EP3409636B1 - Method for damping torsional vibrations of a load-bearing element of a lifting device - Google Patents

Description

The present invention relates to a method for damping a torsional vibration about a vertical axis of a load-bearing element of a lifting device with a damping controller with at least one controller parameter, the load-bearing element being connected to at least three holding elements with a supporting element of the lifting device and the length of at least one holding element between the load-bearing element and the supporting element an actuator acting on the at least one holding element is adjusted by the damping controller.

Lifting devices, in particular cranes, are available in many different designs and are used in many different areas of application. For example, there are tower cranes that are mainly used for building and civil engineering, or there are mobile cranes, for example for the assembly of wind turbines. Bridge cranes are used, for example, as hall cranes in factory halls and portal cranes, for example, for the manipulation of transport containers at transshipment locations for intermodal goods handling, such as in ports for the handling of ships by rail or truck or at freight stations for handling from the train to the truck or vice versa . The goods for transport are mainly stored in standardized containers, so-called ISO containers, which are equally suitable for transport in the three transport modes road, rail, water. The structure and mode of operation of a gantry crane is well known and is for example in the US 2007/0289931 A1 described using a "ship-to-shore crane". The crane has a supporting structure or a portal on which a boom is arranged. The portal with wheels, for example, is movably arranged on a track and can be moved in one direction. The boom is firmly connected to the portal and a trolley movable along the boom is arranged on the boom. To hold a cargo, for example an ISO container, the trolley is connected to a load-bearing element, a so-called spreader, by means of four ropes. To pick up and manipulate a container, the spreader can be raised or lowered using winches, here using two winches for two ropes each. The spreader can also be adapted to containers of different sizes.

In order to increase the economic efficiency of logistics processes, among other things, very fast goods handling is required, ie for example very rapid loading and unloading processes for cargo ships and correspondingly fast movements of the load-bearing elements and the portal cranes as a whole. However, such rapid movements can lead to undesirable vibrations of the load-bearing element building up, which in turn delay the manipulation process, since the containers are not precisely on the intended Place can be placed. In particular, torsional vibrations of the load-bearing element, that is, vibrations about the vertical axis, are disruptive, since these are difficult to compensate for by the crane operator using conventional cranes. Such torsional vibrations can also be caused or increased by, for example, an uneven loading of the container or by wind.

The US 2007/0289931 A1 mentions, among other things, the problem of oscillations around the vertical axis (skew), but does not propose a satisfactory solution. To measure the deviations of the load-bearing element from a target position and to measure the distance of the load-bearing element from the trolley, a target object consisting of lighting elements is provided on the load-bearing element and a corresponding CCD camera is provided on the trolley. This enables angular deviations around the vertical axis (skew), the longitudinal axis (list) and the transverse axis (trim) to be determined. To compensate for the deviations, an actuator is provided for each tether with which the length of the tether can be changed. Depending on the deviation (trim, list or skew), the actuators are controlled in different ways, so that the individual tethers are shortened or lengthened and the corresponding error is compensated. The disadvantage here is that the method only suggests compensation of angular errors without taking into account the dynamics of a torsional vibration. This means that no torsional vibrations can be compensated for.

The DE 102010054502 A1 proposes to compensate for torsional vibrations of the load-bearing element to arrange a slewing gear between the load-bearing element and the tether. However, this is very complex and therefore expensive, and the payload is also reduced by the weight of the slewing gear.

The EP 2 878 566 A1 shows a method for torsional vibration damping of overhead cranes according to the preamble of claim 1, wherein a load is suspended from the crane by means of four ropes and the length of the ropes can be changed by means of adjusting devices. The angle of rotation of the load or a time derivative thereof is measured by means of a detection device and setpoints for the adjusting devices are calculated using a mathematical model, taking into account the geometry of the crane suspension, in order to dampen the torsional vibration.

In the publication Quang Hieu Ngo et. al., 2009, Skew Control of a quay container crane, in: Journal of Mechanical Science and Technology 23, 2009 a control method for compensating torsional vibrations of the load-bearing element of a gantry crane is proposed. The analog is the same US 2007/0289931 A1 an actuator on each tether arranged to change the rope length and a lighting element is arranged on the load-bearing element, which cooperates with a CCD camera arranged on the trolley to measure the angular deviation of the load-bearing element. A mathematical model and an "input-shaping" control method are used to dampen the torsional vibration of the load-bearing element. The input shaping method is a kind of pilot control with which it is possible to adjust the angle of rotation of the load-bearing element. It is not possible to dampen an existing torsional vibration. Another disadvantage is that the mathematical model used in the input shaping process has to be very precise, since there is no way to compensate for parameter deviations.

Accordingly, it is the object of the invention to eliminate the disadvantages of the prior art, in particular to improve the operation of a lifting device, an improved method for damping torsional vibrations of a load-bearing element of the lifting device, which is independent of geometric or mechanical boundary conditions of the lifting device.

According to the invention, the object is achieved in that the load-bearing element is excited to a torsional vibration at a specific lifting height of the load-bearing element, wherein at least one actual angle of rotation of the load-bearing element about the vertical axis and an actual actuator position are recorded, and thus model parameters of the torsional vibration model of the load-bearing element at the given lifting height be identified using an identification method. With this simple method it is possible to dampen a torsional vibration of a load-bearing element at any lifting height without the damping regulator's control parameter or parameters having to be set manually. This significantly simplifies the operation of the lifting device or the rapid movement and precise positioning of a load, which saves time and thus increases productivity. Using a suitable identification method, unknown model parameters of a selected torsional vibration model can be determined, as a result of which an unknown vibration behavior of the load-bearing element can be determined and used for damping the torsional vibration.

The at least one actuator is advantageously actuated hydraulically or electrically, as a result of which standard components such as hydraulic cylinders or electric motors can be used and an existing energy supply system can be used.

If at least four holding elements are provided between the load-bearing element and the carrying element, larger loads can be manipulated.

It is advantageous if at least two actuators are provided, in particular one actuator per holding element. In this way, redundancy of the torsional vibration damping can be realized on the one hand, whereby the reliability can be increased. On the other hand, smaller actuators with lower inertia can be used, which means that the response time of the damping control can be reduced and the control quality can be increased.

The lifting height is advantageously measured by means of a camera system arranged on the carrying element or on the load-bearing element or by means of a lifting drive of the lifting device. This enables the lifting height to be recorded very precisely and in a simple manner.

The angle of rotation of the load-bearing element is preferably measured by means of a camera system arranged on the support element or on the load-bearing element. With this simple method, the angle of rotation of the load-bearing element can be determined very precisely. A camera system is also relatively easy to retrofit on an existing lifting device.

According to a preferred embodiment, the torsional vibration model is a second order differential equation with at least three model parameters, in particular with a dynamic parameter δ, a damping parameter ξ and a section gain parameter i _β . The mathematical modeling of the torsional vibration system using a second order differential equation creates a simple but sufficiently accurate representation of the real torsional vibration.

It is advantageous if the identification method is a mathematical method, in particular an online least-square method. With this common mathematical method, model parameters can be determined easily and with sufficient accuracy.

It is advantageous if a state controller with preferably five controller parameters K _I , K ₁ , K ₂ , K _FF , K _{P is} used as the damping controller. This creates a fast and stable damping controller with high control quality. An integrated pre-control (controller parameter K _FF ) improves the guiding behavior and an integrator (controller parameter K _I ) achieves steady-state accuracy or model uncertainties can be compensated for.

_{Is intended} in a preferred embodiment the damping controller is a target rotation angle given the load receiving member and the damping controller regulates these target rotation angle within a predetermined angular range, in particular in an angular range from -10 ° ≤ β ≤ + 10 °. In this way, a desired rotation of the load-bearing element can be achieved, whereby loads such as containers can also be positioned on targets that are not exactly aligned, such as inclined trucks.

An anti-wind-up protection is advantageously integrated in the damping controller, whereby the damping controller is given actuator restrictions of the at least one actuator, in particular a maximum / minimum permissible actuator position s _perm , a maximum / minimum permissible actuator speed v _perm and a maximum / minimum permissible actuator acceleration a _{perm of} the actuator. This so-called anti-wind-up protection prevents impermissibly high manipulated variables of the at least one actuator, which could lead to destabilization of the damping controller.

• Fig.1 den grundsätzlichen Aufbau einer Hebeeinrichtung anhand eines Containerkrans,
• Fig.2a und 2b ein Lastaufnahmeelement inklusive Last zur Darstellung einer Drehschwingung,
• Fig.3 einen Ausschnitt einer schematischen Hebeeinrichtung,
• Fig.4 eine Reglerstruktur eines Dämpfungsreglers,
• Fig. 5 eine Zustandsschätzeinheit.

The subject invention is described below with reference to the Figures 1 to 4 explained in more detail, which show exemplary, schematic and non-limiting advantageous embodiments of the invention. It shows

• Fig. 1 the basic structure of a lifting device using a container crane,
• 2a and 2b a load-bearing element including a load to represent a torsional vibration,
• Fig. 3 a section of a schematic lifting device,
• Fig. 4 a controller structure of a damping controller,
• Fig. 5 a state estimation unit.

Fig. 1 shows a lifting device 1 by way of example using a schematic container crane 2, which is used, for example, for loading and unloading ships in a port. A container crane 2 usually has a supporting structure 3, which is arranged either fixedly or movably on the floor. In the case of a movable arrangement, the supporting structure 3 can, for example, be arranged to be movable on rails in the Y direction, as schematically in FIG Fig. 1 is shown. Due to this degree of freedom in the Y direction, the container crane 2 can be used flexibly locally. The supporting structure 3 has a cantilever 4 which is fixedly connected to the supporting structure 3. A support element 5 is usually arranged on this boom 4 and can be moved in the longitudinal direction of the boom 4, that is to say in the X direction in the example shown, for example a support element 5 can be mounted in guides by means of rollers. The carrying element 5 is usually connected to a load-bearing element 7 for holding a load 8 by means of holding elements 6. In the case of a container crane 2, the load 8 is usually a container 9, in most cases an ISO container with a length of 20, 40 or 45 feet and a width of 8 feet. However, there are also load-bearing elements 7 which are suitable for simultaneously holding two containers 9 next to one another (so-called dual spreaders). The type and design of the load-bearing element 7 is, however, no longer relevant for the damping method according to the invention; any embodiments of the load-bearing element 7 can be used. The holding elements 6 are usually designed as ropes, with four holding elements 6 being arranged on the carrying element 5 in most cases, but more or fewer holding elements 6 can also be provided, but at least three holding elements 6. For receiving a load 8, such as one Container 9, the lifting height l _H between the support element 5 and the load-bearing element 7 by means of a lifting drive 10 (see Fig. 3 ) adjustable, as in Fig. 1 shown eg in the Z direction. If the holding elements 6 are designed as ropes, the lifting height 1 _{H is} usually adjusted by means of one or more winches 10a, 10b, as schematically in FIG Fig. 3 is shown. In order to manipulate loads 8 or containers 9, the lifting device 1 or the container crane 2 can therefore be moved in the direction of three axes. Due to fast movements, uneven loading of the container 9 or wind influences, it can happen that on the holding elements 6 arranged load-bearing element 7 with the container 9 arranged thereon is excited to vibrate, as follows based on the 2a and 2b is shown.

Fig.2a shows schematically a support element 5, on which a load-bearing element 7 including load 8 is arranged by means of four holding elements 6. The coordinate system shows the degrees of freedom of the load-bearing element 7. The straight double arrows symbolize the possible directions of movement of the load-bearing element 7, the movement in the Y direction in the example shown being effected by a movement of the entire lifting device 1 and the movement in the X direction by movement of the support element 5 on the boom 4 (lifting device 1 and boom 4 in Fig. 1 a not shown) and the movement in the Z direction by changing the lifting height l _H by means of the holding elements 6 and a lifting drive 10 (not shown). The curved double arrows symbolize the possible rotations of the load-bearing element 7 about the respective axis. Rotations about the X-axis or the Y-axis can be compensated for relatively easily by the user of the lifting device 1 or the container crane 2 and are not described in more detail here. A twist around the Z axis (i.e. around the vertical axis) as in Fig. 2b is, as described in the beginning, very disruptive, since in particular a torsional vibration of the load-bearing element 7 about the Z-axis would make positioning of a load 8 at a certain location, such as, for example, on the loading surface of a truck or a railway wagon, more difficult or delayed.

According to the invention, a method is therefore provided with which such a torsional vibration of a load-bearing element 7 about the vertical axis can be damped simply and quickly, so that rapid movements of the load-bearing element 7 with a load 8 arranged thereon are made possible, which should contribute to an increase in the efficiency of goods manipulation. A detailed description of the method is given below using the Fig. 3 and Fig. 4 described.

Of course, the described embodiment of the lifting device 1 as a container crane 2 according to the Fig.1-Fig.3 to be understood only as an example. The lifting device 1 can also be designed in any other way for the application of the method according to the invention, for example as an indoor crane, tower crane, mobile crane, etc. It is only important that the basic function of the lifting device 1 and that the lifting device 1 has the essential components for carrying out the damping method according to the invention, as described below.

In Fig. 3 The essential components of a lifting device 1 are shown, here using the components of a container crane 2. The parts essential for the invention are shown. The structure and functioning of such cranes have already been described, are well known and therefore do not need to be explained in more detail.

According to a preferred embodiment of the invention, between the support element 5 (in Fig. 3 schematically shown in dashed lines) and load-bearing element 7 four holding elements 6a, 6b, 6c, 6d arranged, which can be designed, for example, as high-strength ropes, in particular as steel ropes. A lifting drive 10 is provided for lifting and lowering the load-bearing element 7 in the Z direction, that is to say for adjusting the lifting height l _H. In the example according to Fig. 3 the lifting drive 10 is implemented by cable winches 10a and 10b, two retaining elements 6a, 6c and 6b, 6d being wound onto each cable winch 10a, 10b. Of course, other forms of lifting drive are also conceivable. To carry out the method according to the invention, at least one actuator 11a, 11b, 11c, 11d for changing the length of the holding element 6 is provided on at least one holding element 6a, 6b, 6c, 6d. However, an actuator 11a, 11b, 11c, 11d is advantageously provided on each holding element 6a, 6b, 6c, 6d. Preferably as in Fig. 3 four holding elements 6a, 6b, 6c, 6d, each with an actuator 11a, 11b, 11c, 11d, are arranged on the lifting device 1.

With a linear actuator 10 as in Fig. 3 shown, the holding elements 6a, 6b, 6c, 6d are guided over deflection rollers which are arranged on the load-bearing element 7. The respective free end of the holding elements 6a, 6b, 6c, 6d is fixed at a stationary holding point, for example on the carrying element 5. In this embodiment, an actuator 11a, 11b, 11c, 11d is preferably fixed at a stationary holding point, for example on the carrying element 5, and the free end of the holding elements 6a, 6b, 6c, 6d on the actuator 11a, 11b, 11c, 11d. The length of a holding element 6a, 6b, 6c, 6d can thus be adjusted by adjusting the actuator 11a, 11b, 11c, 11d, which also adjusts the distance between the carrying element 5 and the load-bearing element 7.

An actuator 11a, 11b, 11c, 11d can be controlled by a damping controller 12 to change the length of the corresponding holding element 6a, 6b, 6c, 6d between the carrying element 5 and the load-bearing element 7, preferably the actuator 11a, 11b, 11c, 11d at least one target actuator position s _intended or desired actuator velocity v _{is to} be determined. For damping control, at least one actual actuator position s _ist of at least one actuator 11a, 11b, 11c, 11d can be detected by damping controller 12 (damping controller 12 in Fig. 3 not shown). The damping controller 12 can be designed, for example, as a separate component in the form of hardware and / or software or can also be implemented in an existing crane controller. The at least one actuator 11a, 11b, 11c, 11d can, as will be described in detail later, be controlled by the damping controller 12 in such a way that by changing the actuator position and / or actuator speed on the one hand the load-bearing element 7 is excited to a torsional vibration (as in FIG Fig. 3 is symbolized by the double arrow) or on the other hand can be controlled so that a torsional vibration of the load-bearing element 7 is damped.

In the embodiment shown, the lengths of two diagonally opposite holding elements 6a, 6b between the support element 5 and the load-bearing element 7 are preferably increased by means of the corresponding actuators 11a, 11b and the lengths of the two other diagonally opposite holding elements 6c, 6d for stimulating or damping a torsional vibration reduced by means of the corresponding actuators 11c, 11d or vice versa. For example, only three holding elements 6 could also be arranged between the carrying element 5 and the load-bearing element 7 and only one actuator 11 for changing the length of one of the three holding elements 6. It is only important that the length is achieved by means of the at least one actuator 11a, 11b, 11c, 11d of at least one holding element 6a, 6b, 6c, 6d between the carrying element 5 and the load-bearing element 7 can be changed, so that a torsional vibration of the load-bearing element 7 about the vertical axis, in Fig. 3 around the Z axis, can be excited or damped.

An actuator 11a, 11b, 11c, 11d can be of any design, preferably a hydraulic or electrical embodiment is used which enables longitudinal adjustment. If, as in Fig. 3 shown, actuators 11a, 11b, 11c, 11d in the form of hydraulic cylinders are used, for example the energy for actuating the actuators 11a, 11b, 11c, 11d can be obtained from an existing hydraulic system. An actuator 11a, 11b, 11c, 11d can, however, also be designed, for example, as a cable winch and can be controlled electrically, wherein the actuation energy can be obtained from an existing power supply system. Other embodiments of an actuator 11a, 11b, 11c, 11d are also conceivable, which are suitable for changing the length of a holding element 6 between the carrying element 5 and the load-bearing element 7. In particular, an actuator 11a, 11b, 11c, 11d must master the forces to be expected during the lifting and lowering of a load 8. In order to bring about a required change in length of a holding element 6a, 6b, 6c, 6d under a certain load, an actuator 11a, 11b, 11c, 11d can also have an additional transmission gear, for example.

To carry out the damping method according to the invention, it is provided that at least one actual angle of rotation β _{ist of} the load-bearing element 7 about the Z-axis (or vertical axis) can be detected, for example a measuring device 14 in the form of a camera system can be provided, with one on the carrying element 5 Camera 14a and on the load-bearing element 7 a measuring element 14b cooperating with the camera 14a is arranged, or vice versa. The actual angle of rotation _β, however, can also be measured in other ways, for example by means of a gyro-sensor, it is important that a measurement signal for the actual rotational angle β _is present, which can be fed to the attenuator 12th It is also provided that the lifting height I _H between the support element 5 and the load-bearing element 7 can be recorded. For example, the lifting height l _H can be detected via the lifting drive 10, for example in the form of a position signal of a cable winch 10a, 10b available in the crane control. The lifting height l _H could also be obtained from the crane control. The lifting height l _H may be for example, but also detected by means of the measuring device 14, for example by means of a camera system that both the lifting height _H l and the actual rotational angle β _is able to detect. Such measuring devices 14 are known in the prior art, which is why they are not dealt with in more detail here.

The individual steps of the damping process are shown below using Fig. 4 described.

Fig. 4 shows a block diagram of a possible embodiment of the control structure according to the invention with a damping controller 12, which, as already explained, can either be implemented as a separate component or preferably in the control of the lifting device 1, and a controlled system 15, which is controlled by the damping controller 12. The damping controller 12 is designed as a state controller 13 in the exemplary embodiment shown. In principle, however, any other suitable controller can also be used. The controlled system 15 uses this Fig. 3 system is described. The command of the damping controller 12 is a target rotation angle β _to the load receiving member 7 and the manipulated variable is preferably a desired actuator position s _to the at least one actuator 11a, 11b, 11c, 11d. Alternatively, as the control variable, a target actuator speed v _to be used instead of the target actuator position s _will. As already described, the actual angle of rotation β act _can be recorded using a measuring device 14, for example by means of a camera system. As feedback, at least the detected actual angle of rotation β _{ist of} the load-bearing element 7 is fed to the damping controller 12 (and if the target actuator speed v _{soll is} used, the detected actual actuator position s _{ist is} also used as a manipulated variable). It would also be conceivable to additionally record an actual angular velocity β̇ and feed _it to the damping controller 12, which could further improve the damping control. Of course, if required, an actual angular velocity β̇ _ist or an actual angular acceleration β natürlich _ist can be derived from the recorded actual rotation angle β _ist , for example by derivation according to time.

verwendet werden, siehe dazu Fig. 5). Hierbei können beliebige geeignete und hinlänglich bekannte Beobachter, wie beispielsweise ein Kalman-Filter, verwendet werden, die Schätzwerte der benötigten Istgrößen ermittelt. Im nachfolgenden werden Schätzwerte gegebenenfalls mit ^ gekennzeichnet.The actual values required, ie in particular the actual rotational angle β _and optionally time derivatives thereof may be either measured directly or can be at least partially estimated in an observer. An advantage of the use of the estimated means of an observer actual values, eg actual rotational angle of β _is, is that this can be avoided 14 A possibly existing and undesirable for the damping control measurement noise of measured values of a measuring device. That's the Main reason why in a preferred embodiment Fig. 3 the actual angle of rotation β _{ist is} measured with a measuring device 14, but an estimated actual angle of rotation β̂ _{ist is still} used for the damping control (in addition, an estimated actual angular velocity could also be used ${\stackrel{.}{\widehat{\mathrm{\beta }}}}_{\mathrm{is}}$

can be used, see also Fig. 5 ). Any suitable and well-known observer, such as a Kalman filter, can be used to determine the estimated values of the required actual values. In the following, estimated values are marked with ^ if necessary.

However, it should be noted that the controller structure for the damping method according to the invention is secondary and in principle any suitable controller could be used. Depending on the implementation, the required actual variables are then supplied to the damping controller 12 as measured values or estimated values.

The damping controller 12 has at least one controller parameter, preferably five controller parameters. The characteristic of the control can be set by means of the controller parameter (s), e.g. Responsiveness, dynamics, overshoot, damping, etc., whereby one of the properties can be adjusted by means of a controller parameter. If several properties are to be influenced, a corresponding number of controller parameters is required. This enables the system behavior of the controlled system to be adapted.

mit dem Massenträgheitsmoment J_β der Last 8 samt dem Lastaufnahmeelement 7 und $\mathrm{\xi }=\frac{{\mathrm{d}}_{\mathrm{\beta }}}{{\mathrm{c}}_{\mathrm{\beta }}\left({\mathrm{l}}_{\mathrm{H}}\right)}$

mit einer Federkonstanten c_β und einer Dämpfungskonstante d_β des Schwingungssystems. Die Federkonstante c_β wird dabei von der Hubhöhe l_H abhängig modelliert.For the design of a suitable damping controller 12, the controlled system, i.e. the technical system to be controlled (e.g. as in Fig. 3 shown). In the present case, the torsional vibration behavior of the load-bearing element 7 about the Z-axis is mapped with a torsional vibration model, for example with a 2nd order differential equation in the form δβ̈ + ξβ̇ + β = i _β s. The three model parameters of this torsional vibration model are a dynamic parameter δ, a damping parameter ξ and a section gain parameter i _β , which are defined, for example, as $\mathrm{\delta }=\frac{{\mathrm{J}}_{\mathrm{\beta }}}{{\mathrm{c}}_{\mathrm{\beta }}\left({\mathrm{l}}_{\mathrm{H}}\right)}$

with the moment of inertia J _{β of} the load 8 together with the load-bearing element 7 and $\mathrm{\xi }=\frac{{\mathrm{d}}_{\mathrm{\beta }}}{{\mathrm{c}}_{\mathrm{\beta }}\left({\mathrm{l}}_{\mathrm{H}}\right)}$

with a spring constant c _β and a damping constant d _{β of} the vibration system. The spring constant c _β is modeled depending on the lifting height l _H.

It should be noted that this torsional vibration model is only to be understood as an example, and other torsional vibration models could be used that are capable of mapping or approximating the real torsional vibration.

The model parameters of the torsional vibration model, for example δ, ξ and i _β , can be known, but are generally unknown. Therefore, according to the invention, the model parameters are identified in a first step using an identification method. Such identification methods are well known, for example from Isermann, R.: Identification of dynamic systems, 2nd edition, Springer-Verlag, 1992 or Ljung, L .: System Identification: Theory for the User, 2nd edition, Prentice Hall, 2009 , which is why it is not discussed in more detail here. The identification methods have in common that the system to be identified is excited with an input function (for example a step function) and the output variable is recorded and compared with an output variable of the model. The model parameters are then varied in order to minimize the error between the measured output variable and the output variable calculated with the model. For any identification that may be necessary, the damping controller 12 can be used to excite the load-bearing element 7 with the load 8 arranged thereon at a specific lifting height l _H into a torsional vibration about the Z axis. For this purpose, a separate excitation controller can be implemented in the damping controller 12, for example in the form of a two-point controller. With the two-point regulator 11c, the at least one actuator 11a, 11b, 11d, for example in function of the actual rotation angle β _is controlled the load receiving member 7 at the maximum possible target actuator speed v _soll. This means that, for example, when the angle of rotation β _is ≥ 0 ° of the load-bearing element 7, the at least one actuator 11a, 11b, 11c, 11d is actuated with the maximum possible negative actuator speed v and when the angle of rotation β _is ≤ 0 ° of the load-bearing element 7 the at least an actuator 11a, 11b, 11c, 11d is controlled with the maximum possible positive actuator speed v. In the case of a configuration of the lifting device 1 according to Fig. 3 With four holding elements 6a, 6b, 6c, 6d and four actuators 11a, 11b, 11c, 11d interacting therewith, the excitation advantageously takes place in opposite directions, for example by actuating actuators 11a, 11b with the maximum possible positive actuator speed v and actuators 11c, 11d can be controlled with the maximum possible negative actuator speed v or vice versa. The excitation of the torsional vibration can take place at any but fixed lifting height l _{H of} the load-bearing element 7. The damping controller 12 determines the model parameters of the implemented torsional vibration model from the excited torsional vibration of the load bearing element 7 on the basis of the detected actual angle of rotation β _{ist of} the load bearing element 7 and the detected actual actuator position s _{ist of} the at least one actuator 11a, 11b, 11c, 11d by means of an identification method the specified lifting height l _H. In the case of the above torsional vibration model, the dynamic parameter δ and the damping parameter ξ are preferably determined first and then, preferably when the at least one actuator 11 a, 11b, 11c, 11d (actual actuator speed v _ist = 0), the section gain parameter i _β . As a method of identification According to one embodiment of the invention, a mathematical online least-square method is used to identify the model parameters, but it would also be conceivable to use other methods, for example offline least-square methods or optimization-based methods.

With the known (previously known or identified) model parameters, a damping controller 12 can now be designed for the torsional vibration model. A suitable controller structure is selected for this, for example a PID controller or a status controller. Each controller structure naturally has a number of controller parameters K _k , k≥1, which must be set using a controller design process so that a desired control behavior results. Such controller design methods are also well known and are therefore not described in detail. Examples include the frequency characteristic curve method, the root locus curve method, the controller design by means of pole specification and the Riccati method, although there are of course a wealth of other methods. However, the concrete controller structure and the specific controller design process are not important for the present invention. The desired control behavior can also be chosen essentially arbitrarily for the invention, taking into account stability criteria and other boundary conditions, of course. It is only essential for the invention that the controller parameters are determined as a function of the lifting height l _H. This can also be done in a variety of ways.

It would be conceivable to identify the model parameters for different lifting heights l _H and then to determine the controller parameters K _k for the different lifting heights. In this way, characteristic curves of the controller parameters K _k as a function of the lifting height l _H or characteristic maps as a function of the lifting height l _H and other variables, such as a moment of inertia J _β , can be built up. That would of course be very complex and not very practical. The controller parameters K _{k of} the damping controller 12 are therefore preferably specified as a formula-related relationship as a function of at least the lifting height l _H , and possibly other model parameters, for example K _k = f (l _H ) or K _k = f (l _H , .. .). This means that the controller parameters K _k only have to be defined for a lifting height I _H and can then simply be converted to other lifting heights l _H. From the formula, however, the controller parameters K _k can also be calculated offline for different lifting heights l _H and a characteristic curve or a characteristic map can be created therefrom, which is then used in a further sequence.

For the damping control, the controller parameters K _{k are} adapted to the current lifting height l _H in each time step of the control, for example by reading from a map or by calculation. The damping controller 12 then uses the adjusted controller parameters K _{k to determine} the manipulated variable that is set with the at least one actuator 11a, 11b, 11c, 11d in the respective time step. The controller parameters K _k are thus based on the current one Lifting height I _H adapted to optimally dampen torsional vibrations of the load-bearing element 7 at any lifting height I _H

In the case of a lifting device 1 with a load-bearing element 7 in particular, it is often customary to use different load-bearing elements 7 or load-bearing elements 7 which are adjustable in size for different loads 8, for example for containers of different sizes. This would of course have a direct impact on the moment of inertia J _β . It can therefore be provided that the above procedure is carried out for different load-bearing elements 7. This would give 7 different controller parameters K _k for different load-bearing elements.

The method according to the invention is explained below using a specific exemplary embodiment. A torsional vibration model in the form δβ̈ + ξβ̇ + β = i _β s as described above is assumed. The model parameters of the torsional vibration model, for example δ, ξ and i _β , are identified for a specific lifting height l _H as described. A state controller 13 is used as the controller structure for the damping controller 12 due to its high control quality or control performance, as in FIG Fig. 4 shown. Five parameters K _I , K _P , K ₁ , K ₂ , K _{FF are} provided as controller parameters K _k . For the design of the state controller 13, the system to be controlled is brought into a state space representation with the torsional vibration model as a controlled system 15, for example in the form $$\frac{d}{\mathit{German}}\left[\begin{array}{c}s\\ \beta \\ \dot{\beta }\\ e_{\beta }\end{array}\right]=\left[\begin{array}{cccc}0& 0& 0& 0\\ 0& 0& 1& 0\\ \frac{i_{\beta }}{\delta }& -\frac{1}{\delta }& -\frac{\xi }{\delta }& 0\\ 0& -1& 0& 0\end{array}\right]\left[\begin{array}{c}s\\ \beta \\ \dot{\beta }\\ e_{\beta }\end{array}\right]+\left[\begin{array}{c}1\\ 0\\ 0\\ 0\end{array}\right]v$$

und $\mathrm{\xi }=\frac{{\mathrm{d}}_{\mathrm{\beta }}}{{\mathrm{c}}_{\mathrm{\beta }}\left({\mathrm{l}}_{\mathrm{H}}\right)}$

steckt, wie folgt festgelegt. Dabei ist d₀ ist eine Dämpfungskonstante des geschlossenen Regelkreises, d.h. das beinahe ungedämpfte System wird mit Hilfe des Dämpfungsreglers 12 in ein gedämpftes überführt. Die Parameter ω_i bestimmen die Dynamik und das Ansprechverhalten des Regelkreises und sind an die Systemeigenschaften des zu identifizierenden Drehschwingungsmodells gebunden (der Index i ≥0 steht für die Anzahl der Parameter des Dämpfungsreglers, im ausgehführten Beispiel sind das die Paramter ω₀, ω₁, ω₂). Die Dämpfungskonstante d₀ und die Parameter ω_i sind vorzugsweise vorparametriert bzw. vorgegeben, können aber bei Bedarf vom Benutzer adaptiert werden. $$K_P=2d_0{\omega }_0+{\omega }_1+{\omega }_2$$

$$K_1=\frac{1}{i_{\beta }{K}_P}\left(\left(2d_0{\omega }_0{\omega }_1{\omega }_2+\left({\omega }_1+{\omega }_2\right){\omega }_0^2\right)\delta -K_P\right)$$

$$K_2=\frac{1}{i_{\beta }{K}_P}\left(\left(2d_0{\omega }_0\left({\omega }_1+{\omega }_2\right)+{\omega }_0^2+{\omega }_1{\omega }_2\right)\delta -1-{\mathit{\xi K}}_P\right)$$

$$K_I=\frac{1}{i_{\beta }{K}_P}\left({\omega }_0^2{\omega }_1{\omega }_2\delta \right)$$

$$K_{\mathit{FF}}=K_2+\frac{1}{i_{\beta }}$$

As states of the system, the actuator position s, the rotation angle β, beta is the angular velocity and deviation e _β between target rotation angle β _desired and actual rotational angle β _is used. The controller parameters K _k were a function of the lifting height l _H , which in the model parameters $\mathrm{\delta }=\frac{{\mathrm{J}}_{\mathrm{\beta }}}{{\mathrm{c}}_{\mathrm{\beta }}\left({\mathrm{l}}_{\mathrm{H}}\right)}$

and $\mathrm{\xi }=\frac{{\mathrm{d}}_{\mathrm{\beta }}}{{\mathrm{c}}_{\mathrm{\beta }}\left({\mathrm{l}}_{\mathrm{H}}\right)}$

is stuck as follows. Here, d ₀ is a damping constant of the closed control loop, ie the almost undamped system is converted into a damped one with the aid of the damping controller 12. The parameters ω _i determine the dynamics and the response behavior of the control loop and are linked to the system properties of the torsional vibration model to be identified (the index i ≥0 stands for the number of parameters of the damping controller, in the example shown these are the parameters ω ₀ , ω ₁ , ω ₂ ). The damping constant d ₀ and the parameters ω _i are preferred pre-parameterized or specified, but can be adapted by the user if required. $$K_P=\mathrm{2nd}{d}_0{\omega }_0+{\mathrm{<figure-callout\; id="1"\; label="\omega "\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">\omega </figure-callout>}}_1+{\omega }_{\mathrm{<figure-callout\; id="1"\; label="2nd\; K"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">2nd\; </figure-callout>}}$$

$$K_{}$$$${}_1=\frac{1}{i_{\beta }{K}_P}\left(\left(\mathrm{2nd}{d}_0{\omega }_0{\mathrm{<figure-callout\; id="1"\; label="\omega "\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">\omega </figure-callout>}}_1{\omega }_{\mathrm{2nd}}+\left({\mathrm{<figure-callout\; id="1"\; label="\omega "\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">\omega </figure-callout>}}_1+{\omega }_{\mathrm{2nd}}\right){\omega }_0^{\mathrm{2nd}}\right)\delta -K_P\right)$$

$$K_{\mathrm{2nd}}=\frac{1}{i_{\beta }{K}_P}\left(\left(\mathrm{2nd}{d}_0{\omega }_0\left({\mathrm{<figure-callout\; id="1"\; label="\omega "\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">\omega </figure-callout>}}_1+{\omega }_{\mathrm{2nd}}\right)+{\omega }_0^{\mathrm{2nd}}+{\mathrm{<figure-callout\; id="1"\; label="\omega "\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">\omega </figure-callout>}}_1{\omega }_{\mathrm{2nd}}\right)\delta -1-{\mathit{\xi K}}_P\right)$$

$$K_{\mathrm{I.}}=\frac{1}{i_{\beta }{K}_P}\left({\omega }_0^{\mathrm{<figure-callout\; id="1"\; label="2nd\; \omega "\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">2nd\; </figure-callout>}}{\omega }_{}{}_1{\omega }_{\mathrm{2nd}}\delta \right)$$

$$K_{\mathit{FF}}=K_{\mathrm{2nd}}+\frac{1}{i_{\beta }}$$

In the damping controller 12, the controller parameters of the state controller 13 are then calculated in each time step of the control on the basis of the current lifting height l _H and used as the basis for the control. The torsional vibration of the load-bearing element 7 can thus be effectively damped during a lifting process, because the damping controller 12 automatically adapts to the current lifting height l _H.

As a correcting variable of the control of the damping controller 12 may be an actuator to be set _to s or actuator speed v _soll for the at least one actuator 11a, 11b, 11c, 11d detect and output at an interface sixteenth For this purpose, the damping controller 12 receives the required actual values via an interface 17, for example the actual position s _{ist of} the at least one actuator 11a, 11b, 11c, 11d and the actual rotation angle β _{ist of} the load-bearing element 7. The time derivative of the actual rotation angle β _can be determined in the damping controller 12 or is also measured.

Die Zustandsschätzeinheit 20 kann beispielsweise als hinlänglich bekannter Kalman-Filter implementiert sein. Das Drehschwingungsmodell kann dazu auch in der Zustandsschätzeinheit 20 verwendet werden.Alternatively, a state estimation unit 20 ( Fig. 5 ), Be provided in the form of hardware and / or software that _is found in the load receiving member 7, estimated values for the required input of the variable attenuator 12 from measured actual values, for example of the actual rotational angle β, in this case, for example-an estimated actual rotational angle β _is and an estimated actual angular velocity ${\stackrel{.}{\widehat{\mathrm{\beta }}}}_{\mathrm{is}}.$

The state estimation unit 20 can be implemented, for example, as a well-known Kalman filter. The torsional vibration model can also be used in the state estimation unit 20 for this purpose.

The damping controller 12 is given a target rotation angle β _{soll of} the load-bearing element 7, which is adjusted by the damping controller 12. Normally, a target rotation angle is set _to β = 0, with which torsional vibrations are compensated by a defined zero position. However, a target rotation angle β target deviating therefrom can also _be specified be, with which the load-bearing element 7 is controlled by the damping controller 12 and independently of the lifting device 1 to this angle and thereby also torsional vibrations are damped by this angle. In this way, for example, a load 8, such as a container 9, can be rotated in a predetermined angular range and can thus also be unloaded, for example, onto a loading area of an inexactly positioned truck. No additional device for rotating the load-bearing element 7 about the vertical axis is required for this. Depending on the type and design of the lifting device 1 and its components, the damping controller 12 can set a rotation angle β of the load-bearing element 7 in a range of, for example, ± 10 °.

According to an advantageous embodiment of the invention, an anti-wind-up protection is integrated in the damping controller (12), whereby the damping controller 12 is given actuator restrictions of the at least one actuator 11, in particular a maximum / minimum permissible actuator position s _zul , a maximum / minimum permissible actuator speed v _perm and a maximum / minimum permissible actuator acceleration a _{zul of} the actuator 11. By means of this integrated anti-wind-up protection, the damping controller 12 can be adapted to the type of actuator (s) 11 available for the lifting device 1. To dampen the torsional vibration of the load-bearing element 7, the damping controller 12 calculates, as described, a manipulated variable of the at least one actuator 11, for example the target actuator speed v _soll . Exceeds this target actuator speed v _to a maximum allowable Aktuatorbeschränkung, for example, the actuator speed v _perm, the target actuator speed v _soll is limited v _perm to this maximum actuator velocity. Without Aktuatorbeschränkung or anti-wind-up protection it could for example be that the SAS 12 _{is to} too high a target actuator speed v calculated that at least one actuator 11 due to its design could not follow. This would result in a control error and the SAS 12, in particular integrated in SAS 12 integrator, would try to compensate this control error by the manipulated variable, for example, the target actuator speed v _should, would be further increased. This "charging" of the damping controller 12 or, in particular, of the integrator integrated in the damping controller could lead to a destabilization of the damping controller 12, which can be reliably avoided by the integrated anti-wind-up protection. In addition, from the target actuator speed v _soll on a target Aktuatorbeschleunigung a _{is to} be calculated and this _permissible with a maximum / minimum allowable Aktuatorbeschleunigung of a respective actuator 11a, 11b, 11c are compared, 11d. If this maximum / minimum permissible actuator acceleration a _{zul is} exceeded, this can also _be taken into account by limiting the target actuator speed v _soll . Different embodiments and sizes of Actuators 11a, 11b, 11c, 11d are taken into account in the damping controller, as a result of which the method can be used very flexibly on a wide variety of lifting devices 1.

Claims (11)

1. A method for damping rotational oscillation about a vertical axis (Z) of a load-handling element (7) of a lifting device (1) by means of a damping controller (12) having at least one controller parameter, wherein the load-handling element (7) is connected to a suspension element (5) of the lifting device (1) by means of at least three holding elements (6) and the length of at least one holding element (6) between the load-handling element (7) and the suspension element (5) is adjusted by the damping controller (12) by means of an actuator (11), which acts on the at least one holding element (6), wherein the at least one controller parameter is determined by means of a rotational oscillation model of the load-handling element (7) as a function of the lifting height (l_H), wherein in order to damp the rotational oscillation of the load-handling element (7) at any lifting height (l_H), the at least one controller parameter is adapted to said lifting height (l_H), characterized in that the load-handling element (7) is excited to rotationally oscillate at a certain lifting height (l_H) of the load-handling element (7), that at the same time at least an actual angle of rotation (β_ist) of the load-handling element (7) about the vertical axis and an actual actuator position (s_ist) are sensed and, by means thereof, model parameters of the rotational oscillation model of the load-handling element (7) at the given lifting height (l_H) are identified by means of an identification method.
2. The method according to claim 1, characterized in that the at least one actuator (11) is hydraulically or electrically actuated.
3. The method according to claim 1 or 2, characterized in that at least four holding elements (6) are provided between the load-handling element (7) and the suspension element (5).
4. The method according to claim 1 to 3, characterized in that at least two actuators (11) are provided, particularly one actuator (11) per holding element (6).
5. The method according to claim 1 to 4, characterized in that the lifting height (l_H) is measured by means of a camera system (14) arranged on the suspension element (5) or on the load-handling element (7) or by means of a lifting drive (10) of the lifting device (1).
6. The method according to claim 1 to 5, characterized in that the actual angle of rotation (β_ist) of the load-handling element (7) is measured by means of a measuring device (14) arranged on the suspension element (5) or on the load-handling element (7), preferably by means of a camera system or a gyro sensor.
7. The method according to claim 1 to 6, characterized in that the rotational oscillation model is a second-order differential equation having at least three model parameters, particularly a dynamic parameter (δ), a damping parameter (ξ), and a system gain parameter (i_β).
8. The method according to claim 1 to 7, characterized in that the identification method is a mathematical method, particularly an online least-squares method.
9. The method according to claim 1 to 8, characterized in that the damping controller (12) is a state controller having preferably five controller parameters (K_I, K₁, K₂, K_FF, K_P).
10. The method according to claim 1 to 9, characterized in that a desired angle of rotation (β_soll) of the load-handling element (7) is specified to the damping controller (12) and the damping controller (12) attains the desired angle of rotation (β_soll) of the load-handling element (7) in a specified angle range, particularly in an angle range of -10° ≤ β_soll ≤ +10°.
11. The method according to claim 1 to 10, characterized in that anti-windup protection is integrated in the damping controller (12), wherein actuator limits of the at least one actuator (11), particularly a maximum permissible actuator position (s_zul), a maximum permissible actuator velocity (v_zul), and a maximum permissible actuator acceleration (a_zul) of the actuator (11), are specified to the damping controller (12).

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