Belt conveyor speed detection system and method based on line scanning laser

Abstract

The present invention discloses a belt conveyor speed detection method and detection system based on a line-scanning laser. The method comprises: using a laser scanner to obtain two frames of point cloud data along the belt's motion direction in real time; converting the two frames of point cloud data obtained in real time into new point cloud data with the same horizontal coordinate spacing; and calculating the belt conveyor speed using the two new point cloud data frames. This method solves the problem of existing laser measurement methods being unable to measure belt conveyor speed, achieving completely non-contact belt conveyor speed measurement without affecting the normal operation of the belt conveyor system, and achieving high measurement accuracy and reliability.

Description

Technical Field

[0001] The invention relates to the field of measurement technology, in particular to a method for measuring the speed of a solid material belt conveyor.

[0002] A solid material belt conveyor speed measurement method based on line scanning laser and cross-correlation principle is proposed, which can realize real-time non-contact and accurate measurement of belt conveyor speed. Background Art

[0003] Real-time solid velocity is a key measurement parameter for various belt conveyor systems. Accurately measuring velocity is crucial for controlling the operation of belt conveyor equipment. For example, in coal-fired power plants, the amount of coal conveyed by a belt needs to be regulated in real time based on load conditions. Belt speed is not only a crucial parameter for calculating the real-time coal flow but also serves as a direct feedback signal for adjusting the speed of the belt conveyor electrodes.

[0004] The current method for measuring the flow rate of solid materials conveyed by belt conveyors mainly uses a speed wheel, which can obtain the instantaneous speed of the material. However, over time, slippage and surface dust adhesion will occur, resulting in large measurement deviations. In the case of severe powder leakage, the speed wheel may even get stuck, directly causing the speed measurement to fail.

[0005] Laser ranging is a non-contact measurement method that does not affect the movement of the object being measured. It has high accuracy, a large measurement range, a short detection time, and high spatial resolution. Currently, laser scanning ranging technology has been used to measure the cross-sectional area of ​​belt conveyed materials. However, it needs to be combined with a speed wheel device to further calculate the belt conveyor flow rate, so there are problems with measurement deviation or measurement failure. Summary of the Invention

[0006] In order to achieve non-contact and accurate measurement of belt conveyor speed, the technical problem to be solved by the present invention is to propose an online real-time non-contact measurement method and system for improving measurement accuracy.

[0007] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0008] The belt conveyor speed detection method based on line scanning laser includes:

[0009] Use a laser scanner to obtain two frames of point cloud data along the belt's moving direction in real time;

[0010] Convert the two frames of point cloud data acquired in real time into new point cloud data with the same horizontal coordinate spacing;

[0011] Calculate conveyor belt speed using new point cloud data.

[0012] The first frame of point cloud data obtained by the laser scanner in real time is (X1, Z1), (X2, Z2), (X3, Z3)… (X k ,Z k )…(X n ,Z n ), horizontal axis X k =-l k ×cosθ k , vertical coordinate Z k =-l k ×sinθ k ,θ k is the kth scanning angle, and θ k =θ+(k-1)Δβ, Δβ is the laser scanning angle resolution, l k is the distance corresponding to the kth scanning angle of the scanner; the second frame point cloud data is consistent with the scanning angle of the first frame, and the data is (X'1, Z'1), (X'2, Z'2), (X'3, Z'3) ... (X' n ,Z' n ).

[0013] Convert two frames of point cloud data acquired in real time into new point cloud data with the same horizontal coordinate spacing, including:

[0014] Calculate the horizontal coordinates X1, X2, X3...X of the first frame of point cloud data n The average interval

[0015]

[0016] make according to X1, X2, X3......X n Convert to equally spaced horizontal coordinate values

[0017] Determine the horizontal axis sequence with equal intervals The corresponding vertical coordinate:

[0018]

[0019] Among them, Y i * is the horizontal axis The corresponding vertical coordinate; (X L ,Z L ) and (X R ,Z R ) is the distance X i The coordinates of the nearest left and right points, i.e. and if Then Yi * Can be 0.

[0020] According to the horizontal and vertical coordinates obtained by the above calculation, the new point cloud data of the first frame data under the condition of equal interval is obtained.

[0021] Similarly, the horizontal coordinates of the second frame point cloud data are X1', X'2, X3'......X' n It also matches the equally spaced horizontal coordinate values ​​obtained from the first frame data Then the new point cloud data of the second frame point cloud data under the condition of equal interval can be calculated

[0022] Calculate conveyor belt speed using new point cloud data, including:

[0023] According to the cross-correlation function R(j) of two adjacent frames of new point cloud data, calculate the horizontal coordinate J corresponding to the maximum value of R(j):

[0024]

[0025] in, Is the first frame sequence The average value of The second frame sequence The average value of

[0026] According to the calculated horizontal coordinate J, the displacement difference ΔL between the two frames of scanning results is determined as:

[0027]

[0028] According to the displacement difference ΔL between the two adjacent frames of scanning results, the belt speed measurement value v is calculated:

[0029] v=ΔL / Δt

[0030] Wherein, Δt is the time interval between obtaining two frames of point cloud data.

[0031] Beneficial effects:

[0032] (1) The present invention utilizes a line scanning laser combined with cross-correlation signal processing technology to achieve real-time measurement of the solid material belt conveyor speed, solving the problem that the existing laser measurement method cannot solve the belt conveyor speed measurement problem.

[0033] (2) Compared with the traditional speed wheel measuring device, the present invention realizes completely non-contact belt conveyor speed measurement, does not affect the normal operation of the belt conveyor system, and has high measurement accuracy and reliability. Description of the drawings:

[0034] Figure 1 This is a schematic diagram of the belt speed measurement system of the present invention.

[0035] Figure 2 Schematic diagram of the model scanned by the laser scanner;

[0036] Figure 3 Laser scanner speed measurement principle diagram;

[0037] Figure 4 Schematic diagram of height calculation at equally spaced locations. DETAILED DESCRIPTION

[0038] The present invention proposes a belt conveyor speed detection system and method using a line scanning laser and the cross-correlation principle. Only a laser scanner is used to obtain the material accumulation height on the laser line along the direction of belt movement, and then combined with a cross-correlation algorithm, the real-time speed of the belt conveyor material can be measured.

[0039] Figure 1 The diagram is a principle diagram of belt speed measurement. The steps of the belt conveyor speed detection method using a line scanning laser and the cross-correlation principle are as follows:

[0040] 1) Calculation of point cloud data:

[0041] Establish a two-dimensional rectangular coordinate system XOZ, such as Figure 2 As shown. The laser scanner obtains two data: the distance from the scanning center point to the scanning point on the material contour surface and the angle between the scanning point and the axis. The angular resolution of the laser scanner is very small Δβ<1. For each frame scan, the kth scanning angle is set to θ k =θ+(k-1)Δβ, the distance corresponding to the kth frame of the scanner is l k , corresponding to point M on the material contour line k , its horizontal coordinate X k =-l k ×cosθ k , vertical coordinate Z k =-l k ×sinθ k From points M1, M2...M n The enclosed contour line is the outer contour curve of the material.

[0042] Therefore, the external contour curves of the material at the time t and t+Δt of the two frame scans are as follows: Figure 3 As shown in Figure 2, the solid line is the profile curve graph measured by the laser scanner at time t, and the dotted line is the profile curve graph measured by the laser scanner at time t+Δt.

[0043] At time t, the first frame of point cloud data obtained by the scanner is (X1, Z1), (X2, Z2), (X3, Z3)... (X n,Z n ); At time t+Δt, the second frame of point cloud data obtained by the scanner is (X'1, Z'1), (X'2, Z'2), (X'3, Z'3)... (X' n ,Z' n ).

[0044] 2) Point cloud data equal interval conversion

[0045] First calculate the horizontal coordinates X1, X2, X3......X of the first frame point cloud data n The average interval

[0046]

[0047] make X1, X2, X3......X n Convert to equally spaced horizontal coordinate values but:

[0048]

[0049] Determine the horizontal axis sequence with equal intervals The corresponding vertical coordinate. Figure 4 As shown, the horizontal axis is The point is calculated by the following formula: i * Make a linear approximation:

[0050]

[0051] Among them, (X L ,Z L ) and (X R ,Z R ) is the distance X i The point cloud coordinates obtained in real time by the nearest laser scanners on the left and right sides are and if Then Y i * Can be 0.

[0052] According to the horizontal and vertical coordinates obtained by the above calculation, the new point cloud data of the first frame data under the condition of equal interval is obtained.

[0053] Similarly, the horizontal coordinates of the second frame point cloud data are X1', X'2, X3'......X' n It also matches the equally spaced horizontal coordinate values ​​obtained from the first frame data Then the new point cloud data of the second frame point cloud data under the condition of equal interval can be calculated

[0054] 3) Speed ​​calculation:

[0055] Get a sequence of equally spaced coordinates After obtaining the corresponding two frames of new point cloud data ordinate sequence, the cross-correlation function can be calculated according to the following formula:

[0056]

[0057] in, and is a sequence and When R(j) is the largest, its corresponding horizontal coordinate j=J, and the displacement difference ΔL of the two scanning results can be determined as:

[0058]

[0059] The measured belt speed v is:

[0060] v = ΔL / Δt.

Claims

1. A belt conveyor speed detection method based on a line scanning laser, characterized in that: include: Use a laser scanner to obtain two frames of point cloud data along the belt's moving direction in real time; Convert the two frames of point cloud data acquired in real time into new point cloud data with the same horizontal coordinate spacing; Calculate the belt conveyor speed using the new point cloud data; The first frame of point cloud data obtained by the laser scanner in real time is (X1, Z1), (X2, Z2), (X3, Z3)… (X k ,Z k )…(X n ,Z n ); horizontal axis X k =-l k ×cosθ k , vertical coordinate Z k =-l k ×sinθ k ,θ k is the kth scanning angle, and θ k =θ+(k-1)Δβ, Δβ is the laser scanning angle resolution, l k is the distance corresponding to the kth scanning angle of the scanner; The second frame of point cloud data obtained by the laser scanner in real time is consistent with the scanning angle of the first frame of point cloud data. The second frame of point cloud data is (X'1, Z'1), (X'2, Z'2), (X'3, Z'3)... (X' n ,Z' n ); Convert two frames of point cloud data acquired in real time into new point cloud data with the same horizontal coordinate spacing, including: Calculate the horizontal coordinates X1, X2, X3...X of the first frame of point cloud data n The average interval make according to X1, X2, X3......X n Convert to equally spaced horizontal coordinate values Determine the horizontal axis sequence with equal intervals The corresponding vertical coordinate: in, is the horizontal axis The corresponding vertical coordinate; (X L ,Z L ) and (X R ,Z R ) is the distance X i The point cloud coordinates obtained in real time by the laser scanners on the nearest left and right sides are and if but Take it as 0; According to the horizontal and vertical coordinates obtained by the above calculation, the new point cloud data of the first frame data under the condition of equal interval is obtained. The horizontal coordinates of the second frame point cloud data are X1', X'2, X3'......X' n Match the equally spaced horizontal coordinate values ​​obtained from the first frame data Then calculate the new point cloud data of the second frame under the condition of equal interval Calculate conveyor belt speed using new point cloud data, including: According to the cross-correlation function R(j) of the two frames of new point cloud data, calculate the horizontal coordinate J corresponding to the maximum value of R(j): in, Is the first frame sequence The average value of The second frame sequence The average value of According to the calculated horizontal coordinate J, the displacement difference ΔL between the two frames of scanning results is determined as: According to the displacement difference ΔL between the two frames of scanning results, the belt speed measurement value v is calculated: v=ΔL / Δt Wherein, Δt is the time interval between obtaining two frames of point cloud data.

2. The belt conveyor speed detection system based on line scanning laser is characterized by: include: A line scanning laser is set above the conveyor belt to obtain two frames of point cloud data along the belt's movement direction in real time; A processor processes the two frames of point cloud data acquired in real time by the line scanning laser using the belt conveyor speed detection method based on the line scanning laser according to claim 1 to obtain the belt conveyor speed.

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