Detection and control system for tower crane hook swing angle based on GNSS and inertial measurement unit

Abstract

The application discloses a tower crane hook swing angle detection and control system based on GNSS and an inertial measurement unit, belongs to the technical field of safety monitoring, and comprises a GNSS-RTK positioning unit, an inertial measurement unit, a binocular vision acquisition unit, a laser auxiliary calibration unit, a data fusion processing module and an anti-swing closed-loop control module. The application fuses GNSS-RTK and inertial measurement unit data, combines Kalman filtering, binocular vision and laser feature extraction algorithms, and high-precision resolves a three-dimensional swing angle of a tower crane hook, solves the problems of complex installation of a traditional swing angle sensor and poor environmental adaptability, realizes closed-loop anti-swing control by relying on an input shaping algorithm, automatically suppresses residual swing of the hook, matches 5G and low-frequency dual-redundancy communication architecture, guarantees stable command transmission, simultaneously sets a quantitative grading early warning mechanism, effectively avoids collision risks, and is modularized in overall structure, is suitable for new and old tower crane retrofitting, and significantly improves hoisting stability and construction safety level.

Description

Technical Field

[0001] This invention belongs to the field of safety monitoring technology, specifically, it relates to a tower crane hook swing angle detection and control system based on GNSS and inertial measurement units. Background Technology

[0002] Tower cranes are core lifting equipment in construction. Traditional tower cranes rely entirely on operators' visual judgment of the hook's swing amplitude, lacking professional and precise swing angle detection devices. Currently, the few swing angle detection devices available in the industry mostly use mechanical swing angle sensors, which suffer from complex installation and wiring, dust obstruction at construction sites, poor adaptability to electromagnetic interference, and low measurement accuracy. Relying solely on GNSS satellite positioning to detect the hook's position is easily affected by building obstruction and electromagnetic interference at the construction site, causing positioning drift. While using an inertial measurement unit alone provides high instantaneous attitude detection accuracy, long-term integration calculations can lead to data divergence, making long-term stable measurements impossible.

[0003] Meanwhile, most existing tower crane anti-sway control systems use fixed parameter control algorithms, which cannot adaptively adjust the control strategy according to the actual swing angle frequency of the hook, and cannot achieve closed-loop linkage between swing angle detection and mechanism operation; traditional tower cranes are only equipped with a single communication method, relying on 5G networks to transmit control commands, and communication is prone to interruption when the construction floor is raised or the building blocks the view. There is no emergency communication backup link, which poses a safety hazard of tower crane loss of control.

[0004] In addition, conventional tower cranes lack a multi-coordinate system transformation mechanism, making it impossible to achieve accurate mapping from global satellite coordinates to the local operating coordinates of the tower crane; images acquired by binocular vision are easily affected by strong light and material obstruction, resulting in invalid images; after laser contour acquisition, there are broken or missing stripes, making it impossible to accurately extract swing angle feature points; there is also no swing offset compensation combined with the boom lifting angle and wire rope length, and there is a lack of a graded and quantified swing angle over-limit early warning mechanism. Overall, the intelligence, safety, and detection accuracy cannot meet the application requirements of intelligent construction unmanned tower cranes. Summary of the Invention

[0005] To address the aforementioned problems and technical deficiencies, this invention employs the following technical solution: a tower crane hook swing angle detection and control system based on GNSS and inertial measurement units, comprising: a GNSS-RTK positioning unit, including multiple sets of GNSS positioning instruments deployed at the tail, head, and both ends of the hook pin of the tower crane jib, used to acquire the global spatial coordinates of the tower crane jib and hook in the WGS-84 coordinate system; an inertial measurement unit, fixed to the hook body, used to acquire the hook's attitude acceleration and angular velocity in real time; a binocular vision acquisition unit, including at least two cameras, respectively installed on opposite sides of the tower crane main jib along the horizontal direction and perpendicular to the jib extension direction, used to simultaneously capture real-time detection images of the hook; a laser-assisted calibration unit, used to project a laser contour line onto the hook and acquire the laser projection curve of the hook contour; and a data fusion processing module, configured to: use the WGS-84 coordinate system... The first coordinate system is used as the standard system. A local second coordinate system of the tower crane is established with the boom head hinge point as the origin. The transformation parameters between the two coordinate systems are solved. The Kalman filter algorithm is used to perform complementary correction on the GNSS-RTK positioning data and the data collected by the inertial measurement unit. Feature extraction is performed on the image collected by the binocular vision acquisition unit and the projection curve collected by the laser-assisted calibration unit. The corrected hook coordinates are transformed to the second coordinate system. The results of the feature extraction are fused to calculate the three-dimensional tangential swing angle and radial swing angle of the hook load. The anti-sway closed-loop control module is configured to: receive the three-dimensional tangential swing angle and radial swing angle, and have a built-in input shaping anti-sway algorithm. It links the frequency converters of the tower crane's hoisting, slewing, and luffing mechanisms through the PLC controller. Based on the swing angle, it adaptively adjusts the operating speed and acceleration / deceleration curves of each mechanism to form a closed-loop linkage for detection and sway suppression.

[0006] Furthermore, when solving for the transformation parameters between the two coordinate systems, the data fusion processing module determines the coordinate translation parameters, scale ratio parameters, and rotation parameters based on the coordinates collected by the GNSS positioning instruments at the tail and head of the arm.

[0007] Furthermore, when performing complementary correction, the data fusion processing module uses the relative displacement obtained by short-time integration of the inertial measurement unit as the state prediction value of the Kalman filter, and the absolute coordinates output by the GNSS-RTK positioning instrument as the observation, to make the optimal estimation of the spatial position of the hook.

[0008] Furthermore, when the data fusion processing module extracts features from the projection curve, it extracts the center line of the laser stripe with a single pixel width from the laser projection curve, separates the laser stripe region of the hook contour through connected component analysis, and extracts the coordinates of key inflection points for swing angle measurement; when calculating the swing angle, it performs calculations by combining the vector angle formed by the key inflection points extracted from the laser stripe.

[0009] Furthermore, when extracting the coordinates of key inflection points, the data fusion processing module sequentially performs median filtering, morphological dilation erosion, adaptive threshold binarization, and skeleton extraction on the laser projection image to obtain the center line of the laser stripe with a single pixel width; then, it combines a quadratic interpolation algorithm to complete the missing data of the laser stripe.

[0010] Furthermore, when the data fusion processing module extracts features from the images acquired by the binocular vision acquisition unit, it performs grayscale conversion and gradient value calculation on the images. By comparing the total gradient value of the images with a preset gradient threshold, it filters valid frame images and eliminates invalid interference images.

[0011] Furthermore, the anti-sway closed-loop control module has a built-in input shaping anti-sway algorithm, which is a ZV or ZVD input shaper, and its transfer function is adaptively adjusted according to the real-time swing frequency of the hook load.

[0012] Furthermore, it also includes a boom angle sensor and a hook distance sensor; the boom angle sensor is used to detect the lifting angle of the main boom relative to the horizontal direction, and the hook distance sensor is used to detect the real-time rope length from the hook to the front end of the telescopic joint; when calculating the swing offset distance, the data fusion processing module introduces the lifting angle and the real-time rope length as compensation parameters; it also includes an audible and visual warning module, whose alarm triggering logic is configured to: when the ratio of the calculated hook swing offset distance to the real-time rope length exceeds a preset range of 0.05 to 0.2, determine that the swing angle exceeds the limit and output an alarm signal.

[0013] Furthermore, it also includes a dual-redundant communication module, which includes a 5G communication main link and a low-frequency radio wave emergency communication link using the 230MHz or 433MHz frequency band; the low-frequency radio wave emergency communication link is only used to transmit emergency control commands and is configured to automatically activate when the 5G communication main link is detected to take over the core control of the tower crane.

[0014] Furthermore, it also includes an RTK reference station, which is deployed in an open and unobstructed area around the tower crane; the RTK reference station is used to receive the observation data returned by each group of GNSS positioning instruments and perform differential error correction, and transmit the corrected high-precision spatial position coordinates to the data fusion processing module.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention integrates GNSS-RTK differential positioning with an IMU inertial measurement unit, combined with binocular vision screening, laser stripe feature extraction, Kalman filtering, and coordinate system transformation algorithms, to accurately calculate the three-dimensional tangential and radial swing angles of the tower crane hook. This replaces traditional mechanical swing angle sensors, overcoming their drawbacks of cumbersome installation and poor adaptability to construction environments. Through built-in ZV and ZVD adaptive input shaping algorithms, it achieves closed-loop linkage control between swing angle detection and the tower crane frequency converter, autonomously suppressing residual hook sway and reducing the difficulty of manual operation. Simultaneously, it employs a dual-redundant communication architecture of 5G and 230MHz to ensure stable and uninterrupted command transmission. Furthermore, it utilizes a graded audible and visual warning system based on the rope length ratio to effectively avoid the risk of collisions during hoisting. Attached Figure Description

[0016] In the attached diagram: Figure 1 This is a system overall architecture diagram according to an embodiment of the present invention; Figure 2 This is a data fusion flowchart according to an embodiment of the present invention. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments. Generally, the components of the embodiments of the present invention described and shown in the accompanying drawings can be arranged and designed in various different configurations.

[0018] Example 1: The tower crane hook swing angle detection and control system based on GNSS and inertial measurement units, as disclosed in the first embodiment, is applied to intelligent hoisting operations of tower cranes at construction sites. It primarily achieves high-precision detection of the three-dimensional spatial swing angle of the tower crane hook, multi-source data fusion calculation, adaptive closed-loop anti-sway control, and safety over-limit warning. This system overcomes the inherent defects of traditional mechanical swing angle sensors, such as complex installation and poor field adaptability. Relying on a multi-sensor fusion architecture to replace the single detection mode, it can operate stably in environments with construction site obstructions and electromagnetic interference. As an intelligent electrical control subsystem of the tower crane, this system works in conjunction with the tower crane's PLC, crane frequency converter, and vehicle-mounted sensor network to form an intelligent safety control system for the tower crane. It collects hook position, attitude, and swing angle data in real time, automatically suppressing hoisting sway and avoiding collision and weightlessness safety risks.

[0019] refer to Figures 1-2All modules of this system can communicate with the tower crane's onboard industrial communication bus. The onboard communication bus simultaneously hosts functional electronic control units (ECUs) such as a GNSS processing ECU, an inertial sensing ECU, a vision acquisition ECU, a laser calibration ECU, and an anti-sway control ECU. All ECUs act as network nodes to exchange data. Some core modules can also communicate directly via serial ports or Ethernet hardware connections without going through the communication bus, ensuring low-latency transmission of high-frequency sensor data and control commands. The overall sensing and control architecture of the system includes a GNSS-RTK positioning unit, an inertial measurement unit, a binocular vision acquisition unit, a laser-assisted calibration unit, a data fusion processing module, an anti-sway closed-loop control module, a dual-redundant communication module, and an audible and visual warning module. It also includes boom angle sensors and hook distance sensors as condition compensation and data acquisition components, forming a complete integrated system for detection, calculation, control, and early warning.

[0020] The GNSS processing ECU is a dedicated processing unit with a built-in processor, RAM, and storage unit. It is electrically connected to the RTK base station and multiple GNSS positioning devices deployed on-site. The GNSS processing ECU receives differential correction data from the RTK base station and performs differential error correction on the spatial coordinates collected by the GNSS positioning devices deployed at the boom tail, boom head, and both ends of the hook pin shaft to calculate high-precision global position information. At the same time, it uploads the corrected coordinate data to the data fusion processing module in real time, providing the original positioning data source for dual coordinate system transformation and hook spatial position calculation, including translation parameters, scale ratio parameters, and rotation parameters.

[0021] The inertial sensing ECU is electrically connected to the IMU (Inertial Measurement Unit) rigidly mounted on the hook body, continuously acquiring raw attitude data of the hook's three-axis acceleration and three-axis angular velocity at a frequency of 200Hz. The inertial sensing ECU performs noise reduction and smoothing preprocessing on the raw inertial data, and obtains the short-time relative displacement increment of the hook through integration calculation. The processed inertial measurement data is pushed to the data fusion processing module in real time, which can be used as an attitude prediction benchmark to compensate for the short-time drift defect of GNSS positioning and achieve complementary adaptation of the two types of sensor data.

[0022] The visual acquisition ECU is electrically connected to the binocular visual acquisition units installed on both sides of the tower crane's main boom, synchronously acquiring real-time images of the hook's working area. The visual acquisition ECU has image grayscale conversion and pixel gradient calculation functions, capable of statistically analyzing the overall gradient value of the image frame by frame. It accurately compares the total image gradient value with a preset standard threshold, automatically filtering valid frames and eliminating invalid images caused by dust obstruction or strong light interference. Only valid and reliable image data is output to the data fusion processing module for auxiliary feature recognition, ensuring the purity and effectiveness of the visual data source from the outset.

[0023] The laser calibration ECU is electrically connected to the laser-assisted calibration unit installed at the bottom of the tower crane's luffing trolley, and is responsible for acquiring the laser projection curve image of the hook surface. The laser calibration ECU has a built-in dedicated image processing algorithm that can sequentially perform median filtering, adaptive threshold binarization, morphological dilatation and erosion, skeleton extraction, and connected component analysis. It can refine broadband laser stripes into single-pixel-width center lines and identify the boundaries of stripe breakage areas. At the same time, it uses a quadratic interpolation algorithm to fill in the missing parts of the laser stripes caused by corrosion and occlusion, and accurately extracts the coordinates of key inflection points for swing angle measurement, providing reliable feature parameters for three-dimensional swing angle calculation.

[0024] As the core control unit of the system, the anti-sway control ECU receives the tangential swing angle, radial swing angle, and horizontal swing offset distance output by the data fusion processing module. It incorporates a built-in ZV and ZVD dual-input shaping anti-sway algorithm, capable of identifying the inherent vibration frequency of the hook swing in real time and adaptively adjusting the algorithm transfer function and control coefficients according to changes in the frequency. The anti-sway control ECU is linked with the tower crane PLC and the lifting frequency converters of each mechanism, adaptively adjusting the operating speed and acceleration / deceleration curves of the hoisting, slewing, and luffing mechanisms to achieve a closed-loop linkage throughout the entire process of swing angle detection and anti-sway control.

[0025] refer to Figures 1-2 The following sections will provide a detailed explanation of the overall hardware composition, module architecture, and working principle of this system.

[0026] The overall hardware architecture of this system mainly consists of a GNSS-RTK positioning unit, an RTK base station, an inertial measurement unit (IMU), a binocular vision acquisition unit, a laser-assisted calibration unit, a boom angle sensor, a hook distance sensor, a data acquisition module, a data fusion processing module, an anti-sway closed-loop control module, a dual-redundant communication module, and an audible and visual early warning module. All hardware is adapted to complex working conditions such as dust, vibration, and electromagnetic interference on construction sites, and its installation and layout are compatible with the original structure of the tower crane, requiring no major modifications to the overall mechanical structure. The dual-redundant communication module uses a 5G cellular network as the primary transmission link, paired with a 230MHz unlicensed low-frequency radio as an emergency backup link, forming a hot-backup communication architecture to ensure uninterrupted control commands even in complex and obstructed environments.

[0027] The GNSS-RTK positioning unit is equipped with five sets of GNSS positioning instruments, which are fixedly installed at the tail of the tower crane's counterweight boom, the head of the boom, both ends of the hook pin, and the outside of the hook's moving pulley block guard plate. The tail and head positioning instruments are used to construct the spatial reference vector of the tower crane boom, the positioning instruments at both ends of the hook are deployed in pairs to form differential measurement points, and the remaining set serves as a backup verification point. All positioning instruments output raw observation data in NMEA-0183 format at a frequency of 10Hz to ensure the synchronization and continuity of position acquisition.

[0028] The RTK reference station is deployed in an open, hardened area 50 to 200 meters away from the tower crane foundation. The site is free from obstructions by tall buildings and electromagnetic interference from high-voltage lines. Its geographical coordinates are fixed in advance through static observation. The reference station broadcasts differential correction data to all GNSS mobile stations via a data transmission radio to perform global error correction on the positioning coordinates, ensuring that the hook's planar positioning accuracy is stably controlled at the centimeter level. This hardware-level guarantee ensures the basic accuracy of the swing angle calculation.

[0029] The inertial measurement unit (IMU) is rigidly bolted to the flat side of the hook body. During installation, its sensitive axis is strictly aligned with the geometric axis of the hook to avoid attitude measurement errors caused by installation deviations. The IMU integrates a three-axis accelerometer and a three-axis gyroscope to capture instantaneous swing and attitude deflection changes of the hook during hoisting at high frequency, providing a high-frequency, highly sensitive inertial data source for subsequent Kalman filter algorithm fusion.

[0030] The binocular vision acquisition unit consists of two industrial cameras, which are symmetrically installed at both ends of the crossbeam below the luffing trolley along the horizontal direction and perpendicular to the extension direction of the boom. The optical axis of the camera is tilted inward by 15° to fully cover the field of view of the hook throughout its entire working stroke. Images are acquired synchronously at 30 frames per second and 1920×1080 resolution for subsequent effective frame screening and hook contour auxiliary recognition.

[0031] The laser-assisted calibration unit consists of a green line laser emitter and an industrial camera with a narrow-band filter. The laser emitter projects a horizontal laser line vertically downwards, forming a stable and clear projection outline on the hook surface. The industrial camera is equipped with a filter to match the laser wavelength, filtering out stray light and strong light interference from the field, and accurately acquiring laser stripe images, providing a dedicated image basis for subsequent inflection point extraction and spatial swing angle calculation.

[0032] This system uses the stationary tower crane as the reference to define spatial directions: the direction of travel of the tower crane is the front-back direction, the width of the crane body is the left-right direction, and the vertical horizontal plane is the up-down direction. All coordinate transformations, swing angle calculations, and distance calculations follow this spatial reference.

[0033] The boom angle sensor uses an absolute encoder and is installed at the hinge point at the root of the boom to detect the lifting angle of the main boom relative to the horizontal plane in real time. The hook distance sensor uses a laser rangefinder to detect the actual rope length of the wire rope between the hook and the front end of the telescopic joint vertically downward. The data collected in real time by the two types of sensors are synchronously connected to the data acquisition module for geometric compensation calculation of swing offset distance, providing basic parameters for safety threshold determination.

[0034] The data acquisition module serves as the system's data hub, centrally accessing signals from all GNSS positioning devices, IMUs, binocular cameras, laser cameras, and angle and distance sensors. It features multi-source data synchronization and timing, analog-to-digital conversion, and protocol encapsulation functions. After unifying the format, the data is pushed to the data fusion and processing module in real time via gigabit Ethernet.

[0035] The data fusion processing module adopts an industrial embedded controller and is equipped with a Linux real-time system. It is the core computing unit of this system and has core functions such as coordinate system transformation, Kalman filter correction, visual image filtering, laser stripe feature extraction, and three-dimensional swing angle calculation, which fully covers all the computing logic of multi-source data fusion.

[0036] The data fusion processing module uses WGS-84 as the global first coordinate system and establishes a local second coordinate system for the tower crane with the boom head hinge point as the origin. Using the known coordinates of the boom tail and boom head in the two coordinate systems, it solves the coordinate translation parameters, scale ratio parameters, and rotation parameters around the Z-axis to complete the accurate mapping and matching of the global coordinates to the local coordinates of the tower crane operation.

[0037] Due to building obstructions and electromagnetic interference at the construction site, GNSS is prone to short-term positioning drift. While IMU has high short-term accuracy, its long-term integration is prone to divergence. This module uses a Kalman filter algorithm for complementary correction: the triaxial displacement increment obtained by IMU acceleration integration is used as the filtered state prediction value, and the measured absolute coordinates of GNSS-RTK are used as the observation value. Through iterative filtering calculation, the optimal spatial coordinates of the hook that are smooth, continuous and drift-free are output. The line connecting the two points is used to construct a stable hook attitude vector.

[0038] The data fusion processing module performs grayscale conversion and global pixel gradient total value calculation on the binocular vision images. By comparing them with the system's preset gradient threshold range, it automatically removes invalid frames caused by occlusion and strong light interference, retaining only valid images to participate in subsequent contour calculations, thus ensuring the stability of visual recognition.

[0039] Meanwhile, the module processes the laser projection image according to a fixed process: median filtering for noise reduction, adaptive threshold binarization, morphological dilation and erosion, Zhang-Suen skeleton extraction, and connected component analysis are performed in sequence. After refining the stripes into single-pixel center lines, a quadratic interpolation algorithm is used to fill in the missing stripes in the local area. The curvature change points are accurately identified as key inflection points of the swing angle, thus completing the restoration of pixel coordinates to spatial coordinates.

[0040] The module integrates the hook attitude vector and the laser inflection point vector, and calculates the hook load tangential swing angle and radial swing angle through planar projection decomposition and arctangent calculation. Simultaneously, it incorporates measured parameters such as the boom lifting angle and wire rope length, and calculates the hook's horizontal swing offset distance through spatial geometric relationships. The system uses the ratio of the swing offset distance to the wire rope length as the safety criterion, setting two fixed threshold levels of 0.05 and 0.2, and can implement graded safety warnings and control interventions based on the ratio range.

[0041] To achieve the above functions, the data fusion processing module executes the internally stored control program to divide the system into three major functional logic units: information acquisition, data reception, and display control, thereby enabling modular scheduling and operation.

[0042] The information acquisition unit connects to the industrial communication bus and various sensing units to uniformly acquire GNSS coordinate data, IMU inertial data, binocular image data, laser feature data, boom angle and rope length data, and simultaneously collect manual / automatic mode switching commands to provide a complete input source for subsequent calculations.

[0043] The data storage unit is a built-in storage area of ​​the module, which can be configured in RAM or on-chip memory to store coordinate system transformation parameters, Kalman filter coefficients, laser image processing parameters, swing angle warning thresholds, ZV / ZVD algorithm configuration parameters, etc., for real-time calculation process to call at any time.

[0044] The data storage unit has pre-stored basic parameters that are compatible with different boom lengths and tower crane models, allowing for quick adaptation to various crane deployments without reprogramming.

[0045] The display control unit coordinates and controls the overall operation logic of the machine. Based on the acquired multi-source data and built-in parameters, it automatically decides the swing angle calculation mode, anti-sway algorithm switching, and early warning triggering timing, and generates control commands to be sent to the anti-sway closed-loop control module and the audible and visual early warning module.

[0046] The display control unit can adaptively call the ZV or ZVD input shaping algorithm according to the real-time swing angle frequency, and dynamically adjust the transfer function coefficient of the shaper. Unlike the traditional fixed parameter control method, it can accurately adapt to the swing characteristics under different loads and rope lengths.

[0047] Tower crane mechanical adjustments and data transmission have inherent processing delays. This module completes parameter preloading and algorithm warm-up in advance before mode switching and anti-sway intervention, eliminating control incoordination problems caused by delays.

[0048] Specifically, before the system is about to switch to the precise swing angle detection and automatic anti-sway mode, it completes coordinate transformation, filtering convergence and feature pre-extraction in advance. When the mode is triggered, it directly outputs mature swing angle parameters to achieve a seamless and smooth switch.

[0049] The system preloading process is divided into two stages: the first stage completes basic data preprocessing, initial coordinate transformation and initial image screening; the second stage simultaneously completes filtering refinement and inflection point extraction during the working condition switching process, gradually converging the calculation accuracy.

[0050] The two stages employ different computational priorities to ensure both response speed and swing angle detection accuracy.

[0051] When the system switches back from automatic anti-sway mode to normal manual mode, the shaping algorithm is stopped immediately, the basic swing angle detection is not interrupted, and the closed-loop control is exited to avoid operational fluctuations caused by sudden changes in operating conditions.

[0052] This system works in conjunction with the tower crane's existing PLC electrical control system to synchronously adjust the inverter's output logic when the swing angle exceeds the limit or the sway deviation exceeds the standard, thereby achieving smooth sway suppression without affecting the operator's control feel.

[0053] During the switching of operating conditions, the system gradually fine-tunes the acceleration and deceleration limit parameters of the frequency converter, slowly restrains the over-excitation of the mechanism, and guides the hoisting operation to become more stable, without sudden deceleration, sudden stop or other abrupt operating conditions.

[0054] Once the swing angle detection enters the high-precision locking state, the system locks the inverter's speed range, restricts excessive human operation, and prevents human manipulation from exacerbating the hook swing, thus assisting in safe operation from the control level.

[0055] When the operating conditions are reset to normal, the system automatically unlocks the speed range and restores normal operating permissions, without affecting the driver's normal hoisting operation habits.

[0056] The dual-redundant communication modules ensure the transmission of system data and commands throughout the entire process. The 5G main link undertakes the transmission of high-definition video and high-capacity data for positioning and swing angle, while the 230MHz low-frequency emergency link only transmits core commands for tower crane start / stop and swing angle exceeding limits. The system monitors the 5G signal strength and link connectivity in real time. Once the signal falls below the threshold or is interrupted, it can automatically switch to the emergency communication link within 2 seconds, seamlessly taking over core control authority and eliminating the risk of tower crane loss of control caused by building obstruction and electromagnetic interference.

[0057] The audible and visual warning modules are installed in the tower crane cab and at both ends of the counterweight boom. The warning level is divided according to the ratio of swing offset distance to rope length. At the same time, it distinguishes three alarm modes: single-direction swing over the X-axis and Y-axis and simultaneous bidirectional over the limit, so as to realize differentiated audible and visual prompts and facilitate operators to quickly identify the risk type.

[0058] The specific implementation process under different working conditions will be explained one by one below, based on the core application scenarios of this invention.

[0059] Over-limit warning condition for hook swing angle: During routine tower crane hoisting operations, the system is always in real-time monitoring mode, continuously calculating the hook tangential swing angle, radial swing angle, and horizontal swing offset distance.

[0060] The data fusion processing module calculates the ratio of the swing offset distance to the length of the wire rope in real time, and uses 0.05 and 0.2 as two-level warning thresholds as the basis for warning triggering.

[0061] The system continuously outputs the basic swing angle value under normal detection conditions. When the ratio reaches 0.05, it completes the secondary fine extraction of laser features and the smoothing preprocessing of swing angle data.

[0062] The system then officially triggered a Level 1 warning, with the audible and visual warning module illuminating a yellow indicator light and intermittently beeping to prompt the operator to smoothly slow down their control actions.

[0063] If strong winds or sharp turns cause the ratio to exceed 0.2, the system will immediately trigger a level-two hazard warning, with the red warning light constantly on and a high-decibel continuous alarm.

[0064] At the same time, the anti-sway closed-loop control module automatically intervenes, smoothly adjusting the speed of each mechanism through the input shaping algorithm, actively suppressing further swing of the hook, and avoiding the risk of collision.

[0065] During the warning process, the system maintains uninterrupted multi-source data fusion detection. Once the swing angle returns to the safe range, the alarm and anti-sway intervention are automatically deactivated, and the system resumes normal detection.

[0066] Adaptive anti-shake condition: When the tower crane is performing constant speed cruise and follow-up hoisting operations, the system monitors the swing status of the hook in real time.

[0067] When the operator adjusts the hoisting speed or luffing position, the system uses the change in swing angle as the trigger condition to activate the adaptive anti-sway process.

[0068] The data fusion processing module identifies the inherent main frequency of the hook swing in real time, automatically switches between ZV / ZVD algorithm modes, and matches the current load and rope length characteristics.

[0069] The anti-sway closed-loop control module sends the operator's original control commands to the input shaper, convolves them to generate a smooth speed curve, and then sends it to the frequency converters of each mechanism.

[0070] The frequency converter accelerates and decelerates according to the shaped curve to counteract the swaying excitation during the hoisting process, achieving smooth operation without residual sway.

[0071] After the vehicle spacing is adjusted, the system maintains anti-sway low-gain operation to ensure stable hoisting without the need for repeated manual fine-tuning.

[0072] Turning and luffing path guidance conditions: When tower cranes perform large-scale slewing and long-distance luffing turns for hoisting, the system plans the operating path in advance and simultaneously detects the trend of swing angle changes.

[0073] As the device approaches the turning point, the binocular vision and laser unit enhance contour acquisition, and the data fusion module predicts the sway increment in advance.

[0074] The system pre-adjusts the acceleration and deceleration slopes of the mechanism to avoid large swings caused by sudden turns.

[0075] Simultaneously, the swing angle parameters are calculated in real time. If the swing angle shows an increasing trend, the anti-sway algorithm gain is automatically enhanced to suppress the expansion of the swing in advance.

[0076] Obstacle recognition and avoidance operation: The system can combine binocular vision and laser calibration to collaboratively detect obstacles such as building components and temporary stacks at the construction site, and judge the collision risk by combining swing angle parameters.

[0077] The system directly determines the safe zone through multi-source data fusion, calculates the allowable swing range of the hook in real time, marks obstacle boundaries, and prompts operators to control the swing amplitude to avoid collision risks.

[0078] Example 2: The second embodiment of this disclosure is a variation of the first embodiment. The overall system architecture and core principles are consistent with the first embodiment. The main difference lies in the optimized design of the communication architecture and hardware layout.

[0079] This implementation simplifies system dependencies. All swing angle calculations and anti-sway control logic are completed autonomously by the data fusion processing module, without relying on other external electrical control units for data calculation, making it more suitable for intelligent retrofitting of older tower cranes.

[0080] This implementation optimizes and upgrades the dual-redundant communication module, while still retaining the 5G main communication link and the 230MHz low-frequency radio emergency link. The 5G main link is responsible for transmitting high-definition images, high-precision positioning, and large amounts of swing angle data; the 230MHz emergency link only carries core commands for tower crane start / stop, emergency braking, and swing angle exceeding limits.

[0081] The system adds a real-time monitoring mechanism for communication links, which can detect 5G signal strength and data packet loss rate in real time. When the link is abnormal, it will automatically switch to the emergency communication link within 2 seconds, effectively eliminating the risk of tower crane loss of control caused by construction obstruction and electromagnetic interference.

[0082] This implementation method sets up a standard detection level and a high-precision detection level, which can automatically switch according to the load weight and lifting distance. The standard level is suitable for ordinary low-rise, short-distance lifting, while the high-precision level is suitable for high-rise, heavy-load, and long-span lifting.

[0083] The gear shifting follows the pre-load smoothing logic of the first implementation method. There are no sudden speed changes or control lags during the shifting process, and the overall machine operates smoothly and consistently.

[0084] The second implementation retains all the swing angle detection, data fusion, adaptive anti-sway, and graded early warning functions of the first implementation, while reducing the difficulty of system modification and hardware costs, and is suitable for two application scenarios: pre-installation on newly built tower cranes and modification of existing tower cranes.

[0085] Example 3: The third implementation method expands upon the first implementation method by adding a millimeter-wave radar ECU and a construction site V2X communication terminal to the existing industrial communication bus.

[0086] The millimeter-wave radar ECU connects to an external radar detection unit to detect the distance and relative position of obstacles, construction machinery, and temporary structures around the tower crane in real time. The detection information is then fed into a data fusion processing module and fused with GNSS-RTK positioning data, IMU inertial data, and sway angle detection data to achieve dual safety protection of sway angle detection and obstacle distance.

[0087] The V2X communication terminal at the construction site supports information exchange between multiple tower cranes and between tower cranes and ground control equipment. It can receive the real-time operating status of surrounding equipment and predict additional swing interference from hooks caused by cross-lifting and adjacent tower operations.

[0088] The third implementation method expands upon the original basic operating conditions by adding extended functions such as early warning of forward risks and obstacles, hoisting assistance in confined spaces, and sway angle compensation in low visibility and windy / rainy weather.

[0089] All extended functions retain the original core technical architecture, including coordinate system four-parameter transformation, Kalman filter complementary correction, binocular vision gradient threshold screening, laser stripe skeleton extraction and interpolation completion, and ZV / ZVD input shaping anti-shake. Only the fusion dimension of external environment perception data is added, while the core detection and control logic remains unchanged.

[0090] This third embodiment further improves the accuracy of swing angle detection and operational safety of the system under complex multi-equipment construction and adverse weather conditions by incorporating radar detection and construction site interconnection communication technology.

[0091] Beneficial Effects: This invention utilizes complementary correction between GNSS-RTK satellite differential positioning and IMU inertial measurement unit Kalman filtering, relying on a four-parameter coordinate transformation model to achieve accurate global and local coordinate mapping, effectively solving the industry pain points of positioning drift and integral divergence caused by single detection methods. Through automatic filtering of invalid images using binocular visual gradient thresholding, multi-step laser stripe processing, and secondary interpolation completion, it eliminates the need for traditional mechanical swivel sensors, completely resolving their cumbersome installation and poor environmental adaptability.

[0092] This invention features a multi-condition preload smooth switching mechanism, preheating the algorithm and parameters in advance to eliminate control delays caused by hardware and data transmission, resulting in smooth and seamless transitions between operating conditions. The system incorporates ZV and ZVD adaptive input shaping algorithms, which can identify the inherent frequency of the hook swing online, dynamically adjust the control coefficients, and achieve millisecond-level closed-loop linkage between swing angle detection and inverter speed regulation, automatically suppressing residual swing during hoisting.

[0093] Equipped with a 5G+230MHz dual-redundant hot backup communication architecture, big data and emergency commands are transmitted via separate links. Link failures can be automatically switched over within 2 seconds, eliminating the risk of tower crane loss of control from a communication perspective. Based on real-time data collection of boom angle and wire rope length, a tiered early warning threshold of 0.05–0.2 is used, supporting independent alarms for multi-directional swing, providing clear and quantifiable safety assessments.

[0094] The system adopts a modular hardware and software design. The hardware is adapted to the harsh working conditions of the construction site. The entire architecture is fully adapted to the application requirements of multiple GNSS deployments, RTK differential correction, and multi-source data fusion and calculation. It can be directly adapted to the pre-installation of new tower cranes and the transformation of old tower cranes without changing the original operating habits, and has strong compatibility.

[0095] This invention is not limited to the three embodiments described above. Without deviating from the core technical principles of this invention, the number of GNSS positioning devices deployed, coordinate transformation parameters, image processing algorithm coefficients, anti-shake algorithm configuration, and early warning threshold range can be flexibly adjusted and adapted.

[0096] It can add dedicated detection logic for lateral swing angle to adapt to special hoisting conditions such as inclined pull and lateral lifting; it can also customize the warning level and ratio threshold according to the construction specifications of different regions.

[0097] It can simplify some sensor configurations, retain the core GNSS-RTK+IMU detection architecture, and is suitable for low-configuration, economical tower crane retrofit projects.

[0098] The system processor can adopt a CPU and FPGA composite computing architecture, and the functions of data fusion, swing angle calculation and anti-sway control can be implemented by software programs or by dedicated hardware logic circuits. The hardware form can be flexibly replaced.

[0099] The embodiments described above are merely preferred embodiments of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications, improvements, and substitutions without departing from the concept of the present invention, and these all fall within the protection scope of the present invention.

Claims

1. A tower crane hook swing angle detection and control system based on GNSS and inertial measurement unit, characterized in that, include: The GNSS-RTK positioning unit includes multiple GNSS positioning instruments deployed at the tail and head of the tower crane boom and both ends of the hook pin, used to collect the global spatial coordinates of the tower crane boom and hook in the WGS-84 coordinate system. An inertial measurement unit, fixed to the hook body, is used to collect the hook's attitude acceleration and angular velocity in real time; The binocular vision acquisition unit includes at least two cameras, which are respectively installed on opposite sides of the tower crane main boom along the horizontal direction and perpendicular to the boom extension direction, for synchronously capturing real-time detection images of the hook; The laser-assisted calibration unit is used to project a laser contour line onto the hook and acquire the laser projection curve of the hook contour. The data fusion processing module is configured to: establish a local second coordinate system for the tower crane using the WGS-84 coordinate system as the first coordinate system and the boom head hinge point as the origin; solve for the transformation parameters between the two coordinate systems; use a Kalman filter algorithm to perform complementary correction on the GNSS-RTK positioning data and the data collected by the inertial measurement unit; extract features from the images collected by the binocular vision acquisition unit and the projection curves collected by the laser-assisted calibration unit; transform the corrected hook coordinates to the second coordinate system; fuse the results of the feature extraction; and calculate the three-dimensional tangential and radial swing angles of the hook load. The anti-sway closed-loop control module is configured to: receive the three-dimensional tangential sway angle and radial sway angle, incorporate an input shaping anti-sway algorithm, and link the frequency converters of the tower crane's hoisting, slewing, and luffing mechanisms through the PLC controller, adaptively adjust the operating speed and acceleration / deceleration curves of each mechanism according to the sway angle, forming a closed-loop linkage for detection and sway suppression.

2. The tower crane hook swing angle detection and control system based on GNSS and inertial measurement unit according to claim 1, characterized in that, When solving for the transformation parameters between the two coordinate systems, the data fusion processing module determines the coordinate translation parameters, scale ratio parameters, and rotation parameters based on the coordinates collected by the GNSS positioning instruments at the arm tail and arm head.

3. The tower crane hook swing angle detection and control system based on GNSS and inertial measurement unit according to claim 1, characterized in that, When performing complementary correction, the data fusion processing module uses the relative displacement obtained by short-time integration of the inertial measurement unit as the state prediction value of the Kalman filter, and the absolute coordinates output by the GNSS-RTK positioning instrument as the observation, to make the optimal estimation of the spatial position of the hook.

4. The tower crane hook swing angle detection and control system based on GNSS and inertial measurement unit according to claim 1, characterized in that, When the data fusion processing module extracts features from the projection curve, it extracts the center line of the laser stripe with a single pixel width from the laser projection curve, separates the laser stripe region of the hook outline through connected component analysis, and extracts the coordinates of key inflection points for swing angle measurement; when calculating the swing angle, it performs calculations by combining the vector angle formed by the key inflection points extracted from the laser stripe.

5. The tower crane hook swing angle detection and control system based on GNSS and inertial measurement unit according to claim 4, characterized in that, When extracting the coordinates of key inflection points, the data fusion processing module sequentially performs median filtering, morphological dilation erosion, adaptive threshold binarization, and skeleton extraction on the laser projection image to obtain the center line of the laser stripe with a single pixel width; then, it combines a quadratic interpolation algorithm to complete the missing data of the laser stripe.

6. The tower crane hook swing angle detection and control system based on GNSS and inertial measurement unit according to claim 1, characterized in that, When the data fusion processing module extracts features from the images acquired by the binocular vision acquisition unit, it performs grayscale conversion and gradient value calculation on the images. It filters valid frame images and removes invalid interference images by comparing the total gradient value of the images with a preset gradient threshold.

7. The tower crane hook swing angle detection and control system based on GNSS and inertial measurement unit according to claim 1, characterized in that, The anti-sway closed-loop control module has a built-in input shaping anti-sway algorithm, which is a ZV or ZVD input shaper. Its transfer function is adaptively adjusted according to the real-time swing frequency of the hook load.

8. The tower crane hook swing angle detection and control system based on GNSS and inertial measurement unit according to claim 7, characterized in that, It also includes a boom angle sensor and a hook distance sensor; the boom angle sensor is used to detect the lifting angle of the main boom relative to the horizontal direction, and the hook distance sensor is used to detect the real-time rope length from the hook to the front end of the telescopic joint; the data fusion processing module introduces the lifting angle and the real-time rope length as compensation parameters when calculating the swing offset distance; it also includes an audible and visual warning module, whose alarm triggering logic is configured to: when the ratio of the calculated hook swing offset distance to the real-time rope length exceeds a preset range of 0.05 to 0.2, determine that the swing angle exceeds the limit and output an alarm signal.

9. The tower crane hook swing angle detection and control system based on GNSS and inertial measurement unit according to claim 1, characterized in that, It also includes a dual-redundant communication module, which includes a 5G communication main link and a low-frequency radio wave emergency communication link using the 230MHz or 433MHz frequency band; the low-frequency radio wave emergency communication link is only used to transmit emergency control commands and is configured to automatically activate when the 5G communication main link is detected to take over the core control of the tower crane.

10. The tower crane hook swing angle detection and control system based on GNSS and inertial measurement unit according to claim 1, characterized in that, It also includes an RTK reference station, which is deployed in an open and unobstructed area around the tower crane; the RTK reference station is used to receive the observation data returned by each group of GNSS positioning instruments and perform differential error correction, and transmit the corrected high-precision spatial position coordinates to the data fusion processing module.

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