Frequency converter of hoisting mechanism and control method of frequency converter
By using an encoder to judge the load hook and automatically brake and drop the load in the frequency converter of the lifting mechanism, the problem of safety risks after the load hook is solved, and the safe load drop and reliable shutdown of the equipment are achieved.
Patent Information
- Application Number
- CN202411984068.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-26
- Publication Date
- 2025-04-29
AI Technical Summary
In the lifting industry, load hooking is a serious safety issue, and it is difficult for the existing technology to effectively avoid secondary accidents caused by human factors.
A frequency converter of a lifting mechanism and its control method are provided. The load hook fault is judged by the pulse count value feedback from the encoder, and the lifting motor brake load is automatically started, and the load is automatically locked and shut down after the load falls.
It realizes that no operator intervention is required after the load is slipped, and the load is automatically braked and safely lowered, reducing the safety risks after slipping, and avoiding secondary accidents caused by improper operation caused by human factors.
Smart Images
Figure CN119898688A_ABST
Abstract
Description
Technical Field
[0001] The present application relates to the technical field of frequency converters, and in particular to a frequency converter for a lifting mechanism and a control method thereof. Background Art
[0002] In the lifting industry, load slipping is a serious safety issue. When the inverter stops and the motor stops outputting power, if the brake device and the inverter control timing are not properly matched and fail to engage in time, or the brake device itself is abnormal and cannot engage in braking, the load will fall due to its own gravity, which is extremely dangerous.
[0003] The inverter can determine whether the hook slips through the change of the encoder count value. When the hook slips, the inverter immediately controls the motor output to control the load braking, then hovers at zero speed and alarms. The worker lowers the load to the ground, or slowly descends at a preset speed and stops the machine after it falls to the ground.
[0004] When the load is suspended at zero speed after the hook slips, if there is no one on duty on site or the worker does not drop the suspended load in time, the motor cooling fan of some motors is coaxial with the rotor, and the inverter runs at zero speed for a long time, the motor may overheat and cause failure, which in turn causes the load to lose control. If the load is slowly lowered at the preset speed, and the worker does not stop the machine in time after the load lands, it may be lowered too much, causing the drum rope to be tangled and affecting subsequent use. In addition, when the load falls, if the worker violates the rules and continues production when the brake mechanism is not sure whether it can be braked normally, there will also be great safety hazards. Summary of the invention
[0005] In view of this, the purpose of the present application is to provide a frequency converter for a lifting mechanism and a control method thereof, so as to reduce the safety risk after the load slips off the hook and avoid secondary accidents caused by improper operation due to human factors after the load slips off the hook.
[0006] The technical solutions adopted by this application to solve the above technical problems are as follows:
[0007] In a first aspect, the present application provides a frequency converter control method for a lifting mechanism, wherein the lifting mechanism further includes an encoder, a brake device, and a lifting motor; the control method includes:
[0008] Determine whether a load hook slip failure occurs based on the pulse count value fed back by the encoder;
[0009] If a load hook slip failure occurs, it will automatically start to drive the lifting motor to brake the load and drive the lifting motor to control the load to be lowered;
[0010] During the control of load lowering, determine whether the load has landed;
[0011] If the load has landed, the brake device will be controlled to brake and stop the machine.
[0012] A second aspect of the present application provides a frequency converter for a lifting mechanism, the frequency converter for the lifting mechanism includes a control unit, the control unit includes a memory and a processor, the memory is configured to store a computer program, and when the processor executes the computer program, it implements the frequency converter control method for the lifting mechanism of the first aspect.
[0013] The frequency converter of the lifting mechanism and the control method thereof provided in the embodiment of the present application can actively brake and safely lower the load in a controllable manner without the intervention of an operator after identifying that the load has slipped off the hook, and automatically shut down when the load is detected to have landed. This reduces the safety risk after the load has slipped off the hook, and effectively avoids secondary accidents caused by improper operation due to human factors after the load has slipped off the hook, such as improper manual lowering by workers after the brake has slipped abnormally, pressing the emergency stop switch when the hook has slipped, and putting the brake device into use again without maintenance, and other risky operations. BRIEF DESCRIPTION OF THE DRAWINGS
[0014] Figure 1 A schematic diagram of a lifting mechanism provided in an embodiment of the present application;
[0015] Figure 2 A schematic diagram of a frequency converter control method for a lifting mechanism provided in an embodiment of the present application;
[0016] Figure 3 Schematic diagram of the change in output torque of a load-dropping motor provided in an embodiment of the present application.
[0017] The realization of the purpose, functional features and advantages of this application will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION
[0018] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present application clearer and more understandable, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.
[0019] like Figure 1 As shown, the lifting structure provided in the embodiment of the present application includes a joystick, a frequency converter, an encoder, a brake device, a lifting motor and an alarm module.
[0020] The control process of the lifting mechanism is roughly as follows; the joystick sends a running command through the digital input (DI) and sends the running frequency setting value to the inverter through the analog input (AI). After receiving the running command, the inverter controls the brake device to release the brake through the relay. After the brake is released, it drives the lifting motor to run, thereby lifting or lowering the load, and the encoder feeds back the actual operating frequency of the motor to the inverter.
[0021] Based on the above lifting mechanism, Figure 2 As shown, an embodiment of the present application provides a frequency converter control method for a lifting mechanism, the control method comprising the steps of:
[0022] S11, judging whether a load hook slip failure occurs according to the pulse count value fed back by the encoder;
[0023] Before starting the inverter, it is necessary to check whether the brake device can hold the brake normally and whether there is any slippage. After verifying that the brake device is normal, it can be released and run normally. After the inverter is finished running and the brake command is issued and stopped, the pulse count of the encoder feedback is used to confirm whether a load slipping fault occurs.
[0024] The release control sequence is as follows: When the start command is received during the shutdown phase, the inverter first performs torque verification, increases the output frequency to the release frequency, and then starts to detect the output torque. When the output torque is greater than the set release speed threshold, the verification is passed and the pre-release delay wait begins. After the pre-release delay is reached, a release command is issued, and the post-release delay is continued to ensure that the brake device is completely released. After the post-release delay is reached, the inverter starts to accelerate from the release frequency to the target frequency for normal operation.
[0025] The brake control sequence is similar to the brake release control sequence. The inverter starts to decelerate when receiving the stop command, and maintains and waits for the pre-brake delay after reaching the brake frequency. After the pre-brake delay arrives, the brake command is issued, and the post-brake delay arrives to ensure that the brake device is fully braked. The inverter can stop only after the post-brake delay arrives.
[0026] In one example, judging whether the load hook slip phenomenon occurs according to the pulse count value fed back by the encoder includes:
[0027] During the period from the end of the operation of the inverter to the shutdown, or after the inverter is shut down and before the next startup, it is determined whether the load slip phenomenon occurs according to the pulse count value fed back by the encoder.
[0028] Specifically, when the inverter ends its operation, the post-braking delay arrives and the brake device completes the braking, the output torque will not return to zero immediately, that is, the inverter will not immediately stop and remove the output, but will linearly reduce the output torque within a preset time period. During this period, if the brake device is normal and the load does not slip, the pulse count value fed back to the inverter by the encoder will not change, and the inverter will complete the shutdown when the output torque is reduced to zero. If the encoder pulse count value changes during the linear decrease of the output torque or in the time period before the next startup after shutdown, for example, if the change is greater than the set change threshold, it is judged that the load has slipped.
[0029] S12, if a load hook slip failure occurs, self-starting to drive the lifting motor to brake the load and drive the lifting motor to control the load to be lowered;
[0030] In one example, the control method further includes:
[0031] If a load hook slip failure occurs, the alarm module is controlled to send out an alarm message.
[0032] In one example, the control method further includes:
[0033] If a load hook slip failure occurs, all faults except the inverter hardware failure are shielded; among them, all faults include emergency stop signals.
[0034] Specifically, if the load is detected to be hooked, the inverter will immediately start the output to participate in braking to prevent the load from accelerating down. At the same time, the digital output (DO) output is used to control the alarm module to issue an alarm message, such as an audible and visual alarm.
[0035] If the inverter is in a fault state before the hook is released, it will immediately reset the fault and start automatically. During the entire hook release response period, all faults except the inverter hardware fault (including the emergency stop signal) will be shielded to ensure that the hook release response has the highest priority. After that, the load is controlled to hover at zero speed and slowly lowered alternately, so that the load can be controlled to fall slowly and slowly, reminding the operator that the load is being lowered in a controllable manner. Due to the brake failure, the emergency stop signal will no longer be responded to during the entire lowering period.
[0036] In one example, the control method further includes:
[0037] During the control of the load lowering, if an operation instruction from an operator is received, the execution of the load lowering is interrupted.
[0038] Specifically, during the period when the load is slowly lowered, the operator can manually interrupt the execution of the slow lowering, and when the operation is completed and the machine is stopped again, the machine will be stopped by braking according to the normal braking control sequence mentioned above.
[0039] S13, during the control of lowering the load, determining whether the load has landed;
[0040] In one example, during the control of lowering the load, determining whether the load has landed includes:
[0041] During the control of lowering the load, if the inverter output torque is lower than a preset torque threshold, it is determined that the load has landed.
[0042] In a specific implementation, if the inverter output torque is lower than a preset torque threshold, it is determined that the load has landed, including:
[0043] If the inverter output torque is lower than the preset torque threshold for a continuous period of time that reaches a preset period of time, it is determined that the load has landed.
[0044] The following combination Figure 3 To explain:
[0045] When the normal lifting equipment is lowered at a constant speed with a load, the motor works in the fourth quadrant, in a reverse power generation state, the motor speed is negative, the torque is positive, the rope tension F and its own gravity G are balanced, and the load is controlled to be lowered slowly at a constant speed. Once the load falls to the ground, the rope slack F quickly becomes 0, the gravity G on the load and the ground support force N are balanced, and the motor output torque will also decrease rapidly. If the gravity of the rope alone cannot overcome the friction to maintain the motor to continue to run at the current frequency, the motor will quickly switch to the third quadrant to work, in an electric state, the speed continues to remain negative, and the output negative torque is used to overcome the friction and continue to maintain the load lowering speed. Based on this feature, the output torque during no-load lowering can be tested in advance and used as a judgment threshold, that is, a preset torque threshold. Hook slip trigger, when the inverter controls the load to descend at a constant speed, the torque change is detected. If the output torque is less than or equal to the threshold and maintained for a fixed period of time, it can be determined that the load has fallen.
[0046] S14: If the load has landed, control the brake device to brake and stop the machine.
[0047] In one example, after controlling the brake device to brake and shut down, the method further includes:
[0048] After the inverter is shut down and before the next start-up, the brake device is tested; if the brake device is abnormal, the brake device is prohibited from releasing and restarting the inverter until the brake device is repaired and normal.
[0049] The step of testing the brake device after the inverter is shut down and before the next startup includes:
[0050] After the inverter is shut down and before the next startup, the brake device is detected after a set time; wherein, the operator is allowed to perform temporary operation within the set time to adjust the position of the load.
[0051] Specifically, after the load falls to the ground, the operator can be allowed to use it temporarily within a certain period of time; specifically, during this time, the brake device detection can be skipped, allowing the operator to temporarily operate and adjust the load to a suitable position. The timing starts after the shutdown, and after the delay, the hook slipping protection fault is reported to remind the operator. After the fault is reported, when the operator gives the operation command to start again, the change of the encoder pulse count value will be judged at the same time during the torque verification stage. Since it is in the brake state at this time, if the encoder pulse count value changes before the torque verification is completed, it means that the brake device is not secure and there is a risk of hook slipping. At this time, the inverter will report a fault to terminate the inverter startup, that is, it is prohibited to run again until the brake device is repaired, to avoid the safety risk caused by the worker's operation again when the brake is abnormal.
[0052] Through the above implementation strategy, it can be ensured that the load can land safely after a hook slip accident occurs, the equipment can be shut down reliably and prohibited from running, which greatly reduces the safety risk after the load slips.
[0053] Another embodiment of the present application provides a frequency converter for a lifting mechanism, wherein the frequency converter for the lifting mechanism includes a control unit, wherein the control unit includes a memory and a processor, wherein the memory is configured to store a computer program, and when the processor executes the computer program, the frequency converter control method for the lifting mechanism described in the above embodiment is implemented.
[0054] It should be noted that in the above description, “higher than” may mean greater than or equal to, or only greater than; and “lower than” may mean less than or equal to, or only less than.
[0055] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working processes of the systems, devices and units described above can refer to the corresponding processes in the aforementioned method embodiments and will not be repeated here.
[0056] In the several embodiments provided in the present application, it should be understood that the disclosed systems, devices and methods can be implemented in other ways. For example, the device embodiments described above are only schematic. For example, the division of the units is only a logical function division. There may be other division methods in actual implementation, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be an indirect coupling or communication connection through some interfaces, devices or units, which can be electrical, mechanical or other forms.
[0057] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.
[0058] In addition, each functional unit in each embodiment of the present application may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit. The above-mentioned integrated unit may be implemented in the form of hardware or in the form of software functional units.
[0059] If the integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present application is essentially or the part that contributes to the prior art or all or part of the technical solution can be embodied in the form of a software product, and the computer software product is stored in a storage medium, including a number of instructions to enable a computer device (which can be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the method described in each embodiment of the present application. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), disk or optical disk and other media that can store program code.
[0060] As described above, the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application.
Claims
1. A frequency converter control method for a lifting mechanism, wherein the lifting mechanism further comprises an encoder, a brake device and a lifting motor; characterized in that: The control method comprises: Determining whether a load hook slip failure occurs according to the pulse count value fed back by the encoder; If a load hook slip failure occurs, the system automatically starts to drive the lifting motor to brake the load and drives the lifting motor to control the load to be lowered; During the control of lowering the load, determining whether the load has landed; If the load has landed, the brake device is controlled to brake and stop the machine.
2. The control method according to claim 1, characterized in that: The step of judging whether the load slipping phenomenon occurs according to the pulse count value fed back by the encoder includes: During the period from the end of the operation of the inverter to the shutdown, or after the inverter is shut down and before the next startup, it is determined whether the load slip phenomenon occurs according to the pulse count value fed back by the encoder.
3. The control method according to claim 1, characterized in that: The lifting mechanism also includes an alarm module; The control method further comprises: If a load hook slip failure occurs, the alarm module is controlled to send out an alarm message.
4. The control method according to claim 1, characterized in that: The control method further comprises: If a load hook slip failure occurs, all faults except the inverter hardware failure are shielded; among them, all faults include emergency stop signals.
5. The control method according to claim 1, characterized in that: The control method further comprises: During the control of the load lowering, if an operation instruction from an operator is received, the execution of the load lowering is interrupted.
6. The control method according to claim 1, characterized in that: During the control of lowering the load, determining whether the load has landed includes: During the control of lowering the load, if the inverter output torque is lower than a preset torque threshold, it is determined that the load has landed.
7. The control method according to claim 6, characterized in that: If the inverter output torque is lower than the preset torque threshold, it is determined that the load has landed, including: If the inverter output torque is lower than the preset torque threshold for a continuous period of time that reaches a preset period of time, it is determined that the load has landed.
8. The control method according to claim 1, characterized in that: After controlling the brake device to brake and shut down, the method further includes: After the inverter is stopped and before the next start, the brake device is tested; If an abnormality occurs in the brake device, it is prohibited to release the brake device and restart the inverter until the brake device is repaired and returned to normal.
9. The control method according to claim 8, characterized in that: The step of testing the brake device after the inverter is stopped and before the inverter is started next time includes: After the inverter is shut down and before the next startup, the brake device is detected after a set time; wherein, the operator is allowed to temporarily operate within the set time to adjust the position of the load.
10. A frequency converter for a lifting mechanism, characterized in that: The frequency converter of the lifting mechanism includes a control unit, the control unit includes a memory and a processor, the memory is configured to store a computer program, and when the processor executes the computer program, it implements the frequency converter control method of the lifting mechanism described in any one of claims 1-9.