EP2327651A1 - System for attenuating the oscillation of a container crane - Google Patents

Abstract

A system for damping vibration on a crane comprises a vibration sensor (11) which can be mounted on a crane frame (21). In addition, a linear motor (14) which can be mounted on the crane frame (21) is provided. Furthermore, the system according to the invention comprises a mass (15) which can be moved by the linear motor (14) and is mechanically coupled to the crane frame (21). In addition, a control device (13) is provided whose Meßgrößeneingang is connected to the vibration sensor (11), and the manipulated variable output to the linear motor (14) is connected.

Description

For loading and unloading container ships usually container bridges are used as loading and unloading. Containers are taken on the water side by a container crane from a ship, brought by a trolley movement to the land side and dropped there for further transport. When moving the trolley, the container crane is excited to a vibration in the direction of travel of the trolley. This vibration has an amplitude that can be up to one meter depending on the design and size of the container crane. Occurring wind can reinforce this even further.

When picking up and setting down containers, tolerance limits must also be observed. Usually, up to about 10 mm deviation can be tolerated when picking up or dropping off a container in the ship or on land. If the container bridge vibrates too much, it is necessary to wait until the vibration has subsided to a tolerable minimum, before the loading or unloading can be continued. Maintenance costs a lot of time in container handling and is undesirable due to the associated additional costs.

If the vibration of a container crane is to be reduced, for example, it makes sense to build a crane portal stiffer. It is often not enough to provide thicker sheets. In order to construct a stiffer crane gantry, it is often necessary to change the track width, cross-sectional areas, and passage heights at a container crane. However, this is extremely problematic in many container crane systems.

As an alternative to a structural modification of a container crane, vibration absorbers can be used. Vibration dampers usually comprise dampers with spring elements and, as a central active element, have their own vibration mass which oscillates in opposite directions to a main object to be damped. In container cranes, vibration absorbers are tuned to crane vibration frequencies. The oscillating mass together with the damper forms a pendulum, to which kinetic energy of the crane vibration is transmitted, which is damped by the pendulum. The more mass a pendulum of a vibration absorber, the more effective is the vibration absorber, since with a larger mass higher forces can be transmitted. For effective vibration damping but very heavy vibration masses in the range of a few tens of tons are required for container cranes.

The present invention has for its object to provide a simple to be integrated into a container crane system system for the effective damping of crane frame vibrations.

This object is achieved by a system having the features specified in claim 1. Advantageous developments of the present invention are given in the appended claims.

The system according to the invention for damping a vibration on a container crane comprises a vibration sensor mountable on a crane frame. In addition, a mountable on the crane frame linear motor is provided. Furthermore, the system according to the invention comprises a movable by the linear motor and mechanically coupled to the crane frame mass. In addition, a control device is provided whose Meßgrößeneingang is connected to the vibration sensor, and whose manipulated variable output is connected to the linear motor. The mass that can be moved by the linear motor is only a fraction of the weight of conventional passive vibration absorbers. In addition, the system according to the invention can be integrated into existing system essentially without any structural changes to container cranes.

Figur

eine schematische Darstellung eines Containerkrans mit einem aktiven Schwingungsdämpfungssystem,

The present invention will be explained in more detail using an exemplary embodiment with reference to the drawing. It shows the

figure

a schematic representation of a container crane with an active vibration damping system,

The container crane shown in the figure comprises a system for damping a crane frame vibration with a mounted on the crane frame 21 vibration sensor 11 connected to a crane frame 21 boom 22 along which a trolley 23 with a held by a gripper 25 container 26 between a quay 31st and a water-side dock 32 for container ships, a speed-controlled linear motor 14 is mounted. The linear motor 14 is movable in the direction of travel of the trolley 23. On the linear motor 14, a mass 15 is fixed, which is movable by the linear motor 14 along a direction of travel 24 of the trolley 23 and mechanically coupled via the linear motor 14 and the boom 22 to the crane frame 21. As an alternative to an arrangement on a boom 22, the linear motor 14 with the mass 15 can also be mounted on a bridge girder of a container crane. On the boom 22 or bridge girder 21, a balance weight 27 is mounted to stabilize the crane frame.

In addition, the system for damping a crane frame oscillation comprises a control device 13 whose Meßgrößeneingang is connected via a filter 12 to the vibration sensor 11. A manipulated variable output of the control device 13 is connected to the linear motor 14 and serves to transmit a speed setpoint value V _LM to a speed controller integrated into the linear motor 13. In addition, the vibration damping system shown in the figure comprises a linear measuring system for controlling and commutating the linear motor 14. In addition or as an alternative to the speed controller, a current or force regulator assigned to the linear motor 14 may be provided. In this case, a force or current setpoint for the force or current controller is transmitted via the manipulated variable output of the control device.

The filter 12 provided between the vibration sensor 11 and the control device 13 is tuned to an oscillation frequency spectrum of the crane frame 21 and also serves, for example, for conditioning a measurement signal detected by the vibration sensor 11. In addition, the vibration sensor 11 is designed to detect a vibration in the direction of travel 24 of the trolley 23.

The speed-controlled linear motor 14 accelerates the mass 15 to generate a retroactive on the crane frame 21 compensation movement. In this case, one of the acceleration of the mass 15 opposing force via the boom 22 acts on the crane frame 21, which is utilized for damping vibrations of the crane frame 21 and the boom 22. In this case, a movement of the linear motor 14 is limited and is varied via an adjustment of the control device 13 and the moving mass 15 according to given boundary conditions.

A speed control of the linear motor can be realized for example by means of a sto-optimal setting or a damping-optimal setting. In the damping-optimal setting, parameters of the speed controller integrated into the linear motor 14 are set to a vibration frequency of the crane frame 21 or of the boom 22 to be damped. This linear motor 14 and mass 15 can be operated without sensor signal or control by the control device 13 as a passive absorber. A control stiffness of the linear motor 14 with integrated speed controller can be adjusted, for example, software-based on the moving through the linear motor 14 effective mass 15. With the superimposed control device 13 for vibration damping, the linear motor 14 becomes the active absorber. By means of an embodiment as an active absorber, a considerable reduction of the effective mass 15 can be realized in comparison to a passive absorber.

In the present embodiment, the speed controller comprises a proportional-integral controller whose gain Kp and reset time T _{N is set} to a value which is dependent on a resonance frequency f _{0 of} the crane frame 21 and the mass m _LM moved by the linear motor 14. By the gain Kp and the reset time T _N , the control stiffness C _{REG of} the speed-controlled linear motor 14 is determined: $$c_{\mathit{REG}}=\frac{K_P}{T_N}\mathrm{,}$$

This control stiffness C _REG is selected at the optimal damping setting as a function of the mass m _LM moved by the linear motor 14 such that the frequency f _{LM of} the linear motor 14 and the resonant frequency f _{0 of} the crane frame or boom 22 correspond: $$f_{\mathit{LM}}=f_0=\frac{1}{2\mathit{\pi }}\sqrt{\frac{c_{\mathit{REG}}}{m_{\mathit{LM}}}}\mathrm{,}$$

Thus, the linear motor 14 is tuned as a passive absorber to the resonance frequency of the container crane. The gain Kp is therefore to be set according to the following equation: $$K_P=\left(2{\mathit{\pi \; f}}_0\right)m_{\mathit{LM}}{T}_N\mathrm{,}$$

Without control by the control device 13 of the speed-controlled linear motor 14 is already working as a classic passive absorber. Its action in this case, however, depends heavily on the effective mass 15. By active control via the control device 13, the linear motor 14 becomes an active absorber whose effect is no longer achieved solely by inertial forces of the oscillating mass 15, but via a driving force of the linear motor 14. As a result, are much lower in an active absorber by the linear motor 14 moving masses required.

In the sto-optimal setting, the parameters of the speed controller are set so that the speed controller has the widest possible bandwidth. With such a rigid setting of the linear motor acts as firmly attached to the container crane and represents an additional mass. Only by an active control of the control device 13, a vibration damping can be realized. The linear motor 14 then generates the force required for vibration damping, which acts as a counterforce on the boom 22 and the crane frame 21. The greater the gain, the greater the speed setpoint for the linear motor. The larger the speed command value, the larger the force generated by the linear motor 14. Accordingly, the required effective mass 15 is smaller. An advantage of using the linear motor 14 for active damping of crane oscillations is that controller parameters can be adapted at any time to changing boundary conditions without effort. Compared to a passive absorber with a mechanical damping element, a linear motor is also nearly maintenance and wear-free.

According to a preferred embodiment, a cascaded control system associated with the linear motor 14 is provided, which in addition to a current or force controller comprises a speed controller and a position controller with programmable control circuit elements. The speed controller can be parameterized in such a way that a vibratory system that can be parameterized according to oscillation frequency and damping results, which acts as a damper. In addition, a control device that processes a Schwingungsmeßgröße be parameterized such that approximately results in the place of action of the linear motor predeterminable, absolute damping in space. In this case, a position or speed controller assigned to the linear motor 14 is parameterized in such a way that the absolute damping which can be predetermined at the point of action of the linear motor is maintained and at the same time it is ensured that the linear motor moves within a defined working range.

The application of the present invention is not limited to the present embodiment.

Claims (16)

System for damping a vibration on a crane with a vibration sensor mountable on a crane frame, a linear motor mounted on the crane frame, a mass movable by the linear motor and mechanically coupled to the crane frame, - A control device whose Meßgrößeneingang is connected to the vibration sensor, and the manipulated variable output is connected to the linear motor. System according to claim 1,
in which a linear measuring system is provided for controlling and commutating the linear motor. System according to one of claims 1 or 2,
in which a speed controller assigned to the linear motor is provided, and in which a manipulated variable transmitted via the manipulated variable output of the closed-loop control device is a speed setpoint for the speed controller. System according to claim 3,
wherein the speed controller comprises a proportional-integral controller whose gain and reset time is set to a value dependent on a resonant frequency of the crane frame and the mass movable by the linear motor. System according to one of claims 1 or 2,
in which a current and / or force regulator assigned to the linear motor is provided, and in which a manipulated variable transmitted via the manipulated variable output of the regulating device is a force and / or current setpoint for the power and / or current controller. System according to one of claims 1 or 2,
in which a speed controller assigned to the linear motor and a current and / or force controller assigned to the linear motor are provided, and in which a control variable transmitted via the manipulated variable output of the control device is a speed setpoint and a force and / or current setpoint for the force or current controller. System according to one of claims 1 to 6,
in which a cascaded control system associated with the linear motor is provided which comprises a current and / or force controller, a speed controller and a position controller with parameterizable control circuit elements. System according to claim 7,
in which the speed controller is parameterized in such a way that a vibratory system which can be parameterised according to oscillation frequency and damping results, which acts as a damper. System according to one of claims 1 to 8,
in which a control device which processes a Schwingungsmeßgröße is parameterized in such a way that approximately results in the place of action of the linear motor predetermined absolute damping in space. System according to claim 9,
in which a position and / or speed controller assigned to the linear motor is / are parameterized such that the absolute damping which can be predetermined at the point of action of the linear motor is maintained and at the same time it is ensured that the linear motor moves within a defined working range. System according to one of claims 1 to 10,
wherein a filter is provided between the vibration sensor and the control device, which is tuned to a vibration frequency spectrum of the crane frame. System according to one of claims 1 to 11,
in which the vibration sensor for detecting a vibration in the direction of travel of a trolley of the crane is configured. System according to one of claims 1 to 12,
in which the linear motor is designed to move in the direction of travel of a trolley of the crane. System according to one of claims 1 to 13,
in which the mass mechanically coupled to the crane frame is mounted on the linear motor. System according to one of claims 1 to 14,
in which the linear motor is mounted on a bridge girder of the crane. System according to one of claims 1 to 14,
in which the linear motor is mounted on a jib of the crane.

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