A bridge type crane girder deflection detection system and a crane control method thereof

Abstract

This invention discloses a main beam deflection detection system and crane control method for a bridge-type crane, belonging to the field of special equipment safety monitoring technology. It addresses the problems of low accuracy in main beam deflection detection and the inability to pinpoint the deflection change area. The system includes a laser emitter and multiple laser detectors, spaced apart along the length of the crane's main beam. These detectors enable multi-point real-time monitoring of the entire main beam's length. When the crane's main beam deflects, the position of the responding laser detectors can be quickly determined to pinpoint the area of ​​deflection change. Each laser detector includes a detection element and vias. The detection element senses laser deflection and generates an electrical signal. The laser beam emitted by the laser emitter passes through all the vias, the shape and size of which are adapted to the projected cross-section of the laser beam. Once the main beam undergoes deflection causing laser beam deflection, it can be immediately captured by the detection element, improving sensitivity.

Description

Technical Field

[0001] This invention belongs to the field of special equipment safety monitoring technology, and more specifically, it relates to a main beam deflection detection system for a bridge crane and a crane control method thereof. Background Technology

[0002] As the core load-bearing component of a bridge crane, the main beam of a bridge crane is subject to permanent deformation during crane operation due to factors such as stress release during welding, overload use, high-temperature environment, improper storage, hoisting and installation, and localized heating operations. These factors directly affect the safety performance and service life of the crane.

[0003] Therefore, regular or real-time accurate detection of crane main beam deflection is a crucial aspect of crane maintenance and safety assessment. Current detection methods include leveling, wire drawing, and single-point laser beam measurement. For example, Chinese invention patent application CN99101428.6 uses a target perpendicular to an emitted laser beam, reflecting a portion of the light back. The laser measuring device converts the optical signal into an electrical signal and outputs a data signal, which is then input into a computer via a connected transmission cable. The computer displays and predicts the deflection of the main beam. While this method can detect beam deflection, setting a single laser measurement point in the middle of the main beam only detects the deflection value at that point, failing to reflect the overall deformation of the main beam, resulting in a very limited detection range. Furthermore, when abnormal deflection occurs in the main beam, the specific deformation area cannot be determined. Further improvements are needed to address the shortcomings of current detection technologies. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a main beam deflection detection system for a bridge-type crane and its crane control method. Through multi-point monitoring design and a high-sensitivity detection mechanism, it can detect changes in the main beam deflection of the crane with high sensitivity and also lock the area of ​​change, thereby solving the technical problems of low accuracy in main beam deflection detection and inability to lock the area of ​​deflection change in existing technologies.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A deflection detection system for the main beam of a bridge-type crane includes a laser emitter and multiple laser detectors arranged at intervals along the length of the main beam. Each laser detector includes a detection element and a via. The detection element is used to sense laser deflection and generate an electrical signal. The laser beam emitted by the laser emitter passes through all the vias. The shape and size of the vias are adapted to the projected cross section of the laser beam to trigger a response from the detection element when the laser beam deflects.

[0007] The shape and size of the through hole are adapted to the projection section of the laser beam, which allows the laser to pass smoothly when the main beam of the crane is not deformed. Once the main beam undergoes deflection and causes the laser beam to deviate, it can be immediately captured by the detection component, thus improving the sensitivity.

[0008] By setting up multiple detectors, real-time monitoring of the entire length of the main beam is achieved at multiple points, rather than monitoring a single location, which improves the comprehensiveness of the detection. When the deflection of the crane main beam changes, the area of ​​deflection change can be quickly located by determining the position of the response laser detector.

[0009] Further specifying, the laser detector includes multiple reflectors arranged in a ring and forming a through-hole at the center. The reflectors are tilted to the same side. The detection element consists of multiple detection plates, with each reflector corresponding to a specific detection plate. When the laser beam illuminates a reflector, the laser beam is reflected onto the corresponding detection plate. By using reflectors and appropriately configuring the deflection angles and spacing between the reflectors and detection plates, the path of the laser beam from the laser emitter to the detection plate is lengthened, and the angle of laser beam deflection is amplified, thereby improving detection sensitivity.

[0010] Further specifying, each laser detector contains four reflectors, with two reflectors arranged symmetrically vertically and two mirrors arranged symmetrically horizontally. By arranging the four reflectors symmetrically, similar to a cross, the deflection and lateral bending of the crane's main beam can be accurately detected regardless of the direction of the crane's main beam's deflection deformation.

[0011] Further specifying, the detection board includes a board body and multiple photodiodes, with the multiple photodiodes arrayed on one side of the board body. The arrayed photodiodes can accurately capture the specific position of the laser reflection spot falling on the detection board. By determining which photodiodes(s) are triggered, the laser offset can be converted into specific electrical signal matrix data, providing a basis for subsequent calculation of deflection values.

[0012] Further specifying, the laser detector includes a mounting base and a cylindrical mounting cylinder. The mounting base is disposed on the main beam of the crane, and the mounting cylinder is disposed on the mounting base. The plate and the reflector are both housed within the mounting cylinder. Both the plate and the reflector have a fan-shaped structure, and the arc-shaped edges of the plate and the reflector are in contact with the inner wall of the mounting cylinder. The combination of the cylindrical mounting cylinder and the fan-shaped structure of the plate and the reflector results in a compact overall design, fully utilizing the annular space within the mounting cylinder. This ensures a tight fit between the plate, the reflector, and the mounting cylinder, preventing light leakage and improving the reliability of the system's detection.

[0013] Furthermore, the mounting base is equipped with an air passage, one end of which connects to the hollow area inside the mounting cylinder, and the other end connects to an air supply pipe. High-pressure gas is introduced through the air supply pipe to blow away dust from the reflectors and photodiodes inside the mounting cylinder, ensuring the accuracy of the detection signal.

[0014] Further specifying, the laser emitter is located at one end of the crane main beam, and a laser receiver is provided at the other end of the crane main beam. The laser beam emitted by the laser receiver passes through all the through holes and illuminates the laser receiver.

[0015] The baseline status of the entire optical path is monitored by a laser receiver at the end. If the laser receiver at the end and all laser detectors fail to receive a laser signal, it indicates a malfunction or severe misalignment of the laser transmitter itself, rather than necessarily a problem caused by deformation of the crane's main beam. This provides a criterion for judging the overall smoothness of the optical path, enhancing the system's self-diagnostic capabilities and reliability.

[0016] Further specifying, the number of laser detectors is an odd number greater than or equal to five, symmetrically arranged with the geometric center of the crane's main beam as the center of symmetry. One laser detector is located at the geometric center, and the remaining laser detectors are symmetrically distributed towards both ends along the length of the main beam. From the center to both ends, the spacing between adjacent laser detectors increases progressively, and the increase matches the deflection gradient of the crane's main beam. This non-uniform arrangement ensures monitoring accuracy by focusing on areas with large deformations while avoiding sensor waste, optimizing resource allocation, and better reflecting the actual stress and deformation characteristics of the main beam.

[0017] To achieve this objective, the present invention also provides a crane control method, which utilizes the aforementioned bridge crane main beam deflection detection system and specifically includes the following steps:

[0018] S1: Real-time acquisition of signals detected by the laser detector;

[0019] S2: Control the crane to stop in an emergency by detecting the signal.

[0020] By linking the crane's control system with its detection system, the crane control system can respond immediately once it detects that the main beam deflection is too large and exceeds the safe range, thus preventing structural damage or safety accidents caused by excessive deformation of the main beam.

[0021] Further specifying, step S2 includes the following steps:

[0022] S21: Set the signal level A to trigger emergency stop of the crane;

[0023] S22: Determine the current signal level B by the position of the photodiodes that trigger the response in the array of photodiodes;

[0024] S23: Determine whether the signal level B has reached or exceeded the signal level A. If so, control the crane to stop in an emergency. If not, the crane will operate normally.

[0025] By setting specific threshold levels, normal minor vibrations and dangerous severe deformations can be effectively distinguished, avoiding accidental shutdowns caused by slight disturbances and improving the robustness and practicality of the system.

[0026] This invention provides a main beam deflection detection system for a bridge crane and a crane control method thereof, which has the following advantages:

[0027] 1. By adapting the shape and size of the through hole to the projection cross section of the laser beam, the laser can pass smoothly through the crane main beam when it is not deformed. Once the main beam undergoes deflection and causes the laser beam to deviate, it can be immediately captured by the detection component, thus improving sensitivity.

[0028] 2. By setting up multiple detectors, real-time monitoring of the entire length of the main beam is achieved, rather than monitoring a single location, which improves the comprehensiveness of the detection. When the deflection of the crane main beam changes, the area of ​​deflection change can be quickly located by determining the position of the response laser detector.

[0029] 3. By arranging the four reflectors symmetrically up and down and left and right, the deflection and bending of the crane's main beam can be matched. No matter which direction the crane's main beam deflects, the offset direction can be accurately captured by the reflectors and detection plates in the corresponding directions.

[0030] 4. By linking the crane's control system with its detection system, the crane control system can respond immediately once it detects that the main beam deflection is too large and exceeds the safe range, thus preventing structural damage or safety accidents caused by excessive deformation of the main beam. Attached Figure Description

[0031] The present invention can be further illustrated by the non-limiting embodiments given in the accompanying drawings:

[0032] Figure 1 This is a schematic diagram of the deflection detection system provided in Embodiment 1.

[0033] Figure 2 This is a schematic diagram of the structure of the via and the detection element provided in this embodiment.

[0034] Figure 3 This is a schematic diagram of the structure of the laser detector provided in Embodiment 1;

[0035] Figure 4This is a schematic diagram of the reflection path of the laser beam provided in this embodiment.

[0036] Figure 5 This is a schematic diagram of the reflector arrangement provided in Embodiment 1;

[0037] Figure 6 This is a schematic diagram of the detection plate provided in this embodiment.

[0038] The symbols for the main components are explained below:

[0039] In the diagram: 1. Laser emitter; 2. Laser detector; 21. Via; 22. Mirror; 23. Detection plate; 231. Plate body; 232. Photodiode; 24. Mounting base; 25. Mounting cylinder; 26. Air duct; 3. Crane main beam; 4. Air supply pipe; 5. Laser receiver. Detailed Implementation

[0040] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that similar or identical parts are referred to by the same reference numerals in the drawings or description. Implementations not shown or described in the drawings are forms known to those skilled in the art. In addition, directional terms mentioned in the embodiments, such as "up," "down," "top," "bottom," "left," "right," "front," and "back," are only for reference to the directions in the drawings and are not intended to limit the scope of protection of the present invention.

[0041] This invention provides the following technical solutions:

[0042] Example 1:

[0043] A deflection detection system for the main beam of a bridge crane, such as Figure 1 As shown, the system includes a laser emitter 1 and multiple laser detectors 2, which are arranged at intervals along the length of the crane main beam 3. By setting multiple detectors, real-time monitoring of the entire length of the main beam is achieved, rather than monitoring a single location, thus improving the comprehensiveness of the detection. When the deflection of the crane main beam changes, the area of ​​deflection change can be quickly located by determining the position of the responding laser detectors 2.

[0044] Specifically, such as Figure 2As shown, the laser detector 2 includes a detection element and vias 21. The detection element senses laser deflection and generates an electrical signal. The laser beam emitted by the laser emitter 1 passes through all the vias 21. The shape and size of the vias 21 are adapted to the projection cross-section of the laser beam to trigger a response from the detection element when the laser beam deflects. For example, a circular laser cross-section corresponds to a circular via 21. By adapting the shape and size of the via 21 to the projection cross-section of the laser beam, the laser can pass smoothly through the crane main beam when it is undeformed. Once the main beam undergoes deflection, causing the laser beam to deflect, it can be immediately captured by the detection element, thus improving sensitivity.

[0045] Regarding the detection components: These are primarily photosensitive elements that convert optical signals into electrical signals, such as phototransistors, photoresistors, or CMOS image sensors. Specifically, taking photodiodes as an example, a PIN photodiode consists of P-type, intrinsic (I-type), and N-type semiconductor layers. When irradiated by laser light, photon energy excites electrons in the intrinsic layer, generating electron-hole pairs and forming a photocurrent. The output signal type depends on the characteristics of the incident light: continuous laser light generates a DC signal, while modulated laser light generates an AC signal. By connecting the electrical signals collected in real-time by the photosensitive elements to a control terminal system with display and operation capabilities, such as a computer or monitor, it is possible to monitor the crane's main beam 3 in real time.

[0046] It should be noted that the detection component can be a photosensitive element set on a mounting plate. If the detection component only has a photosensitive element, then the photosensitive elements are arranged with gaps left in the middle to form a through hole 21.

[0047] To further improve the sensitivity of the deflection detection system, such as Figure 3 As shown, the laser detector 2 includes multiple reflectors 22 arranged in a ring and forming a through-hole 21 at the center. The reflectors 22 are tilted to the same side, forming a "flower" shape. The detection element consists of multiple detection plates 23, with each reflector 22 corresponding to one detection plate 23. When a laser beam shines on a reflector 22, the laser beam is reflected by the reflector 22 onto the corresponding detection plate 23. Figure 4 As shown, by using the reflector 22 and by properly configuring the deflection angle of the reflector 22 and the detection plate 23 and the distance between them, the path of the laser from the laser emitter 1 to the detection plate 23 is lengthened, and the angle of laser beam deflection is amplified, thereby improving the detection sensitivity.

[0048] Considering the possibility that the crane's main beam 3 may bend in different directions, therefore, as Figure 5As shown, each laser detector 2 contains four reflectors 22. Two of the four reflectors 22 are arranged symmetrically vertically, and two are arranged symmetrically horizontally. By arranging the four reflectors 22 symmetrically, similar to a cross, the deflection and bending of the crane main beam 3 can be accurately detected regardless of the direction of the deflection deformation of the crane main beam 3.

[0049] If each detection plate 23 has only one photosensitive element, it can only detect whether the crane main beam 3 has undergone deflection changes. To further improve the functionality of the detection system, such as... Figure 6 As shown, the detection board 23 is designed as a board body 231 with multiple photodiodes 232, which are arrayed on one side of the board body 231. The arrayed photodiodes can accurately capture the specific position of the laser reflection spot falling on the detection board 23. By determining which photodiodes 232 or more are triggered, the laser offset can be converted into specific electrical signal matrix data, providing a basis for subsequent calculation of deflection values.

[0050] It should be noted that the laser spot needs to be larger than the gap between the photodiode 232 and the photodiode 232 to avoid it falling into the gap and becoming undetectable. Changing the size of the laser spot changes the thickness of the beam.

[0051] Regarding the installation of laser detector 2:

[0052] like Figure 3 As shown, the laser detector 2 includes a mounting base 24 and a cylindrical mounting cylinder 25. The mounting base 24 is mounted on the main beam 3 of the crane, and the mounting cylinder 25 is mounted on the mounting base 24. The plate 231 and the reflector 22 are both housed within the mounting cylinder 25. Both the plate 231 and the reflector 22 have a fan-shaped structure, and their arc-shaped edges are in contact with the inner wall of the mounting cylinder 25. The combination of the cylindrical mounting cylinder 25 with the fan-shaped structure of the plate 231 and the reflector 22 makes the overall design compact, fully utilizes the annular space within the mounting cylinder 25, and ensures a tight fit between the plate 231, the reflector 22, and the mounting cylinder 25, avoiding light leakage and improving the reliability of the system's detection.

[0053] Considering the working environment of the detection system, which is constantly covered in dust, in order to avoid dust affecting the light sensing, such as Figure 1 Figure 3As shown, an air passage 26 is provided in the mounting base 24. One end of the air passage 26 is connected to the hollow area inside the mounting cylinder 25, and the other end is connected to the air supply pipe 4. High-pressure gas, such as compressed air, is introduced through the air supply pipe 4. During cleaning, the dust on the reflector 22 and photodiode 232 inside the mounting cylinder 25 can be blown away by intermittent blowing. Regular blowing cleaning can ensure the accuracy of the detection signal and the stability of the detection system.

[0054] In addition, clean gas, such as compressed air, can be introduced into the mounting cylinder 25 through the air supply pipe 4 to form positive pressure or air curtain, which can effectively prevent dust and impurities in the crane working environment from entering the detector.

[0055] Regarding the arrangement of laser detector 2:

[0056] Considering that the deflection deformation of the crane main beam 3 under load is typically parabolic, with the largest deformation in the middle and near zero deformation at both ends, this arrangement avoids the problem of denser detection points in the middle of the area with large deformation and sparser points at the ends of the area with small deformation. Therefore, the number of laser detectors 2 is designed to be an odd number greater than or equal to five, and they are symmetrically arranged with the geometric center of the crane main beam 3 as the center of symmetry. One laser detector 2 is located at the geometric center, and the remaining laser detectors 2 are symmetrically distributed along the length of the main beam towards both ends. From the center to both ends, the spacing between adjacent laser detectors 2 increases progressively, and the increase matches the deflection deformation gradient of the crane main beam 3. This non-uniform arrangement ensures monitoring accuracy by focusing on monitoring areas with large deformation while avoiding sensor waste, optimizing resource allocation, and better reflecting the actual stress and deformation characteristics of the main beam.

[0057] The detection response in this embodiment is based on a laser beam, therefore it is essential to ensure that the laser emitter 1 is functioning correctly. Specifically, firstly, a laser beam of predetermined brightness needs to be emitted, and secondly, the emitted laser beam needs to irradiate along a predetermined direction; both of these points are indispensable. To confirm the normal operation of the laser emitter 1, such as... Figure 1 As shown, a laser emitter 1 is positioned at one end of the crane main beam 3, and a laser receiver 5 is positioned at the other end of the crane main beam 3. Under normal conditions, the laser beam emitted from the laser receiver 5 passes through all the through holes 21 and illuminates the laser receiver 5.

[0058] It should be noted that the laser receiver 5 uses a photosensitive element, which generates an electrical signal when it receives laser irradiation.

[0059] The deflection change of the crane's main beam 3 is monitored by the laser receiver 5 at the end, and the determination is made based on the following conditions:

[0060] 1. If the laser receiver 5 can receive the laser signal, but the signal is weak, it may indicate that the laser transmitter 1 is faulty. A weak laser may prevent the photodiode 232 from responding.

[0061] Second: If the laser receiver 5 at the end and all laser detectors 2 do not receive laser signals, it indicates that the laser transmitter 1 itself has malfunctioned or is severely misaligned, rather than it being a problem caused by the deformation of the crane main beam 3.

[0062] By setting up laser receiver 5 to verify the optical path, a basis for judging whether the overall optical path of the system is unobstructed can be provided, thereby enhancing the system's self-diagnostic capability and reliability.

[0063] The specific usage and function of this embodiment are as follows:

[0064] like Figure 1 As shown, when using this invention, the laser emitter 1 is activated, and then the response of the laser detector 2 and the laser receiver 5 is observed to detect the change in deflection of the crane main beam 3. Specifically, the following conditions are used to determine the situation:

[0065] Under normal conditions, the laser beam emitted by the laser emitter 1 passes through the vias 21 on all the laser detectors 2 and finally hits the laser receiver 5.

[0066] If neither the laser receiver 5 nor any of the laser detectors 2 receive a laser signal, it indicates that the laser transmitter 1 itself has malfunctioned or is severely misaligned, or that the crane main beam 3 is broken or severely bent, requiring immediate work stoppage and inspection.

[0067] If laser receiver 5 does not receive a laser signal, but laser detector 2 does, it determines which location of laser detector 2 is responding, thus identifying the deflection range of the crane main beam 3. Simultaneously, it uses the array of photodiodes 232 in laser detector 2 to determine which photodiodes 232 or more are triggered, thus determining the level of deflection change in the crane main beam 3. Based on the level of deflection change, it is determined whether maintenance shutdown or normal operation is required.

[0068] Example 2:

[0069] This embodiment provides a crane control method, which is implemented using the main beam deflection detection system of the bridge crane described in Embodiment 1 above. The method specifically includes the following steps:

[0070] S1: Real-time acquisition of signals detected by laser detector 2;

[0071] S2: Control the crane to stop in an emergency by detecting the signal.

[0072] By linking the crane's control system with its detection system, the crane control system can respond immediately once it detects that the main beam deflection is too large and exceeds the safe range, thus preventing structural damage or safety accidents caused by excessive deformation of the main beam.

[0073] Step S2 includes the following steps:

[0074] S21: Set the signal level A to trigger emergency stop of the crane;

[0075] S22: Determine the current signal level B by the position of the photodiode 232 that triggers the response in the array of photodiodes 232;

[0076] S23: Determine whether signal level B has reached or exceeded signal level A. If so, control the crane to stop in an emergency.

[0077] If not, the crane will operate normally.

[0078] By setting specific threshold levels, normal minor vibrations and dangerous severe deformations can be effectively distinguished, avoiding accidental shutdowns caused by slight disturbances and improving the robustness and practicality of the system.

[0079] The foregoing has provided a detailed description of a main beam deflection detection system for a bridge-type crane and its crane control method. The specific embodiments described are merely for the purpose of helping to understand the method and core ideas of this invention. It should be noted that those skilled in the art can make various improvements and modifications to this invention without departing from its principles, and these improvements and modifications also fall within the scope of protection of the claims of this invention.

Claims

1. A deflection detection system for the main beam of a bridge crane, comprising a laser emitter (1) and a laser detector (2), characterized in that: There are multiple laser detectors (2), and the multiple laser detectors (2) are arranged at intervals along the length direction of the main beam (3) of the crane. Each laser detector (2) includes a detection element and a via (21). The detection element is used to sense the laser offset and generate an electrical signal. The laser beam emitted by the laser emitter (1) passes through all the vias (21). The shape and size of the via (21) are adapted to the projection section of the laser beam to trigger the response of the detection element when the laser beam is offset.

2. The main beam deflection detection system for a bridge-type crane according to claim 1, characterized in that: The laser detector (2) includes multiple reflectors (22), which are arranged in a ring and form a through hole (21) in the center. The multiple reflectors (22) are tilted to the same side. The detection element is multiple detection plates (23), and each reflector (22) corresponds to a detection plate (23). When the laser beam irradiates the reflector (22), the laser beam is reflected by the reflector (22) onto the corresponding detection plate (23).

3. The main beam deflection detection system for a bridge-type crane according to claim 2, characterized in that: Each laser detector (2) has four reflectors (22), with two reflectors (22) arranged symmetrically vertically and two reflectors (22) arranged symmetrically horizontally.

4. The main beam deflection detection system for a bridge-type crane according to claim 2, characterized in that: The detection board (23) includes a board body (231) and a plurality of photodiodes (232), which are arrayed on one side of the board body (231).

5. The main beam deflection detection system for a bridge-type crane according to claim 4, characterized in that: The laser detector (2) includes a mounting base (24) and a cylindrical mounting cylinder (25). The mounting base (24) is mounted on the main beam (3) of the crane, and the mounting cylinder (25) is mounted on the mounting base (24). The plate (231) and the reflector (22) are both housed in the mounting cylinder (25). The plate (231) and the reflector (22) are both fan-shaped structures, and the arc-shaped edges of the plate (231) and the reflector (22) are in contact with the inner wall of the mounting cylinder (25).

6. The main beam deflection detection system for a bridge-type crane according to claim 5, characterized in that: An air passage (26) is provided in the mounting base (24). One end of the air passage (26) is connected to the hollow area inside the mounting cylinder (25), and the other end is connected to the air supply pipe (4).

7. The main beam deflection detection system for a bridge crane according to claim 1, characterized in that: The laser emitter (1) is located at one end of the main beam (3) of the crane, and a laser receiver (5) is provided at the other end of the main beam (3). The laser beam emitted by the laser receiver (5) passes through all the through holes (21) and irradiates the laser receiver (5).

8. The main beam deflection detection system for a bridge crane according to any one of claims 1-7, characterized in that: The number of laser detectors (2) is an odd number greater than or equal to five, and they are arranged symmetrically with the geometric center on the main beam (3) of the crane as the center of symmetry. One laser detector (2) is located at the geometric center, and the remaining laser detectors (2) are symmetrically distributed at both ends along the length of the main beam. From the center to both ends, the spacing between adjacent laser detectors (2) increases gradually, and the increase is matched with the deflection deformation gradient of the main beam (3) of the crane.

9. A crane control method, characterized in that: The main beam deflection detection system for bridge cranes according to claim 4 includes the following steps: S1: Real-time acquisition of the signal detected by the laser detector (2); S2: Control the crane to stop in an emergency by detecting the signal.

10. A crane control method according to claim 9, characterized in that: Step S2 includes the following steps: S21: Set the signal level A to trigger emergency stop of the crane; S22: Determine the current signal level B by the position of the photodiode (232) that triggers the response in the array of photodiodes (232); S23: Determine whether the signal level B has reached or exceeded the signal level A. If so, control the crane to stop in an emergency. If not, the crane will operate normally.

Images