voltage, the torque real-time computing and display and the immediate protection under overload situation. And then we built the experiment platform with the MDU-type motor experiment device as the load device. Finally we can get the measuring accuracy of the identification algorithm and the torque measuring device by comparing the load torque and the identification torque.