Research on equipment status monitoring system based on wireless transmission technology

0 Introduction

In modern industrial production, production operations in many industries are carried out in harsh environments, such as power plants and substations in the power industry, oil wells and oil fields, oil pipelines in the petroleum industry, and the coal industry, etc. Large equipment for production operations in these harsh environments is not suitable for people to approach, and industrial production requires real-time control of the changes in the operating status of equipment in each production link so as to take timely countermeasures. In order to safely observe the operating status of these large equipment, this system uses the virtual instrument platform to remotely observe their operation. Through wireless remote monitoring, technicians can monitor and control the operating status and various parameters of production systems and field equipment without having to go to the site or harsh environment in person, so that professionally trained personnel can "virtually" appear in many monitoring locations, conveniently use local rich software and hardware resources to perform advanced process control on remote objects, so as to maintain the normal operation of equipment, thereby reducing the number of on-duty staff, and ultimately achieving remote unmanned or less-staffed on-duty, achieving the purpose of reducing staff and increasing efficiency. In my country, most industrial production units use wired methods to transmit data for monitoring the operating status of equipment. This method is not only backward, costly, and difficult to maintain, but also has large interference during data transmission. This system uses PTR2000 to transmit data wirelessly to monitor the status of the equipment, reducing interference in data transmission and thus improving transmission reliability. In addition, the software uses Lab-Windows/CVI's powerful data analysis and processing functions, which not only realizes the real-time reception of the collected data on the operating status of the equipment, but also realizes the rapid processing of characteristic values ​​in various data. The system is flexible to use and has low cost, and can be widely used in the field of industrial measurement and control.

1 System composition

The composition of the equipment status monitoring system mainly includes two aspects: 1) The lower computer (i.e., data acquisition end), with the microcontroller as the control core, including sensors, signal conditioning circuits, and data transmission modules; 2) The upper computer (i.e., data processing end), with the industrial computer as the control core, including data receiving modules and level conversion modules. As shown in Figure 1.

First, the sensor transmitter converts the information of the equipment operation status that needs to be detected at the industrial site into electrical quantity. The electrical signal output by the sensor is conditioned by the signal conditioning circuit and input into the single-chip microcomputer. The conversion function of the single-chip microcomputer converts the analog signal into a digital signal. The digital signal is wirelessly transmitted to the PTR2000 of the upper computer through PTR2000, and then the TTL level is converted to RS-232 level through MAX232, and then the RS-232 level is sent to the human control computer, and finally the industrial control computer processes the data.

1.1 Large coal transport import reducer

This system is applied to Fokker A-Plus series parallel shaft gear reducer, which has a transmission ratio of 1.8:1 to 437:1 and a torque range of 2937Nm to 621448Nm. The rated power is 14168kW. It is strong, durable, small in size, high in efficiency, and has extremely wide industrial applications. Its features include: the gears are carburized and ground, and the transmission uses high-strength helical gears, so they have strong impact resistance. The reducer housing is welded from steel plates, with long bearing life, reliable lubrication methods, and Magnum leak-proof and dust-proof sealing methods.

1.2 Sensor

The temperature sensor uses high-precision PT100 platinum thermal resistor, which has the characteristics of high precision and sensitive response, and is suitable for temperature measurement needs of machinery and equipment and other industrial sites. The temperature transmitter uses the XMTD-D81 new fully intelligent digital display regulator, which has advanced technology and stable performance. It uses keyboard digital setting to set functions, mainly including multi-channel alarms and alarm settings and password settings. The instrument can convert the temperature information collected by PT100 into 0-20Ma analog signals, and can also send out switch alarm information when the temperature exceeds the set temperature.

PalacetekVS101 electronic vibration transmitter is used for vibration detection of equipment. This vibration transmitter monitors abnormal vibration of the machine and predicts the damage of the machine. VS101 mainly monitors the following major types of machine failures: rotor imbalance (about 40%), misalignment (about 15%), bearing damage (about 15%), belt damage (about 15%). VS101 will provide an alarm or shut down the machine power to protect the machine from damage. In most cases, vibration can reflect the problem of the machine for a long time before the machine is damaged. It is technologically advanced and uses advanced high-level integrated professional electronic circuits. The entire system has no mechanical parts. It is also easy to install and only needs 2 screws to fix it. It has a built-in probe and a fully enclosed aluminum shell to meet dust and water resistance standards.

1.3 Wireless transmission module PTR2000

PTR2000 is a wireless transmission module that combines receiving and transmitting. Its operating frequency is the internationally used digital transmission frequency band of 433 MHz. It has strong anti-interference ability and is particularly suitable for industrial control occasions. It adopts DDS+PLL frequency synthesis technology and has excellent frequency stability. It has high sensitivity, reaching 105dBm. It has low operating voltage (2.7 V) and low power consumption. It has 2 channels, which is particularly suitable for special occasions that require multi-channel operation. The working rate can reach up to 20kb/s (it can also work at a lower rate such as 9 600 b/s). It can be directly connected to the CPU serial port such as 8031, or the computer RS232 interface. Software programming is very convenient. Due to the design of low transmission power and high receiving sensitivity, no license is required for use.

1.4 Microcontroller

The microcontroller used in this system is ATmega16 produced by Atmel. ATmega16 has A/D conversion function and high-speed processing capability of 1MIPS/MHz (million instructions per second/MHz). ATmega16 has a 10-bit successive approximation model/digital converter ADC. The ADC is connected to an 8-channel analog multiplexer and can sample 8 single-ended input voltages from port A of ATmega16. The single-ended voltage input is based on 0V (GND). The ADC includes a sample-and-hold circuit to ensure that the voltage input to the ADC remains constant during the conversion process. The ADC is powered separately by the AVCC pin of ATmega16. The deviation between AVCC and VCC cannot exceed ±0.3V. ATmega16 provides a reference voltage with a nominal value of 2.56V and AVCC internally. The reference voltage can be decoupled by adding a capacitor to the AREF pin to better suppress noise. The power supply of the microcontroller in the data acquisition part of this system is an external +5V power supply.

2 System Design

2.1 Interface circuit between single chip microcomputer (Atmega16) and PTR2000

As shown in Figure 2, the sensor transmitter converts the information of the equipment operating status in the industrial field into electrical quantity. The electrical signal output by the sensor is conditioned by the signal conditioning circuit and input into the eight analog signal input terminals ADC0~ADC7 of the microcontroller respectively. The A/D conversion function of the microcontroller converts the analog signal into a digital signal. The microcontroller connects PD4 to the CS of PTR2000 (channel selection terminal, when CS=1, the operating frequency of PTR2000 is 433.92MHZ, when CS=0, the operating frequency of PTR2000 is 434.33MHZ), PD5 to the PWR of PTR2000 (energy-saving control terminal, when PWR=1, PTR2000 is in normal working state, when PWR=0, PTR2000 is in standby micro-power consumption state), PD6 to the TXEN of PTR2000 (transmit and receive control terminal, when TXEN=1, PTR2000 works in sending mode, when TXEN=0, PTR2000 works in receiving mode) to control the RXD and TXD connected to the DO and DI of PTR2000 to realize serial port wireless transmission of data.

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2.2 Interface circuit between industrial computer (PC) and PTR2000

The industrial computer is connected to PTR2000 through the serial port, and the data of the running status of the field equipment is collected wirelessly, and the collected data is processed. The interface circuit between the industrial computer and PTR2000 is shown in Figure 3. Because PTR2000 is TTL level, MAX232 is required for level conversion when connected to the serial port of the industrial computer. F1 is a 9-pin standard serial port connector, which is connected to the serial port of the industrial computer. RTS is the serial port request to send signal, which can control the sending and receiving status of PTR2000. RTS is connected to TXEN of PTR2000 wireless MODEM through level conversion. When the computer wants to send data, RTS becomes logic 1 valid, that is, TXEN of PTR2000 is set to 1, and data can be sent at this time; when the computer receives data, RTS becomes logic 0 valid, that is, TXEN of PTR2000 is set to 0, and data can be received at this time.

3 System Software Design

The programming of the software part is mainly divided into two aspects: 1) the lower computer (i.e. the data acquisition end), which mainly programs the microcontroller; 2) the upper computer (i.e. the data processing end), which mainly programs the industrial computer.

The software development platform of the lower computer is ICC AVR, a special development platform for AVR microcontrollers. The program of the lower computer must first initialize the microcontroller and PTR2000, then perform A/D conversion, define the data packet, and send the data packet out.

#define uint unsigned int // macro definition
void transmit(uint adl, uint adh) // add header and tail to the collected data that has been converted by A/D, such as temperature, vibration frequency, etc. And this function can be called directly when sending.
{
USART_Transmit(0xAA); // send header
USART_Transmit(adl); // send temperature data
USART_Transmit(adh); // send vibration frequency data
USART_Transmit(0xFF); // send tail
}

We use LabWindows/CVI to program the host computer. The main function of this system is to complete the correct collection, transmission, reception, processing, display and other functions of various parameter data. The system adopts a modular design concept, dividing the functions into corresponding functional modules for management and maintenance to enhance the versatility and portability of the system. The host computer software of this system can be summarized into two major modules: one is the system setting module, which plays the role of communicating with the lower computer and setting the parameters that have been received. The second is the data management module, including data acquisition, data packet processing, data analysis and other functions; Figure 4 is a schematic diagram of the system software running on the industrial computer.

First open the serial port, initialize it, and then receive the data. The following is a receiving program written in LabWindows/CVI.

MSCommLib_IMSCommSetRTSEnable (objecthandle, NULL, VFALSE); //Set RST to 0 and start receiving.

GetCtrlVal(panelHandle, PANEL_STRING, i); //Get the collected data string.

4 Conclusion

In my country, most industrial production units use wired data transmission to monitor the operation status of equipment. This method is not only backward, but also costly and difficult to maintain. This article mainly introduces a wireless equipment operation status monitoring system suitable for my country's national conditions and suitable for industrial measurement and control occasions. It has strong anti-interference ability, relatively low cost, and is easy to use, flexible, and maintainable. It has broad practical value and application prospects in the field of industrial control. By appropriately changing the hardware or software programming, it can be applied to wireless vehicle systems, remote monitoring and other fields.