EP1992583B2 - Crane control, crane and method - Google Patents

Description

The present invention relates to a crane according to the preamble of claim 1. Such a crane is e.g FR 2445291 disclosed. In particular, the crane is a jib crane which has a boom which can be pivoted about a horizontal axis and which is articulated on a tower which can be rotated about a vertical axis. For this purpose, a luffing gear and a slewing gear are provided as signal boxes. The rope for lifting the load runs over the tip of the boom, in particular over one or more deflection rollers arranged there, so that the load can be moved by rotating the tower in the tangential direction and by luffing the boom in the radial direction. When carrying out the invention with at least a first and a second rope strand, both rope strands run from the tip of the boom to a receiving element such as a hook. The length of the rope can be adjusted using a corresponding drive in order to move the load in a vertical direction. In particular, the crane control according to the invention generally relates to rotating cranes, as well as mobile harbor cranes, ship cranes, off-shore cranes, truck cranes and crawler cranes.

Out of DE100 64 182 and DE 103 24 692 , the entire content of which forms part of the present application, crane controls are known whose control and automation concepts prevent the oscillating movement of the load on the rope when the crane moves.

Out of DE 100 29 579 and DE 10 2006 033 277 , the content of which also forms part of the following application, crane controls are also known which prevent torsional vibration of the load on the rope.

In the crane controls mentioned above, gyroscope units are used to determine the load oscillation, which are arranged in the crane hook and determine the angular velocity of the rope. The rope angle is determined via an observer circuit, which integrates the movement of the rope. In order to be able to compensate for the resulting offset, a freely swinging pendulum is assumed whose rest position corresponds to a vertical cable angle. Such a procedure is well suited for rope sway damping, as the movements of the rope must be monitored when the load swings freely on the rope. However, determining the absolute alignment of the rope, especially before the load can swing freely, is neither provided nor possible with the known crane controls. Furthermore, known sensor arrangements and crane controls had the disadvantage that disruptive influences such as rope field twisting were not taken into account in the load sway damping to dampen the spherical pendulum oscillations of the load.

Well-known systems such as B. are used in cranes with a trolley that can only be moved in the horizontal direction and which use measuring camera systems to determine the absolute rope angle, but cannot be used, especially in jib cranes. Measuring camera systems must always be arranged directly behind the rope fixed point in order to be able to determine the rope angle. However, in jib cranes in which the rope is movably guided over a deflection roller arranged on the boom head, there is no rope fixed point, since the rope exit point also changes with the rope angle. Transducers that mechanically determine the rope angle relative to the boom are also unsuitable for measuring the absolute rope angle, as they work inaccurately and also lead to incorrect results if the crane is deformed. In addition, all of these systems only ever determine the rope angle relative to the boom, and would therefore only be indirectly suitable for determining the absolute rope angle, so that such solutions have so far been dispensed with entirely.

The crane operator must therefore continue to align the crane manually and visually before the lift or at the beginning of the lift so that the rope is essentially aligned vertically. However, this is often extremely difficult, especially given the great distance from the load, which results in deviations of the rope angle from the vertical, which lead to undesirable vibrations when the load is lifted. The same problem arises if, due to an imbalance in the load, the rope is aligned vertically before the lift, but the rope angle is changed when the load is lifted by the movement of the load's center of gravity below the load-bearing point. The crane structure giving way under the strain of lifting the load can also unintentionally change the rope angle. With off-shore cranes, the additional problem arises that the rope angle can be changed by a relative movement of a ship carrying the load to the off-shore crane.

The object of the present invention is therefore to provide a crane control which enables easier and safer alignment of the crane, particularly before and during lifting of the load. A further object of the present invention is to enable improved damping of the spherical pendulum oscillations of the load.

According to the invention, this object is achieved by a crane control according to claim 1. According to the invention, this has a sensor unit for determining a rope angle relative to the direction of gravitational force. With this sensor unit, the rope angle can be determined directly relative to the direction of gravitational force, so that the vertical alignment of the rope is considerably simplified. This also increases safety during the hub.

The sensor unit usually has an element which aligns itself under the influence of the gravitational force and through which the angle of the rope can be determined relative to the direction of the gravitational force. In particular, any type of electric level can be used. In the simplest version it can The sensor unit only determines whether the rope is aligned vertically or not. In more complex versions, the direction of the deviation from the vertical and in other versions the value of the deviation from the vertical can also be determined.

According to the invention, the sensor unit determines the rope angle in at least one direction relative to the direction of gravity, for example in the radial or tangential direction, in order to be able to determine and, if necessary, compensate for a deviation of the rope angle from the vertical in this direction. Advantageously, the rope angle is determined both in the tangential and in the radial direction, since this is the only way an actually vertical alignment of the rope is possible. For this purpose, the sensor unit advantageously has at least two sensors, each of which serves to determine the radial or tangential cable angle relative to the direction of the gravitational force.

Such a sensor unit enables the crane to be precisely aligned when lifting the load, so that the rope is aligned vertically. The sensor unit can also be used for monitoring and security functions.

Furthermore, in addition to the sensor unit for determining a rope angle relative to the direction of gravitational force, at least one gyroscope unit for measuring a rope angular speed is also advantageously provided. In particular, this gyroscope unit can also be used to dampen vibrations when the load is freely swinging, for which the sensor unit for determining the cable angle relative to the direction of the gravitational force usually cannot provide sufficiently precise data. The crane can then initially be aligned based on the sensor unit to determine the rope angle relative to the direction of gravitational force until the load hangs freely on the rope. The automatic cable sway damping, which works based on the gyroscope unit, can then be switched on.

The gyroscope unit measures the rope angular speed in at least one direction, e.g. in the radial or tangential direction. However, both the tangential and the radial cable angular speed are advantageously determined, for which the gyroscope unit advantageously has at least two correspondingly arranged gyroscopes.

If the crane has at least two rope strands for lifting the load, the crane control advantageously comprises at least two sensor units for determining the rope angles relative to the direction of gravitational force, which are assigned to different rope strands. This allows cable field twisting, which corresponds to a rotation of the load, to be taken into account. If only one sensor unit were used for several rope strands, a twist in the rope field would lead to falsified measured values.

In particular, the cable field twist, and thus the twist of the load, can be determined by the at least two sensor units. This makes it possible to control the rope field twist, e.g. B. by rotating the load-carrying device relative to the load.

If the crane has at least two rope strands for lifting the load, at least two gyroscope units are also advantageously provided for measuring the rope angular speeds, which are assigned to different rope strands. So the rope field twist can e.g. B. also be taken into account in the vibration damping control.

Furthermore, the gyroscope unit can advantageously be arranged on a cable follower element, which is connected in particular via a gimbal connection to a boom of the crane and which is guided on the cable. The cable follower element is preferably connected to the boom head of the crane by the gimbal connection and follows the movements of the cable on which it is guided by rollers. By measuring the movement of the rope follower element, the movements of the rope can be determined.

If the crane has at least two rope strands for lifting the load, at least two rope follower elements are advantageously provided, which are assigned to different rope strands. Since the crane's hook usually hangs on several rope strands, rope field twists can also be taken into account.

Furthermore, the crane control according to the invention advantageously has a display unit for displaying a deviation resulting from the measured cable angle, in particular for displaying a cable angle relative to the direction of gravitational force and/or a resulting horizontal deviation of the load. This display makes it much easier for the crane operator to align the rope in a vertical position.

The display advantageously shows a vertical cable position visually and/or acoustically. This makes it possible for the crane operator to align the rope accordingly.

Further advantageously, the display continues to show the direction in which the rope deviates from the vertical. Further advantageously, the display also shows the absolute value of the deviation. It is conceivable here, for example, B. a graphic display in which the angle of the rope relative to the direction of gravitational force and also advantageously the maximum permissible rope angle are displayed. Alternatively or additionally, the horizontal deviation of the load from the position at which the load would be if the rope was in a vertical position can also be displayed, advantageously together with the maximum permissible horizontal deviation. This means the crane operator can work with distance information he is familiar with and can align the crane more easily.

Furthermore, a warning device is advantageously provided which alerts the crane driver if the limit is exceeded a permissible value range for a deviation resulting from the measured rope angle, in particular for the rope angle relative to the direction of gravitational force and/or for the horizontal deviation of the load, in particular by means of an optical and/or acoustic signal. In this way, the crane operator can react if the permissible value range is exceeded and avoid damage to the crane structure or accidents. For example, the crane operator can stop the movement of the crane if the permissible angular range is exceeded, or, if it is an off-shore crane, in which the e.g. B. a load on a ship is moved away from the offshore crane by a relative movement of the ship relative to the crane, avoiding an overload by partially releasing the rope or the slewing gear of the crane.

According to the invention, an overload protection is provided which automatically intervenes in the control of the crane when a permissible value range for a deviation resulting from the measured rope angle, in particular for the rope angle relative to the direction of gravitational force, and/or for the horizontal deviation of the load is exceeded, in order to achieve a To prevent overloading the crane. In particular, the rope angle relative to the direction of gravitational force can be included in the automatic load moment limitation of the crane. This increases the safety of operation considerably, since known load moment limitations could not take this parameter into account and the loads resulting from excessive inclination of the rope had to be taken into account solely via the other sensors.

According to the invention, the overload protection at least partially releases the movement of the crane and/or the rope, particularly when it is an offshore crane. The release is advantageously carried out in a controlled manner with a certain counterforce. Gets caught e.g. B. the hook of the crane on a ship that is driven away by the off-shore crane can z. B. the rope or the rotational movement of the crane can be released in a controlled manner to prevent the crane from being overloaded. The sensor unit for determining a rope angle relative to the direction of gravitational force results in a very reliable overload protection, while known overload protection systems were solely dependent on a rope force sensor, which makes it difficult to distinguish an overload case from a load case.

Furthermore, advantageously, the crane control according to the invention, in particular the warning device and/or the overload protection, additionally evaluates data from a cable force sensor. This allows the data from the sensor unit to determine the rope angle to be checked relative to the direction of gravitational force, so that additional safety is provided through redundancy, particularly when the crane control automatically intervenes in the movement of the crane.

If the crane has at least two rope strands for lifting the load, their rope field twist is advantageously determined. Since when the load is simply twisted, the outer ropes are deflected in opposite directions without the load being deflected from the vertical, this rope field twist is advantageously taken into account when determining the actual rope angle. The rope angle, which is used for the display, the warning device and/or the overload protection, corresponds to the actual deflection of the load relative to the direction of gravitational force, so that the load can be effectively prevented from oscillating and any twisting of the rope field does not lead to incorrect values.

The crane control according to the invention advantageously comprises a display unit for displaying the rope field rotation. The rope field twist itself can also be shown on the display so that it can be compensated for by controlling a corresponding rotor unit on the load-carrying device. Likewise, the cable field twist can advantageously be incorporated into the control of the warning device and the overload protection.

A warning device is therefore advantageously provided in the crane control according to the invention, which warns the crane operator when a permissible value range for the rope field rotation is exceeded, in particular by means of an optical and/or acoustic signal. This warns the crane operator of the load swinging when lifting with a twisted rope field.

In the crane control according to the invention, a safety device, in particular an anti-twist device, is also advantageously provided, which automatically intervenes in the control of the crane if a permissible value range for the rope field rotation is exceeded. For example, lifting the load can be automatically prevented if the rope field is twisted too much.

Furthermore, the crane control according to the invention advantageously has automatic load sway damping. In particular, the movement of the crane can be controlled in such a way that the freely swinging load is prevented from swinging when the crane moves. The sensor unit for determining the rope angle relative to the direction of gravitational force can be used at the beginning of the stroke to align the rope vertically while the load sway control occurs when the load hangs freely on the rope. Correct alignment of the rope can prevent the load from swaying when being lifted, and load sway damping can prevent the load from swaying when it moves in a horizontal direction.

The load sway damping is advantageously based on the data of at least one gyroscope unit. Since the rope angular speed can be determined with a gyroscope, it is particularly suitable for use in load sway control.

Advantageously, the sensor unit is used to determine the cable angle relative to the direction of gravitational force to monitor and/or calibrate the gyroscope unit. In particular, if the lift is started with the rope in an inclined position and the load is supported, the load sway damping, which is usually based on a freely swinging load, would otherwise start with incorrect values. The sensor units or gyroscope units can also be used for mutual monitoring in order to detect malfunctions.

Advantageously, a function for automatically aligning the crane is also provided, through which the rope is aligned vertically above the load. The crane operator no longer has to operate the crane manually, for example. B. align based on the display, but this happens automatically when the crane driver makes a corresponding request via a control unit. A safety function is advantageously provided here, which z. B. cooperates with a rope force sensor to prevent uncontrolled movement of the crane in the event of a malfunction of the sensor unit for determining the rope angle relative to the direction of gravitational force.

Furthermore, a function for automatic alignment of the crane is also advantageously provided, through which cable field rotation is compensated for. This advantageously controls a rotor unit on the load-carrying device, for example on the spreader, through which the part of the load-carrying device connected to the ropes can be rotated relative to the load.

Furthermore, the crane control according to the invention advantageously has a memory for storing load data based on the rope angle, which is used for the service life calculation and/or the documentation, for example. B. from improper use. Such machine data acquisition of the rope position for determining the load spectrum and for documentation enables a more precise service life calculation and thus increased safety while saving costs.

The present description further discloses a method for controlling a crane which has at least one rope for lifting a load. According to the invention, the method is characterized in that a rope angle is determined relative to the direction of the gravitational force. Such a determination of a rope angle relative to the direction of gravitational force results in the advantages already described in more detail with regard to crane control. Advantageously, the radial and/or tangential cable angles are determined relative to the direction of the gravitational force.

In particular, this significantly simplifies the alignment of the crane before and when lifting the load. Advantageously, in addition to a rope angle, which corresponds to the actual deflection of the load against the vertical, the rope field twist is also determined if several rope strands are used to lift the load. For this purpose, the rope angles of at least two rope strands are determined relative to the direction of gravitational force. From this data, both the rope angle, which corresponds to the deflection of the load, and the rope field twist, which corresponds to the twist of the load, can be determined.

Advantageously, the rope is brought into a vertical orientation before the load is lifted. This can prevent the rope from slipping sideways due to an inclined position when the load is being lifted, from being twisted in an uncontrolled manner due to uneven resting on the base, or from performing a pendulum movement when the load is being lifted. The vertical alignment of the load can z. B. by the crane operator based on the display of the rope angle according to the invention relative to the direction of gravitational force. It is also conceivable that this alignment is carried out automatically by the crane control, as already described.

Furthermore, before lifting the load, the rope field twist is brought to zero in order to avoid rotation of the load when lifting. This is done e.g. B. by appropriately rotating the load on the load-carrying device using a rotor arrangement.

Even during the lifting process, different effects can cause the rope angle to deviate from the vertical. Advantageously, any deviation of the rope angle from the vertical is compensated for even while the load is being lifted. For this purpose, the rope angle is advantageously determined relative to the direction of gravitational force while the load is being lifted, so that any deviations that may occur during the lifting process can be compensated for.

Advantageously, when lifting the load, an imbalance in the load is determined by determining the deviation of a rope angle from the vertical. If the load has an imbalance, i.e. the center of gravity of the load is not below the load-bearing point, the load-bearing point initially moves above the center of gravity when the load is raised, so that the rope angle changes. By changing the rope angle, the imbalance in the load can be determined and, if necessary, compensated for. Such an imbalance in the load can also be displayed so that it can be compensated for by the crane driver can be. It is also conceivable to automatically compensate for such an imbalance.

Advantageously, the imbalance of the load is compensated for on the basis of the deviation of a rope angle from the vertical by a movement of the load on the load-carrying device, in particular on the spreader. The spreader is used to hold containers and has a longitudinal adjustment, through which the load pick-up point can be adjusted relative to the container. The crane operator can now e.g. B. based on the deviation of the rope angle from the vertical, which arises when the load is lifted due to the imbalance and is displayed on the display according to the invention, move the load-carrying point on the load-carrying device and thus compensate for the imbalance. If the imbalance of the load is also determined and displayed, this makes the crane operator's work easier. It is also conceivable that the imbalance will be automatically compensated.

Such a compensation of the imbalance of the load, through which the center of gravity of the load is brought below the load-bearing point while the orientation of the load remains unchanged, enables the containers to be moved within the guides in the ship without them tilting due to tilting.

Alternatively, if such compensation for the imbalance of the load is not possible, or if tilting of the load is not a problem, the inclination of the rope caused by the imbalance of the load when lifting the load can also be compensated for by moving the crane. This can also be done manually by the crane operator, e.g. B. based on a display or automatically.

The strain on the crane structure when lifting the load can cause it to deform, causing the rope angle to change even without the load moving. Advantageously, according to the invention, when lifting the load, the yielding of the crane structure under the load is determined by determining a deviation of the rope angle from the vertical and / or the inclination of the rope caused by the yielding of the crane structure is compensated for by a movement of the crane. Here, the determination of the deviation or the compensation of this deviation can in turn be done by the crane operator, for example. B. based on a display, or automatically.

Furthermore, if a permissible value range for a deviation resulting from the measured rope angle is exceeded, in particular for the rope angle relative to the direction of gravitational force and/or for the horizontal deviation of the load, the crane structure is protected by countermeasures. In particular, the movement of the crane can be stopped in order to avoid overloading.

In particular when controlling an off-shore crane, the countermeasures advantageously include at least partial release of the crane movements and/or the rope, for example. B. to prevent the crane from being overloaded if the load handler gets caught on a ship that is moving away from the offshore crane.

The countermeasures can either be initiated by the crane driver, who is advantageously warned by a warning function, or automatically by a corresponding automatic overload protection.

The present description further discloses a crane control of a crane, which has at least one rope for lifting a load, for carrying out one of the methods described above. In particular, the crane control is advantageously designed so that the methods described above are carried out at least partially automatically.

Furthermore advantageously, the present invention comprises a crane, in particular a mobile harbor crane, a ship's crane or an off-shore crane, which has a rope for lifting a load and is equipped with a crane control as described above. The invention also includes corresponding jib and/or rotating cranes, as well as truck cranes and crawler cranes. Obviously, the same advantages already described for the crane control arise for such a crane.

In addition to the previously described embodiment of the present invention with a sensor unit for determining a rope angle relative to the direction of gravitational force, the present description further discloses a crane control, which is also advantageous without such a sensor unit in cranes which have at least a first and a second rope strand for lifting the load can be used. Such a crane control is not part of the present invention.

Such a crane control is shown in claim 37. The crane control according to the invention is used to control the signal boxes of a crane, which has at least a first and a second cable strand for lifting a load, the crane control having a load sway damping for damping spherical pendulum oscillations of the load. In this crane control, a first and a second sensor unit are now provided, which are assigned to the first and second rope strands in order to determine the respective rope angles and/or rope angular speeds of the first and second rope strands. Furthermore, the load sway damping has a control system in which the cable angles and/or cable angular speeds determined by the first and second sensor units are included.

Compared to known arrangements in which a sensor unit is attached to the hook of the crane or just to a rope, this results in numerous advantages: on the one hand, there is redundancy of this safety-critical element, so that if a sensor unit fails, a measurement of the rope angle continues remains possible via the second sensor unit. There is also the possibility of detecting sensor errors. Furthermore, it is possible to achieve a noise reduction by forming the difference between the measured values and to implement torsion compensation using evaluation algorithms, i.e. taking into account a rope field twist when determining the actual deflection angle of the load.

The signal boxes controlled by the crane control are advantageously the slewing gear for turning the crane and/or the luffing gear for luffing up the boom. By appropriately regulating this control via the load sway damping, spherical vibrations of the load on the rope can be prevented.

Advantageously, the first and second sensor units each comprise a gyroscope unit. The gyroscopes measure the cable angular speed, with two gyroscopes advantageously being provided in order to measure the cable angular speed in both the radial and tangential directions. Gyroscopes are particularly well suited to the requirements of controlling load sway damping.

Further advantageously, the first and second sensor units are each arranged in a cable follower element. The rope follower element follows the movement of the rope strand to which it is assigned. The sensor unit then measures the movement of the cable follower element, from which the movement of the cable strand can be determined. The rope follower elements result in a particularly accurate and reliable rope angle measurement.

Advantageously, the cable follower elements are each connected to the boom of the crane via a gimbal joint and follow the movement of the cable strand to which they are assigned. However, the connection of the cable follower elements via a gimbal joint advantageously only serves the mechanical connection and the guidance of the cable follower element, while the sensor units determine the movement of the cable follower elements via the gyroscope units.

Advantageously, the data measured by the first and second sensor units are evaluated by a first and a second observer circuit. Such observer circuits are used to monitor offsets and interference, such as. B. cable harmonics to suppress. The observer circuits serve to integrate the rope angular speeds measured by the gyroscopes and enable the rope angles to be reliably determined.

Furthermore, the data measured by the first and second sensor units with regard to the installation angle of the sensor units and the rotation angle of the crane are advantageously compensated for. This means that disruptive influences caused by incorrect assembly can be compensated for by software. If the sensitivity levels of the gyroscopes used are not exactly in the tangential and radial directions, but are tilted due to incorrect installation, the sensors measure the rotational speed of the crane proportionally. This is taken into account by the compensation.

Furthermore, sensor errors are advantageously detected in the crane control by comparing the data measured by the first and second sensor units. If one of the sensor units fails, the angular velocity is still detected by the other sensor unit. This means that the basic function of the crane control can continue to be ensured. By forming the difference between the angle signals of both sensor units in the respective directions, a sensor error can still be detected if a threshold value is exceeded. If a sensor error occurs, the crane can be immediately brought into a safe state.

Further advantageously, the torsional vibration of the rope field is taken into account in the load sway damping by averaging the rope angles and/or rope angular speeds determined by the first and second sensor units. If only one sensor unit is used, such a cable field twist would influence the control used to dampen the spherical pendulum oscillation of the load. If a torsional vibration of the rope field occurs during the crane control, the sensor units on the two rope follower elements measure exactly the opposite interference vibration in both the tangential and radial directions. However, the influence of this torsional vibration can be eliminated by averaging.

Furthermore, advantageously, the regulation of the crane control is non-linear. Such a non-linear control is particularly advantageous because, particularly in the case of jib cranes, the entire system consists of the crane, signal boxes such as. B. hydraulic cylinders and load is non-linear and therefore significant errors occur with purely linear control. On the other hand, the entire control system consisting of non-linear control and the non-linear behavior of the crane results in a linear system, so that the control of the system is considerably simplified.

Furthermore, the control is advantageously based on the inversion of a physical model of the movement of the load as a function of the movements of the signal boxes. Advantageously, this physical model is a non-linear model, so that the non-linear control results from its inversion. The combination of the inverted physical model and the actual movement of the load depending on the movement of the signal boxes then results in the linear route described above. The input variables of the physical model are the state vector of the crane. Based on these input variables, the non-linear model then specifies the movement of the load as an output variable. By inverting such a system, the movement of the load serves as an input variable to control the crane's signal boxes.

Furthermore, the load sway damping advantageously has a path planning module, which specifies target trajectories for the control. These target trajectories specify the movements that the load should perform and then serve as input variables for the control, especially when using an inverted model. The non-linear control results in a particularly simple implementation of the path planning module, as it only has to specify target trajectories for the linear system of non-linear control and non-linear crane behavior. This makes it possible to achieve extremely fast crane control with an excellent response to the specifications entered by the crane operator using input elements.

Advantageously, the current system state of the crane, in particular the position of the boom and/or the rope angle and/or rope angle speeds determined by the first and second sensor units, is included as an input variable in the path planning module. The position of the boom is particularly important here, since e.g. B. the maximum radial speed that can be achieved depends on this. Advantageously, the rope angles and/or rope angular speeds determined by the first and second sensor units are also included in the path planning module from input variables. This additional control loop thus enables even more precise path planning, taking into account the actual rope angle and/or the actual rope angular speed.

Furthermore, limitations of the system when generating the target trajectories are advantageously taken into account in the path planning module. This prevents the reference variables calculated from the crane operator's specifications from exceeding the system's manipulated variable limitations, such as: B. violate the maximum speed. In particular, if the current system state of the crane is also included as an input variable in the path planning module, system limitations that depend on this system state can also be taken into account. For example, the maximum possible radial speed depends on the position of the boom.

Furthermore, the trajectory generation is advantageously based on optimal control. Such optimal control can be implemented particularly well in real time, as the non-linear control allows the path planning module to be implemented particularly easily.

Furthermore, the path planning module advantageously works in the prediction within the time horizon with an increasing length of the calculation intervals. Such non-equidistant base points for the prediction also make it possible to significantly shorten the computing time. Short intervals between the base points are chosen for the near future, while larger intervals are chosen for the more distant future, so that overall there is a significantly reduced number of calculation steps.

Furthermore, the position and speed of the boom head are also advantageously included in the control of the load sway damping. This results in control loops in the crane control for both the position and speed of the boom head, as well as for the rope angle and/or rope angular speed of the rope.

The second embodiment of the present disclosure with the use of two sensor units, each of which is assigned to different rope strands of the crane, has previously been described independently of the first embodiment with a sensor unit for determining a rope angle relative to the direction of the gravitational force. According to the disclosure, protection is claimed for both versions independently of one another.

However, in a particularly advantageous exemplary embodiment, both versions of the present disclosure are combined. Furthermore, the system with two sensor units advantageously has one or more of the features that were previously described in relation to the implementation of the invention.

The present description further discloses a crane for lifting a load, with signal boxes for moving the crane and the load and with a crane control for controlling the signal boxes, the crane control having a load sway damping for damping spherical pendulum oscillations of the load and the crane having at least two cable strands for lifting the load. Such an embodiment is not part of the present invention. According to the description, two sensor units, which are assigned to the two rope strands, are provided in order to determine the respective rope angles and/or rope angular speeds. Furthermore, the load sway damping has a control system in which the cable angles and/or cable angular speeds determined by the two sensor units are included. Such a crane offers the same advantages as those already described above with regard to the crane control.

Furthermore, this crane has a crane control as described above.

Furthermore, the crane advantageously has, as signal boxes, a slewing gear for rotating the crane and/or a luffing gear for luffing up a boom, which are controlled by the crane control. By appropriately regulating this control via the load sway damping, spherical vibrations of the load on the rope can be prevented.

The present description further discloses a method for controlling the signal boxes of a crane, which has at least a first and a second cable strand for lifting the load, with spherical pendulum oscillations of the load being dampened by load sway damping. Such an embodiment is not part of the present invention. According to the description, the rope angles and/or rope angular speeds of the first and second rope strands are determined via a first and a second sensor unit, which corresponds to the first and the second Rope strand are assigned, determined and included in the control of the load sway damping. This procedure results in the same advantages as those described above with regard to the crane control.

Advantageously, the data measured by the first and second sensor units regarding the installation angle of the sensor units and the rotation angle of the crane are compensated. This allows deviations in the installation angle of the sensor units from an exact radial or tangential alignment to be compensated for.

Furthermore, sensor errors are advantageously detected by comparing the data measured by the first and second sensor units. By using two sensor units, which are assigned to the respective rope strands, the resulting redundancy can be exploited.

Further advantageously, the torsional vibration of the rope field is taken into account in the load sway damping by averaging the rope angles and/or rope angular speeds determined by the first and second sensor units. In this way, load sway damping can be taken into account and torsional vibrations of the cable field also occur, which influence the data from the sensor units.

The method is advantageously carried out using a crane control as described above.

Figur 0a:

ein Ausführungsbeispiel eines erfindungsgemäßen Hafenmobilkrans,

Figur 0b:

ein Ausführungsbeispiel eines erfindungsgemäßen Seilfolgeelements der erfindungsgemäßen Kransteuerung,

Figuren 1a, 1b:

die Schwingung der Last, wenn das Seil vor dem Anheben der Last nicht lotrecht ausgerichtet wurde,

Figuren 2a - 2c:

ein Ausführungsbeispiel des erfindungsgemäßen Verfahrens, bei welchem ein Ungleichgewicht der Last ausgeglichen wird,

Figuren 3a - 3c:

ein Ausführungsbeispiel eines erfindungsgemäßen Verfahrens, bei welchem das Nachgeben der Kranstruktur bei Belastung ausgeglichen wird,

Figur 4a:

ein Ausführungsbeispiel eines erfindungsgemäßen Off-Shore-Krans mit entsprechender Auslenkung des Seiles aus der Lotrechten durch eine Bewegung eines Schiffs und

Figur 4b:

die grafische Darstellung eines zulässigen Seilwinkelbereiches.

Figur 5:

ein weiteres Ausführungsbeispiel, bei welchem zwei Seilstränge mit jeweils zugeordneten Sensoreinheiten vorgesehen sind,

Figur 6:

eine Torsionsschwingung des Seilfeldes aus erstem und zweitem Seilstrang,

Figur 7:

ein Prinzipschaubild der bei einer Torsionsschwingung des Seilfeldes gemessenen Seilgeschwindigkeiten,

Figur 8:

eine Prinzipdarstellung des erfindungsgemäßen Kranes,

Figur 9:

eine Prinzipdarstellung des Wippwerkes des erfindungsgemäßen Kranes,

Figur 10:

eine Prinzipdarstellung einer nicht erfindungsgemäßen Kransteuerung,

Figur 11:

einen Vergleich der Vorgaben des Kranführers mit einer Soll-Trajektorie, welche von einen nicht erfindungsgemäßen Bahnplanungsmodul generiert wird,

Figur 12a:

einen Vergleich einer Soll-Trajektorie mit der tatsächlichen Bewegung der Last bezüglich der Lastgeschwindigkeit,

Figur 12b:

einen Vergleich einer Soll-Trajektorie mit der tatsächlichen Bewegung der Last bezüglich der Lastposition,

Figur 13:

die Geschwindigkeit des Auslegerkopfes im Vergleich mit der Sollgeschwindigkeit der Last sowie dem durch die Bewegung entstehenden radialen Seilwinkel und

Figur 14:

die Zeit, welche zur Berechnung der Soll-Trajektorien benötigt wird.

The present invention will now be illustrated in more detail using exemplary embodiments and drawings. Show:

Figure 0a:

an embodiment of a mobile harbor crane according to the invention,

Figure 0b:

an exemplary embodiment of a rope follower element according to the invention of the crane control according to the invention,

Figures 1a, 1b:

the oscillation of the load if the rope was not aligned vertically before lifting the load,

Figures 2a - 2c:

an embodiment of the method according to the invention, in which an imbalance in the load is compensated for,

Figures 3a - 3c:

an embodiment of a method according to the invention, in which the yielding of the crane structure under load is compensated for,

Figure 4a:

an embodiment of an off-shore crane according to the invention with a corresponding deflection of the rope from the vertical due to a movement of a ship and

Figure 4b:

the graphic representation of a permissible rope angle range.

Figure 5:

a further exemplary embodiment in which two cable strands are provided, each with assigned sensor units,

Figure 6:

a torsional vibration of the rope field made up of the first and second rope strands,

Figure 7:

a schematic diagram of the rope speeds measured during a torsional vibration of the rope field,

Figure 8:

a schematic representation of the crane according to the invention,

Figure 9:

a schematic representation of the luffing gear of the crane according to the invention,

Figure 10:

a schematic representation of a crane control not according to the invention,

Figure 11:

a comparison of the crane operator's specifications with a target trajectory, which is generated by a path planning module not according to the invention,

Figure 12a:

a comparison of a target trajectory with the actual movement of the load in terms of the load speed,

Figure 12b:

a comparison of a target trajectory with the actual movement of the load with respect to the load position,

Figure 13:

the speed of the boom head in comparison with the target speed of the load and the radial cable angle resulting from the movement and

Figure 14:

the time required to calculate the target trajectories.

In Figure 0a An exemplary embodiment of a jib crane according to the invention is shown, here a mobile harbor crane, as is often used to handle cargo handling operations in ports. Such jib cranes can have load capacities of up to 140t and a rope length of up to 80m. The exemplary embodiment of the crane according to the invention includes a boom 1, which can be pivoted up and down about a horizontal axis 2, with which it is articulated on the tower 3. The tower 3 can in turn be rotated about a vertical axis, as a result of which the boom 1 is also rotated. For this purpose, the tower 3 is rotatably arranged on an undercarriage 6, which can be moved via wheels 7. There are signal boxes (not shown) for rotating the tower 3, and the actuator 4 for luffing up the boom 1. The rope 20 for lifting the load 10 is guided over a deflection roller on the boom head, whereby the length of the rope 20 can be adjusted using winches. A load-carrying device is arranged on the rope 20 at a load-carrying point 25, e.g. B. a manipulator or spreader, via which the load 10 can be picked up. In the exemplary embodiment, the load-carrying device additionally has a rotator device, via which the load 10 can be rotated on the load-carrying device. In a further embodiment of the invention, the crane further has at least a first and a second cable strand for lifting the load, with all cable strands running from the boom tip to the load-carrying device.

As shown in particular in the top view, the load can be moved in the tangential direction by rotating the tower 3 and in the radial direction by luffing the boom 1. In the vertical direction, the load 10 is moved by luffing the boom 1 and changing the length of the rope 20. In addition, the load 10 can be rotated by the rotator unit on the load-carrying device.

A first embodiment of the in Figure 0a The mobile crane shown is now equipped with the crane control according to the invention, which has a sensor unit for determining the rope angle relative to the direction of gravitational force. In the exemplary embodiment, the sensor unit has two sensors, through which the radial or tangential cable angle can be determined relative to the direction of the gravitational force. This sensor unit significantly simplifies the alignment of the crane when lifting the load, since this sensor unit allows the rope to be easily aligned vertically above the load 10.

However, the crane control according to the invention can not only be used in the exemplary embodiment shown, i.e. a mobile harbor crane, but also advantageously in other cranes, such as. B. in ship cranes, off-shore cranes, truck cranes and crawler cranes.

The sensor unit according to the invention for determining the rope angle relative to the direction of gravitational force is particularly advantageous in the case of jib cranes, since they use known systems such as those used, for example. B. are used in cranes with a trolley that can only be moved in the horizontal direction and which work via measuring camera systems cannot be used. In the case of jib cranes, such measuring camera systems would move together with the boom and thus only determine the angle of the rope relative to the boom, but not relative to the vertical. In addition, such systems would always have to be arranged directly behind the rope fixation point on the boom head, which is hardly possible with a movable rope guided over a deflection roller on the boom head.

The sensor unit according to the invention for determining the rope angle relative to the direction of gravitational force, on the other hand, is in a rope follower element 35, as shown in Figure 0b is shown, arranged and directly determines the rope angle relative to the direction of gravitational force in the tangential and radial directions. There is no need to determine the rope angle relative to the boom 1. However, if this angle of the rope relative to the boom 1 is of interest, a further sensor unit could also be arranged on the boom 1 to determine the angle of the boom relative to the direction of gravitational force in order to determine the angle between the rope using the difference between the respective angles of the rope and boom to the direction of the gravitational force and boom to determine.

This in Figure 0b Cable follower element 35 shown, on which the sensor unit for determining the cable angle is arranged relative to the direction of gravitational force, is attached to the boom head 30 of the boom 1 by gimbal connections 32 and 33 under the main cable pulley 31. The rope-following element 35 has rollers 36 through which the rope 20 is guided, so that the rope-following element 35 follows the movements of the rope 20. The gimbal connections 32 and 33 allow the cable follower element to move freely about a horizontal and a vertical axis, but prevent rotational movements. The orientation of the rope follower element 35 and thus the rope 20 relative to the direction of the gravitational force can thus be determined via the sensor unit arranged on the rope follower element 35 for determining the rope angle relative to the direction of the gravitational force.

Further advantageously, in the exemplary embodiment, a gyroscope unit is also arranged on the cable follower element 35, via which the cable angular speed can be measured in the radial and tangential directions, for which at least two correspondingly aligned gyroscopes are used. The gyroscope data Advantageously, load sway damping is available, which prevents the load from swaying when the crane moves.

If several cable strands are provided, via which the load-receiving element is suspended on the boom, at least two of these cable strands are advantageously assigned corresponding cable follower elements 35 in order to also be able to take into account the cable field rotation, which results from a rotation of the load-receiving element from the cable field plane. The rope follower elements are advantageously arranged on the rope strands arranged on the outside, so that a rope field twist is expressed at most in the difference in the rope angles. The actual rope angle relative to the direction of gravitational force, which corresponds to a deflection of the load from the vertical, can be determined by averaging the values from the sensor units on the respective rope follower elements, and the rotation of the load from the difference in values.

The cardan joint 32 and 33 only serves to mechanically connect the cable follower element 35 to the boom head 30; the cable angle is measured solely via the sensor units integrated in the cable follower elements 35, but not by determining the angle between the cable follower element 35 and the boom 30. In this way, only the relative orientation of the rope with respect to the boom 30 could be determined, but not the rope angle of the rope 20 relative to the direction of the gravitational force.

In a further exemplary embodiment, in which at least a first and a second cable strand are provided, via which the load-bearing element is suspended on the boom, corresponding cable follower elements 35 are also assigned to these, which are equipped with gyroscope units and thus determine the cable speed of these cable strands. Determining the rope speeds of the first and second rope strands makes it possible to take the rope field twist into account and correct measurement errors when swaying the load to dampen spherical pendulum oscillations of the load. In this exemplary embodiment, the sensor units for determining the cable angle relative to the direction of gravitational force can also be dispensed with and the cable follower elements 35 can only be equipped with gyroscope units.

As an alternative to arranging the sensor unit according to the invention for determining the cable angle relative to the direction of gravitational force on a cable follower element 35, this could also be z. B. can be arranged on the rope receiving means, although the rope follower elements offer an improved possibility for determining the rotation of the load, especially with several rope strands. Such an embodiment is not part of the present invention.

Since the load sway damping, which in DE 100 64 182 , DE 103 24 692 , DE 100 29 579 and DE 10 2006 033 277 are shown, and with which the crane of the exemplary embodiment according to the invention is advantageously also equipped, assume a load hanging freely on the rope and are based on gyroscope data, which are not suitable for determining absolute rope angles, these load pendulum systems can only oscillate the load which is initially free and stationary Prevent the load hanging from the rope when the crane moves.

In order to align the rope vertically before lifting the load or during lifting, so that the load can be lifted without swinging out, the crane according to the invention is now provided with the sensor unit according to the invention for determining a rope angle relative to the direction of gravitational force.

Figure 1a shows the basic problem when the rope 20 is not aligned vertically. The rope 20, which is already connected to the load 10 that is still lying on it via a load-carrying device, has an angle ϕ _Sr relative to the direction of the gravitational force shown in dashed lines due to the incorrect alignment of the boom 1 . If the load 10 is now raised from this position by shortening the length of the rope 20, the result is the in Figure 1b shown oscillation about the vertical when the load 10 is released. Such a vibration when lifting the load 10 is particularly dangerous because it occurs close to the ground and objects in the vicinity of the load 10 can easily be damaged.

In addition, the load 10 can slip uncontrollably before it is released or can be twisted uncontrollably due to uneven release. In Figures 1a and 1b The deflection ϕ _Sr in the radial direction is shown as an example. The same problem also arises for a deflection of the cable 20 in the tangential direction, which is caused by an incorrect position of the tower 3.

In order to avoid such a deflection of the rope 20 from the vertical at the beginning of the stroke, the exemplary embodiment of the crane according to the invention therefore has a display which shows the rope angle φ of the rope 20 relative to the direction of gravitational force, that is to say to the vertical. The display can z. B. on the one hand, display a vertical rope position visually and / or acoustically and also indicate the direction in which the rope 20 is deflected from the vertical.

Such an ad can e.g. B. have display elements for a deflection to the front or rear and display elements for a deflection to the left or right, which indicate a deflection in the radial or tangential direction.

Alternatively, the horizontal deviation of the load from a zero position, which corresponds to a vertical alignment of the rope, can also be displayed. In particular, a graphical display of the zero position and the deviation of the load is conceivable, so that the absolute deflection of the load is directly displayed to the crane operator.

With such a display, the crane operator can easily align the crane at the start of the lift so that that the rope 20 is arranged vertically above the load 10. The correct vertical rope position can then be achieved e.g. B. be indicated acoustically by a signal tone.

In an alternative embodiment, a function for automatically aligning the rope in the vertical direction is provided, if necessary in addition to the display. By activating this function, the crane automatically aligns itself after attaching the load handler to the load so that the rope is vertical. In order to avoid uncontrolled movement of the crane in the event of a malfunction of the sensor unit according to the invention, this automatic function is advantageously z. B. connected to a rope force measuring device, which switches off automatic operation in the event of errors.

When using several rope strands between the boom head and the load-carrying device, the rope field twist can also be determined using several sensor units. This rope field twist corresponds to the twist of the load-carrying device, e.g. B. a spreader, and would cause the load to rotate when lifting the load. In order to prevent this, the twist of the rope field is also advantageously displayed, if necessary in addition to the rope angle relative to the direction of the gravitational force or the horizontal deviation of the load. If the load-carrying device has a rotor device, the cable field twist can be set to 0 before the lift in order to prevent rotation of the load 10 when lifting. In a further exemplary embodiment, a function for automatic alignment of the rotor device can also advantageously be provided for this purpose.

Furthermore, the exemplary embodiment of the crane according to the invention has, in addition to the display, a warning device which alerts the crane operator if the permissible value range is exceeded for a deviation resulting from the measured rope angle, in particular for the rope angle relative to the direction of gravitational force, for the horizontal deviation of the load and / or the rope field rotation warns with a visual and/or acoustic signal. This gives the crane operator the opportunity to prevent the rope from deflection too much and thus e.g. B. to protect against overload. This also prevents the load from swaying too much when being lifted.

In an alternative exemplary embodiment, an automatic safety device, for example in the form of an overload protection, can be provided, if necessary in addition to the warning device, which automatically intervenes in the control of the crane when the permissible value range is exceeded. In particular, the automatic overload protection stops the movement of the crane to prevent overload. The overload protection can be integrated into the load moment limitation of the crane, which protects the crane against stress caused by a rope angle that is too large.

Furthermore, in a further exemplary embodiment it is provided that lifting the load 10 is not possible as long as the rope angle or the rope field twist is not within the permissible range. This effectively prevents unwanted swaying of the load 10 when being lifted.

In Figures 2 and 3 Two situations are now shown in which the rope 20 is initially aligned vertically, but is moved away from the vertical when the load 10 is lifted.

In Figures 2a to 2c This happens because the center of gravity 26 of the load 10 is not below the load receiving point 25 at the start of the lifting process. The load will now be 10, as in Figure 2b shown, raised, this is tilted until the center of gravity 26 of the load is arranged below the load receiving point 25. Due to this tilting of the load 10, the load receiving point 25, at which the rope 20 z. B. is attached to the load-carrying device, but moves in a horizontal direction, in the case shown here in a radial direction inwards. This changes the rope angle relative to the vertical, which would lead to an undesirable oscillation of the load if the load 10 were to come completely free.

Therefore, in one exemplary embodiment of a method, the deviation of the rope angle from the vertical is determined while the load 10 is being lifted. In the simplest exemplary embodiment, the crane operator checks the cable angle or the horizontal deviation on the display and adjusts the crane during the lift in order to compensate for the deviation of the cable angle from the vertical due to the imbalance of the load. In an improved embodiment, the imbalance of the load is determined and displayed from the deviation of the cable angle from the vertical, so that the crane operator can react better.

In the in Figure 2c In the position shown, the crane was now moved in such a way that the inclination caused by the imbalance of the load, in which the center of gravity 26 is arranged below the load receiving point 25, was compensated for. When the load 10 is completely released, this avoids unwanted oscillation of the load due to the imbalance of the load.

In an exemplary embodiment not shown, the load-carrying means has a device for, in particular, linear movement of the load 10 relative to the load-carrying point 25, via which the center of gravity 26 of the load can be arranged below the load-carrying point 25 without tilting the load 10. For this purpose, the load-carrying device, e.g. B. a spreader, e.g. B. a longitudinal displacement of the load receiving point 25 relative to the load, e.g. B. a container.

If a deviation of the rope angle from the vertical is detected when lifting the load, the crane operator can move the load pick-up point relative to the load until the rope is aligned vertically again. The imbalance of the load can also be determined based on the deviation of the rope angle from the vertical displayed so that the crane driver can control the longitudinal adjustment of the spreader using this display. Automatic adjustment of the spreader is also conceivable.

Such an adjustment of the spreader based on the deviation of the rope angle from the vertical is of particular advantage, since tilting of the containers, especially when loading into a ship, can lead to the containers jamming, which can significantly hinder loading.

In Figures 3a to 3c Another effect can now be seen, which can cause a deviation of the rope angle from the vertical when lifting the load. In Figure 3a the rope 20 is still aligned vertically before the start of the stroke. Since the center of gravity 26 of the load is located below the load-bearing point 25, i.e. the load is not imbalanced, the load-bearing point 25 does not shift when the load 10 is lifted in this case. As in Figure 3b shown, however, the crane structure gives way due to the load when lifting the load, in which case tower 3 and boom 1 are bent slightly forward. As a result, the boom tip 30, over which the rope 20 runs, is moved relative to the load-bearing point 25, so that the rope angle deviates from the vertical due to the yielding of the crane structure.

According to the invention, in a first exemplary embodiment of the method, this deviation is compensated for by the crane operator based on the display of the rope angle when lifting the load. Likewise, the deviation of the rope angle from the vertical can be determined by the yielding of the crane structure under the load, which can then be displayed to facilitate the crane operator's work. In a further exemplary embodiment, automatic tracking of the crane for vertical alignment is also possible based on the data from the sensor unit for determining a rope angle relative to the direction of the gravitational force. If the rope angle is again aligned vertically, the load can be carried as in Figure 3c shown can be raised without vibrations.

In Figure 4a Another embodiment of the crane according to the invention can be seen. This is an off-shore crane, which is arranged on an off-shore platform 50 and z. B. is used to load a load 10 from a ship 60 onto the platform 50. Since the ship 60 can move relative to the platform 50, the rope angle of the rope 20 relative to the vertical can also be changed by moving the ship without moving the crane.

In order to take this situation into account, an overload function is provided in an exemplary embodiment of the crane according to the invention, which can optionally be used in addition to the warning and safety functions described above. To e.g. B. to prevent destruction of the crane if the rope 20 gets caught on the ship 60 and the movement of the ship 60 threatens to overload the crane, countermeasures are initiated if the rope angle exceeds a maximum permissible range. In particular, the movement of the crane can be partially enabled, e.g. B. by releasing the rope 20 or the rotational movement of the tower 3. This release takes place in a controlled manner with a certain counterforce in order to avoid sudden force surges.

As a result, an easy-to-implement overload protection can be implemented based on the rope angle relative to the direction of the gravitational force, which is difficult to implement using a rope force sensor. Such an overload protection, which causes a partial release of the crane movement, can also prevent uncontrolled dragging of the load 10 over the ship 60.

The permissible range 70 for the rope angle in the X and Y directions is, for example, in Figure 4b shown hatched. If the rope angle exceeds this permissible range 70, either the warning function or one of the overload functions is triggered.

Figure 4b shows a display element for displaying a deviation from a vertical position of the rope, with a permissible range 70 for the rope angle or for the horizontal deviation in the X and Y directions, that is in the radial and tangential directions. The cable angle is displayed graphically, for example by displaying the cable angle in the in Figure 4b shown diagram is represented as a point. Instead of the rope angle, the horizontal deviation of the load from the zero position in the middle can also be shown, i.e. the distance of the load from the position in which it would be if the crane were in the same position but the rope was vertical. This means the crane driver can directly see the absolute deflection of the load and can therefore more easily estimate how far the crane needs to be moved to correctly align the rope.

Through the inventive determination of the rope angle relative to the vertical by a sensor unit for determining a rope angle relative to the direction of gravitational force and the corresponding crane controls and crane control methods, in addition to simpler operation and alignment of the crane, significantly increased safety when lifting loads is possible.

In a further exemplary embodiment, which is not part of the present invention, the crane has at least a first and a second cable strand, which connect the load-carrying means to the boom tip. In particular, the crane control provides improved damping of the spherical vibrations of the load.

Control and automation concepts for cranes that prevent the load on the rope from swinging during crane movement rely on the precise measurement of the rope angles. In the case of jib cranes in particular, it is advantageous not to determine the rope angle directly using, for example, image processing methods, but rather to measure the angular velocities using gyroscopes.

However, since the gyroscope signals are subject to offset and also detect disruptive influences such as cable harmonics, observer circuits are used to integrate the speeds into the cable angles.

In order to record the angular velocities of the oscillating load, the gyroscopes are attached to the rope under the boom tip using a mechanical structure. Two gyroscopes, which are arranged in tangential and radial directions, are necessary for recording the spherical load vibration.

As in Figure 5 shown, in order to improve load sway damping, it is now proposed to add a cable follower element to both the first and the second cable strand, as in Fig. 0b is shown to be assigned. However, instead of the sensor unit for determining a rope angle relative to the direction of gravitational force, the rope follower elements are equipped with gyroscope units, which are better suited for load sway damping. This is used to record the angular velocity of the oscillating crane load.

Figure 0b shows a first cable follower element 35, on which the first sensor unit assigned to the first cable strand is arranged in the exemplary embodiment shown here. The first cable follower element is attached to the boom head 30 of the boom 1 by gimbal connections 32 and 33 under a first cable pulley 31, over which the first cable strand 20 is guided. The cable follower element 35 has rollers 36 through which the first cable strand 20 is guided, so that the cable follower element 35 follows the movements of the cable strand 20. The gimbal connections 32 and 33 allow the cable follower element to move freely about a horizontal and a vertical axis, but prevent rotational movements. The radial and tangential angular velocity of the first cable follower element 35 and thus of the first cable strand 20 can thus be determined via the first sensor unit arranged on the cable follower element 35, which is designed as a gyroscope unit. A second cable follower element with a second sensor unit, which is assigned to a second cable strand, is constructed analogously to the first cable follower element and is connected to the boom tip. The second rope follower element accordingly measures the angular velocity of the second rope strand.

The gyroscope signals (angular velocities in tangential and radial directions) from both cable follower elements are prepared and processed using identical algorithms. First of all, disruptive influences caused by incorrect assembly are compensated for by software (see equation 0.1). If the sensitivity levels of the gyroscope sensors are not tilted exactly in the tangential and radial directions but are tilted due to incorrect installation, the sensors also measure the rotational speed of the crane proportionally.

The installation or mounting angle for each gyroscope sensor on both cable follower elements is respectively ϕ _installation , ϕ̇ _D is the rotational speed of the crane, ϕ̇ _{t / rmess} is the tangential or radial angular velocity and ϕ̇ _{t / rkomp} is the resulting compensated gyroscope signal.

Furthermore, the compensated measurement signals are integrated offset-free into the cable angles using an observer circuit. After this preparation, the rope angles are now available for both rope follower elements in the tangential and radial directions.

The expansion of the measuring concept to include the second rope-following element leads to two significant advantages compared to the variant with only one rope-following element or the variant with the gyroscope sensors in the hook.

The first advantage is the redundancy of the load swing measurement. If a sensor on one of the two cable follower elements fails, the angular velocity is still recorded by the sensor on the other holder. This allows the basic function of the crane control (sway damping and trajectory sequence) to be ensured. By forming the difference between the angle signals of both cable follower elements in the respective directions, a sensor error can still be detected if a threshold value is exceeded. This means that if a sensor error occurs, the crane can be immediately brought into a safe state.

The second advantage is the possibility of compensating the torsional vibration of the load. As shown in Equation 0.2, the mean value of the angle signals of the two rope follower elements is calculated in the corresponding direction.

The cable angle in the tangential direction ϕ _t is therefore calculated from the average of the observed angle signals of the holder 41 ϕ _{tbeobH 1} and holder 42 ϕ _{tbeobH 2} . The same applies to the rope angle in the radial direction, symbolized by the index r . If a torsion of the load occurs with the angular velocity ϕ̇ _torsion , the gyroscopes on the cable follower elements 41 and 42 measure exactly an opposite spurious vibration in both the tangential and radial directions. This means that the influence of torsional vibration can be eliminated by averaging. The control of the load sway damping, into which the data generated by the two gyroscope units are included, will now be described in more detail below.

In the case under consideration, the dynamics of the cantilever movement is characterized by some predominant nonlinear effects. The use of a linear control device would therefore cause large errors in trajectory tracking and insufficient damping of the load oscillation. To overcome these problems, the present invention utilizes a nonlinear control approach based on the inversion of a simplified nonlinear model. This control procedure for the luffing movement of a jib crane allows a pivot-free load movement in the radial direction. By using an additional stabilizing control loop, the resulting crane control according to the invention shows a high accuracy of trajectory tracking and good damping of the load sway. Measurement results are presented to validate the good performance of the nonlinear trajectory tracking controller.

Jib cranes such as the LIEBHERR mobile harbor crane LHM (see Fig. 1 ) are used to efficiently handle transshipment processes in ports. This type of jib crane is characterized by a load capacity of up to 140 tons, a maximum radius of 48 meters and a rope length of up to 80 meters. During the implementation process, a spherical load oscillation is excited. This load oscillation must be avoided for safety and performance reasons.

As in Fig. 1 shown, such a mobile harbor crane consists of a mobile stage 6, to which a tower 3 is attached. The tower 3 can be rotated about a vertical axis, its position being described by the angle ϕ _D. A boom 1 is pivotally attached to the tower 3 and can be rocked by the actuator 4, its position being described by the angle ϕ _A. The load 10 is suspended from the head of the boom 1 on a rope of length l _S and can oscillate at the angle ϕ _Sr.

In general, cranes are underactuated systems that exhibit oscillating behavior. Therefore, many unregulated and regulated control solutions have been proposed in the literature. However, these approaches are based on the linearized dynamic model of the crane. Most of these contributions do not consider actuator dynamics and kinematics. In a jib crane that is driven by hydraulic actuators, the dynamics and kinematics of the hydraulic actuators are not negligible. The kinematics must be taken into account, especially with the boom actuator (hydraulic cylinder).

The following implementation uses a flatness-based control approach for the radial direction of a jib crane. The approach is based on a simplified nonlinear model of the crane. The law of linearizing control can thus be formulated. Furthermore, it is shown that the zero dynamics of the non-simplified nonlinear control loop guarantees sufficient damping properties.

1. NON-LINEAR MODEL OF CRANE

• Vernachlässigen der Masse und der Elastizität des Seils
• Annahme, dass Last eine Punktmasse ist
• Vernachlässigen der Zentripetal- und Coriolis-Terme

Taking into account the control objectives of preventing load sway and tracking a reference trajectory in the radial direction, the nonlinear dynamic model for the rocking motion must be derived. The first part of the model is obtained by

• Neglecting the mass and elasticity of the rope
• Assumption that load is a point mass
• Neglecting the centripetal and Coriolis terms

Using the Newton/Euler method and taking into account the given assumptions leads to the following differential equation of motion for the load oscillation in the radial direction:

Fig. 8 shows a schematic representation of the rocking movement, where ϕ _Sr is the radial cable angle, ϕ̈ _Sr is the radial angular acceleration, l _S is the cable length, r̈ _A is the acceleration of the boom end and g is the gravitational constant.

The second part of the dynamic model describes the kinematics and dynamics of the actuator for the radial direction. Assuming that the hydraulic cylinder has first-order behavior, the differential equation of motion is obtained as follows:

Where z̈ _zyl and ż _zyl are the cylinder acceleration and speed, T _W is the time constant, A _zyl is the cross-sectional area of the cylinder, u _W is the input voltage of the servo valve and K _VW is the proportional constant of flow rate to u _w .

differenziert.

K _Wz1 und K _Wz3 beschreiben die Abhängigkeit von den geometrischen Konstanten d_a ,d_b ,α ₁,α ₂ und dem Wippwinkel ϕ_A . (siehe Figur 9) l_A ist die Länge des Auslegers. Fig. 9 shows a schematic representation of the kinematics of the actuator with the geometric constants d _a , d _b , α ₁ , α ₂ . To obtain a conversion from cylindrical coordinates ( z _zyl ) to radius coordinates ( r _A ), the kinematic equation

differentiated.

K _{Wz 1} and K _{Wz 3} describe the dependence on the geometric constants d _a , d _b , α ₁ , α ₂ and the rocking angle ϕ _A . (please refer Figure 9 ) l _A is the length of the boom.

Formulating the first-order behavior of the actuator in projection coordinates by using equations (4) results in a nonlinear differential equation.

werden die Gleichungen (1) und (6) verwendet. Hierdurch führen der als Eingabe verwendete Zustand x=[r_A ṙ_A ϕ_Sr ϕ̇_Sr ] ^T und die als Ausgabe vorgesehene radiale Position der Last y = r_LA zu:

To represent the nonlinear model in the form

Equations (1) and (6) are used. As a result, the state x =[ r _A ṙ _A ϕ _Sr ϕ̇ _Sr ] ^T used as input and the radial position of the load y = r _LA intended as output lead to:

2. NON-LINEAR CONTROL APPROACH

The following considerations are made assuming that the right-hand side of the load swing differential equation can be linearized. The excitation of the radial load oscillation is therefore decoupled from the radial cable angle ϕ _Sr.

To find a flat output for the simplified nonlinear system, the relative degree must be determined.

2.1 Relative degree

The relative degree is defined by the following conditions:

wird ein relativer Grad von r = 2 erhalten. Da die Ordnung des vereinfachten nichtlinearen Modells 4 ist, ist y_l eine nicht flache Ausgabe. Doch mit einer neuen Ausgabe

wird ein relativer Grad von r=4 erhalten. Angenommen, dass nur kleine radiale Seilwinkel eintreten, kann die Differenz zwischen der realen Ausgabe y_l und der flachen Ausgabe $y_l^{·}$

vernachlässigt werden. Diese Vereinfachung wird gewählt, um die Rechenzeit für die in Kapitel 3 beschriebene Trajektoriengenerierung so gering wie möglich zu halten.The operator L _{f t} represents the Lie derivative along the vector field f _l or L _{g t} along the vector field g _l . With the real output

a relative degree of r = 2 is obtained. Since the order of the simplified nonlinear model is 4, y _l is a non-flat output. But with a new edition

a relative degree of r =4 is obtained. Assuming that only small radial rope angles occur, the difference between the real output y _l and the flat output $y_l^{·}$

be ignored. This simplification is chosen to keep the computing time for the trajectory generation described in Chapter 3 as short as possible.

2.2 Exact linearization

und das linearisierende Steuersignal u_l wird berechnet durch

Since the simplified system representation is differentially flat, exact linearization can be carried out become. Therefore, a new input is defined as

and the linearizing control signal u _l is calculated by

To stabilize the resulting linearized system, an error feedback is derived between the reference trajectory and the derivatives of the output y *.

The feedback gains k _l,i are obtained through the pole placement technique. Figure 10 shows the resulting structure of the linearized and stabilized system.

verwendet. Die resultierende interne Dynamik ist dabei in der noch nicht veröffentlichten DE 10 2006 048 988 gezeigt, deren Inhalt einen Bestandteil der vorliegenden Anmeldung darstellt.The tracking control unit is based on the simplified load oscillation ODE (8) and not on the load oscillation ODE (1). Furthermore, the fictitious output is used for the control unit design $y_l^{·}$

used. The resulting internal dynamics are not yet published DE 10 2006 048 988 shown, the content of which forms part of the present application.

3. Path planning/trajectory generation A. Formulation of the optimal control problem

The trajectory generation problem is formulated as a constrained open chain optimal control problem for the linearized system with state feedback. Due to the relevant calculation time for solving the optimal control problem, the model predictive trajectory generation is carried out with a non-negligible sampling time. The numerical solution method itself also introduces a discretization of the time axis. However, for the sake of simplicity, the optimal control problem is presented continuously in continuous time.
The model equations are given by:

berücksichtigt zum einen die quadratische Abweichung der prognostizierten Ausgänge y_lin von deren Referenzprognose w(t) und zum anderen die quadratische Änderung der Eingangsgröße u_lin . Der Optimierungshorizont t_f -t ₀, die symmetrische, positiv semi-definite Wichtungsmatrix Q und der Wichtungskoeffizient r > 0 sind wesentliche Einstellungsparameter für die Modellprädiktive Trajektoriengenerierung.
Der Optimierungshorizont t_f -t ₀ sollte das wesentliche dynamische Verhalten des Prozesses/Systems erfassen. Dieses ist definiert durch die Periodendauer des Lastpendelns (bis 18 Sekunden für den betrachteten Kran). Versuche zeigen, dass 10 Sekunden für den Optimierungshorizont ausreichen.The state variables x _lin are the states of the integrator chain, which results from the linearized system, consisting of a flatness-based controller (equation (14)) and a nonlinear system (equation (6)), and the states of the integrator chain for the reference trajectory. Additional states are introduced to obtain a smooth input ν. The initial state x _{lin ,0} is derived from the states of these integrators, the current system output and its derivatives. The outputs y _lin of the linear system (Equation (15)) are variables that correspond to the flat output y* (Equation (12)) and its first and second derivatives. These variables are the position, velocity and acceleration of the load in the radial direction.
The quality functional

takes into account, on the one hand, the squared deviation of the predicted outputs y _lin from their reference forecast w ( t ) and, on the other hand, the squared change in the input variable u _lin . The optimization horizon t _f - t ₀ , the symmetrical, positive semi-definite weighting matrix Q and the weighting coefficient r > 0 are essential setting parameters for model predictive trajectory generation.
The optimization horizon t _f - t ₀ should capture the essential dynamic behavior of the process/system. This is defined by the period of the load swing (up to 18 seconds for the crane under consideration). Experiments show that 10 seconds is sufficient for the optimization horizon.

The reference forecast w ( t ) for the load position, speed and acceleration is generated from the crane driver's hand lever signals (target speeds). The prediction takes into account speed reductions as the load approaches the limits of the work area.
The model predictive trajectory generation takes restrictions for the process variables into account as constraints of the optimal control problem.

Restrictions on changing the input are used to avoid high frequency excitations of the system.

This means that the rates of change u̇ _lin must be taken into account as manipulated variables when formulating the optimal control problem.
The generation of the reference trajectories leads to an external control loop ( figure (10 )). The results of the stability considerations of model predictive controls are therefore applicable. Conditions for guaranteed stability of the closed control loop under nominal conditions normally require stabilizing restrictions on the states at the end of the optimization horizon together with an appropriate evaluation of the final state. For a "zero-state terminal constraint" one would have to introduce fixed end values, which depend on the stationary states in connection with the reference inputs, for the states that cannot be integrated.

Constraints of this type (Equation (19)) are likely to cause intractable optimal control problems under non-nominal conditions, such as model uncertainties or measurement noise, especially for short optimization horizons. Thus, the equation constraint (19) becomes a quadratic penalty term with a symmetric, positive definite weighting matrix Q approximates, which extends the original quality functional as follows:

B. Numerical solution of the optimal control problem

The continuous-time, constrained, linear-quadratic optimal control problem (15)-(20) is discretized.

, u^k and $y_{\mathit{lin}}^k$

die Werte der entsprechenden Variablen in den Diskretisierungpunkten t^k bezeichnen. Die Matrizen und Vektoren A^k , b^k and C^k erhält man durch Lösen der Transitionsgleichung in [t^k ,t ^k+1] aus A, b und C. Das Gütefunktional (Gleichung (20)) und die Beschränkungen (Gleichungen (17)(18)) werden ebenfalls entsprechend diskretisiert.
Damit wird das zeitkontinuierliche Optimalsteuerungsproblem als eine Aufgabe der quadratischen Programmierung für die Zustandvariablen und Stellgrößen $\left[x_{\mathit{lin}}^k,u_{\mathit{lin}}^k\right]$

des diskreten Problems approximiert und kann mit einem üblichen "Interior Point" Algorithmus gelöst werden. In dem Algorithmus wird die Struktur der diskreten Modellgleichungen in einem RICCATI-ähnlichen Ansatz genutzt, um eine Lösung der NEWTONschritt-Gleichung mit O(K(m ³+n ³)) Operationen zu erhalten. D.h. der Berechnungsaufwand steigt linear mit dem Optimierungshorizont K und kubisch mit der Anzahl der Stellgrößen(m) und Zustandsvariablen(n).
Nicht äquidistante Diskretisierungsschritte ΔT^k =t ^k+l-t^k im Prädiktionshorizont des MPC's helfen die Dimension des Optimalsteuerungsproblems zu begrenzen. Die Darstellung zeigt, dass die Anfangschrittweite durch den Takt der Trajektoriengenerierung bestimmt wird und sich dann innerhalb des Prädiktionshorizontes linear vergrößert.Where $x_{\mathit{lin}}^k$

, u ^k and $y_{\mathit{lin}}^k$

denote the values of the corresponding variables in the discretization points t ^k . The matrices and vectors A ^k , b ^k and C ^k are obtained by solving the transition equation in [ t ^k , t ^{k +1} ] from A, b and C . The quality functional (Equation (20)) and the constraints (Equations (17)(18)) are also discretized accordingly.
This makes the continuous-time optimal control problem a task of quadratic programming for the state variables and manipulated variables $\left[x_{\mathit{lin}}^k,u_{\mathit{lin}}^k\right]$

of the discrete problem and can be solved with a common "interior point" algorithm. In the algorithm, the structure of the discrete model equations is used in a RICCATI-like approach to obtain a solution of the NEWTON step equation with O( K ( m ³ + n ³ )) operations. This means that the calculation effort increases linearly with the optimization horizon K and cubically with the number of manipulated variables ( m ) and state variables ( n ).
Non-equidistant discretization steps Δ T ^k = t ^{k +l} - t ^k in the prediction horizon of the MPC help to limit the dimension of the optimal control problem. The illustration shows that the initial step size is determined by the rate of trajectory generation and then increases linearly within the prediction horizon.

Through the crane control with the corresponding load sway damping, into which data from the two sensor units assigned to the respective rope strands are received and which is constructed as described above, a quick and safe damping of the spherical pendulum oscillations of the load can be achieved with only minimal pendulum deflections. This is shown by the following measurement results, which were carried out with a rope length of 57 m and a load of 3.5 t.

Figure 11 shows the speed of the load, once as it is specified by the crane operator using an input element, and once as it is specified as a target trajectory via the path planning module using optimal control. The limitations of the system are taken into account here, so that the upper limit for the speed of the load depends on the radial load position, since the geometry of the boom and the luffing cylinder allow different maximum speeds for different boom positions. However, a constant limitation is specified for the maximum acceleration.

Figure 12a now compares this target trajectory with the measured speed of the load. The control follows the target trajectory, with the path planning module compensating for uncertainties in the model through model-based path planning. This results in a fast and damped movement of the load without any significant overshoots. Figure 12b then shows the corresponding trajectory of the load position.

The control dampens the spherical vibrations of the load by corresponding compensating movements of the boom during and at the end of each maneuver. This is in Figure 13 shown, from which the counter movements carried out by the boom tip result, which counteract the vibration of the load. This allows the rope angle to be limited to less than 3°.

The computing time required for the online calculation of the optimal solution problem in the path planning module is in Figure 14 shown. This results in calculation times between 54 ms and 66 ms. The decisive factor for this extremely short response of the path planning to the crane operator's specifications is, on the one hand, the quick solvability through the downstream linear route consisting of non-linear control and non-linear crane system, as well as the increasing length of the intervals between the prediction base points within the prediction horizon.

Claims (24)

1. A crane with a boom (1), a crane control and at least one cable (20) for lifting a load (10), wherein in the crane control at least one sensor unit is provided for determining a cable angle relative to the direction of gravitational force, wherein the at least one sensor unit is arranged on a cable follower (35) and is guided on the cable (20),
   characterized in that
   the cable follower (35) is mounted on the boom head (30) of the boom (1) by cardan joints (32) below a first pulley (31) and guided on the cable, wherein an overload protection is provided, which automatically intervenes in the control of the crane when an admissible range of values (70) for a deviation resulting from the measured cable angle and/or for the horizontal deviation of the load (10) is exceeded, to prevent an overload of the crane, wherein the overload protection at least partly enables the movement of the crane and/or the cable (20).
2. The crane according to claim 1, wherein beside the sensor unit for determining a cable angle (70) relative to the direction of gravitational force at least one gyroscope unit is provided for measuring a cable angular velocity.
3. The crane according to claim 1 or 2, wherein the crane includes at least two strands of cables for lifting the load (10), and at least two sensor units are provided for determining the cable angles relative to the direction of gravitational force, which are associated to different strands of cables.
4. The crane according to any of the preceding claims, wherein the crane includes at least two strands of cables for lifting the load (10), and at least two gyroscope units are provided for measuring the cable angular velocities, which are associated to different strands of cables.
5. The crane according to claim 4, wherein the gyroscope unit is arranged on the cable follower.
6. The crane according to claim 5, wherein the crane includes at least two strands of cables for lifting the load (10), and at least two cable followers are provided, which are associated to different strands of cables.
7. The crane according to any of the preceding claims, wherein a display unit is provided for indicating a deviation resulting from the measured cable angle, in particular for indicating a cable angle relative to the direction of gravitational force and/or a horizontal deviation of the load (10) resulting therefrom.
8. The crane according to claim 7, wherein the display optically and/or acoustically indicates a perpendicular cable position.
9. The crane according to any of the preceding claims, wherein a warning means is provided, which warns the crane operator when an admissible range of values (70) for a deviation resulting from the measured cable angle, in particular for the cable angle relative to the direction of gravitational force and/or for the horizontal deviation of the load (10) is exceeded, in particular by an optical and/or acoustic signal.
10. The crane according to any of the preceding claims, wherein the crane control, in particular the warning means and/or the overload protection, additionally evaluates data of a cable force sensor.
11. The crane according to any of the preceding claims, wherein the crane includes at least two strands of cables for lifting the load (10), whose cable field twisting is determined.
12. The crane according to claim 11, wherein a display unit is provided for indicating the cable field twisting.
13. The crane according to claim 11, wherein a warning means is provided, which warns the crane operator when an admissible range of values for the cable field twisting is exceeded, in particular by an optical and/or acoustic signal.
14. The crane according to any of the preceding claims, wherein an antitwist protection is provided, which automatically intervenes in the control of the crane when an admissible range of values for the cable field twisting is exceeded.
15. The crane according to any of the preceding claims, which includes an automatic load oscillation damping.
16. The crane according to claim 15, wherein the load oscillation damping is based on the data of at least one gyroscope unit.
17. The crane according to claim 15, wherein the sensor unit for determining the cable angle relative to the direction of gravitational force is used for monitoring and/or calibrating the gyroscope unit.
18. The crane according to any of the preceding claims, wherein a function for automatically aligning the crane is provided, by means of which the cable (20) is perpendicularly aligned above the load (10).
19. The crane according to any of the preceding claims, wherein a function for automatically aligning the crane is provided, by means of which a cable field twisting is compensated.
20. The crane according to any of the preceding claims, comprising a memory for storing load data on the basis of the cable angle for service life calculation and/or for documentation.
21. The crane according to any of the preceding claims, wherein the data measured by the first and the second sensor unit are evaluated by a first and a second observer circuit.
22. The crane according to any of the preceding claims, wherein a compensation of the data measured by the first and the second sensor unit is effected with respect to the mounting angle of the sensor units and the slewing angle of the crane.
23. The crane according to any of the preceding claims, wherein sensor errors are detected by a comparison of the data measured by the first and the second sensor unit.
24. The crane according to any of the preceding claims, wherein the torsional oscillation of the cable field is considered in the load oscillation damping by forming an average from the cable angles and/or cable angular velocities determined by the first and the second sensor unit.

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