Grab control method and device, electronic equipment and readable storage medium

Abstract

This application provides a grab bucket control method and device, electronic equipment, and readable storage medium, belonging to the field of grab bucket control. The method includes: acquiring an elevation anchor point; calculating the height difference between the current height of the grab bucket and the elevation anchor point; when the height difference narrows to a preset buffer threshold, controlling the grab bucket to switch to a material-seeking state; when the attenuation amplitude of the torque feedback value reaches a preset drop threshold, simultaneously triggering a stop-descent action, a holding action, and a closing action; during the closing action, outputting a target hovering support torque to the frequency converter based on a preset depth requirement; while maintaining wire rope tension, adjusting the grab bucket's sinking depth by the difference between the grab bucket's own weight and the target hovering support torque; and when the grab bucket completes closing and enters the lifting state, acquiring the latest height data and overwriting the elevation anchor point. The grab bucket control method and device, electronic equipment, and readable storage medium provided in this application, through closed-loop control, fundamentally eliminate wire rope slack and grabbing action lag caused by dynamic mismatch.

Description

Technical Field

[0001] This application belongs to the field of grab control technology, and more specifically, relates to grab control methods and devices, electronic equipment, and readable storage media. Background Technology

[0002] As a core hub for continuous bulk cargo loading and unloading operations in ports, the gantry crane's operational efficiency and system stability directly determine the port's overall throughput capacity. During the continuous cyclical operation of unloading, the grab system frequently reciprocates between the ship's cargo hold and the hopper. As unloading continues, the elevation of the bulk cargo surface inside the hold exhibits a non-linear dynamic decline, and is affected by uncertain factors such as changes in the ship's draft and the natural collapse of materials, making the position of this surface highly unpredictable in space. Since the bulk cargo grab and its auxiliary components typically weigh tens of tons, they accumulate significant downward kinetic energy during the lowering and probing phase. The entire high-inertia rigid winch lowering system faces stringent dynamic boundary conditions when physically contacting this dynamically unknown bulk cargo surface.

[0003] To address the control issues during the grab bucket lowering process, existing technologies have explored certain solutions. For example, Chinese invention patent application CN119735099A discloses "A gantry crane wire rope anti-slack rope control system and gantry crane." This system mainly implements the underlying control logic through hardware components such as a hoisting motor mechanism, a hoisting motor drive module, a load detection module, and a rapid stop control module. In the operation mechanism of this solution, the load detection module is responsible for real-time detection of the load applied to the hoisting motor. When the grab bucket falls onto the bulk cargo, the system identifies the sudden change in load within a very short time and triggers the rapid stop control module to output a rapid stop signal to the hoisting motor drive module, thereby controlling the hoisting motor to decelerate to zero. In addition, this solution also includes a hoisting height compensation system, which calculates the slack length of the wire rope after the system confirms the stop, and the crane foundation control system executes an upward rope retraction compensation action to restore the wire rope to a taut state.

[0004] While the aforementioned existing technologies alleviate the problems of rope tangling and derailment caused by excessive slack in the wire rope to some extent, from the perspective of deep dynamics and control timing, they still have significant technical shortcomings in the special scenario of continuous emergency unloading in deep holds. Due to obstructed operator visibility or visual fatigue, the grab bucket often plunges towards the dynamic material surface at extremely high speeds. The existing technology uses serial control logic, relying entirely on the load drop signal generated after the grab bucket actually touches the bottom as the sole trigger condition for deceleration and braking. When the load detection module detects a sudden change in tension, the grab bucket, weighing tens of tons, has already hard-impacted the material surface. At this point, the massive hoist motor and drum, due to their huge rotational inertia, cannot achieve instantaneous braking in a physical sense, inevitably resulting in inertial overwinding. This directly causes the carrying wire rope to completely lose tension and collapse at the moment of bottoming. This post-calculation and compensation-based rope-retraction mechanism essentially accepts the physical fact of wire rope slack. This forces the initial mechanical displacement of the actuator to be used first to tighten the slack wire rope during the ineffective work phase when the system is preparing to execute the next stage of the closed-bucket grabbing operation. This inevitably results in significant system-level motion lag. The dynamic mismatch between the high-inertia rigid hoisting system and the dynamically unknown bulk material surface causes the wire rope to fall into an uncontrollable slack state at the moment of bottoming out, leading to unavoidable rope hysteresis and grabbing motion lag. This has become the fundamental physical bottleneck restricting the improvement of the gantry crane's single-operation cycle efficiency. Summary of the Invention

[0005] The purpose of this application is to provide a grab control method and device, electronic equipment, and readable storage medium that fundamentally eliminates wire rope slack and grab action lag caused by dynamic mismatch through closed-loop control.

[0006] A first aspect of this application provides a grab control method, including: The height data at the moment the grab bucket closes during the previous operation cycle is used as the elevation anchor point; During the current descent phase, the height difference between the current height of the grab bucket and the elevation anchor point is calculated. When the height difference is reduced to a preset buffer threshold, the grab bucket is controlled to switch to the material exploration state. During the material exploration state, the torque feedback value of the frequency converter driving the grab bucket is monitored. When the attenuation amplitude of the torque feedback value reaches the preset drop threshold, the following actions are triggered in parallel: stop descent, maintain the wire rope in tension and do not lift the grab bucket, and close the bucket. When performing the closing action, the target hovering support torque is output to the frequency converter based on the preset deep excavation requirements. While maintaining the tension of the wire rope, the depth of the grab bucket sinks is adjusted by the difference between the weight of the grab bucket and the target hovering support torque. When the grab bucket closes and enters the lifting state, the latest height data is obtained and overwritten to the elevation anchor point, which will serve as the benchmark for calculating the height difference in the next work cycle.

[0007] In one possible implementation, the preset buffer threshold is dynamically calculated based on the current descent speed of the grab and the set deceleration acceleration; During the current descent phase, the grab bucket executes a descent maneuver based on the acquired descent command; The control grab bucket is switched to the material-feeding state, including: When the height difference decreases to the preset buffer threshold, a frequency reduction command is output to the frequency converter driving the grab bucket; The frequency reduction command is used to cut off the descent command, and the frequency converter is controlled to reduce the output frequency to slow down the grab bucket. When the descent speed of the grab bucket drops to the preset target descent speed for the material exploration state, the grab bucket is controlled to switch to the material exploration state.

[0008] In another possible implementation, the step of when the attenuation amplitude of the torque feedback value reaches a preset drop threshold includes: In the material exploration state, the torque feedback value is collected according to a preset sampling period and filtered to generate a smooth torque curve; Extract the difference values ​​of the smooth torque curves under adjacent preset sampling periods, and establish a drop determination time window; When all the difference values ​​included in the drop determination time window are greater than the preset dynamic change threshold, and the total attenuation of the torque feedback value reaches the preset self-weight ratio threshold, it is determined that the attenuation amplitude has reached the preset drop threshold.

[0009] In another possible implementation, the frequency converter driving the grab bucket includes a lifting frequency converter and an opening and closing frequency converter; The parallel triggering of the stopping descent action, the holding action of maintaining the wire rope tension and not raising the grab bucket, and the closing action include the simultaneous execution of the following steps: Cut off the falling pulse output of the lifting frequency converter; A static holding torque is applied to the lifting inverter; Output the closing drive command to the switching frequency converter.

[0010] In another possible implementation, the step of outputting a target hovering support torque to the frequency converter based on a preset depth requirement includes: Obtain the current material density and compare it with a preset density threshold to determine the preset depth requirement; In response to the closed bucket drive command, the static holding torque of the hoisting inverter is switched to the target hovering support torque: When the material density is greater than the preset density threshold, the target hovering support torque is a first hovering support torque that is less than the weight of the grab bucket. When the material density is not greater than the preset density threshold, the target hovering support torque is a second hovering support torque that is greater than the first hovering support torque and less than the weight of the grab bucket.

[0011] In another possible implementation, the step of acquiring the latest height data and overwriting the elevation anchor point when the grab bucket completes closing and enters the lifting state includes: During the response to the closed bucket drive command, the operating current of the switching motor driven by the switching frequency converter is monitored; When the operating current reaches the preset stall current threshold, it is determined that the grab is fully closed; When it is determined that the grab bucket is fully closed and a lifting operation command is received, the latest height data is obtained and the elevation anchor point is overwritten.

[0012] In another possible implementation, after receiving the lifting operation command, the method further includes a step of closed-loop correction of the target hovering support torque for the next work cycle: Obtain the actual grab load of the current job cycle; When the actual gripping load is less than the preset full load threshold and the current output is the first hovering support torque, the setting value of the first hovering support torque in the next work cycle is reduced. When the actual gripping load exceeds the preset overload threshold, the target hovering support torque for the next work cycle will be forcibly switched to the second hovering support torque.

[0013] A second aspect of this application provides a grab control device for implementing the grab control method, characterized in that it includes: The dynamic prediction module is used to obtain the height data of the grab bucket at the moment of closure in the previous operation cycle as the elevation anchor point, calculate the height difference between the current height of the grab bucket and the elevation anchor point in the current descent stage, and control the grab bucket to switch to the material exploration state when the height difference is reduced to a preset buffer threshold. The anti-slackening module is used to monitor the torque feedback value of the frequency converter driving the grab bucket in the material exploration state. When the attenuation amplitude of the torque feedback value reaches the preset drop threshold, it triggers in parallel the stop descent action, the holding action to keep the wire rope taut and not lift the grab bucket, and the closing action. The deep excavation control module is used to output a target hovering support torque to the frequency converter based on the preset deep excavation requirements when performing the closed bucket action. While maintaining the tension of the wire rope, the depth of the grab bucket sinks is adjusted by the difference between the weight of the grab bucket and the target hovering support torque. The closed-loop update module acquires the latest height data and overwrites the elevation anchor point when the grab bucket completes closure and enters the lifting state, so as to serve as the benchmark for calculating the height difference in the next operation cycle.

[0014] A third aspect of this application provides an electronic device, including a memory, a processor, and a computer program stored in the memory and running on the processor, wherein the processor executes the computer program to implement the steps of the grab control method described above.

[0015] A fourth aspect of this application provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the steps of the grab control method described above.

[0016] The beneficial effects of the grab control method and apparatus, electronic device, and readable storage medium provided in this application are as follows: 1. This application fundamentally eliminates the wire rope slack caused by inertial overwinding in traditional serial control logic by simultaneously triggering the stopping of descent, maintaining tension and closing the bucket at the moment the grab bucket touches the bottom. This avoids the ineffective work and motion delay caused by subsequent rope rewinding compensation, and achieves seamless connection of grabbing actions.

[0017] 2. This application uses the height data at the moment the grab bucket closes in the previous operation cycle as the elevation anchor point, dynamically calculates the height difference during the current descent phase and switches to the material exploration state in advance, realizing the forward prediction of the position of the bulk material surface and smooth deceleration, effectively avoiding signal distortion and system oscillation caused by high-speed impact.

[0018] 3. When performing the closing action, this application outputs the target hovering support torque according to the material density classification, and adaptively adjusts the sinking depth by the difference between the grab bucket's own weight and the support torque. This not only improves the grab full rate of hard bulk cargo, but also avoids the risk of excessive grabbing of low-density materials and collision damage to the ship's bottom plate. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 A flowchart illustrating a grab control method provided in an embodiment of this application; Figure 2 This is a structural block diagram of a grab control device provided in an embodiment of this application; Figure 3 This is a schematic block diagram of an electronic device provided in an embodiment of this application.

[0021] Reference numerals: 300, electronic device; 301, processor; 302, input device; 303, output device; 304, memory; 305, communication bus. Detailed Implementation

[0022] In the following description, specific details such as particular system architectures and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of this application. However, those skilled in the art will understand that this application may also be implemented in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods have been omitted so as not to obscure the description of this application with unnecessary detail.

[0023] It is understood that in the embodiments of this application, data such as user information are involved. When the embodiments of this application are applied to specific products or technologies, user permission or consent is required, and the collection, use and processing of related data must comply with relevant laws, regulations and standards.

[0024] It should be noted that the terms "first," "second," etc., used in the specification, claims, and drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such use of data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in sequences other than those illustrated or described herein.

[0025] The prior art has alleviated the problems of rope entanglement and out-of-groove faults caused by excessive slack of wire ropes to a certain extent. However, from the perspectives of deep dynamics and control timing, there are still significant technical flaws in the special scenario of continuous rapid unloading in deep holds. Due to the operator's blocked line of sight or visual fatigue, the grab often dives towards the dynamic material surface at a very high speed. The prior art adopts a serial control logic, completely relying on the load drop signal generated after the grab substantially touches the bottom as the sole trigger condition for deceleration braking. When the load detection module identifies a sudden change in tension, the grab weighing dozens of tons has already hard-impacted the material surface. At this time, the huge hoist motor and drum simply cannot achieve physical instantaneous braking due to their large moment of inertia, inevitably resulting in inertial overwinding. This directly causes the load-bearing wire rope to completely lose tension at the moment of touching the bottom and present a slack state. This processing mechanism based on post-calculation and compensatory rope winding essentially accepts the physical fact of wire rope slack. When the system is ready to execute the next closed-grab operation, the initial mechanical displacement of the actuator is forced to first be used for the ineffective work stage of tightening the slack wire rope, and thus an obvious system-level action lag will inevitably occur. The dynamic mismatch problem between the large-inertia rigid hoist system and the dynamic unknown bulk material surface leads to the uncontrollable slack state of the wire rope at the moment of touching the bottom and the inevitable rope winding backlash and grab operation lag, which has become the underlying physical bottleneck restricting the improvement of the single-operation cycle efficiency of the portal crane.

[0026] To solve the above technical problems, the embodiments of the present application provide a grab control method, which fundamentally eliminates the wire rope slack and grab operation lag caused by dynamic mismatch through closed-loop control.

[0027] To make the objectives, technical solutions, and advantages of the present application clearer, the following will be described through specific embodiments in conjunction with the accompanying drawings.

[0028] Please refer to Figure 1 , Figure 1 which is a schematic flowchart of the grab control method provided by an embodiment of the present application. The grab control method provided by the embodiments of the present application can be executed by a grab control device, and is specifically applied to the grab closed-loop control of a bulk material handling portal crane, and the execution entity is a programmable logic controller PLC supporting the portal crane.

[0029] The hardware system supporting this embodiment includes a programmable logic controller (PLC), a hoisting frequency converter, a closing and opening frequency converter, a hoisting motor, a closing and opening motor, an absolute encoder, and a grab mechanism. The hoisting frequency converter and the closing and opening frequency converter both need to use high-performance frequency converters that support vector control, torque closed-loop control, and PROFINET real-time communication, with a minimum command response time not greater than 10 ms. The absolute encoder is a multi-turn absolute encoder with a single-turn resolution not lower than 13 bits and a total number of turns not lower than 4096 turns. It is coaxially installed at the output shaft end of the hoisting motor and is used to collect the rotation data of the hoisting motor in real time, and convert it into the real-time absolute height data of the grab. The conversion relationship is calibrated on-site based on the reduction ratio of the hoisting motor and the drum and the rope groove diameter of the drum. The measurement error of the height data is not greater than 5 cm. The hoisting frequency converter is electrically connected to the hoisting motor and is used to drive the hoisting motor to rotate forward and backward, realizing the lifting, lowering, and torque holding of the grab, and at the same time, feeding back the output torque value to the PLC in real time. The closing and opening frequency converter is electrically connected to the closing and opening motor and is used to drive the closing and opening motor to rotate forward and backward, realizing the opening and closing of the grab, and at the same time, feeding back the operating current value of the closing and opening motor to the PLC in real time. The PLC communicates with the hoisting frequency converter, the closing and opening frequency converter, and the absolute encoder through PROFINET industrial Ethernet, and the communication cycle is not greater than 20 ms, ensuring the real-time nature of control commands and feedback data and meeting the requirements of millisecond-level control.

[0030] In this application, the torque value corresponding to the rated self-weight of the grab refers to the static torque value that needs to be output at the shaft end of the hoisting motor to completely balance the rated self-weight of the grab. The calibration method for this value is as follows: Open the grab fully with no load and hover it at the midpoint of the rated hoisting height. Control the grab to hover steadily at a constant speed, collect the average value of the stable output torque of the hoisting frequency converter within 100 ms continuously,剔除 the torque value corresponding to the self-weight of the steel wire rope at this height, and the finally obtained torque value is the torque value corresponding to the rated self-weight of the grab, which is stored in the power-off retention type memory register of the PLC.

[0031] The embodiment of this application provides a grab control method, which may include the following steps: S1 Elevation anchor point acquisition and control parameter calibration.

[0032] This step is executed based on the hardware system supporting the aforementioned portal crane, and the execution entity is the programmable logic controller (PLC), which establishes the core reference and control boundary for the entire grab control process, completes the establishment of the reference for predicting the material surface position and the pre-calibration of the control thresholds for the entire process, and ensures the executability and accuracy of subsequent control actions.

[0033] S11 Acquisition of the elevation anchor point.

[0034] The PLC acquires the height data at the moment when the grab is fully closed and the lifting operation command is received in the previous work cycle, and stores the data in the internal power-off retention memory register as the elevation anchor point for the current work cycle.

[0035] When there is no historical working height data for the first work cycle, the PLC obtains the initial elevation anchor point through the operator's manual calibration process. The operator first controls the grab bucket to fully open, then controls the grab bucket to descend smoothly until the jaw plate is in complete contact with the bulk material surface, and then controls the grab bucket to perform the closing action; after the PLC detects that the operating current of the opening and closing motor reaches the preset stall current threshold and determines that the grab bucket is fully closed, at the instant it receives the lifting operation command issued by the operator, it latches the real-time rotation data output by the absolute encoder, converts it into the absolute height data of the grab bucket, and stores this data in the power-off retention memory register as the elevation anchor point for the first work cycle.

[0036] In two adjacent operation cycles, the elevation change of the bulk cargo surface relative to the hull only comes from the material removal of a single grab operation, which has local continuity. Moreover, within a single cycle of about 120 seconds, the change in the ship's draft due to loading and unloading operations is no more than 3 cm. This change will cause the height of the material surface relative to the gantry crane reference plane to shift synchronously. By cyclically acquiring and storing elevation anchor points, the height reference deviation caused by the ship's draft changes can be automatically compensated without the need to set up an additional independent compensation algorithm, providing a stable reference for the forward prediction of the bulk cargo surface position.

[0037] The basis for calibrating and setting the S12 control parameters.

[0038] After acquiring the elevation anchor points, the PLC simultaneously pre-calibrates all control thresholds. All thresholds are determined based on the rated technical parameters of the gantry crane, the working characteristics of port bulk cargo loading and unloading, and the reliability requirements of the control logic. Those skilled in the art can adapt and adjust them according to the actual rated parameters of the target equipment.

[0039] 1. The PLC sets the preset deceleration acceleration to 0.5 m / s². This value is within the rated deceleration acceleration range of 0.3 m / s² to 0.8 m / s² for the gantry crane's hoisting mechanism, balancing work cycle efficiency with the smoothness of the deceleration process. It avoids slowing down the overall work rhythm due to excessively small acceleration leading to an excessively long deceleration stroke, and also avoids causing elastic oscillation of the wire rope due to excessive acceleration, thus preventing interference with subsequent torque feedback data.

[0040] 2. The PLC sets the preset sampling period to 20ms, corresponding to a sampling frequency of 50Hz. This sampling period perfectly matches the PROFINET industrial Ethernet communication period between the PLC and the lifting and switching frequency converters. This not only meets the real-time requirements of millisecond-level status monitoring but also avoids placing excessive computational load on the PLC, ensuring the continuous and stable operation of the control logic.

[0041] 3. The PLC sets the sliding filter window length to 5 sampling periods, corresponding to a duration of 100ms. During the deceleration process of the gantry crane, the inherent elastic oscillation period of the wire rope is usually between 80ms and 120ms. This window length can completely cover the oscillation signal of a single period, effectively eliminating the false drop interference caused by deceleration oscillation, while avoiding excessive smoothing of torque data and preventing the real bottoming torque change signal from being masked.

[0042] 4. The PLC sets the drop detection time window to three consecutive sampling cycles, corresponding to a duration of 60ms. This time window can effectively eliminate random noise interference in a single sampling process, avoid false triggering caused by abnormal data in a single cycle, and at the same time, it will not cause a delay in the triggering of the bottoming state detection due to an excessively long time window, thus balancing the accuracy of the detection and the response speed of the action.

[0043] 5. The PLC sets the preset dynamic change threshold to 3% of the stress torque value relative to the rated self-weight of the grab bucket. This threshold is the minimum judgment threshold for torque decay within adjacent 20ms sampling periods. When the grab bucket jaws are in substantial contact with the bulk material surface, the step decay rate of the torque feedback value is much greater than the torque fluctuation rate caused by normal oscillation of the wire rope. This threshold can effectively distinguish between the actual bottoming torque drop and the false signal fluctuations caused by mechanical vibration, greatly improving the accuracy of bottoming state determination.

[0044] 6. The PLC sets the preset self-weight ratio threshold to 18% of the stress torque value of the grab bucket's rated self-weight. After the grab bucket jaws contact the bulk material surface, the material surface will support at least part of the grab bucket's self-weight, and the torque feedback value will decrease accordingly. This value ensures that the grab bucket has formed a stable and substantial contact with the material surface, rather than an instantaneous contact, and at the same time, it will not cause a delay in the state judgment trigger due to excessively high attenuation requirements, thus avoiding inertial overwinding of the drum. This threshold is adapted to the material characteristics of bulk cargo in ports and can avoid false triggering due to small torque attenuation caused by local collapse of the material surface.

[0045] 7. The preset drop threshold mentioned in this application is a combination of two thresholds for judgment, namely, the torque difference value of all adjacent sampling cycles within the drop judgment time window is greater than the preset dynamic change threshold, and the total attenuation of the torque feedback value relative to the stable value before bottoming out reaches the preset self-weight ratio threshold.

[0046] 8. The PLC sets the preset static holding torque to 8% of the stress torque value of the grab bucket's rated self-weight. The wire rope tension corresponding to this torque value is just enough to offset the slack caused by the wire rope's own sag, keeping the wire rope in a taut state. At the same time, it will not generate an upward lifting force due to excessive torque, ensuring that the contact state between the grab bucket and the bulk material surface does not change.

[0047] 9. The PLC sets the preset density threshold to 2.0 t / m³. This value is based on the physical density characteristics of common bulk cargoes in ports. Bulk cargoes with a density greater than 2.0 t / m³ are usually hard, high-density bulk cargoes such as iron ore and manganese ore, while bulk cargoes with a density not greater than 2.0 t / m³ are usually low-density bulk cargoes such as coal and grain, providing a clear boundary for determining operational needs.

[0048] 10. The PLC sets the preset stall current threshold to 120% of the rated current of the opening and closing motor. After the grab jaws are fully closed, the opening and closing motor can no longer rotate and enters the stall operation state. The motor operating current will rise significantly to more than 120% of the rated current. This threshold can accurately identify the fully closed state of the grab and avoid misjudgment caused by instantaneous current fluctuations.

[0049] 11. The PLC sets the preset full-load threshold to 90% of the grab bucket's rated grab load and the preset overload threshold to 110% of the grab bucket's rated grab load. These values ​​comply with industry standards for loading and unloading operations of port cranes, ensuring both the effective grab bucket full-load rate and avoiding safety risks caused by equipment overload operation, providing clear judgment boundaries for adaptive adjustment of control parameters.

[0050] 12. The PLC sets the target descent speed for the material-probing state to 0.3 m / s. This speed ensures the responsiveness of the grab bucket during the material-probing process, preventing excessively slow speeds from slowing down the overall operation rhythm. It also controls the over-winding amount of the drum inertia when the grab bucket touches the bottom to within 5 mm, thereby reducing the risk of wire rope slack from the source.

[0051] S2 is based on the adaptive deceleration and material exploration state switching of elevation anchor points.

[0052] This step is executed based on the core control parameters already calibrated in S1, such as the elevation anchor point, preset deceleration acceleration, and preset sampling period. The execution entity is a programmable logic controller (PLC). By predicting the position of the bulk material surface in advance, it achieves smooth and undisturbed deceleration during the grab bucket descent process, eliminating system oscillation interference caused by high-speed impact at the source. This solves the problems of lack of material surface position prediction and detection signal distortion caused by high-speed dive in existing technologies, providing a reliable data foundation for the stable acquisition and status determination of subsequent torque signals.

[0053] Calculation of real-time height difference of S21.

[0054] During the descent phase of the current work cycle, the PLC receives the descent command from the operator and outputs a drive signal of the corresponding frequency to the hoisting inverter, controlling the hoisting inverter to drive the hoisting motor to rotate forward, thus driving the grab bucket to perform a high-speed descent. Simultaneously, the PLC reads the motor shaft rotation data output from the absolute encoder in real time using the preset sampling period calibrated in S1. According to the conversion relationship calibrated on-site in S1, the PLC converts the rotation data into the current absolute height of the grab bucket. The PLC synchronously calculates the height difference between the current absolute height of the grab bucket and the elevation anchor point obtained in S1. This height difference represents the relative distance between the grab bucket and the reference position of the material surface in the previous work cycle, providing a core basis for triggering subsequent deceleration actions. When the calculated height difference is negative, the PLC immediately triggers a frequency reduction command, controlling the grab bucket to quickly decelerate to the material-feeding state, avoiding the risk of collision due to over-descent.

[0055] S22 Dynamic calculation of preset buffer threshold.

[0056] The PLC dynamically calculates a preset buffer threshold based on the current real-time descent speed of the grab bucket and the preset deceleration acceleration calibrated in S1. The preset buffer threshold is the shortest stroke required for the grab bucket to smoothly decelerate from the current real-time descent speed to the target speed for material exploration. The calculation process is derived based on the classical uniform deceleration linear motion mechanics formula.

[0057] The relationship between velocity and displacement in uniformly decelerated linear motion is as follows:

[0058] In the formula: To slow down the real-time descent speed of the front grab, This is the target descent speed during the material exploration phase after deceleration is complete. The preset deceleration acceleration calibrated in S1, The minimum travel required for the deceleration process is the preset buffer threshold.

[0059] Based on the above formula, the complete calculation formula for the preset buffer threshold is derived as follows:

[0060] In the formula: This is a preset buffer threshold, in meters (m). The current real-time descent speed of the grab bucket is expressed in m / s; The target descent velocity of the probe in the calibrated state in S1 is expressed in m / s. This is the preset deceleration acceleration calibrated in S1, in m / s². All parameters in the formula use the International System of Units (SI) for uniformity of dimensions, and the calculation results can be directly used for engineering control.

[0061] The PLC simultaneously sets a minimum lower limit of 0.8m and a maximum upper limit of 3.0m for the preset buffer threshold. Both the minimum lower limit of 0.8m and the maximum upper limit of 3.0m are determined based on the rated lifting height, maximum descent speed, and rated deceleration of the gantry crane. Those skilled in the art can adjust these proportionally according to the rated parameters of the target equipment. The minimum lower limit of 0.8m is set based on the target descent speed and preset deceleration acceleration during the grab bucket's material-feeding state, combined with the inverter's command response time and mechanical response lag characteristics. This provides sufficient margin for deceleration and state switching, preventing the calculated buffer threshold value from being too small when the grab bucket is running at low speed, which would cause the material surface reference position to be reached before the deceleration action is completed. The maximum upper limit of 3.0m is set based on the operational efficiency requirements of port bulk cargo loading and unloading, preventing the calculated buffer threshold value from being too large when the grab bucket is running at high speed, which would cause premature entry into the deceleration state and prolong the single operation cycle time.

[0062] S23 Control for switching the material probe state.

[0063] The PLC uses the preset sampling period calibrated in S1 to compare the currently calculated height difference with the dynamically calculated preset buffer threshold in real time. When the height difference shrinks to the preset buffer threshold, the PLC immediately outputs a frequency reduction command to the hoisting inverter. The frequency change rate of the frequency reduction command perfectly matches the preset deceleration acceleration calibrated in S1, ensuring the linearity and smoothness of the grab bucket deceleration process. The PLC uses the frequency reduction command through an internal logic interlock mechanism to intercept high-speed descent commands issued by the operator and block high-speed descent signal input from manual operation, prioritizing the execution of frequency reduction deceleration control. This controls the hoisting inverter to continuously reduce the output frequency according to the frequency reduction command, driving the grab bucket to decelerate smoothly according to the preset deceleration acceleration.

[0064] When the descent speed of the grab bucket drops to the target low-speed material-seeking speed of 0.3 m / s calibrated in S1, the PLC controls the hoisting frequency converter to maintain a stable output frequency, allowing the grab bucket to seamlessly switch to material-seeking mode and continue descending. This low-speed material-seeking speed can significantly reduce the elastic oscillation amplitude of the wire rope during deceleration and descent, keeping the fluctuation amplitude of the torque data fed back by the hoisting frequency converter within 3% of the rated value, providing a stable signal basis for accurate determination of the subsequent bottoming state.

[0065] S3 uses torque feedback to determine bottoming out and trigger parallel actions.

[0066] This step is based on the material probing state that has been seamlessly switched in S2. The execution body is a programmable logic controller (PLC). The entire process relies on the core control parameters calibrated in S1 to complete signal processing and state determination. Through precise bottom-reaching identification logic and multiple sets of time-synchronized control actions, the phenomenon of wire rope slack is avoided from the root, solving the problems of action delay and tension loss caused by the existing technology that can only rely on the load signal to trigger braking after bottom-reaching and serial control logic.

[0067] Acquisition and filtering of S31 torque feedback value.

[0068] During the material exploration phase, the PLC continuously collects the torque feedback value from the hoisting inverter in real time according to the preset sampling period of 20ms calibrated in S1, and simultaneously constructs a sliding data window of 5 sampling periods calibrated in S1. The PLC performs equal-weighted moving average filtering on the torque sequence within the sliding window, that is, takes the arithmetic mean of 5 consecutive sampled values ​​within the window as the smoothed torque value of the current period, eliminating periodic interference and outliers caused by small vibrations of the wire rope, mechanical vibrations, and deceleration oscillations, generating a smooth torque curve, and completely eliminating the false drop interference caused by deceleration oscillations caused by the frequency reduction command in S2. The moving average filtering effect on suppressing periodic interference is adapted to the on-site working conditions of port operations. It can effectively filter out non-steady-state oscillation signals without over-smoothing the data to mask the real step change of the bottoming torque. Combined with the stable torque data in S2, whose fluctuation amplitude has been controlled within 3% of the rated value, it provides a high signal-to-noise ratio signal foundation for subsequent bottoming determination.

[0069] Differential determination and threshold verification of S32 torque drop.

[0070] The PLC extracts the difference value of the smoothed torque curve under the preset sampling period calibrated in adjacent S1. The difference value is the difference between the smoothed torque value of the previous sampling period and the smoothed torque value of the current sampling period, which directly represents the real-time attenuation of torque within a single sampling period. The PLC simultaneously establishes a drop judgment time window for three consecutive sampling periods calibrated in S1. This time window corresponds to a duration of 60ms, which can fully cover the continuous torque change process, eliminate random noise interference in the single sampling process, avoid false triggering caused by abnormal data in a single period, and prevent the triggering delay of the bottoming state judgment due to the time window being too long.

[0071] The PLC continuously monitors all differential values ​​within the drop judgment time window, as well as the total attenuation of the torque feedback value. The total attenuation of the torque feedback value is the difference between the smoothed torque average of five consecutive sampling cycles under the stable low-speed material exploration state before bottoming out and the smoothed torque value of the current sampling cycle. When all differential values ​​included in the drop judgment time window are greater than the preset dynamic change threshold calibrated in S1, and the total attenuation of the torque feedback value reaches the preset self-weight ratio threshold calibrated in S1, the PLC determines that the attenuation amplitude of the torque feedback value has reached the preset drop threshold, confirming that the grab jaw plate has substantially contacted the bulk material surface. The dual-threshold judgment logic combines the two dimensions of torque change rate and change amplitude, which can accurately identify the unique torque step characteristics when the grab hits the bottom, and effectively eliminate the interference of small continuous fluctuations caused by the normal oscillation of the wire rope. This solves the problem of false triggering or trigger lag in the single-threshold judgment of the existing technology, and greatly improves the accuracy and reliability of bottoming out state judgment.

[0072] S33 stops descent, tension maintenance, and the closed-bucket action are triggered in parallel.

[0073] At the instant the PLC completes the bottoming-out determination, within the same PROFINET industrial Ethernet communication cycle, control commands are synchronously sent to the hoisting inverter and the switching inverter. The timing difference between the command issuance for the three actions does not exceed 20ms, achieving near-parallel triggering, eliminating the action lag caused by serial control, and ensuring that the three actions are executed synchronously. 1. The first action is that the PLC immediately locks the downward pulse output of the hoisting inverter, prohibits all downward drive signal inputs, and seamlessly switches the hoisting inverter to torque control mode to completely eliminate the inertial overwind of the drum and physically prevent the wire rope from becoming slack due to the continuous rotation of the drum.

[0074] 2. The second action is that the PLC synchronously applies the static holding torque calibrated in S1 to the lifting frequency converter in torque control mode, so that the wire rope is kept in a critical state of tension without lifting the grab bucket. The wire rope tension corresponding to this torque can just offset the slack caused by the sag of the wire rope itself. This can maintain the stable tension of the wire rope throughout the process, and will not change the contact state between the grab bucket and the bulk material surface due to excessive torque, thus ensuring the consistency of subsequent grabbing actions.

[0075] 3. The third action is that the PLC synchronously outputs the bucket-closing drive command to the switching frequency converter. The bucket-closing drive command is the frequency command corresponding to the rated speed of the switching motor, which directly drives the switching motor to perform the bucket-closing action at the rated speed.

[0076] The three parallel actions enable the tension locking and gripping action to start simultaneously at the moment of bottoming out, completely avoiding the physical process of wire rope slack and eliminating the 1 to 2 second rope retraction compensation delay that is unavoidable in traditional serial control logic, thus achieving seamless connection of gripping actions.

[0077] The S4 supports target hovering torque output and sinking depth adjustment based on deep-diving requirements.

[0078] This step is based on the closed bucket drive command that has been synchronously triggered in S3, the continuously applied static holding torque, and the wire rope tension that is maintained throughout the process. The execution body is a programmable logic controller (PLC). The torque output control and sinking depth adjustment are completed entirely based on the core control parameters calibrated in S1. This solves the problems of existing technologies that do not address adaptive control of the grab depth during the closed bucket process, poor stability of the full bucket rate due to the grab bucket depth relying entirely on manual operation experience, and the susceptibility to overloading, underloading, and collision damage to the bottom plate of the ship's hold.

[0079] S41 is determined based on the depth requirement of the material density.

[0080] The PLC acquires the material density data for the current operation. The material density data can be retrieved directly from the pre-stored physical density database of common bulk cargoes in ports by the operator preset the material type in the human-machine interface, or it can be calculated by converting the actual grab load and grab volume of the grab bucket in the previous operation cycle. The grab volume is determined by the rated geometric volume corresponding to the full stroke of the grab bucket jaw plate.

[0081] The PLC compares the current material density with the preset density threshold calibrated in S1 to determine the preset depth requirement for the current operation. The preset density threshold is calibrated to 2.0 t / m³. This value is based on the physical density and flow characteristics of common bulk cargoes in ports. Bulk cargoes with a density greater than 2.0 t / m³ are usually hard, high-density bulk cargoes such as iron ore and manganese ore. These materials have a large internal friction angle and poor flowability, requiring a greater cutting depth to ensure a full grab bucket rate. Bulk cargoes with a density not greater than 2.0 t / m³ are usually low-density bulk cargoes such as coal and grain. These materials have a small internal friction angle and strong flowability, and excessive grabbing can easily lead to material overflow and grab bucket overload.

[0082] When the material density is greater than the preset density threshold, the PLC determines the preset deep digging requirement as deep gripping, which is suitable for gripping hard, high-density bulk materials; when the material density is not greater than the preset density threshold, the PLC determines the preset deep digging requirement as shallow gripping, which is suitable for low-density bulk materials and ship hold cleaning operations.

[0083] The S42 target hovering support torque is output in stages.

[0084] While responding to the closed bucket drive command synchronously issued in S3, the PLC seamlessly switches the static holding torque continuously applied on the hoisting inverter. The switching process adopts a linear ramp transition, and the transition time covers 3 consecutive preset sampling periods (corresponding to 60ms) to avoid abrupt changes in torque output and maintain the tension of the wire rope throughout the process.

[0085] The target hovering support torque is divided into two levels, each corresponding to a preset deep digging requirement. The settings for both levels are based on the torque value corresponding to the rated self-weight of the grab bucket, ensuring the consistency and adjustability of the control logic. 1. When the preset deep excavation requirement is a deep grab, the target hovering support torque output by the PLC is the first hovering support torque. The first hovering support torque is calibrated as 55% of the stress torque value of the grab bucket's rated self-weight. This torque value is less than the grab bucket's self-weight, which can reserve sufficient self-weight driving force for the grab bucket to sink. At the same time, it is always greater than the static holding torque calibrated in S1, so that the wire rope tension will not be lost and slack due to the torque being too small.

[0086] 2. When the preset deep excavation requirement is shallow grabbing, the target hovering support torque output by the PLC is the second hovering support torque. The second hovering support torque is calibrated to 85% of the stress torque value of the grab bucket's rated self-weight. This torque value is greater than the first hovering support torque, which can offset most of the grab bucket's self-weight, effectively limiting the grab bucket's sinking range, while maintaining the stable tension of the wire rope throughout the process to avoid tension fluctuations.

[0087] The S43 grab bucket's sinking depth is adaptively adjusted.

[0088] The PLC adjusts the depth of the grab during the closing process in real time by measuring the difference between the grab's own weight and the target's hovering support torque. The entire adjustment process is synchronized with the closing action of the opening and closing motor, without the need for additional control commands.

[0089] When the first hovering support torque is output, the difference between the grab bucket's own weight and the support torque is large. During the horizontal retraction process of the jaw plate closing, the grab bucket relies on the difference in its own weight and the horizontal retraction force when the bucket is closed to cut into the interior of the material pile. The continuous sinking is completed synchronously throughout the entire stroke of the bucket closing action, maximizing the depth of digging, allowing the jaw plate to completely wrap the hard bulk cargo, and effectively improving the full grab rate of hard, high-density bulk cargo.

[0090] When the second hovering support torque is output, the difference between the grab's own weight and the support torque is small. The grab can only sink slightly in the initial stage of the closing action. It maintains the current height throughout the entire closing stroke, achieving stable shallow closing grabbing. This avoids overflow and overloading problems caused by excessive grabbing of low-density bulk cargo. At the same time, it prevents the grab from sinking excessively and contacting the bottom plate of the ship's hold during the cleaning operation, thus avoiding collision damage to the equipment structure.

[0091] Throughout the adjustment process, the PLC monitors the torque feedback data of the hoisting inverter in real time with the preset sampling period calibrated in S1. Once abnormal torque fluctuations occur, the target hovering support torque is immediately fine-tuned to keep the wire rope tension within a stable range. This avoids the problem of insufficient depth control accuracy caused by wire rope slack in traditional control, allowing the adjustment of the grab bucket's sinking depth and the closing action to form a precise synergy.

[0092] S5 grab bucket closed state determination, elevation anchor point closed-loop update and control parameter adaptive correction.

[0093] This step is based on the closed bucket action and sinking depth adjustment process executed synchronously in S4. The execution entity is a programmable logic controller (PLC). The entire process relies on the core control parameters calibrated in S1 to complete status monitoring, benchmark updates, and parameter corrections. It forms a fully nested closed-loop control with the previous steps, solving the problems of existing technologies that do not form a continuous operation cycle benchmark dynamic adaptation and control parameter self-optimization, and the lack of feedback linkage between operation effect and control logic. This ensures the stability of control accuracy and the consistency of operation efficiency during multi-cycle continuous operation.

[0094] Accurate determination of the fully closed state of the S51 grab bucket.

[0095] Throughout the entire cycle of responding to the bucket closing drive command, the PLC collects the operating current of the opening and closing motor from the frequency converter in real time, using a preset sampling period of 20ms calibrated in S1. The PLC compares the collected operating current with the preset stall current threshold calibrated in S1 in real time. The preset stall current threshold is calibrated as 120% of the rated current of the opening and closing motor. After the grab jaws complete full-stroke closure and fully engage, the mechanical output shaft of the opening and closing motor is completely locked and cannot continue to perform rotation. The motor enters the stall operating condition. Under the stall condition, the stator winding current of the opening and closing motor will rapidly rise to more than 120% of the rated current. This threshold can accurately distinguish between the dynamic current fluctuations during normal grab closing operation and the steady-state stall current after full closure.

[0096] When the PLC detects that the operating current of the switching motor reaches the preset stall current threshold, it can determine that the grab is fully closed. As a preferred implementation, to eliminate false judgments caused by instantaneous current spikes, the grab is finally confirmed to have completed the fully closed action when the operating current continuously reaches the preset stall current threshold and covers three consecutive sampling cycles. The three consecutive sampling cycles correspond to a duration of 60ms, which effectively eliminates random noise interference from single sampling, ensuring the stability and accuracy of the closed state determination. Simultaneously, it forms a unified anti-interference design logic with the drop judgment time window parameters calibrated in S1, improving the consistency of the entire process control.

[0097] Dynamic overwriting and benchmark updating of S52 elevation anchor points.

[0098] After the PLC determines the fully closed state of the grab bucket, it continuously monitors the operator's command input channel. The moment the PLC receives the lifting operation command from the operator, it immediately latches the rotation data of the lifting motor shaft end synchronously output by the absolute encoder. Following the conversion relationship calibrated on-site in step S1, the PLC converts the latched rotation data into the latest absolute height data of the grab bucket. The conversion relationship is based on the reduction ratio between the lifting motor and the drum, and the diameter of the drum's rope groove. The measurement error of the height data is no greater than 5cm, maintaining consistency with the accuracy of the previous height acquisition step. The PLC writes the converted latest height data into its internal power-off retention memory register, completely overwriting the elevation anchor point data stored in the previous operation cycle.

[0099] Between two adjacent operation cycles, the elevation change of the bulk cargo surface relative to the hull only comes from the material removal during a single grab operation. The change process has local continuity, and within the duration of a single operation cycle, the change in the ship's draft due to loading and unloading operations is no more than 3cm. By overwriting the original elevation anchor point with the height data at the moment of lifting at the end of this operation cycle, the overall offset of the height reference caused by the change in the ship's draft and the dynamic descent of the material surface can be automatically compensated. No additional independent compensation algorithm is required. This provides a stable and accurate reference for the prediction of the material surface position and the triggering of deceleration action in the next operation cycle S2 step, while realizing closed-loop control of the entire operation process without the need for continuous manual intervention and calibration.

[0100] Real-time acquisition of load and verification of operation effect of S53.

[0101] Once the PLC receives the lifting operation command and the grab enters a stable lifting state, it continuously collects the torque feedback value from the lifting inverter at a preset sampling period of 20ms as calibrated in S1. The stable lifting state is determined by the lifting motor's operating speed reaching at least 80% of the rated lifting speed, and this duration being no less than 5 preset sampling periods. During the lifting process from a stationary state, the grab generates a dynamic torque impact due to starting acceleration. When the lifting speed reaches at least 80% of the rated speed, the lifting action enters a uniform and stable phase. The torque feedback value from the lifting inverter accurately reflects the total load of the grab and the material being grabbed, eliminating the interference of dynamic acceleration torque on load calculation and ensuring the accuracy of load data. Five sampling periods correspond to a duration of 100ms, consistent with the sliding filter window length calibrated in S1, covering the small speed fluctuation range during the lifting process and ensuring that the collected torque data is under stable operating conditions. The PLC takes the arithmetic mean of 10 consecutive sets of torque feedback values ​​collected under stable lifting conditions, and combines this with the torque benchmark value corresponding to the rated self-weight of the grab bucket calibrated in S1 to calculate the actual grab load for the current work cycle. The conversion formula for the actual grab load is as follows:

[0102] In the formula: The actual load being grabbed is expressed in kg. The arithmetic mean of 10 consecutive sets of torque feedback values, in N·m; The torque reference value corresponding to the rated self-weight of the grab bucket as specified in S1, in N·m; This represents the torque at the motor shaft end corresponding to the self-weight of the wire rope at the current grab bucket height, in N·m. This represents the motor shaft torque corresponding to the frictional resistance of the pulley block, in N·m. This is the reduction ratio between the hoisting motor and the drum; Let be the acceleration due to gravity, and take . ; The radius of the rope groove on the drum is in meters (m). During the conversion process, the PLC simultaneously eliminates torque deviations caused by the self-weight of the wire rope and the frictional resistance of the pulley system at the current height. The calibration method for the torque value corresponding to the self-weight of the wire rope is as follows: under the unloaded state of the grab bucket, the stable output torque values ​​of the hoisting frequency converter at 10 height points evenly distributed throughout the entire stroke are collected, and the height-wire rope self-weight torque curve is fitted and stored in the PLC's memory register. During operation, the corresponding wire rope self-weight torque value is retrieved in real time according to the current height of the grab bucket. The torque value corresponding to the frictional resistance of the pulley system is calibrated during the on-site commissioning phase and stored in the PLC's memory register to ensure that the deviation between the load calculation result and the actual grab volume is no more than 3%, providing a reliable basis for subsequent control parameter correction.

[0103] S54 target hovering support torque closed-loop adaptive correction.

[0104] After the PLC completes the calculation of the actual grab load for the current work cycle, it compares the actual grab load with the preset full load threshold and preset overload threshold calibrated in S1 in real time. The preset full load threshold is calibrated as 90% of the grab bucket's rated grab load, and the preset overload threshold is calibrated as 110% of the grab bucket's rated grab load. This set of thresholds conforms to the industry standards for loading and unloading operations of port cranes. The 90% full load threshold can effectively determine whether the grab bucket's grab full rate meets the operational requirements, avoiding a decrease in operational efficiency due to insufficient grab volume. The 110% overload threshold meets the redundancy design requirements for the safe operation of crane equipment, effectively identifying the risk of equipment overload operation and avoiding fatigue damage and safety accidents caused by long-term overload operation.

[0105] 1. When the actual gripping load is less than the preset full-load threshold, and the target hovering support torque output by the PLC in the current work cycle is the first hovering support torque, the PLC performs a downward adjustment correction operation on the first hovering support torque. The adjustment step size is calibrated to 2% of the rated self-weight of the grab bucket relative to the stress torque value, and the first hovering support torque after a single correction must not be lower than 30% of the rated self-weight of the grab bucket relative to the stress torque value. If the actual gripping load does not reach the full-load threshold, it indicates that the self-weight difference provided by the current first hovering support torque is insufficient, and the depth of the grab bucket cutting into the material pile has not reached the optimal value. By slightly reducing the first hovering support torque, the difference between the grab bucket's self-weight and the support torque can be increased, improving the grab bucket's cutting depth, thereby increasing the grab full-bucket rate in the next work cycle. A 2% correction step ensures the smoothness of the correction process, avoids sudden changes in the gripping amount due to excessive single correction, and adapts to the linear change characteristics of the continuous descent of bulk material surface; a 30% lower limit ensures that the corrected torque can always maintain the tension of the wire rope, avoids slack failure due to loss of wire rope tension caused by excessively low torque, and provides a safety redundancy with the static holding force rectangle calibrated in S1.

[0106] 2. When the actual gripping load exceeds the preset overload threshold, the PLC executes a forced switching correction operation on the target hovering support torque, forcibly switching the target hovering support torque for the next work cycle to the second hovering support torque. Simultaneously, it locks the output permission of the first hovering support torque, with the lock duration covering a complete work cycle. If the actual gripping load exceeds the overload threshold, it indicates that the current grab's cutting depth is too large, posing an overload risk. The second hovering support torque can offset most of the grab's own weight, significantly limiting the grab's sinking range and fundamentally reducing the probability of excessive gripping, ensuring the safe operation of the equipment. The lock duration for one work cycle ensures that the equipment completes a stable shallow gripping operation, quickly reducing the single gripping load and avoiding the safety risks caused by continuous overload operations. Furthermore, the lock duration will not affect the normal deep excavation operation of subsequent high-density materials.

[0107] 3. When the actual gripping load is between the preset full load threshold and the preset overload threshold, the PLC determines that the gripping effect of the current work cycle meets the work requirements, and does not perform a correction operation on the target hovering support torque for the next work cycle, maintaining the original torque setting value unchanged to ensure the stability of the work process.

[0108] This implementation method achieves a comprehensive breakthrough over the core defects of existing technologies through a fully nested closed-loop control logic. The elevation anchoring mechanism based on historical operation data enables proactive prediction of the bulk material surface position, solving the lag problem of existing technologies that rely solely on feedback after bottoming out. Adaptive deceleration and low-speed material exploration control eliminate system oscillations caused by high-speed impacts, ensuring the accuracy of bottoming out determination. Parallel triggering actions at the moment of bottoming out fundamentally avoid the physical process of wire rope slack, completely eliminating the action lag caused by rope retraction compensation. Torque-antagonistic deep digging adjustment achieves adaptive control of the grabbing depth, improving the stability of the bucket full rate under different bulk material working conditions. Dynamic overwriting and parameter self-correction of elevation anchor points enable the control logic to dynamically adapt to the continuous descent of the material surface without continuous manual intervention. This implementation method can shorten the single operation cycle time of a gantry crane from the conventional 125s to approximately 122s, significantly improving the efficiency of continuous operation, while greatly reducing the probability of wire rope fatigue wear, rope tangling, and derailment failures.

[0109] Based on the same inventive concept, this application also provides a grab control device for implementing the grab control method described above. The solution provided by this system is similar to the solution described in the above method; therefore, the specific limitations in the grab control device embodiments provided below can be found in the limitations of the grab control method described above, and will not be repeated here.

[0110] This application provides a grab control device, such as... Figure 2 As shown, the grab bucket control device achieves closed-loop control of the entire process through functional modules integrated within the PLC. The specific implementation methods of each module are as follows: 1. Dynamic prediction module This module is used to establish a benchmark for predicting the material surface position and to complete the adaptive deceleration and material exploration state switching during the grab bucket's descent. The module pre-stores the height data of the grab bucket being fully closed and receiving the lifting operation command in the previous work cycle as the elevation anchor point. When there is no historical data for the first work cycle, the initial elevation anchor point is obtained through a manual calibration process: after the operator controls the grab bucket to be fully open and descends smoothly until the jaw plate is in complete contact with the bulk material surface, the grab bucket is closed. After the module detects that the operating current of the opening and closing motor reaches the preset stall current threshold and determines that the grab bucket is fully closed, it latches the encoder data and converts it into absolute height at the moment it receives the lifting operation command, which is used as the initial elevation anchor point.

[0111] During the descent phase of the grab bucket's current operating cycle, the module collects encoder data in real time with a preset sampling period of 20ms, calculates the grab bucket's current absolute height, and simultaneously calculates the height difference between the current height and the elevation anchor point. Simultaneously, based on the grab bucket's real-time descent speed and a preset deceleration acceleration of 0.5m / s², it dynamically calculates a preset buffer threshold, using the following formula: In the formula To set a preset buffer threshold, To control the real-time descent speed of the grab, Assuming the target descent speed is 0.3 m / s during the probing phase, The module sets a minimum lower limit of 0.8m and a maximum upper limit of 3.0m for the buffer threshold to prevent abnormal deceleration stroke.

[0112] When the height difference shrinks to the preset buffer threshold, the module immediately outputs a frequency reduction command to the hoisting inverter that matches the deceleration acceleration. Through logic interlocking, the high-speed descent command issued by the operator is intercepted, and the inverter is controlled to smoothly reduce the frequency, driving the grab bucket to decelerate to 0.3m / s and then maintain stable operation, seamlessly switching to the material exploration state.

[0113] 2. Anti-slack module This module is used to accurately identify the bottoming state of the grab bucket and simultaneously trigger multiple sets of control actions to prevent wire rope slack from the root cause. In the material exploration state, the module continuously collects the torque feedback value of the hoisting frequency converter with a sampling period of 20ms, constructs a sliding data window of 5 sampling periods, performs equal-weighted moving average filtering on the torque sequence within the window, eliminates false drop interference caused by deceleration oscillation and mechanical vibration, and generates a smooth torque curve.

[0114] The module extracts the difference values ​​of the smoothed torque curves of adjacent sampling periods, establishes a drop judgment time window of 3 consecutive sampling periods, and continuously monitors the difference values ​​and the total torque attenuation within the time window. When all difference values ​​within the time window are greater than the preset dynamic change threshold of 3% of the rated self-weight of the grab bucket relative to the stress torque value, and the total attenuation of the torque feedback value relative to the stable value before bottoming out reaches the preset self-weight ratio threshold of 18% of the rated self-weight of the grab bucket relative to the stress torque value, it is determined that the torque attenuation amplitude has reached the preset drop threshold, confirming that the grab bucket jaw plate has made substantial contact with the bulk material surface.

[0115] Within the same communication cycle after the bottoming-out determination is completed, the module synchronously sends control commands to the hoisting inverter and the opening / closing inverter. The timing difference between the three action commands is no more than 20ms, achieving parallel triggering: First, the descent pulse output of the hoisting inverter is immediately locked, prohibiting all descent drive signal inputs, while seamlessly switching the hoisting inverter to torque control mode; Second, a static holding torque of 8% of the rated self-weight of the grab bucket on the hoisting inverter is applied, keeping the wire rope continuously taut and in a critical state without lifting the grab bucket; Third, a bucket closing drive command is output to the opening / closing inverter, driving the opening / closing motor to perform the bucket closing action at the rated speed.

[0116] 3. In-depth analysis of the control module This module is used to adaptively adjust the depth of the grab bucket during the closing process to match the grabbing requirements of different materials. The module first obtains the material density data of the current operation, compares the material density with the preset density threshold of 2.0t / m³, and determines the preset depth requirement: when the material density is greater than the threshold, it is determined to be a deep grabbing requirement; when the material density is not greater than the threshold, it is determined to be a shallow grabbing requirement.

[0117] While responding to the bucket closing drive command, the module seamlessly switches the static holding torque of the lifting inverter to the target hovering support torque that matches the deep excavation requirements through a linear ramp transition of three consecutive sampling cycles, maintaining the wire rope tension throughout the process: For deep grabbing requirements, a first hovering support torque of 55% of the bucket's rated self-weight relative to the stress torque value is output. This torque is less than the bucket's self-weight, and through the difference between the self-weight and the support torque, the bucket smoothly cuts into the material pile during the jaw plate closing process, and the bucket continuously sinks synchronously throughout the entire closing stroke, maximizing the depth of excavation; For shallow grabbing requirements, a second hovering support torque of 85% of the bucket's rated self-weight relative to the stress torque value is output. This torque is greater than the first hovering support torque, which can offset most of the bucket's self-weight, limiting the bucket to only complete a small sinking in the initial stage of closing the bucket, and maintaining the current height unchanged in the subsequent closing stroke, achieving stable shallow grabbing.

[0118] During the adjustment process, the module monitors the torque feedback data of the lifting inverter in real time with a sampling period of 20ms. When abnormal torque fluctuations occur, the target hovering support torque is immediately fine-tuned to keep the wire rope tension within a stable range.

[0119] 4. Closed-loop update module This module is used to determine the grab bucket's closed state, dynamically update the elevation anchor point, and adaptively correct control parameters, forming a closed-loop control throughout the entire process. During the entire cycle of the closed bucket drive command execution, the module collects the operating current of the switching motor fed back by the switching frequency converter in real time at a sampling period of 20ms. When the operating current reaches the preset stall current threshold of 120% of the rated current of the switching motor for three consecutive sampling cycles, the grab bucket is determined to be fully closed.

[0120] After completing the closed state determination, the module continuously monitors the operation command input channel. Upon receiving the lifting operation command, it latches the rotation data synchronously output by the encoder and converts it into the latest absolute height data of the grab bucket. This data is written into the PLC power-off retention memory register, completely overwriting the elevation anchor point of the previous operation cycle, providing a predictive benchmark for the next operation cycle, and automatically compensating for the height benchmark offset caused by changes in the ship's draft and the dynamic drop of the material surface.

[0121] After the grab bucket enters a stable lifting state, the module collects the average torque feedback value of 10 consecutive sets of lifting frequency converters. Combined with the grab bucket's rated self-weight relative to the stress torque benchmark, the current height's wire rope self-weight torque, and the pulley block friction resistance torque, the actual grab load for the current work cycle is calculated using the following formula: In the formula To actually capture the load, This is the average value of the torque feedback. The rated self-weight of the grab bucket represents the reference value of the stress moment. The stress moment of the steel wire rope under its own weight at the current height. The frictional resistance of the pulley system is related to the stress torque. This refers to the reduction ratio between the hoisting motor and the drum. The acceleration due to gravity is 9.8 m / s². The radius of the drum rope groove is given.

[0122] The module compares the actual gripping load with a preset threshold and adaptively adjusts the target hovering support torque for the next work cycle: when the actual gripping load is less than the preset full-load threshold of 90% of the grab bucket's rated gripping load, and the current cycle output is the first hovering support torque, the first hovering support torque for the next cycle is reduced in steps of 2% of the stress torque value relative to the grab bucket's rated self-weight, and the corrected torque value is not less than 30% of the stress torque value relative to the rated self-weight; when the actual gripping load is greater than the preset overload threshold of 110% of the grab bucket's rated gripping load, the target hovering support torque for the next cycle is forcibly switched to the second hovering support torque, and the output permission of the first hovering support torque is locked for one complete work cycle; when the actual gripping load is between the full-load threshold and the overload threshold, the original torque setting value is maintained unchanged.

[0123] The various modules of this device work together to form a nested, closed-loop control system. It achieves forward prediction of material surface position through elevation anchoring, fundamentally eliminates wire rope slack and motion lag through parallel actions at the moment of bottoming, achieves adaptive control of gripping depth through torque antagonistic adjustment, and adapts to changes in material surface during continuous operation through dynamic benchmark updates and parameter self-optimization. It can effectively improve the efficiency, operational stability, and equipment safety of gantry cranes for bulk cargo loading and unloading without continuous manual intervention.

[0124] See Figure 3 , Figure 3This is a schematic block diagram of an electronic device provided according to an embodiment of this application. Figure 3 The electronic device 300 in this embodiment may include one or more processors 301, one or more input devices 302, one or more output devices 303, and one or more memories 304. The processors 301, input devices 302, output devices 303, and memories 304 communicate with each other via a communication bus 305. The memories 304 store computer programs, including program instructions. The processors 301 execute the program instructions stored in the memories 304. Specifically, the processors 301 are configured to invoke the program instructions to perform the functions of each module / unit in the above-described device embodiments, for example... Figure 2 The functions of each module are shown.

[0125] It should be understood that, in the embodiments of this application, the processor 301 may be a central processing unit (CPU), or it may be other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor may be a microprocessor or any conventional processor.

[0126] Input device 302 may include a touchpad, a fingerprint sensor (for collecting the user's fingerprint information and fingerprint orientation information), a microphone, etc., and output device 303 may include a display (LCD, etc.), a speaker, etc.

[0127] The memory 304 may include read-only memory and random access memory, and provides instructions and data to the processor 301. A portion of the memory 304 may also include non-volatile random access memory. For example, the memory 304 may also store device type information.

[0128] In specific implementations, the processor 301, input device 302, and output device 303 described in the embodiments of this application can execute the implementation methods described in the embodiments of this application, or they can execute the implementation methods of the electronic devices described in the embodiments of this application, which will not be repeated here.

[0129] In another embodiment of this application, a computer-readable storage medium is provided. This computer-readable storage medium stores a computer program, which includes program instructions. When executed by a processor, the program instructions implement all or part of the processes in the methods described above. Alternatively, the computer program can instruct related hardware to implement these processes. The computer program can be stored in a computer-readable storage medium, and when executed by a processor, it can implement the steps of the various method embodiments described above. The computer program includes computer program code, which can be in the form of source code, object code, executable files, or certain intermediate forms. The computer-readable medium can include any entity or device capable of carrying computer program code, a recording medium, a USB flash drive, a portable hard drive, a magnetic disk, an optical disk, a computer memory, a read-only memory (ROM), a random access memory (RAM), an electrical carrier signal, a telecommunication signal, and a software distribution medium, etc.

[0130] The computer-readable storage medium can be an internal storage unit of the electronic device in any of the foregoing embodiments, such as a hard disk or memory of the electronic device. The computer-readable storage medium can also be an external storage device of the electronic device, such as a plug-in hard disk, SmartMediaCard (SMC), Secure Digital (SD) card, FlashCard, etc., equipped on the electronic device. Furthermore, the computer-readable storage medium can include both internal and external storage units of the electronic device. The computer-readable storage medium is used to store computer programs and other programs and data required by the electronic device. The computer-readable storage medium can also be used to temporarily store data that has been output or will be output.

[0131] Those skilled in the art will recognize that the modules / units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of both. To clearly illustrate the interchangeability of hardware and software, the components and steps of the various examples have been generally described in terms of functionality in the foregoing description. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementations should not be considered beyond the scope of this application.

[0132] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working process of the electronic devices and units described above can be referred to the corresponding process in the foregoing method embodiments, and will not be repeated here.

[0133] In the several embodiments provided in this application, it should be understood that the disclosed electronic devices and methods can be implemented in other ways. For example, the device embodiments described above are merely illustrative. For instance, the division of modules / units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple modules, units, or components may be combined or integrated into another system, or some features may be ignored or not executed. In addition, the mutual coupling or direct coupling or communication connection shown or discussed may be indirect coupling or communication connection through some interfaces or modules / units, or it may be an electrical, mechanical, or other form of connection.

[0134] The modules / units described as separate components may or may not be physically separate. Similarly, the components shown as modules / units may or may not be physical modules / units; they may be located in one place or distributed across multiple network modules / units. Some or all of the modules / units can be selected to achieve the purpose of the embodiments of this application, depending on actual needs.

[0135] Furthermore, the functional modules / units in the various embodiments of this application can be integrated into one processing module / unit, or each module / unit can exist physically separately, or two or more modules / units can be integrated into one module / unit. The integrated modules / units described above can be implemented in hardware or in the form of software functional modules / units.

[0136] The above are merely specific embodiments of this application, but the scope of protection of this application is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in this application, and these modifications or substitutions should all be covered within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A grab control method, characterized in that include: The height data at the moment the grab bucket closes during the previous operation cycle is used as the elevation anchor point; During the current descent phase, the height difference between the current height of the grab bucket and the elevation anchor point is calculated. When the height difference is reduced to a preset buffer threshold, the grab bucket is controlled to switch to the material exploration state. During the material exploration state, the torque feedback value of the frequency converter driving the grab bucket is monitored. When the attenuation amplitude of the torque feedback value reaches the preset drop threshold, the following actions are triggered in parallel: stop descent, maintain the wire rope in tension and do not lift the grab bucket, and close the bucket. When performing the closing action, the target hovering support torque is output to the frequency converter based on the preset deep excavation requirements. While maintaining the tension of the wire rope, the depth of the grab bucket sinks is adjusted by the difference between the weight of the grab bucket and the target hovering support torque. When the grab bucket closes and enters the lifting state, the latest height data is obtained and overwritten to the elevation anchor point, which will serve as the benchmark for calculating the height difference in the next work cycle.

2. The grab bucket control method according to claim 1, characterized in that, The preset buffer threshold is obtained by dynamic calculation based on the current descent speed of the grab and the set deceleration acceleration; During the current descent phase, the grab bucket executes a descent maneuver based on the acquired descent command; The control grab bucket is switched to the material-feeding state, including: When the height difference decreases to the preset buffer threshold, a frequency reduction command is output to the frequency converter driving the grab bucket; The frequency reduction command is used to cut off the descent command, and the frequency converter is controlled to reduce the output frequency to slow down the grab bucket. When the descent speed of the grab bucket drops to the preset target descent speed for the material exploration state, the grab bucket is controlled to switch to the material exploration state.

3. The grab bucket control method according to claim 2, characterized in that, When the attenuation amplitude of the torque feedback value reaches a preset drop threshold, the following is included: In the material exploration state, the torque feedback value is collected according to a preset sampling period and filtered to generate a smooth torque curve; Extract the difference values ​​of the smooth torque curves under adjacent preset sampling periods, and establish a drop determination time window; When all the difference values ​​included in the drop determination time window are greater than the preset dynamic change threshold, and the total attenuation of the torque feedback value reaches the preset self-weight ratio threshold, it is determined that the attenuation amplitude has reached the preset drop threshold.

4. The grab bucket control method according to claim 3, characterized in that, The frequency converter driving the grab bucket includes a lifting frequency converter and a switching frequency converter. The parallel triggering of the stopping descent action, the holding action of maintaining the wire rope tension and not raising the grab bucket, and the closing action include the simultaneous execution of the following steps: Cut off the falling pulse output of the lifting frequency converter; A static holding torque is applied to the lifting inverter; Output the closing drive command to the switching frequency converter.

5. The grab bucket control method according to claim 4, characterized in that, The step of outputting a target hovering support torque to the frequency converter based on preset depth requirements includes: Obtain the current material density and compare it with a preset density threshold to determine the preset depth requirement; In response to the closed bucket drive command, the static holding torque of the hoisting inverter is switched to the target hovering support torque: When the material density is greater than the preset density threshold, the target hovering support torque is a first hovering support torque that is less than the weight of the grab bucket. When the material density is not greater than the preset density threshold, the target hovering support torque is a second hovering support torque that is greater than the first hovering support torque and less than the weight of the grab bucket.

6. The grab bucket control method according to claim 5, characterized in that, When the grab bucket closes and enters the lifting state, the latest height data is obtained and overwritten to the elevation anchor point, including: During the response to the closed bucket drive command, the operating current of the switching motor driven by the switching frequency converter is monitored; When the operating current reaches the preset stall current threshold, it is determined that the grab is fully closed; When it is determined that the grab bucket is fully closed and a lifting operation command is received, the latest height data is obtained and the elevation anchor point is overwritten.

7. The grab bucket control method according to claim 6, characterized in that, After receiving the lifting operation command, the process also includes a step of closed-loop correction of the target hovering support torque for the next work cycle: Get the actual grab load of the current job cycle; When the actual gripping load is less than the preset full load threshold and the current output is the first hovering support torque, the setting value of the first hovering support torque in the next work cycle is reduced. When the actual gripping load exceeds the preset overload threshold, the target hovering support torque for the next work cycle will be forcibly switched to the second hovering support torque.

8. A grab bucket control device for implementing the steps of the grab bucket control method as described in any one of claims 1 to 7, characterized in that, include: The dynamic prediction module is used to obtain the height data of the grab bucket at the moment of closure in the previous operation cycle as the elevation anchor point, calculate the height difference between the current height of the grab bucket and the elevation anchor point in the current descent stage, and control the grab bucket to switch to the material exploration state when the height difference is reduced to a preset buffer threshold. The anti-slackening module is used to monitor the torque feedback value of the frequency converter driving the grab bucket in the material exploration state. When the attenuation amplitude of the torque feedback value reaches the preset drop threshold, it triggers in parallel the stop descent action, the holding action to keep the wire rope taut and not lift the grab bucket, and the closing action. The deep excavation control module is used to output a target hovering support torque to the frequency converter based on the preset deep excavation requirements when performing the closed bucket action. While maintaining the tension of the wire rope, the depth of the grab bucket sinks is adjusted by the difference between the weight of the grab bucket and the target hovering support torque. The closed-loop update module acquires the latest height data and overwrites the elevation anchor point when the grab bucket completes closure and enters the lifting state, so as to serve as the benchmark for calculating the height difference in the next operation cycle.

9. An electronic device comprising a memory, a processor, and a computer program stored in the memory and running on the processor, characterized in that, When the processor executes the computer program, it implements the steps of the method as described in any one of claims 1 to 7.

10. A computer-readable storage medium storing a computer program, characterized in that, When the computer program is executed by a processor, it implements the steps of the method as described in any one of claims 1 to 7.

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