Abstract: The intelligent valve control system gradually replaces the traditional mechanical valve control system and is widely used in the field of modern industrial control. In order to further improve the control performance of the controller, a new intelligent valve controller has been developed based on the ARM architecture. The main components and key technologies of the controller are introduced. The controller uses a high-precision linear adjustable differential transformer as the valve position sensor, and utilizes the software technology of quick response to improve the positioning accuracy and the response speed of the intelligent valve controller. Test shows that the instrument has the advantages of low power consumption, high reliability, the development of related products has important guiding significance.
Keywords: ARM; intelligent valve controller; human interaction; fast acquisition chip DOIDOI: 10.11907 / rjdk.171307
CLC number: TP319
Document code: A article number Article ID: 1672-7800 (2017) 008-0073-03
0 Introduction With the rapid development of industrial automation, microelectronic technology and advanced algorithms are gradually applied to the electric valve control, valve control system began to intelligent, efficient and accurate direction, the safety performance of the equipment [1-4] is improved .
The intelligent valve controller based on ARM is designed with the hardware circuit that automatically detects the input and output short circuit and the circuit breaking function. The software design highlights the concept of ultra-fast response and the overall optimization design greatly reduces the response time and the total power consumption of the circuit [5] . Test data show that the change from the input command to the servo current output change time is less than 20ms, reaching the leading domestic level.
1 controller overall design The new intelligent valve controller system consists of CPU module, power supply, signal detection (LVDT displacement sensor), feedback (output circuit short circuit and open circuit detection), output driver and human-computer interaction Part of the system structure shown in Figure 1.
The intelligent valve controller manually inputs the valve control signal through the upper computer of the human-computer interaction module and obtains the direct current or the alternating current feedback input signal through the signal sampling circuit of the signal detection module. After being processed by A / D, it enters the CUP module and is adjusted by the PI algorithm to obtain the output Signal, the output drive module servo current output is given, while the CPU module will collect the valve instruction signal transmitted to the host computer.
The power module adopts external power supply, and generates several groups of voltages of 3.3V, 5V, -15V and + 15V respectively through the power conditioning circuit for CPU and peripheral hardware circuits and driver circuits. The power module adopts the integrated modulation technology, which not only reduces the quiescent current consumption but also realizes the function that the output current value is automatically adjusted according to the load size [6-7].
The human-computer interaction module includes the host computer and the LED indicator. It is a window for realizing the interaction between human-machine information and data. It can perform the initial value setting and real-time display of variables and related parameters.
2 Hardware Design Intelligent valve controller hardware circuit consists of SVP channel card and SVP_CPU card, CPU card provides power access, power isolation and buck and 485 communications and other functions. Channel card as the main part of the circuit to provide the master chip and the channel output input circuit, programming interface, jumper selection and status indicators and other functions. Hardware circuit shown in Figure 2.
Each unit circuit and function as follows:
(1) AC-DC feedback circuit is mainly used to collect the valve position signal LVDT, divided into six-wire AC voltage input signal and two-wire DC current input signal. The collected AC voltage input signal is relatively weak, after rectification, filtering and compensation, can be sent to the CPU. Therefore, an AC LVDT feedback conditioning circuit is designed to process the input signal.
AC LVDT feedback conditioning circuit, the exchange of the AC input signal after the exchange of full-wave rectifier conditioning, and then add +5 V level compensation, the rectified voltage control 0 ~ 10V, then reduced to 0 ~ 2V, and finally Reduce the voltage difference into the AD chip for signal sampling, by the SPI communication and CORTEX-M3 exchange data.
(2) The LVDT primary winding must be powered by AC voltage. The change in the position of the ferromagnetic core causes the difference in induced voltage between the two secondary windings of the same name reversed in series to change [8]. By detecting the voltage difference, it is possible to determine the amount of movement of the non-ferromagnetic rod. In order to drive LVDT normal work, specially designed six-wire LVDT excitation generating circuit.
The six-wire LVDT excitation circuit generates a sine wave with a frequency of 1 kHz from the waveform generator chip, amplifies the power through the amplifier chip, and finally generates an excitation voltage of ± 9 V to drive the AC LVDT operation.
(3) The servo output circuit is used to output high current to drive the load operation. First, the output voltage generated by the DA chip, and then processed by the conditioning circuit into positive and negative voltage, and finally by the op amp conditioning circuit used to drive the load. Servo output circuit with output off switch, the circuit can be quickly shut down the servo output current failure, play a role in protecting the drive.
(4) AC feedback circuit and short circuit detection circuit used to detect the feedback signal wiring is normal. The circuit design principle is the feedback circuit at both ends of the signal differential amplitude calculation, and then compare the results with a specific voltage (2V or so). If the wiring is normal, the signal must reach the optocoupler after the pulse waveform output; if the circuit is short or open circuit there is no pulse output, in order to determine the feedback circuit wiring, which is the difficulty of the circuit design.
(5) In order to test the servo output circuit wiring is normal, also designed a servo output current circuit and short circuit detection circuit. The circuit is the servo output circuit terminals connected to both ends of the circuit, after the op amp to reduce the amplitude, increased by the voltage compensation, and finally into the AD differential voltage, with this circuit can be detected in real time terminal voltage difference. The sampling voltage compared with the normal voltage, according to the sampling signal exceeds or falls below the normal voltage to determine the circuit is open or short circuit.
(6) In view of the operation safety of the controller, the open dog processing is done by using the X5043 device so that the microcontroller can be reset in time when the controller runs out, and the output shutdown processing is taken as the first time [9].
3 software design SUPMAX2000 intelligent valve controller program mainly by the system software and PC software.
3.1 System Software System software from the management module, control module and channel module and other components. Management module to complete the system monitoring and initialization tasks, but also with the CPU, the peripherals and peripherals used A / D, D / A chipset and initialization, system self-test and card self-calibration, card calibration and other functions. Control module is the core of software design and key links, mainly to complete the core tasks of data acquisition and processing, servo output. Communication software includes communication between the bus and the channel board CPU following the SPI protocol, serial data communication following the I2C protocol between the CPU and the off-chip EEROM chip, UART communication used in calibration mode, etc. [10-12]. Both use the master-slave mode of work to interrupt the way the data is sent and received, both to ensure real-time data transmission, but also improve the CPU's work efficiency. The field application requires that the controller can be debugged and can be used normally. At the same time, the controller needs to be zeroed and full, and some device control should be fine-tuned. To this end, set in the main program normal mode, debug mode, self-calibration mode, the output fine-tuning mode.
The main program flow shown in Figure 3.
3.2 PC software Host PC parameters calibration and communication functions. Parameter calibration is the focus of PC software design, its working principle is input or output current value sent to the host computer through the serial communication, the current value of the host computer algorithm calibration sent to the SVP card, SVP card receives the new calibration parameters After the data conversion again, the conversion of the data if the accuracy requirements have been met the end of the calibration, otherwise continue the process. After a certain number of retries, the calibration ends when the accuracy of the parameters meets the requirements, otherwise the SVP card can not be calibrated.
Controller through the RS485 communication with the host computer. Communication before the need for RS485 communication port number, baud rate and stop bit configuration [13]. Communication according to different instructions issued by the host computer to achieve the controller data read, modify and main program mode switching, and the controller status alarm is displayed on the host computer interface. PC software process shown in Figure 4.
4 system design key technologies To meet the needs of field devices to speed up the system speed, the use of fast acquisition chip AD7190, measured data show that the sampling time is 2ms, together with the controller of the parameters of the processing time and current output control time, from the control command input Servo output changes in the system response time of less than 20ms, far ahead of the domestic level. The response time comparison between this product and similar products is shown in Table 1.
To save hardware resources and controller costs, A / D configurations are handled flexibly. During the design process, the unneeded channels are temporarily closed, and the channels that are not strict with time are polled, for example, the polling method is adopted for the detection of the output wiring. In the process of running parameters into memory in the process of making multiple checks, there is no problem.
5 Conclusion Intelligent valve controller is one of the core components of modern process control system [14], the development of new intelligent valve controller has an important strategic significance.
The intelligent valve controller developed in this paper belongs to the utility model product, has excellent ultra-low power consumption performance and high self-test capability. Its unique quick response design not only improves the reliability of product operation but also reduces the production cost , Enhance the market competitiveness of products, in order to promote domestic new intelligent valve controller industry has played a positive role.
references:
[1] Huang Chunying. New valve electric actuator research and development [D]. Dalian: Dalian University of Technology, 2002.
[2] Hu Shousong. Automatic control theory [M]. 3rd edition. Beijing: National Defense Industry Press, 1999.
[3] Lu Huiming. Control devices and instruments [M]. Beijing: Mechanical Industry Press, 2011.
[4] Hao Zhonghong. Talking about intelligent valve positioner [C]. The Seventh China Petroleum and Chemical Automation Technology Conference Proceedings, 2008.
[5] Cai Ming, Bai Xuelian, Zhang Ying.Design of Domestic New Intelligent Valve Positioner [J]. Process Automation Instrumentation, 2011,32 (7): 73-79.
[6] Yang Yiwei. Research on Electric Valve Controller Based on ARM [D]. Taiyuan: Taiyuan University of Science and Technology, 2014.
[7] R BROWN.CortexTM-M3 (revisio: rlpl) technical reference manual [M]. ARM Limited, 2006.
Ma Jingmin. Simulation Analysis of RC Bridge Sine Wave Oscillation Circuit Based on Multisim 10 [J]. Journal of Bohai University, 2012,33 (4): 324-328.
[9] Liang Haifeng. Intelligent valve controller embedded design and development [D]. Shanghai: Shanghai Jiao Tong University, 2007.
[10] Tao Yonghua. New PID control and its application [M]. 2nd edition. Beijing: Mechanical Industry Press, 2003.
Wang Wei.Research Status and Application Prospect of Intelligent PID Control Method [J]. Process Automation Instrumentation, 2008,29 (10): 1-7.
[12] Wang Lixin. Fuzzy Systems and Fuzzy Control Tutorial [M]. Beijing: Tsinghua University Press, 2013.
[13] Lin Hui. Research and development of intelligent electric valve positioner [D]. Tianjin: Tianjin University, 2003.
[12] PAUL SCHERZ. Fundamentals of Practical Electronic Components and Circuits [M]. 2nd ed. Beijing: Publishing House of Electronics Industry, 2009.
Keywords: ARM; intelligent valve controller; human interaction; fast acquisition chip DOIDOI: 10.11907 / rjdk.171307
CLC number: TP319
Document code: A article number Article ID: 1672-7800 (2017) 008-0073-03
0 Introduction With the rapid development of industrial automation, microelectronic technology and advanced algorithms are gradually applied to the electric valve control, valve control system began to intelligent, efficient and accurate direction, the safety performance of the equipment [1-4] is improved .
The intelligent valve controller based on ARM is designed with the hardware circuit that automatically detects the input and output short circuit and the circuit breaking function. The software design highlights the concept of ultra-fast response and the overall optimization design greatly reduces the response time and the total power consumption of the circuit [5] . Test data show that the change from the input command to the servo current output change time is less than 20ms, reaching the leading domestic level.
1 controller overall design The new intelligent valve controller system consists of CPU module, power supply, signal detection (LVDT displacement sensor), feedback (output circuit short circuit and open circuit detection), output driver and human-computer interaction Part of the system structure shown in Figure 1.
The intelligent valve controller manually inputs the valve control signal through the upper computer of the human-computer interaction module and obtains the direct current or the alternating current feedback input signal through the signal sampling circuit of the signal detection module. After being processed by A / D, it enters the CUP module and is adjusted by the PI algorithm to obtain the output Signal, the output drive module servo current output is given, while the CPU module will collect the valve instruction signal transmitted to the host computer.
The power module adopts external power supply, and generates several groups of voltages of 3.3V, 5V, -15V and + 15V respectively through the power conditioning circuit for CPU and peripheral hardware circuits and driver circuits. The power module adopts the integrated modulation technology, which not only reduces the quiescent current consumption but also realizes the function that the output current value is automatically adjusted according to the load size [6-7].
The human-computer interaction module includes the host computer and the LED indicator. It is a window for realizing the interaction between human-machine information and data. It can perform the initial value setting and real-time display of variables and related parameters.
2 Hardware Design Intelligent valve controller hardware circuit consists of SVP channel card and SVP_CPU card, CPU card provides power access, power isolation and buck and 485 communications and other functions. Channel card as the main part of the circuit to provide the master chip and the channel output input circuit, programming interface, jumper selection and status indicators and other functions. Hardware circuit shown in Figure 2.
Each unit circuit and function as follows:
(1) AC-DC feedback circuit is mainly used to collect the valve position signal LVDT, divided into six-wire AC voltage input signal and two-wire DC current input signal. The collected AC voltage input signal is relatively weak, after rectification, filtering and compensation, can be sent to the CPU. Therefore, an AC LVDT feedback conditioning circuit is designed to process the input signal.
AC LVDT feedback conditioning circuit, the exchange of the AC input signal after the exchange of full-wave rectifier conditioning, and then add +5 V level compensation, the rectified voltage control 0 ~ 10V, then reduced to 0 ~ 2V, and finally Reduce the voltage difference into the AD chip for signal sampling, by the SPI communication and CORTEX-M3 exchange data.
(2) The LVDT primary winding must be powered by AC voltage. The change in the position of the ferromagnetic core causes the difference in induced voltage between the two secondary windings of the same name reversed in series to change [8]. By detecting the voltage difference, it is possible to determine the amount of movement of the non-ferromagnetic rod. In order to drive LVDT normal work, specially designed six-wire LVDT excitation generating circuit.
The six-wire LVDT excitation circuit generates a sine wave with a frequency of 1 kHz from the waveform generator chip, amplifies the power through the amplifier chip, and finally generates an excitation voltage of ± 9 V to drive the AC LVDT operation.
(3) The servo output circuit is used to output high current to drive the load operation. First, the output voltage generated by the DA chip, and then processed by the conditioning circuit into positive and negative voltage, and finally by the op amp conditioning circuit used to drive the load. Servo output circuit with output off switch, the circuit can be quickly shut down the servo output current failure, play a role in protecting the drive.
(4) AC feedback circuit and short circuit detection circuit used to detect the feedback signal wiring is normal. The circuit design principle is the feedback circuit at both ends of the signal differential amplitude calculation, and then compare the results with a specific voltage (2V or so). If the wiring is normal, the signal must reach the optocoupler after the pulse waveform output; if the circuit is short or open circuit there is no pulse output, in order to determine the feedback circuit wiring, which is the difficulty of the circuit design.
(5) In order to test the servo output circuit wiring is normal, also designed a servo output current circuit and short circuit detection circuit. The circuit is the servo output circuit terminals connected to both ends of the circuit, after the op amp to reduce the amplitude, increased by the voltage compensation, and finally into the AD differential voltage, with this circuit can be detected in real time terminal voltage difference. The sampling voltage compared with the normal voltage, according to the sampling signal exceeds or falls below the normal voltage to determine the circuit is open or short circuit.
(6) In view of the operation safety of the controller, the open dog processing is done by using the X5043 device so that the microcontroller can be reset in time when the controller runs out, and the output shutdown processing is taken as the first time [9].
3 software design SUPMAX2000 intelligent valve controller program mainly by the system software and PC software.
3.1 System Software System software from the management module, control module and channel module and other components. Management module to complete the system monitoring and initialization tasks, but also with the CPU, the peripherals and peripherals used A / D, D / A chipset and initialization, system self-test and card self-calibration, card calibration and other functions. Control module is the core of software design and key links, mainly to complete the core tasks of data acquisition and processing, servo output. Communication software includes communication between the bus and the channel board CPU following the SPI protocol, serial data communication following the I2C protocol between the CPU and the off-chip EEROM chip, UART communication used in calibration mode, etc. [10-12]. Both use the master-slave mode of work to interrupt the way the data is sent and received, both to ensure real-time data transmission, but also improve the CPU's work efficiency. The field application requires that the controller can be debugged and can be used normally. At the same time, the controller needs to be zeroed and full, and some device control should be fine-tuned. To this end, set in the main program normal mode, debug mode, self-calibration mode, the output fine-tuning mode.
The main program flow shown in Figure 3.
3.2 PC software Host PC parameters calibration and communication functions. Parameter calibration is the focus of PC software design, its working principle is input or output current value sent to the host computer through the serial communication, the current value of the host computer algorithm calibration sent to the SVP card, SVP card receives the new calibration parameters After the data conversion again, the conversion of the data if the accuracy requirements have been met the end of the calibration, otherwise continue the process. After a certain number of retries, the calibration ends when the accuracy of the parameters meets the requirements, otherwise the SVP card can not be calibrated.
Controller through the RS485 communication with the host computer. Communication before the need for RS485 communication port number, baud rate and stop bit configuration [13]. Communication according to different instructions issued by the host computer to achieve the controller data read, modify and main program mode switching, and the controller status alarm is displayed on the host computer interface. PC software process shown in Figure 4.
4 system design key technologies To meet the needs of field devices to speed up the system speed, the use of fast acquisition chip AD7190, measured data show that the sampling time is 2ms, together with the controller of the parameters of the processing time and current output control time, from the control command input Servo output changes in the system response time of less than 20ms, far ahead of the domestic level. The response time comparison between this product and similar products is shown in Table 1.
To save hardware resources and controller costs, A / D configurations are handled flexibly. During the design process, the unneeded channels are temporarily closed, and the channels that are not strict with time are polled, for example, the polling method is adopted for the detection of the output wiring. In the process of running parameters into memory in the process of making multiple checks, there is no problem.
5 Conclusion Intelligent valve controller is one of the core components of modern process control system [14], the development of new intelligent valve controller has an important strategic significance.
The intelligent valve controller developed in this paper belongs to the utility model product, has excellent ultra-low power consumption performance and high self-test capability. Its unique quick response design not only improves the reliability of product operation but also reduces the production cost , Enhance the market competitiveness of products, in order to promote domestic new intelligent valve controller industry has played a positive role.
references:
[1] Huang Chunying. New valve electric actuator research and development [D]. Dalian: Dalian University of Technology, 2002.
[2] Hu Shousong. Automatic control theory [M]. 3rd edition. Beijing: National Defense Industry Press, 1999.
[3] Lu Huiming. Control devices and instruments [M]. Beijing: Mechanical Industry Press, 2011.
[4] Hao Zhonghong. Talking about intelligent valve positioner [C]. The Seventh China Petroleum and Chemical Automation Technology Conference Proceedings, 2008.
[5] Cai Ming, Bai Xuelian, Zhang Ying.Design of Domestic New Intelligent Valve Positioner [J]. Process Automation Instrumentation, 2011,32 (7): 73-79.
[6] Yang Yiwei. Research on Electric Valve Controller Based on ARM [D]. Taiyuan: Taiyuan University of Science and Technology, 2014.
[7] R BROWN.CortexTM-M3 (revisio: rlpl) technical reference manual [M]. ARM Limited, 2006.
Ma Jingmin. Simulation Analysis of RC Bridge Sine Wave Oscillation Circuit Based on Multisim 10 [J]. Journal of Bohai University, 2012,33 (4): 324-328.
[9] Liang Haifeng. Intelligent valve controller embedded design and development [D]. Shanghai: Shanghai Jiao Tong University, 2007.
[10] Tao Yonghua. New PID control and its application [M]. 2nd edition. Beijing: Mechanical Industry Press, 2003.
Wang Wei.Research Status and Application Prospect of Intelligent PID Control Method [J]. Process Automation Instrumentation, 2008,29 (10): 1-7.
[12] Wang Lixin. Fuzzy Systems and Fuzzy Control Tutorial [M]. Beijing: Tsinghua University Press, 2013.
[13] Lin Hui. Research and development of intelligent electric valve positioner [D]. Tianjin: Tianjin University, 2003.
[12] PAUL SCHERZ. Fundamentals of Practical Electronic Components and Circuits [M]. 2nd ed. Beijing: Publishing House of Electronics Industry, 2009.
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