Controller for field equipment signal to enter DCS (Distributed Control System)

Abstract

The embodiment of the invention provides a controller for a field equipment signal to enter a DCS (Distributed Control System), which belongs to the technical field of electrical electronics and comprises a communication circuit and a single chip microcomputer, when the controller is arranged on a field device, the communication circuit is used for converting DO and AO signals, collected by the single-chip microcomputer, of the field device into digital signals and transmitting the digital signals to a DCS device comprising the controller. And when the controller is arranged on the DCS, the communication circuit is used for restoring the received digital signals into DO and AO signals of the field equipment, inputting the DO and AO signals into the DCS as DI and AI signals, collecting output signals DO and AO signals of the DCS, converting the output signals DO and AO signals into digital signals and transmitting the digital signals to the field equipment comprising the controller so as to control the field equipment. According to the controller provided by the embodiment of the invention, a large number of control cables from field instrument equipment to a DCS are changed into one optical cable for transmission, a cable line used in the past is replaced, daily maintenance is facilitated, and meanwhile, the installation and construction cost is reduced.

Description

Technical Field

[0001] The present invention relates to the field of electrical and electronic technology, and in particular to a controller for field device signals to enter a DCS. Background Art

[0002] In industrial automation production, such as the automation processes in petrochemical, metallurgical, electric power, pharmaceutical and other industries, instrumentation equipment is required to input data into the distributed control system DCS. Among them, the closed and open signals are used to monitor the valve position. When the valve is closed and opened, they can detect the state of the valve in a timely and accurate manner, and transmit the signal to the DCS for subsequent control processing. The existing technology uses a switch valve to give open and closed signals, and a simple switch valve requires 3 control cables, resulting in a large number of cables from the site to the DCS equipment. Moreover, when subsequent industrial production requires additional instrumentation equipment, it is also necessary to add cables simultaneously. The current laying method is to use cable tray laying. The more cables are placed in the tray, the more interference will increase on the one hand, and the installation and laying costs of the tray will also increase accordingly on the other hand. Summary of the invention

[0003] The purpose of the embodiment of the present invention is to provide a controller for a field device signal to enter a DCS. The embodiment of the present invention can solve or at least partially solve the above-mentioned defects of the prior art.

[0004] In order to achieve the above-mentioned object, an embodiment of the present invention provides a controller for field device signals to enter a DCS, the controller comprising a communication circuit and a single chip microcomputer;

[0005] When the controller is set on the field equipment, the communication circuit is used to convert the DO and AO signals of the field equipment collected by the single-chip microcomputer into digital signals and transmit them to the DCS equipment including the controller;

[0006] When the controller is set on the DCS, the communication circuit is used to restore the received digital signals into DO and AO signals of the field equipment and input them into the DCS as DI and AI signals, and collect and convert the output signals DO and AO signals of the DCS into digital signals and transmit them to the field equipment including the controller to control the field equipment.

[0007] Optionally, the communication circuit includes a first communication unit and a second communication unit, and the single chip microcomputer is connected to the first communication unit and the second communication unit;

[0008] When the first communication unit fails, the single chip microcomputer controls the communication circuit to switch to the second communication unit for signal processing.

[0009] Optionally, when the first communication unit fails, the single chip microcomputer controls the communication circuit to switch to the second communication unit for signal processing, including:

[0010] The sender sends a confirmation frame to the receiver at a preset frequency, and the receiver sends a corresponding confirmation frame to the sender after receiving the confirmation frame and verifying it successfully. When the time the sender waits for the confirmation frame sent by the receiver exceeds a preset threshold or the confirmation frame sent by the receiver fails to be verified, the single-chip microcomputer controls the communication circuit to switch to the second communication unit for signal processing;

[0011] Among them, one of the sender and the receiver is a controller set by the field device, and the other is a controller set by the DCS.

[0012] Optionally, the first communication unit and the second communication unit are 485 differential circuits, and the 485 differential circuits include RS485 transceivers;

[0013] When the RS485 transceiver transmits a signal, it is used to convert the DO and AO signals into differential signals in the communication line;

[0014] When the RS485 transceiver receives a signal, it is used to restore the differential signal in the communication line into DO and AO signals.

[0015] Optionally, the digital signal is transmitted between the field device and the DCS via Category 5 wire or optical cable.

[0016] Optionally, the controller includes a photoelectric isolator, which is used to electrically isolate the single-chip microcomputer and the communication circuit.

[0017] Optionally, the digital signal converted by the communication circuit is transmitted in a point-to-point mode, and the address code is removed from the transmission control word.

[0018] Optionally, the controller includes: a power supply circuit, the power supply circuit is used to supply power to the single-chip microcomputer, and includes a first power supply, a second power supply, and a voltage regulator;

[0019] The voltage regulator is used to adjust the source input voltage to a target voltage value;

[0020] The first power supply and the second power supply are connected in parallel to the voltage regulator, the first power supply is connected in series with a first diode; the second power supply is connected in series with a second diode;

[0021] The first diode is used to prevent the first power supply from affecting the power supply circuit when the first power supply fails; the second diode is used to prevent the second power supply from affecting the power supply circuit when the second power supply fails;

[0022] When the first power supply and the second power supply are both normal, the first power supply and the second power supply supply power to the single chip microcomputer simultaneously;

[0023] The second power supply provides backup power to the single chip microcomputer when the first power supply fails.

[0024] Optionally, the single chip microcomputer is an STM32 single chip microcomputer.

[0025] Optionally, the controller includes an alarm output control circuit;

[0026] The single chip microcomputer comprises a first output terminal;

[0027] The alarm output control circuit includes a relay, a third diode, a triode, and a second output terminal;

[0028] The base of the transistor is connected to the first output terminal of the single chip microcomputer;

[0029] The coil of the relay is connected in anti-parallel to the third diode and then in series to the collector of the transistor; when the transistor is turned off, the current in the coil of the relay is released through the third diode to avoid the high voltage caused by sudden shutdown from damaging the transistor;

[0030] When the single chip microcomputer detects that the controller has a fault, it controls the first output terminal to output a high level, controls the transistor to conduct to close the relay, closes its normally open point, and outputs a signal from the second output terminal to the DCSDI point, which is recognized by the DCS and a corresponding prompt appears on the DCS screen.

[0031] Through the above technical solution, the embodiment of the present invention provides a controller for field device signals to enter the DCS, which changes a large number of control cables from field instrument equipment to DCS to one optical cable transmission, replacing the cable lines used in the past. The controller uses 485 half-duplex communication and transmits through Category 5 lines or optical cable lines, and its length can reach 10KM. If the line is more than 200 meters, the cost of one cable can be saved by 2,000 yuan, calculated at 10 yuan per meter of cable. If a certain circuit board is considered to have 50 cables, the cost of the cable will also be 100,000 yuan, plus the cost of the bridge and labor costs, which will bring a lot of economic benefits to the DCS installation and use project, and at the same time can improve the reliability of the transmission signal and the work efficiency of the maintenance personnel, and ensure the reliable operation of the electrical instrument equipment.

[0032] Other features and advantages of the embodiments of the present invention will be described in detail in the subsequent detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The accompanying drawings are used to provide a further understanding of the embodiments of the present invention and constitute a part of the specification. Together with the following specific implementations, they are used to explain the embodiments of the present invention, but do not constitute a limitation on the embodiments of the present invention. In the accompanying drawings:

[0034] Figure 1 is a schematic diagram of the structure of a controller provided by an embodiment of the present invention;

[0035] Figure 2 is a schematic diagram of a communication circuit provided by an embodiment of the present invention;

[0036] Figure 3 is a schematic diagram of a power supply circuit provided by an embodiment of the present invention;

[0037] Figure 4 is a schematic diagram of an alarm output control circuit provided by an embodiment of the present invention;

[0038] Figure 5 Schematic diagram of an input-output controller provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0039] The specific implementation of the embodiment of the present invention is described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation described here is only used to illustrate and explain the embodiment of the present invention, and is not used to limit the embodiment of the present invention.

[0040] Figure 1 Schematic diagram of the controller structure provided by the embodiment of the present invention. Figure 1 As shown, the controller includes: a communication circuit 101, a single chip computer 102, a power supply circuit 103, an alarm output control circuit 104, and an input-output controller 105.

[0041] Wherein, the single chip microcomputer is preferably a STM32V107 single chip microcomputer.

[0042] The controller is provided on the field equipment and is also provided in the remote DCS control room, wherein the DCS is a distributed control system;

[0043] First, the controller set up in the field equipment converts the DO and AO signals of the field equipment collected by the single chip microcomputer into digital signals, and transmits them over a long distance to the DCS controller including the controller.

[0044] Then, in the DCS control room, another controller is used to restore the received digital signals into DO and AO signals of the field equipment, and input them into the DCS as DI and AI signals; after further processing the input DI and AI signals, the DCS outputs the corresponding control signals, i.e., outputs DO and AO signals; the controller collects the DO and AO signals output by the DCS and converts them into digital signals for transmission to the field equipment containing the controller.

[0045] Finally, the controller set up by the field equipment restores the received digital signal into the DO and AO signals output by the DCS, and inputs them into the field equipment as DI and AI signals to control the field equipment.

[0046] Among them, the DI signal is a digital input signal, which represents the input signal of the switch quantity, and can give the PCL or DCS the command to open and close; the DO signal is a digital output signal, which can send a stop or start signal to the device through the PLC or DCS to start and stop the device accordingly; the AI ​​signal is an analog input signal, that is, a 4-20mA or 0-10V current or voltage signal, which is input into the DCS and restored to its original value after transformation; the AO signal is an analog output signal, which is opposite to the AI ​​signal. The DCS outputs a 4-20mA or 0-10V signal to control the operating parameters of the equipment.

[0047] It should be noted that the process of converting DO and AO signals into digital signals and restoring digital signals into DO and AO signals is realized by the communication circuit of the controller; the digital signals are transmitted between the field equipment and the DCS via Category 5 cables or optical cables. Specifically, when the transmission distance is less than or equal to 200 meters, it is preferred to use Category 5 cables to transmit signals, and when the transmission distance is greater than 200 meters, it is preferred to use optical cables to transmit signals.

[0048] Figure 2 is a schematic diagram of a communication circuit provided by an embodiment of the present invention; Figure 2 The communication circuit provided by the embodiment of the present invention is described in detail.

[0049] The communication circuit includes a first communication unit 201 and a second communication unit 202, wherein the first communication unit and the second communication unit are 485 differential circuits, and the 485 differential circuit includes an RS485 transceiver; wherein the RS485 transceiver of the first communication unit is preferably a 6LB184 chip, and the RS485 transceiver of the second communication unit is preferably an SP3485 chip.

[0050] When the RS485 transceiver transmits a signal, it is used to convert the DO and AO signals into differential signals in the communication line; when the RS485 transceiver receives a signal, it is used to restore the differential signal in the communication line into DO and AO signals.

[0051] It should be noted that the controller includes photoelectric isolators DG1, DG2, and DG3, which are used to electrically isolate the RS485 transceiver power supply VCC and the embedded microcontroller STM32 power supply 3.3V to avoid affecting the normal operation of the microcontroller CPU and effectively suppress interference signals in the transmission line.

[0052] Furthermore, the 485 differential circuit is specifically described by taking the first communication unit 201 as an example.

[0053] The photoelectric isolator DG2 includes a first light-emitting diode and a first transistor, wherein the anode of the first light-emitting diode is connected to VCC, and a variable resistor RT4 is arranged between VCC and the anode of the first light-emitting diode; the cathode of the first diode is connected to pin 1 of the 6LB184 chip; the collector of the first transistor is connected to a 3.3V voltage, and variable resistors RT3 and 485RX pins are connected between the 3.3V voltage and the collector of the first transistor in sequence, and the emitter of the first transistor is connected to GND.

[0054] The photoelectric isolator DG3 includes a second light-emitting diode and a second transistor, wherein the anode of the second light-emitting diode is connected to a 3.3V voltage, a variable resistor RT5 is arranged between the 3.3V voltage and the anode of the second light-emitting diode, and the cathode of the second light-emitting diode is connected to the 485DR pin; the collector of the second transistor is connected to VCC, the emitter of the second transistor is connected to pin No. 3 of the 6LB184 chip, the emitter of the second transistor is connected to GND, and a variable resistor Rt1 is arranged between the emitter of the second transistor and GND.

[0055] The photoelectric isolator DG1 includes a third light-emitting diode and a third transistor, wherein the anode of the third light-emitting diode is connected to a 3.3V voltage, a variable resistor RT7 is arranged between the 3.3V voltage and the anode of the third light-emitting diode, and the cathode of the third light-emitting diode is connected to the 485TX pin; the collector of the third transistor is connected to pin No. 4 of the 6LB184 chip, the collector of the third transistor is also connected to VCC, a variable resistor RT6 is arranged between the collector of the third transistor and VCC, and the emitter of the third transistor is connected to GND.

[0056] Pin 8 of the 6LB184 chip is connected to VCC, and pin 8 of the 6LB184 chip is also connected to GND through capacitor Ct1; pins 7 and 6 of the 6LB184 chip are used to output or receive 485 differential signals, among which pin 7 of the 6LB184 chip outputs or receives 485out+ signal, pin 6 of the 6LB184 chip outputs or receives 485out- signal, and pin 5 of the 6LB184 chip is connected to GND.

[0057] When pin 2 of the 6LB184 chip is at a low level, pins 7 and 6 of the 6LB184 chip are used to output 485 differential signals. When pin 2 of the 6LB184 chip is at a high level, pins 7 and 6 of the 6LB184 chip are used to receive 485 differential signals.

[0058] Furthermore, the single chip microcomputer is connected to the first communication unit and the second communication unit;

[0059] The second communication unit is a redundant backup for signal transmission of the first communication unit. When the first communication unit fails, the single chip controls the communication circuit to switch to the second communication unit for signal processing. Figure 2 Switch 485OUT in to 485OUT1.

[0060] The prior art usually adopts RTU-MOSBUS protocol (master-slave mode) to transmit signals. When this protocol is applied to industrial production, it cannot meet the instantaneous control requirements. To solve this problem, the embodiment of the present invention is designed to adopt point-to-point mode to transmit signals, that is, the address code is removed from the transmission control word; the signal is transmitted immediately when the state of the field device changes, thereby reducing the amount of data transmission. It can ensure that after the field device takes action, the corresponding signal is transmitted to the remote DCS within 10ms, and the DCS responds in time and transmits the corresponding control signal back to the field device.

[0061] To ensure smooth transmission lines, the controllers set up in the DCS control room and the controllers set up in the field equipment need to send confirmation frames to each other every 100ms. They can continue to run after receiving the confirmation frame responded by the other controller and successfully verifying the confirmation frame responded by the other controller.

[0062] If the confirmation frame from the other controller is not received after exceeding the preset threshold, or the confirmation frame sent by the other controller fails to be verified, the single-chip microcomputer controls the communication circuit to switch to another communication unit for signal processing, sends the confirmation frame again, and continues to transmit using this link. At the same time, the single-chip microcomputer drives the circuit board fault indicator to light up, indicating that a fault has occurred, and drives the relay to close, giving a signal to the DCS, prompting the operator to contact the maintenance personnel for inspection and replacement. Faults can be handled in a timely manner without affecting the normal operation of the system to ensure the normal operation of the equipment.

[0063] It should be noted that the preset threshold can be adjusted according to the actual operation situation, and is preferably 100ms. The confirmation frame can be checked using any of the following methods, such as a parity check, an LRC longitudinal redundancy check, or a CRC cyclic redundancy check.

[0064] Figure 3 is a schematic diagram of a power supply circuit provided by an embodiment of the present invention; Figure 3 The power supply circuit provided by the embodiment of the present invention is described in detail.

[0065] The control process of DCS in industrial production has very high requirements and must be safe and reliable. After research, it was found that the controller power supply is the key to ensuring the reliability of the DCS control process. The power supply circuit of the controller provided in the embodiment of the present invention uses an external 5V power supply to convert it into 3.3V through the voltage regulator SPX1117 to power the single-chip microcomputer STM32. Considering that the external 5V power supply may not be able to supply power normally due to poor contact or other reasons, a two-way 5V power supply method is designed to ensure the reliability of the power supply.

[0066] Figure 3 The power supply 1 and power supply 2 are 5V switching power supplies from different circuits, and the power supply 1 and power supply 2 are connected in parallel to the voltage regulator SPX1117. Among them, the power supply 1 is connected to the positive electrode of the diode D1, and the power supply 1 is also connected to the positive electrode of the light-emitting diode LED1, and the negative electrode of the light-emitting diode LED1 is connected to GND; the power supply 2 is connected to the positive electrode of the diode D2, and the power supply 2 is also connected to the positive electrode of the light-emitting diode LED2, and the negative electrode of the light-emitting diode LED2 is connected to GND.

[0067] When both power supply 1 and power supply 2 are operating normally, the two power supplies supply power simultaneously, and the three light-emitting diodes LED1, LED2, and LED all emit light;

[0068] When one of the power sources fails, for example, when power source 1 fails, power source 2 can still reliably supply power through diode D2. Due to the blocking effect of diode D1, power source 1 will not have any impact on the circuit, and LED 1 will go out, indicating that power source 1 has failed.

[0069] Figure 4 is a schematic diagram of an alarm output control circuit provided by an embodiment of the present invention; Figure 4 The alarm output control circuit provided by the embodiment of the present invention is described in detail.

[0070] The single chip microcomputer is provided with a PE2 terminal;

[0071] The alarm output control circuit includes a relay K, a diode Dr, a transistor, and a Reout terminal;

[0072] The base of the transistor is connected to the PE2 terminal of the single-chip microcomputer, and a resistor Rr2 is provided between the base of the transistor and the PE2 terminal of the single-chip microcomputer;

[0073] After the coil of the relay K is connected in anti-parallel to the diode Dr, it is connected in series to the collector of the transistor, and the cathode of the diode Dr is connected to a +5V voltage. The function of the anti-parallel diode Dr of the coil of the relay K is to release the current in the coil of the relay K through the diode Dr when the transistor is turned off, so as to avoid the high voltage generated by the sudden shutdown from damaging the transistor;

[0074] When the single chip microcomputer detects that the controller has a fault, it controls the PE2 terminal to output a high level, thereby controlling the transistor to conduct and close the relay, closing its normally open point, and outputting a signal from the Reout terminal to the DCSDI point, which is recognized by the DCS and a corresponding prompt appears on the DCS screen.

[0075] Figure 5 Schematic diagram of an input-output controller provided by an embodiment of the present invention. Figure 5 As shown, the controller for field device signals entering the DCS provided by the embodiment of the present invention adopts a modular structure for easy maintenance, that is, the input and output parts are separated from the main board, in order to reduce interference and facilitate maintenance.

[0076] The input-output controller is connected to the single-chip microcomputer through the socket in the figure and is controlled by the single-chip microcomputer. Specifically, the single-chip microcomputer is provided with PB0, PB1, PB2, PB10, PE7, PE8, PE9, PE10, PE11, PE12, PE13, PE14, and PE15 terminals. Socket No. 36 of the input-output controller is connected to the PB0 terminal of the microcontroller, socket No. 2 is connected to the PB10 terminal of the microcontroller, socket No. 3 is connected to the PE15 terminal of the microcontroller, socket No. 4 is connected to the PE14 terminal of the microcontroller, socket No. 5 is connected to the PE13 terminal of the microcontroller, socket No. 6 is connected to the PE12 terminal of the microcontroller, socket No. 7 is connected to the PE11 terminal of the microcontroller, socket No. 8 is connected to the PE10 terminal of the microcontroller, socket No. 9 is connected to the PE9 terminal of the microcontroller, socket No. 10 is connected to the PE8 terminal of the microcontroller, socket No. 11 is connected to the PE7 terminal of the microcontroller, socket No. 12 is connected to the PB2 terminal of the microcontroller, and socket No. 13 is connected to the PB1 terminal of the microcontroller.

[0077] In order to prevent the socket from loosening and failing to correctly transmit the input and output signals, the input and output controller adds the corresponding PB0 socket. During normal operation, the microcontroller reads PB0 as a high potential. If the output part is inserted, the external circuit is closed and grounded, so PB0 is read as a low potential. If this circuit reads a low potential, it is normal. If it reads a high potential, the alarm indicator light will be turned on immediately and the fault relay will be controlled to be energized, prompting the DCS that a fault has occurred.

[0078] The above are only embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application may have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included within the scope of the claims of the present application.

Claims

1. A controller that receives field device signals from DCS. It is characterized in that The controller includes a communication circuit and a single chip microcomputer; When the controller is set on the field equipment, the communication circuit is used to convert the DO and AO signals of the field equipment collected by the single-chip microcomputer into digital signals and transmit them to the DCS equipment including the controller; When the controller is set on the DCS, the communication circuit is used to restore the received digital signals into DO and AO signals of the field equipment and input them into the DCS as DI and AI signals, and collect and convert the output signals DO and AO signals of the DCS into digital signals and transmit them to the field equipment including the controller to control the field equipment.

2. The controller according to claim 1, It is characterized in that The communication circuit includes a first communication unit and a second communication unit, and the single chip microcomputer is connected to the first communication unit and the second communication unit; When the first communication unit fails, the single chip microcomputer controls the communication circuit to switch to the second communication unit for signal processing.

3. The controller according to claim 2, It is characterized in that When the first communication unit fails, the single chip microcomputer controls the communication circuit to switch to the second communication unit for signal processing, including: The sender sends a confirmation frame to the receiver at a preset frequency, and the receiver sends a corresponding confirmation frame to the sender after receiving the confirmation frame and verifying it successfully. When the time the sender waits for the confirmation frame sent by the receiver exceeds a preset threshold or the confirmation frame sent by the receiver fails to be verified, the single-chip microcomputer controls the communication circuit to switch to the second communication unit for signal processing; Among them, one of the sender and the receiver is a controller set by the field device, and the other is a controller set by the DCS.

4. The controller according to claim 2, It is characterized in that The first communication unit and the second communication unit are 485 differential circuits, and the 485 differential circuits include RS485 transceivers; When the RS485 transceiver transmits a signal, it is used to convert the DO and AO signals into differential signals in the communication line; When the RS485 transceiver receives a signal, it is used to restore the differential signal in the communication line into DO and AO signals.

5. The controller according to claim 1, It is characterized in that The digital signal is transmitted between the field device and the DCS via Category 5 wires or optical cables.

6. The controller according to claim 1, It is characterized in that The controller comprises a photoelectric isolator, and the photoelectric isolator is used for electrically isolating the single chip microcomputer and the communication circuit.

7. The controller according to claim 1, It is characterized in that The digital signal converted by the communication circuit is transmitted in a point-to-point mode, and the address code is removed from the transmission control word.

8. The controller according to claim 1, It is characterized in that The controller comprises: a power supply circuit, which is used to supply power to the single-chip microcomputer and comprises a first power supply, a second power supply and a voltage regulator; The voltage regulator is used to adjust the source input voltage to a target voltage value; The first power supply and the second power supply are connected in parallel to the voltage regulator, the first power supply is connected in series with a first diode; the second power supply is connected in series with a second diode; The first diode is used to prevent the first power supply from affecting the power supply circuit when the first power supply fails; the second diode is used to prevent the second power supply from affecting the power supply circuit when the second power supply fails; When the first power supply and the second power supply are both normal, the first power supply and the second power supply supply power to the single chip microcomputer simultaneously; The second power supply provides backup power to the single chip microcomputer when the first power supply fails.

9. The controller according to claim 1, It is characterized in that The single chip microcomputer is an STM32 single chip microcomputer.

10. The controller according to claim 1, It is characterized in that The controller includes an alarm output control circuit; The single chip microcomputer comprises a first output terminal; The alarm output control circuit includes a relay, a third diode, a triode, and a second output terminal; The base of the transistor is connected to the first output terminal of the single chip microcomputer; The coil of the relay is connected in anti-parallel to the third diode and then in series to the collector of the transistor; when the transistor is turned off, the current in the coil of the relay is released through the third diode to avoid the high voltage caused by sudden shutdown from damaging the transistor; When the single chip microcomputer detects that the controller has a fault, it controls the first output terminal to output a high level, controls the transistor to conduct to close the relay, closes its normally open point, and outputs a signal from the second output terminal to the DCSDI point, which is recognized by the DCS and a corresponding prompt appears on the DCS screen.

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