CN201748029U

CN201748029U - Intelligent electric valve positioner based on HART communication

Info

Publication number: CN201748029U
Application number: CN2009202144280U
Authority: CN
Inventors: 李倩如
Original assignee: Shanghai Automation Instrumentation Co Ltd
Current assignee: Shanghai Automation Instrumentation Co Ltd
Priority date: 2009-11-30
Filing date: 2009-11-30
Publication date: 2011-02-16
Anticipated expiration: 2019-11-30

Abstract

The utility model relates to an intelligent valve positioner based on HART communication, wherein a microprocessor as the core receives external data through an HART communication interface, a digital signal and an analog signal can be transmitted without mutual interference to realize bidirectional communication, and the positioner has the function of checking the actuating mechanism character, dynamic deviation, step response and other information of the valve besides the rich software functions of the valve positioner. The valve positioner is convenient in installation, adjustment, maintenance and control, saves substantial cost, the control precision and use ratio of the intelligent valve positioner is improved, and the function of the positioner in the control field is greatly enhanced.

Description

Intelligent electric valve positioner based on the HART communication

Technical field

The utility model relates to a kind of valve control field, is specifically related to a kind of intelligent electric valve positioner based on the HART communication.

Background technique

Valve positioner is one of important auxiliary accessory of modulating valve, is widely used in industries such as electric power, metallurgy, petrochemical industry, light textile, food, medicine.Along with the application of field bus technique in industrial process control field, the networking of automatic system, total linearize are big trend, original intelligent valve positioner can not carry out digital communication by the control of 4～20mA analogue signal, can not satisfy the requirement of modern industry system.

Because the HART agreement has the characteristics of compatible with digital signal and analogue signal, under the prerequisite that does not influence analogue signal control, can carry out digital communication, have on-the-spot and remote parameter monitoring function, have incomparable advantage aspect reduction system cost, raising control accuracy and the system reliability.

The intelligent instrument that has the HART agreement is at present monopolized by The foreign chicken products on the market at home always, because the monopolization of its fancy price and technology, the cost of production of domestic enterprise is increased greatly, reduced the competitive capacity of enterprise, therefore researched and developed intelligent valve positioner and have very big realistic meaning based on the HART communication with independent intellectual property right.

Summary of the invention

The utility model is the problem that can't realize digital communication at existing intelligent valve positioner, a kind of intelligent electric valve positioner based on the HART communication has been proposed, on two-wire system intelligent valve positioner basis, increased digital communication functions, adopt Bell202 fsk signal standard, digital signal and analogue signal are transmitted under non-interfering situation simultaneously, realize both-way communication, selectively realize functions such as configuration, debugging, diagnosis and data management.Except that having the abundant software function of common intelligent valve positioner, also can check the information such as actuator's characteristic, dynamic deviation, step response of valve.In addition, the digital communication of positioning work piece can provide a large amount of information at a terrific speed, quick diagnosis when this breaks down for system is very important, and can be by comparison and assessment to process data, conveniently determine abort situation and reason fastly, and the proposition recovery scenario, strengthened its effect in the control field greatly.

The technical solution of the utility model is: a kind of intelligent valve positioner based on the HART communication, comprise MCU control unit, valve position feedback unit, I/P converting unit and HART communication interface, the MCU control unit comprises microprocessor, power circuit, sample circuit and man-machine interface; The valve position feedback unit comprises feedback potentiometer and valve position feedback lever; The I/P converting unit comprises the gas circuit control and the enlarged portion of two piezo electric valves and composition thereof; The HART communication interface is made of MCU interface and transformer coupled interface, power circuit provides power supply for microprocessor, compare computing from the signal of sample circuit and analogue signal through microprocessor from the valve position feedback unit, output a control signal to the I/P converting unit according to both deviations, I/P converting unit output control stem movement, the stroke of valve rod feeds back to microprocessor by the valve position feedback unit simultaneously and forms closed loop control, extraneous digital signal is sent signal into microprocessor by the HART communication interface after by the HART modem processes, man-machine interface setup parameter output microprocessor, microprocessor output state value shows to man-machine interface.

The data that described HART communication interface sends are sent into microprocessor through transformer coupled again through the operational amplifier amplification to 4～20mA direct current signal.

The beneficial effects of the utility model are: the utility model is based on the intelligent valve positioner of HART agreement, and at first, original cable arrangements and control strategy can continue to play a role; Secondly, can increase extra numerical information (mainly containing device parameter, secondary variable, range and aperture, control, diagnostic message etc.), be convenient to installation, adjustment, maintenance and control, thereby a large amount of expenses have been saved, improve simultaneously the control accuracy and the utilization ratio of intelligent valve positioner again, strengthened its effect in the control field greatly.

Description of drawings

Fig. 1 is the intelligent electric valve positioner theory diagram of the utility model based on the HART communication interface;

Fig. 2 is the intelligent electric valve positioner structural representation of the utility model based on the HART communication interface;

Fig. 3 is the intelligent electric valve positioner communication interface connection diagram of the utility model based on the HART communication interface.

Embodiment

As shown in Figure 1, 2 based on the intelligent valve positioner theory diagram and the structural representation of HART communication, comprise with microprocessor 8 being MCU control unit 1, valve position feedback unit 4, I/P converting unit 3 and the HART communication interface 6 of core, MCU control unit 1 also comprises power circuit 7, sample circuit 9 and man-machine interface 2; Valve position feedback unit 4 also comprises feedback potentiometer and valve position feedback lever; I/P converting unit 3 also comprises the gas circuit control and the enlarged portion of two piezo electric valves and composition thereof; HART communication interface 6 is made of MCU interface and transformer coupled interface.Power circuit 7 provides power supply for microprocessor 8, compare computing from the signal of sample circuit 9 and analogue signal through microprocessor 8 from valve position feedback unit 4, output a control signal to I/P converting unit 3 according to both deviations, 5 motions of I/P converting unit 3 output control valve rods, the stroke of valve rod 5 feeds back to microprocessor 8 by valve position feedback unit 4 simultaneously and forms closed loop control, outer signals is sent signal into microprocessor 8 by HART communication interface 6 after by the HART modem processes, man-machine interface 2 setup parameters output microprocessor 8, microprocessor 8 output state values show for man-machine interface 2.

The utility model is by being provided with HART communication interface, MCU control unit, 4～20mA analog input signal passes through the MCU control circuit unit with the analogue signal from valve position feedback unit 4, compare computing, output a control signal to I/P converting unit 3 according to both deviations, realize the location of intelligent valve positioner and drive valve rod 5 motions, the stroke of valve rod 5 feeds back to the MCU control unit by valve position feedback unit 4 simultaneously and forms closed loop control; Simultaneously, HART communication interface electric circuit inspection is superimposed upon the frequency signal on 4～20mA direct current signal, demodulates digital signal by MODEM, sends MCU to and handles; The result who handles is the alternating signal of HART semaphore request and is superimposed upon on the direct current signal through HART communication interface circuit modulation conversion, thus the digital communication of realization and external information.In the utility model, main variables and control information are transmitted by 4～20mA, and under the situation of needs, other procedure parameters, device configuration, calibration and configuration info are visited in the mode of digital communication by the HART agreement.

(1) MCU control unit

Inner integrated 12 bit A/D converters of MCU control unit, have super low-power consumption and can directly drive LCD, can save many peripheral chips, simplify hardware circuit design greatly up to the FLASH storage of 60KB and the RAM of 2KB.

(2) HART communication interface

This interface usefulness MCU and HART MODEM chip development are based on the intelligent valve positioner of HART communication, and be simple and convenient, dwindled space and cost.The main functional modules of HART MODEM is made up of control logic, carrier wave detection, modulation and demodulation four parts.The function of it is integrated input filtering and output Shaping can be simplified the reliability that interface circuit design realizes system.

The HART agreement adopts the Bell202 frequency shift keying signal of standard to communicate with 1200 baud rates.Its physical layer adopts the sinusoidal signal of two kinds of different frequencies (1200Hz and 2200Hz represent binary " 1 " and " 0 " respectively), is superimposed upon on 4～20mA signal to communicate, because the average of sinusoidal signal is 0, therefore can not influence current value.Adopt this mode can make analogue signal and digital signal can carry out both-way communication simultaneously and do not interfere with each other.

The HART communication interface mainly is made of MODEM interface and transformer coupled interface.MCU itself has the communication interface that serial ports can be used as itself and HART MODEM.

Be illustrated in figure 3 as MCU and HART communication interface connection diagram, semiduplex master slave mode is adopted in HART communication, and this product just can respond as the claim frame that only receives matching addresses from equipment.Do not have communication bus at ordinary times during the free time, HART MODEM detects less than signal of communication, and carrier wave detects output OCD pin and is always low level; When bus (4～20mA direct current signal) goes up the frequency signal that 1200 (± 10) Hz or 2200 (± 20) Hz occur, the band-pass filter of HART MODEM chip A5191 can intercept the frequency signal of this segment limit, therefore just can detect the HART signal of communication, the OCD pin of A5191 is output as high level, and demodulation circuit is demodulated into logic level signal by the output of ORXD pin with the frequency signal of input simultaneously.The P1.6 pin of MCU receives pin with serial ports and links to each other with ORXD with the OCD of A5191 respectively, after MCU detects P1.6 level saltus step from low to high, starts serial ports and receives, and the claim frame data are received by byte one by one with receiving interrupt mode; The HART frequency signal finishes on bus, OCD returns back to low level, the MCU serial ports finishes receiving and closes, MCU resolves, judges the data of receiving, press the claim frame regulation and carry out corresponding operating, result data is packaged as a frame response frame, starts the serial ports transmit mechanism, send one by one by byte with sending interrupt mode.The P1.3 pin of MCU sends pin with serial ports and links to each other with ITXD with the INRTS pin of A5191 respectively, in case enter the transmission state, the P1.3 pin zero clearing output low level of MCU, control HART MODEM switches to modulation system, be about to serial ports and send the frequency signal that data are modulated into 1200Hz or 2200Hz, by the operational amplifier amplification and through transformer coupled on bus, finish a HART communication after the shaping.

What the utility model adopted is semiduplex communication, and the system interconnection structural model according to the OSI organization prescribed is reduced to three-decker with traffic model, i.e. first layer physical layer, second layer data link layer and layer 7 application layer.Physical layer specifies the transmission method of signal, transmission medium; Data link layer has been stipulated the form of HART frame, and the link communication function realizes setting up, safeguards, terminates; Application layer regulation HART command set.Order is divided three classes, i.e. generic command, commonly used command and specific command.Generic command provides all and field apparatus function associated, and is the prerequisite function of HART equipment, and these orders comprise: read manufacturing firm and device type; Read initializaing variable and unit; Read the percentage of electric current output and range; Read 4 predefined dynamic variabless; Read and write 8 character items, 16 character descriptors, date; Read and write 32 character informations; Read range, unit and damping time constant; Read transducer serial number and boundary; The final assembling of read-write number; Write polling address.Commonly used command provides the function in the common multiple field apparatus, but is not that all equipment can provide these functions selectively.Commonly used command comprises reads a group selection of 4 dynamic variabless altogether; Write variable damping period; Write range; Calibration measurement (with current measured value zero setting or put maximum range); Fixing output current is set; Carry out self check; Carry out host reset; Adjustment equipment zero point; Write master variable unit; Adjust digital-analog convertor zero point and gain; Output-transfer function is set; The writing sensor sequence number; Write synchronizing code number etc.Specific command only provides at the special function of the field apparatus of this type, and it is peculiar, not compatible to be that the utility model is controlled oneself.

Because HART agreement predetermined data transfer rate is 1200bit/s, 10 milliseconds around an of character of every transmission, so adopt the mode of interrupting to receive and dispatch data in the software, all the other times can make MCU handle other affairs.The reception of the USART module of MSP430, transmission buffer memory all can produce independently and interrupt, and program is finished the various processing to the HART information frame in this interruption.In the receiving course of frame, unusual whenever detecting, corresponding state information can be set automatically, program interrupts focusing on mistake, the delay that occurs in the transmission course at timer, and calls corresponding processing procedure according to different request functions.The process of transmitting of information frame similarly, when system works during in group schema, MCU is released news by the timer control cycle, sending the solicited message (detection of OCD carrier wave) that whether has main frame to upload on the first detection line before the data, if do not detect OCD at the appointed time, then can send the form of the relevant information of equipment operation automatically with the HART information frame; If just there is main frame to communicate by letter, then preferentially carries out Host Command, or postpone or cancel the transmission of burst data according to the Host Command type.

Claims

1. the intelligent valve positioner based on the HART communication comprises MCU control unit, valve position feedback unit, I/P converting unit and HART communication interface, it is characterized in that the MCU control unit comprises microprocessor, power circuit, sample circuit and man-machine interface; The valve position feedback unit comprises feedback potentiometer and valve position feedback lever; The I/P converting unit comprises the gas circuit control and the enlarged portion of two piezo electric valves and composition thereof; The HART communication interface is made of MCU interface and transformer coupled interface, power circuit provides power supply for microprocessor, compare computing from the signal of sample circuit and analogue signal through microprocessor from the valve position feedback unit, output a control signal to the I/P converting unit according to both deviations, I/P converting unit output control stem movement, the stroke of valve rod feeds back to microprocessor by the valve position feedback unit simultaneously and forms closed loop control, extraneous digital signal is sent signal into microprocessor by the HART communication interface after by the HART modem processes, man-machine interface setup parameter output microprocessor, microprocessor output state value shows to man-machine interface.

2. the intelligent valve positioner based on the HART communication according to claim 1 is characterized in that, the data that described HART communication interface sends are sent into microprocessor through transformer coupled again through the operational amplifier amplification to 4～20mA direct current signal.