Electrification of the hoist

Abstract

The present invention describes a method for operating a cable drum of a hoist or winch for a crane or mobile crane, driven by one or more electric motors, which can be held in the holding or resting state by means of one or more brakes, wherein when a lift is stopped without setting down the load, the last applied torque of the electric motor(s) is stored before the brake(s) is activated and / or before the electric motor(s) are relieved.

Description

[0001] The invention relates to a crane or mobile crane, as well as a lifting device or a lifting winch for such a crane, which is controlled by one or more electric motors, and methods for operating these devices.

[0002] From DE 10 2011 007 663 A1, a lifting device and a method for operating the lifting device are known, which is designed as a transmission such that at least one transmission element performs a movement when a load is attached to the lifting device due to at least a component of the dead weight force and the weight force of the load, wherein the lifting device has a device for energy recuperation with which the kinetic energy generated during the movement is converted into electrical energy.

[0003] The following individual aspects of a procedure for operating a crane, as well as the design of a crane, can be implemented independently of each other, either individually or in combination with one or more of these aspects.

[0004] The invention generally comprises an electric drive for a hoist, winch, or cable drum of a crane, specifically a mobile crane, consisting of one or more electric motors and their control system. Electric crane winches offer many advantages, such as better controllability, higher efficiency, and improved safety compared to crane winches driven by other power sources such as hydraulics or internal combustion engines.

[0005] The hoist can be optionally combined with a brake, which can be actuated electrically, electromagnetically, hydraulically, pneumatically, or mechanically. When the brake is applied, the cable drum is held in place by the brake; that is, a motor driving the cable drum can be relieved of load or switched off when the brake is engaged, preventing any movement of the cable drum, for example, by the weight of a load suspended from the cable. The brake can be engaged when the hoist is stationary and can optionally also serve as a dynamic emergency brake, e.g., in the event of a malfunction.

[0006] In the following text, the term "lifting movement" should be understood to mean not only raising but also lowering a load. Generally, a lifting movement can be understood as a winch being driven by a motor or rotated in one direction or the opposite direction. Torque evaluation

[0007] According to one aspect, the invention relates to a method for operating a cable drum of a hoist or winch for a crane or mobile crane, driven by an electric motor, which can be held in a holding or resting state by means of a brake, wherein, when a lift is stopped without setting down the load, the last applied torque of the electric motor is stored before the brake is activated and / or before the electric motor is relieved of its load. When the lift is stopped without setting down the load, a control unit can store the last applied torque of the drive, e.g., directly as a measured torque or indirectly based on measured electrical performance data, such as motor current and / or motor voltage, in a memory before the brake is activated and the electric motor is relieved of its load.In the case of a constant motor voltage, it may be sufficient to use only the motor current, which is then directly proportional to the power, and thus also proportional to the generated motor torque. The control system therefore knows the holding torque required to hold the load, which the motor had to apply before the brake was activated.

[0008] For example, the torque applied by the motor can be continuously measured and stored directly or indirectly during motor operation, for example using motor data or performance data, whereby the torque should preferably be applied again by the motor at the time when the brake is activated, i.e., when a braking or holding function is effected, before or when the brake is released.

[0009] When a rotary movement of the lifting mechanism is requested again, a holding torque equal to the last applied torque of the electric motor can be generated at the electric motor, either during or before the brake is released, based on the stored torque, motor or power data, so that when the lifting movement is resumed the load can be moved or started as smoothly or jerk-free as possible.

[0010] Based on the stored information, for example, if a rotational movement of the hoist is requested again before the brake is released, a holding torque of the same magnitude – i.e., a torque calculated by the control system – can be generated at the electric motor. This allows for smooth starting or acceleration of the hoist when the brake is released, thus preventing the load from sagging.

[0011] Alternatively, the holding torque can be applied with a deliberate deviation of, for example, +10% or -10%, or any other deviation from the last applied torque of the electric motor at or before the brake is released. This may be necessary, for example, to prioritize or compensate for sagging (e.g., -5 mm), brief lifting (+5 mm), or jerking of the load, or to ensure the system safely handles a load that changes while the brake is engaged. High-frequency evaluation of engine data

[0012] By recording and high-frequency analysis of electrical performance data, such as current and voltage, and by recording and high-frequency analysis of the motor's rotational movement via a control system, detailed conclusions can be drawn about the behavior and operating status of the hoist. For example, a load being set down or a load speed that is too low compared to the rope speed can be detected, and slack in the rope (a phenomenon known as rope slippage) can be prevented.

[0013] Another aspect concerns a method for operating a cable drum driven by an electric motor in a hoist or winch for a crane or mobile crane. This method involves recording the electrical power data of the electric motor and / or operating data of the hoist during operation. Based on this recorded data, the behavior and / or operating state of the cable drum or winch is determined, and / or the electric motor is controlled. As mentioned above, data acquisition can be "high-frequency," meaning it can occur regularly at very short intervals, such as 500 kHz, 10 kHz, every millisecond, or every 10 ms. This allows for continuous or quasi-continuous power acquisition and storage.

[0014] Operating data for the hoist can include, for example, the rotational speed of the motor and the rope drum, the angular position of the motor and the rope drum, and / or the rope speed and / or the speed of the load. Since a reduction gear between the motor and the rope drum is usually used, it can be advantageous to record the operating data at the motor.

[0015] Electrical performance data for an electric motor can include, for example, the motor current and / or the motor voltage. As mentioned above, in the case of a constant voltage, it may be sufficient to record only the motor current as performance data.

[0016] If, for example, a decrease in the electrical power consumed by the electric motor is detected—for instance, a decrease of more than a predefined percentage, such as 1%, 3%, or 10% of the last measured power or average power over a predefined period, such as the last 1 second or the last 10 seconds—or if a decrease exceeding a predefined power reduction threshold is detected, the electric motor can be slowed down or stopped. This can be considered a safety measure, as there are normally no or only minor power fluctuations during continuous lifting operation. Therefore, if a larger power fluctuation, especially a significant power decrease as described above, is detected, it could indicate a fault or malfunction, such as a slack rope, since the load may have already been lowered, but the motor continues to run.Optionally, a warning signal can be issued to an operator. hoist rope winding

[0017] The design of mobile crane cable drums, with their multi-layered cable windings, necessitates changes in cable layer position when winding and unwinding the cable. A cable layer position change is a process in which a cable on a winch or drum with a multi-layered cable winding is deflected in the opposite direction upon reaching one drum wall and wound or unwound towards the opposite drum wall and onto a different layer. This means that when winding the cable, the cable is wound onto a higher layer with a larger winding radius (increasing torque), and when unwinding the cable, it is wound onto a lower layer with a smaller winding radius (decreasing torque). Due to the change in the direction of the cable winding during the cable layer position change, there are points from layer to layer where the cable "crosses over" itself (cable crossings).The rope crosses the profile of the layer below it (unless the first layer is reached), resulting in a locally changing winding radius. Therefore, the winding radius of the hoist rope (i.e., the distance from the rope's center to the drum's center of rotation) during a full revolution of the hoist is not constant, even within a single layer.

[0018] Winches can be operated with a constant winding pitch ( Fig. 2 a), with a change of winding ( Fig. 2 b), or several changes of winding ( Fig. 2 c) must be carried out. The type of execution influences the position and angle of the rope crossings and thus the profile of the winding radius changes.

[0019] Therefore, when a constant load acts on the hoist, the torque output varies from rope layer to rope layer, and even within a single rope layer. These torque variations can also be determined through high-frequency analysis of the recorded power and rotational frequency data. Rope layer changes, rope crossings, and changes in the number of turns during winding and unwinding can thus be detected. This allows for adjustments to the torque and speed of the hoist drive to maintain a constant lifting speed. Furthermore, the control system can calculate the length of the unwound rope (and thus the position of the suspended load), and this data can be used to draw conclusions about potential damage to the rope or the wear condition of the system.

[0020] The control system can monitor the lifting torque and the load calculated by the safety system or Rated Capacity Limiter (RCL). When the load is constant, it is possible to measure the rope wraps based on their "torque" signature. By comparing baseline torque signatures with encoder position data, the system can warn the crane operator if the torque signature deviates significantly from previously recorded values. This can warn the user of irregular winding of the hoist before the hoist rope is damaged.

[0021] One aspect concerns a method for operating a cable drum of a hoist or winch for a crane or mobile crane, driven by an electric motor. The electric motor is controlled in such a way that the winding state of the hoist cable on the drum is taken into account to achieve a constant lifting speed. For example, if the winding radius increases, the motor must rotate more slowly to maintain a constant cable speed. Conversely, if the winding radius decreases, the motor must rotate more quickly to maintain a constant cable speed.

[0022] The winding state of the hoist rope on the drum can specify the winding radius, which can vary and can be determined based on rope crossings, changes in rope layers, and / or changes in turns. These crossings, changes in rope layers, and / or changes in turns can be determined, for example, depending on the angular or rotational position of the drum and stored in a data logger. This makes it possible to evaluate the data over time and generate a hoist rope winding state profile for use as a reference. This assumes that the winding of a rope on a drum is reproducible, meaning it is the same or essentially the same for every winding or unwinding process. Alternatively or additionally, the winding radius can also be measured directly or determined from hoist data or drum data.The winding radius can be defined as the distance of the lifting rope running tangentially away from the pulley, or the distance of the lifting rope's center axis at the point where it runs away from the drum to the pulley's center point. For example, the winding radius increases with each layer of winding on a rewinding pulley.

[0023] The torque and / or rotational speed of the electric motor can be adjusted by a controller based on known and stored rope winding data, i.e., rope crossings and / or rope layer changes and / or winding changes, to achieve a constant rope speed or lifting speed. Furthermore, the data storage can be connected to an external data storage system that remotely records and analyzes the signatures of many similar hoists. This information can then be used to analyze the local signature of the hoist control system, thus significantly increasing the data available for evaluating the locally available signature.

[0024] The power and / or rotational frequency data of the operated electric motor can be determined in order to identify and / or compensate for torque deviations or torque fluctuations.

[0025] Rope layer changes and / or winding changes and / or rope crossings during winding or unwinding of the rope can be detected and this information can be stored in a memory to which the motor control has access, whereby this information can be used for later control of the electric motor.

[0026] For example, rope layer changes and / or winding changes and / or rope crossings can be stored in memory as a function of the rope length or the total rotation angle of the rope drum, where the total rotation angle can be defined as (number of complete windings * 360°) + current rotation angle. Recuperation

[0027] When the rotation is slowed and / or the load is lowered in a controlled manner, the electric motor must generate an opposing torque and can act as a generator. The resulting or generated electrical energy can be used immediately, for example, to meet an energy demand elsewhere, and / or it can be stored in an energy storage device (preferably a battery) for later use (recuperation). Optionally, this energy can also be converted into, for example, heat energy. Recuperation can thus increase efficiency. Recuperation is possible in all the applications described above.

[0028] In general, the invention relates to one of the methods described above, or several of these methods in combination, as well as a lifting device, a hoist, or a crane with a control system and corresponding elements suitable for carrying out this or these methods. Aspects of the invention are explained below with reference to exemplary embodiments. The following are shown: Fig. 1. A schematic representation of a lifting mechanism for a crane with an electric motor and control system; and Fig. 2a to 2c several groove constructions with the corresponding sectional view of the rope stacking they produce.

[0029] Fig. Figure 1 schematically shows a cable drum 3 of a hoist, which is driven by an electric motor 8 connected to the cable drum 3. A torque, or more generally a force, can be transmitted both from the electric motor 8 to the cable drum 3, for example to drive or hold the cable drum 3, and from the cable drum 3 to the electric motor 8, for example to generate energy or recuperate it when lowering the load L. The motor 8 is connected to a control unit 10, which is linked to a storage device 11, and can be controlled via the control unit 10, thus initiating a lifting, holding, or lowering operation of the cable drum 3. A crane operator (not shown) can provide the control unit 10 with corresponding control signals.The electric motor 8 is schematically shown with one or more sensors 12a, which can generally detect the operating state of the motor 8, such as its angular position or power data. This data can also be stored in the controller 10 itself and optionally in the memory 11. The cable drum 3 is equipped with one or more sensors 12b, which can measure or determine operating data of the cable drum 3, such as its angular position and / or winding radius. This data can also be stored in the memory 11. The cable drum 3 is equipped with a locking brake 9, which can be used to lock the cable drum 3. The brake 9 is controlled by the controller 10, i.e., moved into a locking or release position. A cable 6 is wound onto the cable drum 3, on which, as in [reference missing], [further details missing]. Fig. Figure 1 shows a load L suspended from the end opposite the cable drum 3. The cable 6 runs from the cable drum 3 to the tip of the telescopic boom 7 and there, via a deflection pulley, to the load L. The control unit 10 can be used to execute the procedures described above, for example, measuring the holding torque of the electric motor 8 before the brake 9 is engaged and reapplying it before the brake 9 is released after the motor 8 has been temporarily switched off, in order to prevent the suspended load L from sagging momentarily during the start-up process.For example, the electric motor 8 can also be controlled by the controller 10 in such a way that the load L is raised or lowered at a constant speed, whereby the winding radius measured by a sensor 12b and changing during operation causes the electric motor 8 to counteract this in the controller 10, i.e. rotating slightly slower when the winding radius becomes slightly larger or rotating faster when the winding radius becomes slightly smaller.

[0030] Fig. Figure 2 shows three different groove designs with the corresponding sectional view of the rope stacking they produce. These show: Fig. 2a - spiral grooves with constant pitch Fig. 2b - parallel grooves with simple slanted transition (turn change) Fig. 2c - parallel grooves with double slanted transition (turn change) 1 slanted grooves 2 parallel grooves 3 drum bodies of the winch 4 inlet / outlet wedges 5 Rope crossing zone φ Wrap angle in the crossing zone

[0031] As in the Fig. As shown in Figures 2a to 2c, the position of the crossing zones corresponds to the angular position of the grooves in the drum. The crossing zones vary depending on the position. In this way, the signal from a hoist position sensor (encoder) and the slight change in torque (with a constant load on the rope) can be related to the wound position. Changes in radius also occur when the rope changes direction at the drum walls.

[0032] Fig. Figure 3 shows the difference Δr i between winding radius rw i with parallel rope winding and r kbi at the maximum of the rope crossing area. 3 - Rope drum with rope grooves 6 - Lifting rope r w1 - Winding radius 1st layer r w2 - Winding radius of the 2nd layer, rope in the area parallel to the 1st layer r w3 - Winding radius of the 3rd layer, rope in the area parallel to the 2nd layer r kb1 - Winding radius 1st layer, r kb1 = r w1 r kb2 - Winding radius of the 2nd layer, maximum in the area of ​​the rope crossing with the 1st layer. r kb3 - Winding radius of the 3rd layer, maximum in the area of ​​the rope crossing with the 2nd layer.

[0033] The difference Δr w2 or Δr w3The increase in the winding radius at the rope crossing point can be detected, for example, by high-frequency analysis of the electrical power data of the electric motor driving the winch, i.e., 500,000 analyses per second. This reveals, for instance, that the power consumption of the electric motor increases at the rope crossing point because the torque is higher there. It can then be checked, for example, using previously recorded data, whether this electrically detected increase in power consumption corresponds to the previously stored profile of the winch (winch signature of the winding process) and is therefore expected (i.e., normal operation).If a change in the electrical performance data of the electric motor driving the winch, as expected according to the stored profile of the winch (winch signature of the winding process), fails to occur, or if an unexpected change occurs, this may indicate other causes or malfunctions, and may, for example, be displayed as a warning and / or automatically trigger a safety reaction, such as switching off the electric motor and / or locking the winch. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2011 007 663 A1

[0002]

Claims

[1] Method for operating a cable drum (3) of a hoist or winch for a crane or mobile crane, driven by one or more electric motors (8), which can be held in the holding or resting state by means of one or more brakes (9), wherein when stopping a lift without setting down the load the last applied torque of the electric motor(s) (8) is stored before the brake(s) (9) is activated and / or before the electric motor(s) (8) is relieved. [2] Method according to claim 1, wherein the last applied torque of the electric motor (8) is stored as electrical performance data, i.e. current and / or voltage, in a memory (11). [3] Method according to one of the preceding claims, wherein, upon a renewed request for a rotary movement of the lifting mechanism before releasing the brake (9), a holding torque equal to the last applied torque of the electric motor (8) is generated on the electric motor (8) based on the stored torque or power data. [4] Method for operating a rope drum (3) of a hoist or winch for a crane or mobile crane driven by an electric motor (8), wherein the electrical power data of the electric motor (8) and / or operating data of the hoist are recorded during operation, e.g. by high-frequency evaluation, and based on the recorded electrical power data of the electric motor (8) and / or operating data of the hoist, the behavior and / or the operating state of the rope drum (3) or the winch of the hoist is determined and / or the electric motor (8) is controlled, whereby, for example, an irregular operating state, such as a damaged rope or slippage of the rope without or with too little load (“slack rope”), can be detected. [5] Method according to the preceding claim, wherein the operating data of the hoist are the rotational speed of the rope drum (3) and / or the angular position of the rope drum (3) and / or the rope speed and / or the speed of the load. [6] Method according to one of the two preceding claims, wherein the motor current and / or the motor voltage are recorded as electrical performance data of the electric motor (8). [7] Method according to one of the three preceding claims, wherein, in the event of a decrease in the electrical power consumed by the operated electric motor (8) by more than a predetermined percentage or power reduction limit value, the electric motor (8) is slowed down or stopped. [8] Method for operating a cable drum (3) of a hoist or winch for a crane or mobile crane driven by an electric motor (8), wherein the electric motor (8) is controlled in such a way that the winding state of the hoist cable (6) on the cable drum (3) is taken into account in such a way that a constant speed of the lifting movement is achieved. [9] Method according to the preceding claim, wherein the winding state of the lifting rope (6) on the rope drum (3) specifies the winding radius, which can be determined by means of rope crossings and / or rope layer changes and / or winding changes. [10] Method according to one of the two preceding claims, wherein the torque and / or rotational speed of the electric motor (8) is adjusted to achieve a constant rope speed or speed of the lifting movement. [11] Method according to one of the preceding three claims, wherein the power and / or rotational frequency data of the operated electric motor (8) are determined in order to detect and / or compensate for torque deviations or torque fluctuations. [12] Method according to one of the four preceding claims, wherein rope layer changes and / or winding changes are detected during the winding or unwinding of the rope (6) and this information is stored in a memory (11), wherein this information is used to control the electric motor (8). [13] Method according to the preceding claim, wherein rope position changes and / or winding changes are stored as a function of the rope length or the total rotation angle of the rope drum (3). [14] Method according to one of the preceding claims, wherein an electric motor (8) of the lifting mechanism generates electricity in generator mode. [15] Method according to one of the preceding claims, wherein a high-frequency evaluation of one or more motors is carried out to, for example, determine and / or verify a winch signature and / or compare it with stored data. [16] Crane with a hoist comprising a hoist winch with which a suspended load can be lifted or lowered, wherein the hoist winch has a rope drum (3) which can be driven by an electric motor (8) to perform a lifting or lowering operation, and with a control (10) which is connected to the electric motor (8) of the hoist and controls it according to one of the preceding claims.

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