Design of coal belt flow measurement system based on multiple ultrasonic sensors

Coal mining measurement is of great significance in coal mining. Conveyor belt is a key component of coal transportation, which is of great significance to coal mine system scheduling. A system consisting of 3 ultrasonic sensors is designed to determine the movement time of the coal mining section, and then add the tape speed to the comprehensive evaluation over a period of time to estimate the coal mining volume. The system is developed on the basis of determining the amount of coal to be extracted during excavation, with the aim of achieving efficient and low-cost coal transportation and information collection. This paper discusses the design of coal belt flow measurement system based on multiple ultrasonic sensors, in order to provide suggestions for the development of the industry.

Belt conveyor is the main equipment of coal transportation, which is widely used, and its energy saving and consumption reduction has become an important research topic. The traditional coal flow starting mode of belt conveyor requires the conveyor to start and load smoothly by multiple overlapping belt conveyor before feeding, which increases the no-load running time of belt conveyor, resulting in a lot of energy waste and serious mechanical wear. The important basis for the speed regulation of the belt conveyor is the coal flow on the conveyor, which is measured by the material flow detection device. In the existing belt conveyor material flow detection device, the electronic belt scale can detect the material flow, but the mechanical installation is complicated, and the mechanical structure of the original belt conveyor needs to be lifted. Nuclear scale is a non-contact test, easy to install, but the measurement accuracy is easily affected by the uneven distribution of materials, intermittent, radioactive and other factors. Some researchers propose to install the ultrasonic coal flow sensor directly above the measured belt, and measure the highest point of the coal pile section on the belt by using the echo ranging principle. The coal pile section approximately intersects with two standard circular arcs, and then calculates the cross-sectional area through the stacking Angle, roller length and roller Angle, and then calculates the coal flow. A system consisting of 3 ultrasonic sensors is designed to determine the movement time of the coal mining section, plus the speed of the tape, after a period of comprehensive evaluation, so as to estimate the coal mining volume. The basis for the development of this system is to determine the amount of coal to be extracted during excavation.

1 System hardware and software construction

The measurement of coal mining amount per unit time is an important part of tracking the production of a single machine and is of great significance for the system scheduling of a mine, which can be realized by measuring the distance of three ultrasonic sensors at three points [4]. The principle of multi-point ultrasonic counting and ranging technology is shown in Figure 1. The ultrasonic probe is installed on the upper and lower sides of the belt, and the probe is arranged on the upper equidistant of the bracket perpendicular to the running direction of the belt, which is located between the two adjacent sets. As shown in Figure 1, the distance between the ultrasonic probe and the probe is d, and the height of the bracket is ho. The specifications of the belt conveyor are different, and the size of the corresponding roller is also different, so the height and width of the belt are also different. However, the width and height of different belts are similar, so the height h of the device can be uniformly designed. The spacing of ultrasonic probes can be designed to different sizes to meet the requirements of most belt conveyors. The detector is installed in the middle position, that is, the origin of the coordinate, the horizontal direction is the x axis, the vertical direction is the y axis. A, B and C refer to the detection points of the upper interface of the coal sample by the upper sensor, and D, E and F refer to the detection points of the lower interface of the coal sample by the lower sensor. The distance between the upper detector and the coal sample is respectively gal, m2 and m3, and the distance between the lower detector and the coal sample is ni, n and "3." The six measuring points in Figure 1 are (-D, mJ, (0, m2), (D, m), (-D, h-n), (0, h-n) and (D, h-n) respectively, and the cross-sectional area of the material can be calculated according to specific algorithms (that is, the first convolution algorithm is adopted, etc.).

FIG. 2 is a schematic diagram of the coal belt flow measurement system based on multiple ultrasonic sensors. In Figure 2, sensors T1, T2, and T3 are mounted on the convex and concave belts and transmit information collected by computer system USON-UC-LCD, which processes this information and calculates the volume of coal. The instantaneous current in the section flows on the belt, and the combined belt speed can determine the amount of coal mining. The software package (PP USON) developed to determine the material flow of large volume tape conveyor is written in C++ assembly language. Computers need USON to provide useful data packers. Once the application has finished executing, the computer will wait 50 ms before executing. If the USON does not respond during this time, there are two possibilities, namely wireless communication interruption and insufficient USON supply voltage. When it is determined that USON does not respond, it is recorded in the file as a serial error "ComErr.dat", transmitted on the serial interface COM2 in the excavator cab. A display unit in the excavator cab with a 2x16 character LCD, 80C552 microcontroller and a serial interface is functionally compatible with a PC. The computer is not equipped with any video card or graphics display device, and an LCD display is installed on the front panel. The physical diagram of the centralized control system is shown in Figure 3.

FIG. 2 Schematic diagram of coal belt flow measurement system based on multiple ultrasonic sensors

Figure 3. Physical diagram of centralized control system

Multi-point ultrasonic counting and ranging technology is used to achieve multi-point coordinate positioning of the belt surface (as shown in Figure 1). The system is implemented by scanning the response information of 3 ultrasonic sensors and the revolution number of induction encoder, so all the obtained values are digital signals, and these values are dynamic. Depends on the band (the thickness of the coal seam excavated in time t and the speed of excavation). The device also has a feature that displays the condition of the coal (normal/abnormal) on 3 sensors. The data obtained by USON is sent to the UC series. This is actually an industrial computer equipped with a fast microprocessor that interprets the data and manages to correlate three ultrasonic sensors related to the dynamic speed of the belt to a single value. This dynamic value is displayed on two functionally independent systems (i.e. display data devices). UC allows for a lot of data computation because it has a fast microprocessor that has the right processing speed. In addition to recording the dynamic behavior of the hard disk, UC also mines contact information through the serial data bus to provide data flow according to the device range. USON-UC's communication rate is so high that it can detect any missing devices to eliminate possible defects in the interconnect. From a functional point of view, USON-UC builds a number of data structures that correspond to the descriptions issued by the microcontroller. Serial communication is the communication between the local device USON and the machine on the PC structure, and between the PC and the mining cabin display unit.

2 System effect verification

Taking A coal bunker conveyor belt in A mining area as the research object, the effectiveness of the system is verified. Two kinds of material flow sensors are used to measure the coal flow of belt conveyor. One adopts the system designed in this paper, called system 1, and the other adopts the traditional single point sensor. The system 2o 2 sensors are 1 m apart and installed 2 m away from the downstream direction of the coal feeder. The coal bunker height is 20 m, the diameter of the 3 mo conveyor belt is 2.5 m/s, the bandwidth is 1000 mm, and the transmission volume is controlled in the range of 14~17 m3/min. The system uses computer to control the start and stop of the bunker, and records the data of the position sensor and two flow sensors at the same time. The coal is discharged for 5 minutes each time, and the data is repeated 3 times, as shown in Table 1.

The system designed in this paper converts the cross-section shape of the material into polygon according to the cross-sectional area approximation algorithm. By calculating the polygon area, the approximate cross-sectional area of the material is obtained, and the coal discharge is finally obtained. The results of engineering practice show that the error of this method is smaller than that of single point ultrasonic ranging. The traditional ultrasonic flow detection method needs to set the installation height, probe Angle and other parameters according to the actual situation.

The method adopts multi-point ultrasonic ranging technology, and all parameters are measured by sensors, which is convenient for users to operate and avoids errors caused by human installation factors. Multi-point detection technology is conducive to detecting the transverse distribution of coal material. When the material is concentrated on one side of the tape for a long time, the fault alarm can be given to the crown of the tape. To improve the automation of transport continuous belt equipment, they must be equipped with sensors and sensor systems to track the production process online. The continuous drive control unit must do the following operations: automatic control of the status belt, large adjustment force, measurement of material delivery, to avoid material caking.

In addition, in the future, the control of the state of the conveyor belt will also include the following functions: the detection of longitudinal fracture of the belt, all or part of the transverse fracture, and part of the coal material dispersed on the lower support plate, causing premature wear and additional energy consumption.

3 Conclusion

In summary, the coal belt flow measurement system based on multiple ultrasonic sensors can effectively achieve accurate measurement of coal flow. In the future design, it is also necessary to pay attention to the optimization of the structural parameters of the conveyor belt, and use the constantly updated online database to carry out dynamic operation control to optimize the process parameters of the conveyor belt. The ultrasonic sensor is used to solve the problem of measuring the amount of coal extracted per unit time

The cost of producing products and the profitability of tracking the different segments of each band are critical. In the measurement process, with the increase of coal flow, the measurement of the system will become more accurate, to a certain extent, greatly enhance the fine operation of the coal mine, can be actively promoted in the industry.

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