Aiming at the problems of large volume, low control precision and difficulty in field calibration and maintenance of hydraulic valve controllers currently used in the market. An intelligent electric actuator for hydraulic valves based on 32-bit embedded RISC microprocessor with ARM core is designed.
Compared with the traditional hydraulic valve electric actuator, the practical application results further improve the accuracy and reliability of industrial process control. It has the characteristics of small size, high reliability, high precision and low cost. In the research and development of hydraulic valve controller, how to achieve braking more effectively is an urgent problem to be solved.
The control precision in the process of opening and closing control is directly related to the quality of products. Aiming at the problems of large volume, thermostatic element low control precision and difficulty in field calibration and maintenance of hydraulic valve controllers currently used in the market. We use advanced information processing technology to design a hydraulic valve positioner control system based on ARM, which satisfies the opening and closing accuracy of the hydraulic valve controller. This has important practical significance for the formation of new intelligent electric valve actuator products produced by our country. The system uses low power ARM9 S3C2410 as the core of the control circuit. When working, the set valve opening current signal is input through the HART communication module. After working, the signal is compared with the actual opening signal fed back by the hydraulic valve controller through the JTAG debugging circuit. The deviation and deviation change rate signal are adjusted by the parameter tuning algorithm, and the pulse signal of the corresponding width is output.
The solenoid valve opens and closes, thus realizing the accurate liquid output. The hydraulic valve controller is a typical computer control system. The control principle of the system is shown in Figure 1.
The basic composition of the hardware system is shown in Figure 2. It consists of 32-bit ARM microprocessor S3C2410, JTAG debugging circuit, optocoupler driving circuit, LCD display, signal feedback, temperature, reset circuit, I/V conversion circuit and power supply. In the valve position control circuit, a 0.5-4.5V DC signal from the opening potentiometer is designed to represent the position signal of the valve opening. Therefore, the sampling process of this position signal will directly affect the control accuracy of the valve opening.
In order to eliminate the high frequency interference in the signal process and improve the control accuracy, we use the digital filtering method to achieve. The parameter tuning of the hydraulic valve controller includes zero point, stroke and sensitivity parameter tuning. A 12-bit A/D converter is used to adjust the positive parameters. Its resolution is 1/4096. The system unifies the relative values into 0.00025 units for comparison. In software programming, 25% of the zero adjustment is converted to 0-1023, while the voltage conversion range of the feedback potentiometer is processed to 0-4095.
In the process of control, sensitivity adjustment should be added to satisfy the condition that the zero value and feedback value are equal and the motor stops turning. In order to prevent system vibration, the sensitivity adjustable range of this protocol and system is 0-0.5%. That is, the difference between the opening value and the remote given value is within the range of 0.5% and the opening value is consistent with the given value. In software programming, 000H-0FFFH, i.e. 0-4095, is used to represent the corresponding A/D conversion value. The sensitivity A/D conversion is realized by the formula PROP=PROP*40/4095, which simplifies the calculation procedure.
On the basis of zero adjustment, travel adjustment is also needed. The adjustment range is 20%-100%, and the numerical range after conversion is 819-4096, which corresponds to the opening value of 20%-100%. The LCD display system is designed, which can be adjusted by the LCD stroke. This intelligent hydraulic valve electric actuator based on ARM takes 32-bit embedded RISC microprocessor of ARM core as the core, and adopts improved parameter setting algorithm to meet the opening and closing accuracy of hydraulic valve controller.
Compared with the traditional hydraulic valve electric actuator, the control accuracy and reliability have been further improved. Practical application shows that it has certain practical value.