Design of multi-point coal flow monitoring system for belt conveyor based on ultrasonic wave
A multi-point coal flow monitoring system based on ultrasonic wave is designed to solve the problem of instantaneous coal flow measurement in high speed and large volume belt conveyor. The hardware, software and coal flow detection algorithm of the system are introduced. In this system, ultrasonic sensor and speed sensor are used to obtain parameters such as coal height, coal pile cross-sectional area and conveyor speed under high-speed operation of belt conveyor, and coal flow detection method is used to fit and analyze the data. Calculate coal flow. The test results show that the system can accurately measure the coal flow in the conveyor belt, and the measurement accuracy can reach 91%.
0 import
The belt conveyor has the characteristics of long conveying distance, large conveying capacity and continuity, easy to realize automatic control and centralized control, and relative construction, etc., which has been widely used in coal mine production. Because of the particularity of coal mine production, the amount of coal transported by belt conveyor system is not uniform, and the instantaneous coal flow of belt conveyor is difficult to measure accurately. At present, belt conveyors are running at full speed, and there is no effective means to adjust the motor speed according to the load. Light load
When there is no load, the high-speed operation of the belt conveyor system will make the mechanical transmission system wear more seriously, shorten the service life of the equipment, and generate a lot of electrical energy.
In recent years, due to the advantages of frequency conversion technology, such as smooth speed regulation, high transient stability and energy saving, researchers at home and abroad have proposed a frequency conversion speed regulation method based on real-time load of conveyor belt. In order to make the conveyor run under the optimal load state, the instantaneous flow rate of coal becomes an important indicator of the running speed of the adjustable belt conveyor [3]. At present, the instantaneous flow measurement of coal is mostly measured by the contact side such as electronic tape measure and nuclear scale, and the measurement accuracy is easily affected by the uneven distribution of materials and other factors. With the development of belt conveyor to high belt speed and large volume, real-time and accurate instantaneous coal flow detection method is of great significance to ensure production safety, energy saving and improve production efficiency of belt conveyor system.
Ultrasonic technology is a kind of technology that can measure the physical height of the measured object in high efficiency, high precision and real time. It has the advantages of non-contact measurement, coal texture characteristics and small dust shade, and has been widely used in coal mine production. According to the requirement of real-time, continuous and accurate measurement of coal flow in belt conveyor, a multi-point coal flow monitoring system based on ultrasonic wave is designed. The embedded technology is used to control the ultrasonic sensor and speed sensor, and obtain the parameters of coal height, coal pile cross-sectional area and conveyor speed during high-speed operation of belt conveyor. Using coal flow measurement algorithm to fit and analyze the data, the instantaneous coal flow of belt conveyor is calculated. The system has the advantages of high measurement accuracy, good real-time performance and high reliability, and can provide real-time and accurate data source for adaptive energy-saving control technology of belt conveyor.
1.1 Hardware design of embedded processing unit
The multi-point coal flow monitoring system of belt conveyor is based on RAM processing device sm32f103z et6. The embedded processing unit is composed of power module, DM9000 network card, SSD RAM, etc. The RAM processor controls ultrasonic transducers, speed transducers and temperature sensors for data acquisition, and converts the acquired signals through integrated A/D and D/A interface input signals and stores them in SRRAM. The instantaneous value of coal flow in the conveyor belt is calculated by fitting and analyzing the logarithmic data. Finally, the monitoring data is sent to the host computer through the dm9000 network card.
1.2 Software Design
The system software mainly completes the control of reading, sending and receiving signals of external sensors, and adopts a fixed calculation method to fit and calculate data such as temperature, speed and coal pile height, so as to obtain the instantaneous flow value of coal in the conveyor belt. Finally, the monitoring data is sent to the host computer control system through the network card. When the ultrasonic sensor sends ultrasonic waves vertically to the coal pile, the RF processor starts to count at the same time, when the ultrasonic wave meets the obstacle and reflects back, when the ultrasonic sensor receives the reflected ultrasonic wave, the RF processor stops timing. The height of distance from the starting point of the measured object is calculated according to the propagation speed 73 and the propagation time t of the ultrasonic wave in the air, and then the installation height of the ultrasonic sensor, the length of the roller, the Angle of the roller, the speed of the conveyor belt and other parameters are combined. Calculate coal flow in real time. In addition, the propagation speed of ultrasound in the air is greatly affected by temperature, and the process temperature needs to be compensated. The system software flow path is shown in Figure 3.
2. Principle and calculation method of accurate detection of coal flow and coal quantity
2. 1 Principle of ultrasonic coal measurement
The system uses ultrasonic sensor to collect the data of coal height on the conveyor belt when the belt conveyor is running at high speed, and integrates the real-time belt speed information measured by the speed sensor to achieve accurate and efficient measurement of the instantaneous flow of materials. First, the two-dimensional coordinate scale of ultrasonic coal flow measurement was established, as shown in Figure 4. The ultrasonic sensor is installed vertically at h above the conveyor belt. Under the control of an embedded processing terminal, the probe sends an ultrasonic pulse to the coal pile on the conveyor belt. The ultrasonic wave is reflected by the surface of the object, and part of the reflected echo is received by the probe and converted into a telecommunications number. The time between ultrasonic transmission and reception is proportional to the distance between the probe and the object being measured. The embedded processing terminal measures the total time elapsed from transmission to reception and calculates the distance distance based on the known ultrasonic propagation velocity meter.
2.2 Instantaneous flow detection algorithm of coal in conveyor belt
The principle of transient flow detection is to measure the height of coal pile by ultrasonic wave, calculate the cut volume by stacking Angle, roller length, roller clamping Angle and other parameters, and then calculate the coal flow. The formula for calculating the propagation speed of ultrasonic wave in the air is
Where T is the field temperature.
The calculation formula of coal pile height H on conveyor belt is
Where: t is the time that the ultrasonic wave passes from transmission to reception.
The cross-sectional area of the coal pile on the conveyor belt is approximately regarded as a trapezoid, and the formula for calculating the cross-sectional area S is
Where: L is the length of the idler; 0 is the idler pinch Angle.
The formula for calculating the instantaneous coal flow M of the conveyor belt is
Where: is the running speed of the conveyor belt; P is the density of coal.
3.2 Accurate calculation of accumulated coal quantity on conveyor belt
The accumulated coal amount on the conveyor belt is composed of the original coal amount and the incoming coal amount. The data acquisition frequency of the ultrasonic sensor is 10 times/s, and the calculation formula of the accumulated coal amount N on the conveyor belt within time t is as follows
Where: N is the amount of coal outflow; M1 is the instantaneous discharge of coal on the conveyor belt.
3 Field Test
In order to verify the reliability of multi-point coal flow monitoring system based on ultrasonic wave, the system function test was carried out in Guojiawan Coal Mine. Coal mining in Guojiawan Coal Mine has passed through the conveyor belt of transportation lane, the driving conveyor belt and the main conveyor belt. The coal flow monitoring system based on ultrasonic wave is installed at the coal drop point and the main shaft opening of the belt conveyor in the main inclined shaft. The coal pulled by 2 tons of cars is evenly distributed on belt conveyors of 5110 3 transport lanes. Then the main conveying system is started, and the coal flow monitoring system records the amount of coal passed through, and finally compares the monitored coal amount data with the actual coal amount to verify the reliability of the system. The installation of multi-point coal flow monitoring system based on ultrasonic wave is shown in Figure 5.
Based on the data obtained by the sensor in the field, it is calculated that the coal quantity collected by the coal flow monitoring system of 51103 conveyor head is M z 12. At 176 t, the coal volume collected by the coal flow monitoring system at the coal drop point of the main inclined shaft belt conveyor is M.12 2. 125 7 t, the main wellhead coal flow monitoring, loading coal volume is M 4-2. 22 t, detection accuracy P ===2 / E(m2 + M). + m2) / 3] = 9 1. It can be seen from the above data that the multi-point coal flow monitoring system based on ultrasonic wave can detect coal flow accurately.
4 Conclusions
The coal flow multi-point monitoring system of belt conveyor based on ultrasonic wave adopts the embedded processing unit based on AM to control the ultrasonic sensor and speed sensor to obtain the data of coal height and conveyor speed. The coal flow rate is calculated by combining the parameters of pile Angle, roller length and roller clamping Angle. The actual field test results show that the system can accurately detect the coal flow in the conveyor belt in real time, and the detection accuracy is up to 91. The system can provide real-time and accurate data source for the adaptive energy saving control technology of belt conveyor, and has great application value for improving the level of coal mine automation and production efficiency.
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