Author: mild Teng Zhao Sheng Liang column height Yunpeng Abstract: lack of existing electric actuators, proposed and designed a network of electric actuators is given based on the basic structure and working principle of networked electric actuators msp430f449 MCU introduced Motor drive control circuit, ddz2 ⅲ type signal interface, communication interface hardware circuit design. The network electric actuator realizes long-distance communication and the management through the field bus, adopts the complex intelligent control method based on the bang-bang + fuzzy control, which improves the real-time and reliability of the system. The actual operation shows that the networked electric actuator runs stably and reliably , Stroke control accuracy of 1 ‰. The electric actuator drives the motor running according to the deviation between the given signal output by the regulator and the feedback value of the displacement of the regulating Valve to realize the automatic control of the position of the regulating valve through the output angular displacement or linear displacement of the transmission and the transmission mechanism. 1 shown. Figure 1 Block diagram of the electric actuator With the improvement of the level of industrial automation, the traditional electronic electric actuator in the function, accuracy, cost-effective and so has been difficult to meet the practical application needs. The author developed a new type of network-based electric actuator with msp430f449 as the information processing unit, fieldbus communication, intelligent control and network management functions, and developed a host computer system and a portable controller based on the virtual instrument to improve the electric execution Machine operability and reliability. A network of electric actuators as shown in Figure 2, the networked electric actuator system includes networked electric actuators, field bus conversion, portable controller and host computer system and other 4 parts. The networked electric actuator controls the motor operation according to the deviation between the given quantity and the feedback quantity. The field bus conversion is realized through the conversion of the communication protocol, so as to realize the conversion connection between the rs-485 bus and other different field buses, so that the network electric actuator can match various types of processes Control system; portable controller is used to achieve the network easy to set the parameters of the electric actuator device settings, you can achieve through the infrared communication actuator parameters quickly set; virtual instrument technology based on the host computer system is a network of electric execution Remote management platform, you can rs-485 bus actuator to achieve the operation and management, and access to Ethernet for remote control. Figure 2 networked electric actuator 2 electric actuator control unit circuit design The structure of the electric actuator control unit shown in Figure 3, using the msp430f449 microcontroller produced by ti as the information processing unit, the microcontroller contains 8-channel 12-bit adc (A / D converter, the maximum sampling rate of 200kps) and on-chip temperature sensor to meet the functional requirements of networked electric actuator. Networked electric actuator communicates with host computer system through rs-485 bus and communicates with portable controller through infrared communication. Actuators can be directly connected with the device type ddz ⅲ, by the adc microcontroller comes on the regulator output ddz-ⅲ type signal (4 ~ 20ma or 1 ~ 5v DC signal) after the sample processing. The actuator realizes the real-time temperature measurement of the control circuit unit by using a temperature sensor embedded in the single chip microcomputer, and real-time measurement of the motor temperature is performed by using a 12-bit digital temperature sensor (ds18b20). The position feedback signal of the control valve is composed of a motor- Photoelectric encoder obtained. Figure 3 networked electric actuator block diagram SCM by calculating the given deviation from the feedback, in accordance with the predetermined control method output motor drive signal, the optical isolation drive motor running. In order to prevent the actuator more damage equipment, networked electric actuator installed limit switch limit detection and protection. In the event of a malfunction, the networked electric actuator can be switched to manual mode and motor operation can be controlled by manual operation. 2.1 motor drive circuit networked electric actuator must have positive and negative run function, so choose non-contact solid state relay as single-phase motor positive and negative and start and stop control device. As shown in Figure 4, the logic gate circuit and Darlington drive (mc1413) constitute the forward and reverse control circuit. msp430f449 microcontroller output signal (x2, x4) after the trigger logic control circuit to control the solid state relay off. Figure 4 single-phase motor drive control circuit circuit in the gate (74hc04) and AND gate (74hc08) to interlock the signal to prevent positive and reverse signals at the same time conduction. mc1413 for the reverse drive, play a role in absorbing current, when mc1413 output low, the control of solid-state relay ssr conduction, which drives the motor running. When x4 output high, x2 output low, the motor is connected to the positive winding, the motor forward; when x2 output high, x4 low output, turn the motor anti-winding, the motor reverse; when x4 , X2 are high output or both output low, the circuit self-locking, the motor stops. m is the motor winding, r51, r52, c50, c51 is the absorption circuit, rv is a zinc oxide varistor, together play a role in protecting the solid state relay. The motor winding plus AC power, measured voltage u, current i, the frequency f, the motor winding resistance r, according to equation (1) can calculate the capacitor c53 configuration of the theoretical value of a model such as single-phase motor, the measured parameters are as follows u = 228v, i = 2.4 ~ 10.5a, f = 50.2hz, r = 3.8ω, calculated c53 value of 35 ~ 150μf. When any one of the two ssr is turned off, the voltage at the off ssr output is approximately twice the ac supply voltage. Therefore, the choice of c53 and ssr rated voltage, the power supply voltage should be greater than 2 times, and the commutation time must have more than 30ms delay, to ensure that the motor is not frequently in the process of starting capacitor c53 and ssr breakdown. 2.2 ddz-ⅲ type signal input and output channels ddz-ⅲ-type output channel shown in Figure 5, digital-analog converter is a dual 12-bit serial input digital-analog converter dac7822, msp430f449 microcontroller i / o port p2 .5 and dac7822 data input ldac connected to the channel select terminal a / b then low, select the channel a for analog-digital conversion, dac7822 current output type, the current output pin iout1a and iout2a and opamp u5c (lm324 ) Can be connected to the voltage output. The dac7822 reference voltage terminal vrefa then -10v, after op amp u5c conversion, you can get a positive voltage output. msp430f449 microcontroller dac7822 output data changes between 409 ~ 2048, vout can be obtained 1 ~ 5v voltage signal output. Op amp u7a, u7b and r73, r74, r75, r76, r77, r78, c77 constitute voltage and current conversion circuit, the 1 ~ 5v voltage signal is converted to 4 ~ 20ma current signal output at the iout end, to achieve ddz-iii type of signal Output. Figure 5 ddz2 ⅲ type signal output channel
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