Crane anti-collision protection system and method

Abstract

The application discloses a crane anti-collision protection system and method, and solves the problem of low accuracy of anti-collision protection of a crane in the prior art, has the beneficial effect of accurately judging the size of an obstacle, and has the specific scheme as follows: a crane anti-collision protection system comprises a radar unit, the radar unit is installed at the front end of a crane trolley, the front of the radar unit faces the advancing direction of the crane, the axis of the radar unit is obliquely installed with the vertical direction, and the radar unit obtains surface geometric three-dimensional point cloud data of obstacles in the set range of the moving path of the crane; a processing unit is connected with the radar unit, the processing unit converts the three-dimensional point cloud data fed back by the radar unit into three-dimensional coordinate data; an alarm unit is connected with the processing unit, the processing unit detects whether there is a risk obstacle in the preset protection area in the three-dimensional coordinate data, and if there is a risk obstacle, the processing unit controls the alarm unit to send an alarm signal.

Description

Technical Field

[0001] This invention relates to the field of cranes, and in particular to a crane anti-collision protection system and method. Background Technology

[0002] The statements in this section are merely background information related to the present invention and do not necessarily constitute prior art.

[0003] Cranes have become essential specialized equipment in port logistics due to their advantages in handling diverse materials, varying loads, and wide range of applications. With the expansion of port operations, the number of cranes has gradually increased, and collisions during lifting operations frequently occur at port sites, leading to injuries and economic losses. Therefore, our country has strict requirements for the safety performance of cranes.

[0004] Currently, the traditional anti-collision method for crane trolleys is to use a dual protection system consisting of non-contact detection limit switches and mechanical pressure bar limit switches. Non-contact detection limit switches are installed at both ends of the trolley, facing the direction of trolley travel, using single-point or two-dimensional laser sensor switches. Alternatively, radar or ultrasonic sensor switches can be used. When an obstacle obstructs the limit switch and triggers the signal, it is transmitted to the electronic control system for a deceleration alarm. Mechanical pressure bar limit switches are used where adjacent trolleys use a mechanical impact bar of a certain length at their end to contact the spring pressure bar of the other trolley's limit switch, thus disconnecting the trolley's braking circuit. The inventors discovered that because laser limiters are mostly single-point or two-dimensional lasers, the laser limiter signal sensing is only within a single point or plane. This means that the signal is limited by the installation height of the limiter and can only sense objects within a small range or objects that are larger than the laser installation height. As a result, the anti-collision protection coverage is very small, reducing the comprehensiveness of anti-collision safety protection. In addition, although radar or ultrasonic sensors can detect obstacles within a certain range, they have disadvantages such as a small emission angle that cannot be adjusted, and they are more susceptible to interference and false alarms, causing the crane to frequently enter the protection operation state. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the purpose of this invention is to provide a crane anti-collision protection system that improves the accuracy of anti-collision protection, ensures safe and efficient production, enables equipment operation to meet the requirements of on-site operating conditions, and ensures the safe operation of the crane.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0007] A crane collision avoidance protection system, comprising:

[0008] The radar unit is installed at the front end of the crane trolley, with the front of the radar unit facing the direction of the crane's movement. The radar unit's axis is installed at an angle to the vertical direction. The radar unit acquires geometric three-dimensional point cloud data of the surface of obstacles within the set range of the crane's movement path.

[0009] The processing unit is connected to the radar unit. The processing unit converts the three-dimensional point cloud data fed back by the radar unit into three-dimensional coordinate data, and filters and judges the data.

[0010] An alarm unit is connected to a processing unit. The processing unit detects whether there are any risky obstacles in the three-dimensional coordinate data within the preset protection area. If there are risky obstacles, the processing unit controls the alarm unit to issue an alarm signal.

[0011] In the crane collision avoidance protection system described above, the radar unit is installed at a height of 0.9m-1.4m above the ground on the crane. This allows the laser unit to focus on scanning the area below the set height of the crane, assisting the operator in making a judgment.

[0012] As described above, in a crane anti-collision protection system, the angle between the axis of the radar unit and the vertical direction is 3°-8°. The installation angle of the radar unit on the crane is adjustable. The tilted installation of the radar unit allows the uppermost beam of the laser unit to be parallel to the ground, which can effectively reduce the scanning blind zone and lower the minimum detection height.

[0013] As described above, in a crane anti-collision protection system, the radar unit is a multi-line lidar, which can obtain multiple line beams. The more line beams there are, the more complete the surface contour of the object.

[0014] Secondly, the present invention also provides a crane anti-collision protection method, which employs the aforementioned crane anti-collision protection system.

[0015] The crane anti-collision protection method described above includes the following:

[0016] The radar unit acquires geometric three-dimensional point cloud data of the surface of obstacles within the set range of the crane's movement path;

[0017] The processing unit converts the three-dimensional point cloud data fed back by the radar unit into three-dimensional coordinate data, which includes horizontal angle θ, vertical angle ρ, and point straight-line distance l.

[0018] The processing unit determines points entering the crane's preset anti-collision protection zone as obstacle points based on whether the three-dimensional coordinate data is within the preset anti-collision protection zone. It then performs distance classification and filtering on the three-dimensional coordinate data corresponding to the three-dimensional point cloud data composed of obstacle points, and further filters and judges the width and height of the three-dimensional coordinate data.

[0019] The processing unit determines the location, shape, and surface depth of the obstacle based on the preset anti-collision protection conditions to determine whether there is a risky obstacle. If a risky obstacle is found, the processing unit sends information to the alarm unit, which then issues an alarm signal.

[0020] As described above, in a crane collision avoidance protection method, the processing unit processes the three-dimensional point cloud data A fed back by the radar unit. (ρ,θ) Convert to three-dimensional coordinate data A (X,Y,Z) It includes the following:

[0021] X = l * sinρ * cosθ;

[0022] Z = l*sinρ*sinθ;

[0023] Y = l * cosρ;

[0024] Where X represents the coordinate in the X direction, Y represents the coordinate in the Y direction, and Z represents the coordinate in the Z direction.

[0025] As described above, in a crane collision avoidance protection method, the three-dimensional coordinate data corresponding to the three-dimensional point cloud data composed of obstacle points are classified and filtered according to the distance Y, that is, the depth |Y| of two adjacent obstacle points is determined. i -Y i-1 |Whether it is less than the set depth, for obstacle points whose depth is less than the set depth between two adjacent obstacle points, that is, to filter and judge the continuity of 3D point cloud data of the same distance / depth, and then remove false alarm points and interference points of 3D point cloud data composed of obstacle points.

[0026] The three-dimensional coordinate data is filtered and judged for width and height, that is, obstacle points whose width or height is less than the set width or height are filtered out.

[0027] As described above, the method for preventing crane collisions includes determining the position, outline, and surface depth of an obstacle, which includes the following:

[0028] Determine whether the location of the obstacle is within the preset anti-collision protection area, that is, determine whether the width and height of the obstacle are within the preset anti-collision protection area (X,Z)∈[(X,Z)max,(X,Z)min]);

[0029] Determine the shape of the obstacle by judging whether the difference between the maximum and minimum values ​​of the obstacle's width or height (Xmax-Xmin) or (Zmax-Zmin) is greater than the set width or set height. If it is greater than the set width or set height, it is a dangerous obstacle.

[0030] The surface depth of an obstacle is determined by whether the difference between the maximum and minimum depth values ​​of the obstacle point, Ymax-Ymin, is greater than a set depth. If it is greater than the set depth, it is a dangerous obstacle. The 3D point cloud data is then determined based on the preset collision protection conditions to determine whether it is a 3D point cloud of the obstacle.

[0031] In the crane collision protection method described above, the alarm unit issues alarm signals of different levels, specifically including the following:

[0032] The processing unit calculates the relative position of the dangerous obstacle with respect to the radar unit based on the depth information of the three-dimensional coordinate data of the risk, determines the level of the warning area where it is located, and sends the corresponding information to the alarm unit. The alarm unit issues the corresponding alarm signal based on the corresponding information.

[0033] The processing unit is connected to the crane's control system. When the processing unit sends the corresponding information to the alarm unit, it also sends information to the crane's control system. The crane's control system controls the crane's braking mechanism to decelerate or stop suddenly according to the warning zone level.

[0034] The beneficial effects of the present invention are as follows:

[0035] 1) This invention proposes an anti-collision protection system. The radar unit is installed at a suitable position on the crane. The radar unit returns geometric three-dimensional point cloud data of the relative obstacle surface, which is converted into three-dimensional coordinate data. The processing unit then judges whether there are risky obstacles in the preset anti-collision protection area. If there are, an alarm signal is issued, which effectively ensures the overall safety of the crane operation, avoids accidents, and improves the safety and efficiency of the crane during movement and operation.

[0036] 2) The present invention uses a radar unit installed at the front end of a crane trolley to scan for possible obstacles in the crane's forward direction. The radar unit is installed at an angle relative to the vertical direction, so that the uppermost line beam of the laser unit is parallel to the ground, which can effectively reduce the scanning blind zone and lower the minimum detection height.

[0037] 3) This invention provides a collision protection method that, by classifying and filtering three-dimensional coordinate data, can determine the position, shape, and surface depth of obstacles based on preset collision protection conditions to identify the presence of risky obstacles. This allows for a better assessment of the actual size of the obstacle and the risk of collision, leading to more accurate collision judgments. This solves the problem of ensuring the safety of trolley operation, enhances the safety performance of crane loading and unloading operations, ensures its operability and safety performance, improves operational efficiency, and facilitates installation and debugging.

[0038] 4) By connecting the processing unit with the crane controller, the present invention can control the crane's braking mechanism to decelerate or stop suddenly according to the level of the warning area, without the need for driver operation, thus achieving active control.

[0039] 5) This invention uses only one radar unit, which is reasonably installed and adjustable, and the anti-collision protection coverage is also guaranteed. It can obtain three-dimensional coordinate data, further determine the position, shape and surface depth of the obstacle, and determine whether there is a risky obstacle. It can better judge the actual size of the obstacle and the collision risk, thereby making a more accurate collision judgment. Attached Figure Description

[0040] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0041] Figure 1 This is a system topology diagram of a crane anti-collision protection system according to one or more embodiments of the present invention.

[0042] Figure 2 This is a schematic diagram of the radar unit installation in a crane anti-collision protection system according to one or more embodiments of the present invention.

[0043] Figure 3 This is a flowchart illustrating the operation of a crane anti-collision protection system according to one or more embodiments of the present invention.

[0044] The diagram exaggerates the spacing or dimensions between parts to show their positions; the diagram is for illustrative purposes only. Detailed Implementation

[0045] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0046] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, unless otherwise expressly indicated by the invention, the singular form is also intended to include the plural form. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0047] As described in the background section, existing technologies for cranes suffer from low accuracy in collision protection. To address this technical problem, this invention proposes a crane collision protection system.

[0048] Example 1

[0049] In a typical embodiment of the present invention, reference is made to Figure 2 As shown, a crane anti-collision protection system includes:

[0050] The radar unit is installed at the front end of the crane trolley, with the front of the radar unit facing the direction of the crane's movement. The radar unit's axis is installed at an angle to the vertical direction. The radar unit acquires geometric three-dimensional point cloud data of the surface of obstacles within the set range of the crane's movement path.

[0051] The processing unit is connected to the radar unit. The processing unit converts the three-dimensional point cloud data fed back by the radar unit into three-dimensional coordinate data, and filters and judges the data.

[0052] An alarm unit is connected to a processing unit. The processing unit detects whether there are any risky obstacles in the three-dimensional coordinate data within the preset protection area. If there are risky obstacles, the processing unit controls the alarm unit to issue an alarm signal.

[0053] Specifically, the processing unit determines the points entering the crane's preset anti-collision protection area as obstacle points based on whether the three-dimensional coordinate data is within the preset anti-collision protection area. It then performs distance classification and filtering on the three-dimensional coordinate data corresponding to the three-dimensional point cloud data composed of obstacle points, and further filters and judges the width and height of the three-dimensional coordinate data.

[0054] The radar unit faces the direction of the crane's movement and is installed at a height of 0.9m-1.4m above the ground, specifically 1.1m. This allows the laser unit to focus on scanning the area below the crane's set height, assisting the operator in making judgments.

[0055] Specifically, the angle between the radar unit's axis and the vertical direction is 3°-8°, with 5.5° being optional (this angle is determined based on the selected multi-line lidar transmission angle and usage requirements; for example, a transmission angle of ±2.75° is selected). The installation angle of the radar unit on the crane is adjustable, with a hinged connection for manual adjustment. The tilted installation of the radar unit allows the uppermost laser beam to be parallel to the ground, effectively reducing the scanning blind zone and lowering the minimum detection height.

[0056] In this embodiment, the crane has four corners, and each corner trolley is equipped with a radar unit. When the crane is used in the port, it ensures that there is corresponding anti-collision protection in the left and right directions of the two rows of trolleys on the sea side and the land side.

[0057] In this embodiment, the radar unit is a multi-line lidar. The radar unit is connected to the processing unit through a switch. The multi-line lidar has high sensitivity and long detection distance. The multi-line lidar can obtain multiple line beams. The more line beams there are, the more complete the surface contour of the object.

[0058] In addition, the processing unit can be an industrial computer or other types of controllers. In this embodiment, it can be an existing processing and computing unit.

[0059] Specifically, the processing unit determines the points entering the crane's preset anti-collision protection area as obstacle points based on whether the three-dimensional coordinate data is within the preset anti-collision protection area. It then performs distance classification and filtering on the three-dimensional coordinate data corresponding to the three-dimensional point cloud data composed of obstacle points, and further filters and judges the width and height of the three-dimensional coordinate data.

[0060] The processing unit determines the location, shape, and surface depth of the obstacle based on the preset anti-collision protection conditions to determine whether there is a risky obstacle. If a risky obstacle is found, the processing unit sends information to the alarm unit, which then issues an alarm signal.

[0061] The anti-collision protection system provided in this embodiment has a radar unit installed at a suitable position on the crane. The radar unit returns geometric three-dimensional point cloud data of the relative obstacle surface, which is then converted into three-dimensional coordinate data. The processing unit then determines whether there are any risky obstacles within the preset anti-collision protection area. If so, an alarm signal is issued, which effectively ensures the overall operational safety of the crane, avoids accidents, and improves the safety and efficiency of the crane during movement and operation.

[0062] Example 2

[0063] This embodiment provides a crane anti-collision protection method, which adopts a crane anti-collision protection system as described in Embodiment 1.

[0064] In this embodiment, a crane collision protection method is described, referring to... Figure 3 As shown, it includes the following:

[0065] The radar unit acquires geometric three-dimensional point cloud data of the surface of obstacles within the set range of the crane's movement path;

[0066] The processing unit converts the three-dimensional point cloud data fed back by the radar unit into three-dimensional coordinate data, which includes horizontal angle θ, vertical angle ρ, and point straight-line distance l.

[0067] The processing unit determines points entering the crane's preset anti-collision protection zone as obstacle points based on whether the three-dimensional coordinate data is within the preset anti-collision protection zone. It then performs distance classification and filtering on the three-dimensional coordinate data corresponding to the three-dimensional point cloud data composed of obstacle points, filters and judges the continuity of three-dimensional point cloud data of the same distance / depth, eliminates false alarm points and interference points in the three-dimensional point cloud data, and finally filters and judges the width and height of the three-dimensional coordinate data.

[0068] The processing unit determines the location, shape, and surface depth of the obstacle based on the preset anti-collision protection conditions to determine whether there is a risky obstacle. If a risky obstacle is found, the processing unit sends information to the alarm unit, which then issues an alarm signal.

[0069] The method provided in this embodiment classifies and filters three-dimensional coordinate data. It can determine the position, shape, and surface depth of obstacles based on preset anti-collision protection conditions to determine whether there are risky obstacles. Compared with the prior art, which can only obtain the width and distance information of obstacles, this method can detect more comprehensive data, better judge the actual size of objects and collision risks, and make more accurate collision judgments. This solves the problem of ensuring the safety of trolley operation, enhances the safety performance of crane loading and unloading operations, and at the same time ensures its operability and safety performance.

[0070] Specifically, the processing unit processes the three-dimensional point cloud data A fed back by the radar unit. (ρ,θ) Convert to three-dimensional coordinate data A (X,Y,Z) It includes the following:

[0071] X = l * sinρ * cosθ;

[0072] Z = l*sinρ*sinθ;

[0073] Y = l * cosρ;

[0074] Where X represents the coordinate in the X direction, Y represents the coordinate in the Y direction, and Z represents the coordinate in the Z direction.

[0075] In this embodiment, the preset anti-collision protection area is set as A. (X,Y,Z) ∈[(X,Y,Z)max,(X,Y,Z)min], the preset anti-collision protection zone is configured and adjusted according to the working conditions.

[0076] The 3D coordinate data corresponding to the 3D point cloud data composed of obstacle points are categorized and filtered by distance Y, that is, the depth |Y| of two adjacent obstacle points is determined. i -Y i-1|Whether the depth is less than a set depth, such as 300mm, for two adjacent obstacle points with a depth less than the set depth of 300mm, continuous screening and judgment are performed, and then false alarm points and interference points in the 3D point cloud data composed of obstacle points are removed.

[0077] The three-dimensional coordinate data is filtered and judged based on width and height, that is, obstacle points whose width or height is less than the set width or height by 300mm are selected.

[0078] In addition, determining the location, shape, and surface depth of an obstacle includes the following:

[0079] Determine whether the location of the obstacle is within the preset anti-collision protection area, that is, determine whether the width and height of the obstacle are within the preset anti-collision protection area (X,Z)∈[(X,Z)max,(X,Z)min]);

[0080] Determine the shape of the obstacle by judging whether the difference between the maximum and minimum values ​​of the obstacle's width or height (Xmax-Xmin) or (Zmax-Zmin) is greater than the set width or set height of 300mm. If it is greater than the set width or set height of 300mm, it is a dangerous obstacle.

[0081] The surface depth of an obstacle is determined by whether the difference between the maximum and minimum depth values ​​of the obstacle point, Ymax-Ymin, is greater than a set depth of 300mm. If it is greater than the set depth of 300mm, it is a dangerous obstacle. The three-dimensional point cloud data is then obtained based on the preset collision protection conditions to determine whether it is the three-dimensional point cloud of the obstacle.

[0082] It should be noted that the aforementioned set depth, set width, and set height, although all set at 300mm, are determined based on the preset anti-collision protection area, and these three values ​​can be adjusted according to specific circumstances.

[0083] In addition, the alarm unit issues alarm signals of different levels, specifically including the following:

[0084] The processing unit calculates the relative position of the dangerous obstacle with respect to the radar unit based on the depth information of the three-dimensional coordinate data of the risk, determines the level of the warning area where it is located, and sends the corresponding information to the alarm unit. The alarm unit issues the corresponding alarm signal based on the corresponding information.

[0085] Additionally, refer to Figure 1 As shown, the processing unit is connected to the crane's control system. When the processing unit sends the corresponding information to the alarm unit, it also sends information to the crane's control system. The crane's control system controls the crane's braking mechanism to decelerate or stop suddenly according to the warning zone level.

[0086] It's easy to understand that the classification of warning zone levels is based on the distance of the obstacle relative to the crane in the direction of travel. The distance threshold used for classification can be flexibly adjusted according to actual needs through configuration file reading and writing. Alternatively, thresholds for different scenarios (such as different docks or different cranes) can be preset and switched flexibly during use. After the system starts running, it will continuously monitor in real time until it receives a stop monitoring signal from the crane control system or a radar self-test signal indicating an anomaly (radar unit hardware malfunction or 3D point cloud data anomaly).

[0087] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A crane anti-collision protection method, characterized in that, include: The radar unit acquires geometric three-dimensional point cloud data of the surface of obstacles within the set range of the crane's movement path; The processing unit processes the 3D point cloud data A fed back by the radar unit. （ρ,θ） Convert to three-dimensional coordinate data A （X,Y,Z） The 3D point cloud data includes the horizontal angle θ, the vertical angle ρ, and the straight-line distance l between the points; The processing unit determines points entering the crane's preset anti-collision protection zone as obstacle points based on whether the three-dimensional coordinate data is within the preset anti-collision protection zone. It then performs distance classification and filtering on the three-dimensional coordinate data corresponding to the three-dimensional point cloud data composed of obstacle points, and further filters and judges the width and height of the three-dimensional coordinate data. The processing unit determines the location, shape, and surface depth of the obstacle based on the preset anti-collision protection conditions to determine whether there is a risky obstacle. If a risky obstacle is found, the processing unit sends information to the alarm unit, which then issues an alarm signal. The processing unit processes the three-dimensional point cloud data A fed back by the radar unit. （ρ,θ） Convert to three-dimensional coordinate data A （X,Y,Z） It includes the following: X = l * sinρ * cosθ; Z = l * cosρ; Y = l*sinρ*sinθ; Where X represents the coordinate in the X direction, Y represents the coordinate in the Y direction, and Z represents the coordinate in the Z direction; The process of classifying and filtering the 3D coordinate data corresponding to the 3D point cloud data composed of obstacle points by distance Y involves determining the depth |Y| between two adjacent obstacle points. i -Y i-1 | Whether it is less than the set depth, for obstacle points whose depth is less than the set depth between two adjacent obstacle points, that is, to filter and judge the continuity of 3D point cloud data of the same distance / depth, and then remove false alarm points and interference points of 3D point cloud data composed of obstacle points. The three-dimensional coordinate data is filtered and judged for width and height, that is, obstacle points whose width or height is less than the set width or height are filtered out. The determination of the obstacle's position, shape, and surface depth includes the following: Determine whether the location of the obstacle is within the preset anti-collision protection area, that is, determine whether the width and height of the obstacle are within the preset anti-collision protection area (X,Z)∈[(X,Z)max,(X,Z)min]; Determine the shape of the obstacle by judging whether the difference between the maximum and minimum values ​​of the obstacle's width or height (Xmax-Xmin) or (Zmax-Zmin) is greater than the set width or set height. If it is greater than the set width or set height, it is a dangerous obstacle. Determine the surface depth of the obstacle by checking whether the difference between the maximum and minimum depth values ​​of the obstacle point, Ymax-Ymin, is greater than a set depth. If it is greater than the set depth, it is a dangerous obstacle. Based on the preset collision protection conditions, determine whether the 3D point cloud data is the 3D point cloud of the obstacle. The alarm unit emits alarm signals of different levels, specifically including the following: The processing unit calculates the relative position of the dangerous obstacle with respect to the radar unit based on the depth information of the three-dimensional coordinate data of the risk, determines the level of the warning area where it is located, and sends the corresponding information to the alarm unit. The alarm unit issues the corresponding alarm signal based on the corresponding information. The processing unit is connected to the crane's control system. When the processing unit sends the corresponding information to the alarm unit, it also sends information to the crane's control system. The crane's control system controls the crane's braking mechanism to decelerate or stop suddenly according to the warning zone level.

2. The crane anti-collision protection method according to claim 1, characterized in that, The radar unit is installed on the crane at a height of 0.9m-1.4m above the ground.

3. The crane anti-collision protection method according to claim 1, characterized in that, The angle between the axis of the radar unit and the vertical direction is 3°-8°, and the installation angle of the radar unit on the crane is adjustable.

4. The crane anti-collision protection method according to claim 1, characterized in that, The radar unit is a multi-line lidar.

5. A crane anti-collision protection system, characterized in that, A crane anti-collision protection method according to any one of claims 1-4, comprising: The radar unit is installed at the front end of the crane trolley, with the front of the radar unit facing the direction of the crane's movement. The radar unit's axis is installed at an angle to the vertical direction. The radar unit acquires geometric three-dimensional point cloud data of the surface of obstacles within the set range of the crane's movement path. The processing unit is connected to the radar unit. The processing unit converts the three-dimensional point cloud data fed back by the radar unit into three-dimensional coordinate data, and filters and judges the data. An alarm unit is connected to a processing unit. The processing unit detects whether there are any risky obstacles in the three-dimensional coordinate data within the preset protection area. If there are risky obstacles, the processing unit controls the alarm unit to issue an alarm signal.

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