Patent Application
20220089417
The present invention is based on an operating method for a crane, in particular a container crane, which has an upper load suspension point from which a load is suspended via a cable system so that the load can swing around the upper load suspension point,
The present invention is further based on a control program for a control facility of a crane, wherein the control program comprises machine code which can be executed by the control facility, wherein the execution of the machine code by the control facility causes the control facility to operate the crane according to such an operating method.
The present invention is further based on a control facility of a crane, wherein the control facility is programmed with such a control program so that the execution of the machine code by the control facility causes the control facility to operate the crane according to such an operating method.
The present invention is further based on a crane, in particular a container crane,
When operating cranes, handling a load—for example, of a container—may result in collisions of the handled load with an obstacle. The manual operation of the crane is a special case here. In manual operation, the crane is operated by a crane driver or generally an operator. The operator has full responsibility for the crane and the load guided by the crane. In particular, the operator must ensure that the load does not collide with other objects (obstacles), As a rule, the operators of such cranes are well trained and can readily assess situations which could lead to a collision. However, it can happen that—without direct influence from the operator—the control facility of the crane suddenly triggers an emergency stop (safety stop), In this case, the movement of the upper load suspension point is stopped as quickly as possible, The braking of the upper load suspension point acts on the load via the cable system. In some cases, the load is thereby shifted into an undesired pendulum movement which cannot be foreseen by the operator, As a result of the pendulum movement, a collision can occur despite, and even precisely because of the emergency stop.
Similar problems may arise in the case of automated operation of the crane if an emergency stop or safety stop is suddenly triggered.
In the prior art, solutions for collision protection are known per se. However, these solutions require that the load be rigidly connected to the upper load suspension point. In the solutions of the prior art it is therefore assumed that the load cannot swing around the upper load suspension point. For situations in which swinging of the load is possible, solutions are not known in the prior art.
The object of the present invention is to reliably ensure collision protection even when the load can swing around the upper load suspension point.
The object is achieved by an operating method having the features of claim 1. Advantageous embodiments of the operating method are the subject matter of the dependent claims 2 to 10.
According to the invention, an operating method of the abovementioned type is configured in that
It is possible for the control facility to determine only the inner safety zone, However, it is preferably provided that
This embodiment makes it possible to undertake or request a corresponding reduction in the travel speed in advance before the risk of a collision threatens. As a result, the travel movement can be carried out as such, but only at a reduced travel speed. Thus, the travel movement is not immediately interrupted, or such an interruption requested from the operator. The extent of the reduction in travel speed is determined by the fact that, in the event that a safety stop occurs at the reduced travel speed, the upper load suspension point can be stopped without the risk of a collision of the load with an obstacle. If necessary, a plurality of outer safety zones nested one inside the other can also be determined, the travel speed—in relation to the different outer safety zones—being reduced further and further from the outside to the inside.
It is possible for the control facility to operate in an automatic operation in which the control facility independently determines which travel movement the upper load suspension point is to carry out in each case. However, the control facility preferably operates in a manual operation in which the control facility repeatedly receives travel commands from the operator for the upper load suspension point. In this case, the control facility activates the drives at least when no object different from the load object has entered the inner safety zone or the outer safety zone, in each case in accordance with the predefined travel commands.
The control facility preferably determines a braking distance of the upper load suspension point on the basis of the current travel speed of the upper load suspension point and takes into account the braking distance of the upper load suspension point and a pendulum movement of the load around the upper load suspension point when determining the inner safety zone. This procedure makes it possible to assess the inner safety zone as well as possible. Intervention in the actually desired travel movement of the upper load suspension point is thereby reduced to those cases in which it is actually necessary.
As a rule, the control facility bases the determination of the braking distance of the upper load suspension point on a previously known, constant acceleration.
Ideally, in addition to the travel speed of the upper load suspension point and the effective pendulum length, the state variables comprise variables characteristic of the actual pendulum movement. As a result, it is possible for the control facility to determine a maximum deflection of the pendulum movement for that time at which the upper load suspension point is stopped, based on the variables characteristic of the actual pendulum movement, i.e. the specific pendulum movement at the time at which the safety stop occurs, and in the context of determining the inner safety zone, the determined maximum deflection of the pendulum movement is taken into account. As a result, the inner safety zone can be determined very precisely in accordance with the actual conditions.
Alternatively, it is possible that the state variables do not comprise the variables characteristic of the actual pendulum movement. In this case, the control facility can take into account the pendulum movement by taking a value dependent on the travel speed of the upper load suspension point and the effective pendulum length from a pendulum table and taking this value into account when determining the inner safety zone. In this case, a value which in practice corresponds to the worst possible case is stored in the pendulum table. Therefore, a worst-case assessment is carried out. This enables reliable determination of the inner safety zone even if the actual pendulum movement is not known.
It is also possible that the state variables also include a wind velocity of a wind flowing around the load. In this case, when determining the inner safety zone, the control facility can also take into account a deflection of the load by the wind. As a result, the probability of collisions can be further reduced. The wind velocity can be given as an amount independent of the direction or in the form of a vector.
Preferably, the control facility determines the deflection of the load by wind by taking a value from a wind table that is dependent on the wind velocity, a mass of the load and a contact surface of the load for the wind and, based on this value, determines the deflection of the load by the wind. This procedure is particularly efficient.
The object is further achieved by a control program having the features of claim 11. According to the invention, a control program of the abovementioned type is designed in such a way that the processing of the machine code by the control facility causes the control facility to operate the crane according to an operating method according to the invention.
The object is further achieved by a control facility having the features of claim 12. According to the invention, a control facility of the abovementioned type is programmed with a control program according to the invention so that the control facility operates the crane according to an operating method according to the invention.
The object is further achieved by a crane having the features of claim 13. According to the invention, the control facility of the crane is designed as a control facility according to the invention.
The properties, features and advantages of this invention described above and the manner in which these are achieved will become dearer and more readily understandable in connection with the following description of the exemplary embodiments, which are explained in more detail in conjunction with the drawings. These show in diagrammatic view:
According to
Provided the pendulum movement takes place in a vertical plane, the pendulum movement can be fully described by three variables. These three variables are the effective pendulum length l, the current deflection angle φ1 and the current angular velocity ω. As is generally known, the current angular velocity ω corresponds to the time derivative of the current deflection angle φ1. The current deflection angle φ1 has a value of 0° if—within the vertical plane—the load 3 is located exactly below the upper load suspension point 1. The present invention is explained hereinafter in connection with such a pendulum movement. In the case of an additional pendulum movement in a plane orthogonal to the aforementioned vertical plane, a further current deflection angle and a further current angular velocity and, if appropriate, a phase offset of the two pendulum movements relative to one another must be taken into account. However, this is easily possible as the two planes orthogonal to one another can be considered independently of one another. The system therefore remains the same.
According to
In the case of such an embodiment—i.e. as a crane with a basic framework 5, a crossmember 6 and a trolley 7—the crane can, for example, be designed as a gantry crane or as a container bridge. In particular, container bridges are often used for transferring containers to and from ships (STS=ship to shore). However, other embodiments are also possible, for example as gantry cranes. Also, the load 3 need not necessarily be a container, even if this is often the case.
The corresponding set points x*, y*, l* (or the specification of directions of change and if applicable also rates of change) are specified by a control facility 9 which controls the drives 4a, 4b, 4c of the crane. The upper load suspension point 1, and with it the load 3, are moved in accordance with the actuation of the drives 4a, 4b, and the load 3 is raised or lowered in accordance with the actuation of the drive 4c.
The control facility 9 is programmed with a control program 10. The control program 10 comprises machine code 11 which can be executed by the control facility 9. The execution of the machine code 11 by the control facility 9 causes the control facility 9 to operate the crane according to an operating method which is explained in more detail hereinafter.
In the context of the present invention, it is assumed that the crane executes a travel movement in the x direction. For a travel movement in the y direction or a combined travel movement both in the x direction and in the y direction, fully analogous executions apply, where applicable.
According to
In a step S2, the control facility 9 determines—even if only provisionally—control commands C for the drives 4a, 4b, 4c. In an automatic operation, the control facility 9 determines the control commands C independently with the aid of its control program 10. In a manual operation, the control facility 9 determines the control commands C on the basis of travel commands F from an operator 12. The control commands C determine in particular the set points x*, y* and l* for the drives 4a, 4b, 4c.
The manner in which the control commands C are determined is of subordinate importance in the context of the present invention. Preferably, however, the control facility 9 operates in manual operation, in which the control facility 9 repeatedly receives the travel commands F from the operator 12. In this case, the travel commands F comprise, on the one hand, the travel commands for moving the upper load suspension point 1. On the other hand, they comprise the travel commands for raising and lowering the load 3.
In a step S3, the control facility 9 checks whether a safety stop has been triggered. If this is the case, the control facility 9 proceeds to a step S4, in which the control facility 9 ends the movement of the upper load suspension point 1, and with it the load 3, as quickly as possible (emergency stop). In a subsequent step S5, the control facility 9 then checks whether it is again given a release to resume the movement of the upper load suspension point 1. The control facility 9 carries out step S5 repeatedly until this takes place.
If a safety stop has not been triggered, the control facility 9 determines an inner safety zone 13 around the load 3 in a step S6 (see
The inner safety zone 13 is determined as a function of state variables of the crane. These are the state variables as they exist at the time at which the safety stop is triggered. The state variables comprise at bast the position of the upper bad suspension point 1, that is to say, for example, its x and y position, the travel speed v of the upper bad suspension point 1 and the distance of the load 3 from the upper bad suspension point 1, that is to say as a result the effective pendulum length l. It is assumed hereinafter that the corresponding actual values x, y, l are involved. Alternatively, however, it may also be the set points x*, y*, l* that are involved. The determination of the inner safety zone 13 will be explained in more detail later.
In a step S7, the control facility 9 receives information from the surroundings of the bad 3. The information can be made available to the control facility 3 in various ways—possibly also in combination. For example, it may be information about stationary obstacles, for example building structures. Such information need only be specified to the control facility 9 once. It can also be information about temporarily stationary obstacles, for example about other loads which have already been handled or have yet to be handled. Information about loads which have already been handled may be known to the control facility 9 on the basis of its operation in the past. Information about loads yet to be handled can be made known to the control facility 9 in some other way, for example by specifying a sequence to be processed for handling loads. It can also be information about movable obstacles, for example vehicles or persons. Such information can be made known to the control facility 9, for example via images from a camera or a plurality of cameras.
By evaluating the information received, the control facility 9 checks, in a step S8, whether an object 14 different from the load 3 is entering the inner safety zone 13.
If this is not the case, the control facility 9 proceeds to a step S9. In step S9, the control facility 9 executes the control commands C determined in step S2. It thus controls the drives 4a, 4b, 4c accordingly. The upper load suspension point 1, and with it the load 3, are thus operated by the control facility 9 in accordance with the desired actuation. As a result, the control facility 9 thus maintains the movement of the upper load suspension point 1. There is no special message M to the operator 12. In particular, in the case of manual operation, the control facility 9 controls the drives 4a, 4b, 4c in this case in accordance with the predefined travel commands F.
If, on the other hand, the control facility 9 has detected in step S8 that an object 14 different from the load 3 has entered the inner safety zone 13, the control facility 9 stops the movement of the upper load suspension point 1 in a step S10. Also in step S10, the movement of the upper load suspension point 1—analogously to step S4—is terminated as quickly as possible. Alternatively or in addition, in a step S11, the control facility 9 can output the aforementioned special message M to the operator 12. By means of the special message M, the operator 12 is prompted to stop the movement of the upper load suspension point 1.
Both from step S9 and from step S10 or from step S11 onwards, the control facility 9 returns to step S2. As a result, inter alia, the inner safety zone 13 is dynamically determined repeatedly during the movement of the upper load suspension point 1.
Various possibilities for determining the inner safety zone 13 in the horizontal direction are explained hereinafter. The determination in the vertical direction is simple and indiscriminate.
The determination of the inner safety zone 13 begins with the consideration that the upper load suspension point 1 is located at a current position s0 at the time at which the safety stop of step S10 is triggered, and is moving at a travel speed v. Assuming that the braking of the upper load suspension point 1 takes place with a constant acceleration a, the condition applies to the braking distance s1 of the upper load suspension point 1
s1=v2/2a (1)
The acceleration a is—of course—directed counter to the travel speed v.
It is also possible to carry out an analogous procedure for the pendulum length l. In this case, the change in the pendulum length l, that is to say, the lifting speed with which the load 3 is raised or lowered, is reduced to 0 via a speed ramp. The acceleration with which the lifting speed is reduced to 0 can alternatively be load-independent or load-dependent. In particular, when lowering the load 3, the acceleration with which the lifting speed is reduced to 0 can be dependent on the mass m of the load and if applicable, also on the position of the trolley 7 on the crossmember 6. If, on the other hand, the load 3 is being raised, the lifting speed can, as a rule, be reduced to 0 very quickly and independently of the mass of the load 3 and the position of the trolley 7 on the crossmember 6.
However, as a result of the current position s0 and the braking distance s1, the inner safety zone 13 is not yet fully defined. This is because the load 3 executes a pendulum movement at the time at which the safety stop is triggered. It is therefore necessary for the control facility 9 not only to take into account the current position s0 and the braking distance s1 of the upper load suspension point 1 when determining the inner safety zone 13, but rather the control facility 9 must in addition also take into account the pendulum movement of the load 3 around the upper load suspension point 1.
As aforementioned, the pendulum movement can be described by the effective pendulum length l, the current deflection angle φ1 and the current angular velocity ω. The pendulum length l is always known to the control facility 9. It is possible that the current deflection angle φ1 and the current angular velocity ω are also known to the control facility 9. However, it is also possible that they are not known to the control facility 9.
Hereinafter, there is initially no distinction between these two cases—the current deflection angle φ1 and the current angular velocity ω are known or not known to the control facility 9. Instead, it will be explained how a four-dimensional table 15 (see
In order to be able to determine the individual entries for the first pendulum table 15, the four input variables v, l, φ1 and ω must be varied incrementally. The other parameters—for example, acceleration a—are constant and predefined. For each specific combination of the four input variables v, l, φ1 and ω, the respective maximum deflection φ2 can be easily determined. In particular, the equations of motion of the upper load suspension point 1 and the load 3 are known and can be easily solved—analytically or numerically.
The limits for the input variables v, l, φ1 and ω of the first pendulum table 15 can easily be determined in a meaningful way. The maximum possible value for the travel speed v is readily known. The travel speed v has a minimum value of 0. The same applies to the pendulum length l. Here, too, a minimum value and a maximum value can easily be determined in a meaningful way. Reasonable assumptions may be made for the pendulum movement of the load 3 at the time at which the safety stop is triggered. In particular, based on empirical values, it can be known how strong the pendulum movement can be. For example, it can be empirically known that in actual operation there is a maximum oscillation of 5°. The empirical numerical value of 5° is, of course, only purely by way of example. Furthermore, the empirical numerical value may depend in particular on the pendulum length l and if applicable, also on the travel speed v.
In order to fill the first pendulum table 16, the various possible values for the travel speed v and the pendulum length l must therefore be processed incrementally (as a rule, as the outermost and innermost loop). Increments of these two loops can be determined as required. For each specific value of the travel speed v and the pendulum length l, the associated empirically maximum possible pendulum angle—hereinafter provided with the reference character α—is then determined in each case. Now possible values are set in an innermost loop—hereinafter provided with the reference character β—between 0 and the empirically maximum possible pendulum angle α and possible states are calculated in an innermost loop for the respective value β of the pendulum movement. The increments can also be determined as required for these two loops.
In order to explain the procedure somewhat more specifically, a program-like code is reproduced hereinafter, The variables v1, v2 and δv are used for the minimum value, the maximum value, and the increment of the travel speed v. In an analogous manner, the variables I1, I2 and δl are used for the minimum value, the maximum value, and the increment of the pendulum length l. The variable δφ is used for the increment when varying the maximum deflection β. The variable δφ is used for the increment when viewing the individual states of a specific pendulum movement.
A further table 16 can be determined on the basis of the first pendulum table 15. The further table 16 is only two-dimensional as shown in
In order to explain the procedure somewhat more specifically, a program-like code is reproduced hereinafter. The same nomenclature is used here as before for the first pendulum table 15. It is also assumed that the entries for the first pendulum table 15 have already been determined.
It is even possible, within the scope of the determination of the two pendulum tables 15, 16 explained above, to take into account the lifting speed and, if necessary, also the associated acceleration. As a result of this procedure, the two pendulum tables 15, 16 are, with regard to their input variables, possibly increased by one dimension (namely the lifting speed) or by two dimensions (namely the lifting speed and the acceleration with which the lifting speed is reduced to 0). The basic procedure remains the same, however.
It is possible for the control facility 9 to receive the current values for the deflection angle φ1 and the angular velocity ω in a step S21, as shown in
Likewise, the control facility 9 can also receive other values which characterize the pendulum movement. In this case, the control facility 9 can determine the deflection angle φ1 and the angular velocity ω based on the characteristic variables.
Thus, the state variables on the basis of which the control facility 9 determines the inner safety zone 13, that is to say in addition to the travel speed v and to the effective pendulum length l for the actual pendulum movement, comprise characteristic variables φ1, ω. The control facility 9 is therefore not only able to determine the braking distance s1 in a step S22, but rather, in a step S23, the control facility 9 is also able to determine the maximum deflection φ2 on the basis of the four values v, l, φ1 and ω which are now specifically given. In this case, it is possible for the control facility 9 to perform an analytical determination. However, the determination has preferably already been undertaken and is made available to the control facility 9 as shown in
s2=l·sin (2)
In a step S24, the control facility 9 then determines the inner safety zone 13. The inner safety zone 13 is thus obtained from the procedure by taking into account the braking distance s1 and the longitudinal deflection s2. In the simplest case, viewed in the current direction of travel, the position s is obtained as the boundary of the inner safety zone 13 as follows:
s=s0+s1+s2 (3)
In addition, the control facility 9 can also use other variables when determining the inner safety zone 13. In contrast to the aforementioned variables, however, these variables do not change when moving the upper load suspension point 1. Examples of such variables are the dimensions of the load 3 or maximum possible dimensions of the load 3. For example, if the load 3 is a container, it may be known that 48-foot containers maximum are handled. The associated length, width and height would correspond to maximum values for the dimensions of the load 3. Specifically, for example if a 40-foot container or a 20-foot container is handled, however, these values can also be used as an alternative.
Alternatively, it is possible that the control facility 9 does not receive the current values for the deflection angle φ1 and the angular velocity ω (or other values which characterize the actual pendulum movement), In this case, the control facility 9 can only undertake a worst-case assessment. A step S31 (
s2=l−sin(φ3) (4)
In a step S33, the control facility 9 then determines the inner safety zone 13. The step S33 corresponds to the step S24 in
The procedure of
On the basis of the receipt of the wind velocity vW, the state variables on the basis of which the inner safety zone 13 is determined can thus additionally comprise the wind velocity vW. As a result, the control facility 9 is able to determine an additional deflection s3 in a step S42. The additional deflection s3 corresponds to the static deflection of the load 3 caused by the wind velocity vW. It is dependent on the effective pendulum length l, the force exerted by the wind on the load 3 and the mass m of the load 3. The force is in turn dependent on the wind velocity vW. It is therefore possible, for example, to determine a further table 17 as shown in
However, regardless of the manner in which the control facility 9 determines the additional deflection s3, the control facility 9 is able, in a step S43, to take into account not only the braking distance s1 and the longitudinal deflection s2, but additionally also the additional deflection s3 within the scope of the determination of the inner safety zone 13.
The present invention may also be configured in other ways. This will be explained in more detail hereinafter in connection with
In step S51, the control facility 9 determines at least one outer safety zone 18. The outer safety zone 18 surrounds the inner safety zone 13, as shown in
In step S52, the control facility 9 checks whether the object 14 is entering the outer safety zone 18. If this is not the case, the control facility 9 proceeds to step S9. In particular in manual operation, the control facility 9 performs the actuation of the drives 4a, 4b, 4c in this case in accordance with the predefined travel commands F. Any message M′ for reducing the travel speed v is not output to the operator 12. If, on the other hand, this is the case, the control facility 9 proceeds to step S8.
If the control facility 9 determines in step S8 that the object 14 has entered the outer safety zone 18 but not the inner safety zone 13, the control facility 9 proceeds to a step S53. In step S53, the control facility 9 determines modified control commands C. In particular, in step S53 the control facility 9 reduces the travel speed v of the upper load suspension point 1. Alternatively or in addition, it can output a corresponding message M′ to the operator 12 to reduce the travel speed v.
In summary, the present invention thus relates to the following facts:
A crane has an upper load suspension point 1 from which a load 3 is suspended via a cable system 2 so that the load 3 can swing around the upper load suspension point 1. A control facility 9 of the crane controls drives 4a, 4b of the crane so that the upper load suspension point 1, and with it the load 3, are moved by the control facility 9 in accordance with the actuation. The control facility 9 dynamically determines an inner safety zone 13 around the load 3 repeatedly when moving the upper load suspension point 1 as a function of state variables x, v, l, φ1, ω, vW of the crane. The state variables x, v, l, φ1, ω, vW comprise at least one position x of the upper load suspension point 1, one travel speed v of the upper load suspension point 1 and one effective pendulum length l of the load 3 around the upper load suspension point 1. The control facility 9 checks, on the basis of further information known from the control facility 9, whether an object 14 different from the load 3 is entering the inner safety zone 13. As soon as an object 14 enters the inner safety zone 13, the control facility 9 stops the movement of the upper load suspension point 1 or outputs a message M to an operator 12 of the crane to stop the movement of the upper load suspension point 1. Otherwise, the control facility 9 maintains the movement of the upper load suspension point 1 or does not output a message M to the operator 12 of the crane to stop the movement of the upper load suspension point 1.
The present invention has many advantages. In particular, it can be ensured in a simple and efficient manner that the load 3, although it can swing, does not collide with an object (object 14) which suddenly appears, even in the event of a sudden safety stop. This applies equally to manual operation and to automated operation of the crane. Otherwise, this risk exists, although in normal operation a so-called sway control acts. This is because, with the triggering of a safety stop, such a sway control loses its function as the safety stop has priority. Furthermore, the present invention can also be used in cranes in which the effective pendulum length l may reach high values—in some cases over 50 m. In the case of such great pendulum lengths l, inclined stranding, which effectively prevents appreciable swinging of the load 3 in short pendulum lengths l, is virtually ineffective. Furthermore, on the one hand, a simple implementation is possible in which only variables which are readily available during operation of the crane are used, namely the pendulum length l and the travel speed v. This solution is very cost-effective. Alternatively, it is possible to also record the current pendulum movement. As a result, the inner and, if appropriate, also the outer safety zone 13, 18 can be defined to be as small and safe as possible according to the situation.
Although the invention has been illustrated and described in detail by the preferred exemplary embodiment, the invention is not limited by the disclosed examples, and other variations may be derived therefrom by a person skilled in the art without departing from the scope of the invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 19155318.9 | Feb 2019 | EP | regional |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2020/051574 | 1/23/2020 | WO | 00 |
