EP2298687B1 - System for determining the load mass of a load suspended on a lifting rope of a crane - Google Patents

Description

The present invention comprises a system for detecting the load mass of a load suspended on a hoist rope of a crane, with a measuring device for measuring the cable force in the hoist rope and a calculation unit for determining the load mass on the basis of the cable force.

Such a system is out of the US 2002/144968 known.

The exact determination of the load mass of a crane lifted load is for a variety of applications of great importance: z. B. is the load mass for the load moment limitation of the crane, that is important for the anti-tip and for structural protection. In addition, the load mass for data acquisition in terms of performance of the crane is of great importance. In particular, can be determined by an exact determination of the load mass, the entire turnover payload. Furthermore, the load mass is also of great importance as a parameter for other control tasks on the crane, such as load-swing damping.

A common method for determining the load mass is the measurement of the cable force in the hoisting rope. The cable force in the hoist cable corresponds at least in a static state substantially the load mass.

The measuring arrangement for measuring the cable force can be arranged either directly on the load receiving means. This arrangement on the load-carrying means has the advantage that only a few disturbing influences are present and thus greater accuracy can be achieved. Disadvantage of this solution, however, is that a power supply and a corresponding signal line to the load-carrying means is necessary.

Another possibility is the arrangement of a measuring arrangement in a connection region between the crane structure and the hoist rope, for example on a deflection roller or on the hoist. This has the advantage that the measuring arrangement can be made very robust and the wiring is relatively simple. A disadvantage of this arrangement of the measuring arrangement, however, is the fact that further interference makes it difficult to accurately determine the load mass from the cable force.

It is already known to use averaging filter for determining the cable force. On the one hand, however, this has the disadvantage that a relatively high delay in the signal output must be accepted. In addition, many other disturbances can not be eliminated by a mean value filter.

The object of the present invention is therefore to provide a system for detecting the load mass of a load suspended on the hoist rope of a crane, which enables an improved determination of the load mass on the basis of the cable force.

This object is achieved by a device according to claim 1. The system according to the invention for detecting the load mass of a load suspended on a hoist rope of a crane comprises a measuring arrangement for measuring the cable force in the hoist rope and a calculation unit for determining the load mass based on the rope power. According to the invention, the calculation unit has a compensation unit and a load mass observer based on a spring-mass model of the rope and the load, the calculation unit describing the influence of the indirect determination of the load mass on the cable force in a dynamic model, from which the load mass is calculated and at least partially compensated.

On the one hand, it may be provided that the compensation unit at least partially compensates static influences of the indirect determination of the load mass via the cable force. For this purpose, according to the invention, the static influences of the indirect determination are modeled and compensated by the compensation unit. This results in a considerably more accurate determination of the load mass, which was not possible at all over averaging filters, since these can not eliminate static influences at all.

Alternatively or additionally, it may be provided that the compensation unit also at least partially compensates for dynamic influences of the indirect determination of the load mass via the cable force. For this purpose, too, it is provided that the compensation unit models the dynamic influences and compensates for the determination of the load mass.

Advantageously, the invention provides that the compensation unit is based on a physical model of the lifting process, which models the static and / or dynamic influences of the indirect determination of the load mass via the cable force. By means of this model, the compensation unit can at least partially compensate for these static and / or dynamic influences.

Advantageously, it is provided that the compensation unit operates on the basis of data on the position and / or movement of the crane. In particular, data relating to the position and / or movement of the hoisting gear and / or data relating to the position and / or movement of the jib and / or the tower are advantageously entered into the compensation unit.

The system according to the invention is used in particular in cantilever turning cranes in which a boom can be up and down about a horizontal rocking axis and can be rotated about a vertical rotation axis via a tower or superstructure.

Advantageously, it is provided that the measuring arrangement is arranged in a connecting element between an element of the crane structure and the hoist rope, in particular on a deflection roller or on the hoist. Advantageously, it is provided that the compensation unit at least partially compensates static and / or dynamic influences of the arrangement of the measuring arrangement. Advantageously, the compensation unit models the influences of the arrangement of the measuring arrangement on the cable force.

Advantageously, it is provided that the compensation unit comprises a rope mass compensation, which takes into account the weight of the hoisting rope. The hoisting rope has a not to negligible own weight, which no longer falsifies the determination of the load mass by the present invention. Advantageously, the compensation unit takes into account the influence of the change in the cable length when lifting and / or lowering the load in the calculation of the load mass. By changing the rope length, the weight of the hoist rope has a different influence on the cable force depending on the lifting phase. The system according to the invention takes this into account.

Advantageously, the system is used in a hoist, which includes a winch, wherein the angle of rotation and / or the rotational speed of the winch enters as an input in the rope mass - compensation. Based on the angle of rotation and / or the rotational speed of the rope length and / or rope speed can be determined and their influence on the cable force in the calculation of the load mass are taken into account.

Alternatively, the rope length and / or the rope speed can also be detected via a measuring roller. This can e.g. be arranged separately on the rope or formed as a deflection roller.

Further advantageously, it is provided that the rope mass compensation takes into account the weight of the wound on the hoist hoist. This is particularly advantageous if the measuring arrangement for measuring the cable force is arranged on the hoist winch, in particular on a torque arm of the hoist winch, since then the rope wound on the winch is supported on the measuring arrangement and thus influences the measured values.

Further advantageously, it is provided that the cable mass compensation takes into account a changing by the movement of the crane structure length and / or orientation of Hubseilabschnitten. This is particularly important in those cranes in which the Hubverseilung changes in a movement of the crane structure, in particular during a movement of the boom, in their length or orientation. In particular, this is the case when the rope is not guided parallel to the boom on the crane, but when the rope occupies an angle with the boom, which changes by a rocking up and down of the boom. Depending on the position of the crane structure, in particular of the boom, so different lengths and / or orientations of the sections of the hoisting rope, which in turn affects the influence of the own weight of the hoist rope on the output signal of the measuring arrangement.

Further advantageously, it is provided that the compensation unit comprises a Umlenkrollenkompensation, which takes into account friction effects by the deflection of the hoisting rope to one or more pulleys. Advantageously, in particular the bending work necessary for deflecting the hoist rope is considered as a frictional effect. Alternatively or additionally, the rolling friction in the pulleys can be taken into account.

Advantageously, it is provided that the Umlenkrollenkompensation considered the direction of rotation and / or rotational speed of the pulleys. In particular, the direction of rotation has a significant influence on the cable strength.

Advantageously, the Umlenkrollenkompensation calculates the conditional by the movement of the crane structure and the movement of the lifting direction of rotation and / or rotational speed of the pulleys. In particular, with multiple deflections of the hoisting rope between the tower and boom complicated movement patterns can arise here, which have a corresponding effect on the output signal of the measuring arrangement.

Advantageously, the deflection roller compensation determines the friction effects as a function of the measured cable force. The cable force has a decisive influence on the friction effects. Advantageously, the friction effects are determined on the basis of a linear function of the measured cable force, since a linear function represents a relatively good approximation of the physical situation.

Further advantageously, it is provided in the system according to the invention that the compensation unit takes into account the influence of the acceleration of the load mass and / or the hoist on the cable force in the determination of the load mass. The acceleration of the load mass and / or the hoist generates a dynamic component of the cable force, which is at least partially compensated by the compensation according to the invention. The compensation unit operates advantageously on the basis of a physical model, which describes the influence of the acceleration of the load mass and / or the hoist on the cable force.

Further advantageously, it is provided that the calculation unit takes into account the vibration dynamics, which arises due to the extensibility of the hoisting cable, in the determination of the load mass. In addition to the accelerations, which are caused by the induced over the hoist accelerations, the system of rope and load also has a vibration dynamics, which arises due to the extensibility of the hoisting rope. Advantageously, the compensation unit compensates for this vibration dynamics at least partially. Advantageously, the compensation unit for compensating the vibration dynamics is based on a physical model.

According to the invention, the calculation unit of the system according to the invention comprises a load mass observer, which is based on a spring-mass model of the rope and the load. In this case, the mass of the actual load as well as the mass of the load-receiving means and the sling means in the model are advantageously described as the mass. As a spring, however, the rope between the winch and the load-carrying means enters the model.

Advantageously, the load mass observer constantly compares the measured cable force with the cable force predicted on the basis of the previously measured cable force on the basis of the spring-mass model. Based on this comparison, the load mass observer estimates the load mass of the load which is included in the spring-mass model of the rope and the load as parameters. As a result, the load mass can be determined with high accuracy and compensation of dynamic influences.

Advantageously, the load mass observer takes into account the measuring noise of the measuring signals. Advantageously, a mean-free white noise is used for this purpose.

Advantageously, as measurement signals in addition to the output signal of the measuring arrangement for determining the cable force data on the length of the rope. Advantageously, a cable force normalized with respect to the permissible maximum load is used as the parameter of the load mass observer.

The present invention further includes a crane having a system for detecting the load mass of a load suspended on a hoist rope, as described above. The crane is in particular a jib crane, in which the boom can be up and down about a horizontal rocking axis. Further advantageously, the crane can be rotated about a vertical axis of rotation. In particular, the boom is hinged to a tower, which is rotatable relative to an undercarriage about a vertical axis of rotation. In particular, the crane can be a mobile harbor crane. However, the system according to the invention can also be used with other crane types, e.g. for overhead cranes or tower cranes.

Advantageously, the system is used in a crane in which the measuring arrangement for measuring the cable force is arranged in a connecting element between an element of the crane structure and the hoist rope, in particular in a deflection roller or on the hoist. This results in a very robust arrangement, which still allows the inventive system an exact determination of the load mass.

The inventive system a variety of applications are possible, which could not be realized with known inaccurate systems. For example, a slack rope detection can be established which, based on the system of the invention, recognizes that the load has been dropped. Hereupon, an immediate shutdown of the hoist is initiated, which prevents rope damage by unwound ropes. Optionally, this mechanical slack rope switch can be omitted. In addition, a detection of very low loads, such as empty containers, now also possible.

Furthermore, the system according to the invention has the great advantage over mean value filters that the load mass can be determined without much delay. This results in a higher turnover because fewer stops occur when the load mass signal is used for load torque limiting. In addition, will Increases the service life of the crane, since the load torque limit can intervene without a long time delay.

In addition to the system and the crane, the present invention further comprises a method for detecting the load mass of a hoisting rope load with such a system, comprising the steps of:

Measuring the rope force in hoist rope; Calculation of the load mass on the basis of the cable force; wherein the influence of the determination of the load mass on the cable force is described in a model and at least partially compensated.

In particular, the compensation takes place on the basis of a model of the static and / or dynamic influences of this determination. As a result, these influences can be calculated and at least partially compensated by the compensation unit.

The method according to the invention is advantageously carried out as described above with reference to the system and the crane. In particular, the method according to the invention is carried out by means of a system as described above.

The present invention will now be explained in more detail with reference to embodiments and drawings.

Fig. 1

ein Ausführungsbeispiel eines erfindungsgemäßen Kranes,

Fig. 2

eine schematische Darstellung eines Ausführungsbeispiels eines erfindungsgemäßen Systems und Verfahrens,

Fig. 3a und 3b

die Anordnung einer Meßanordnung an der Hubwinde,

Fig. 4

die Anordnung einer Meßanordnung an der Hubwinde und die Seilführung des Hubseils über Umlenkrollen,

Fig. 5

eine Darstellung der bei der Umlenkrollen-Kompensation berücksichtigten Kräfte,

Fig. 6

eine Darstellung der bei der Seilmassen-Kompensation berücksichtigten Kräfte,

Fig. 7

eine Prinzipdarstellung des Masse-Feder-Modells, welches dem erfindungsgemäßen Seilmassenbeobachter zu Grunde liegt, und

Fig. 8

eine schematische Darstellung eines Ausführungsbeispiels eines erfindungsgemäßen Seilmassenbeobachters.

Showing:

Fig. 1

an embodiment of a crane according to the invention,

Fig. 2

a schematic representation of an embodiment of a system and method according to the invention,

Fig. 3a and 3b

the arrangement of a measuring arrangement on the hoist winch,

Fig. 4

the arrangement of a measuring arrangement on the hoist winch and the cable guide of the hoist rope over pulleys,

Fig. 5

a representation of the forces taken into account in deflection pulley compensation,

Fig. 6

a representation of the forces taken into account in rope mass compensation,

Fig. 7

a schematic diagram of the mass-spring model, which is based on the rope mass observer according to the invention, and

Fig. 8

a schematic representation of an embodiment of a cable mass observer according to the invention.

FIG. 1 shows an embodiment of a crane according to the invention, in which an embodiment of a system according to the invention for detecting the load mass of the crane rope hanging load is used. The crane in the exemplary embodiment is a mobile harbor crane. The crane has an undercarriage 1 with a chassis 9. This allows the crane to be moved in the port. At the Hubort the crane can then be supported on support units 10.

On the undercarriage 1, a tower 2 is arranged rotatably about a vertical axis of rotation. On the tower 2, a boom 5 is articulated about a horizontal axis. The boom 5 can be pivoted about the hydraulic cylinder 7 in the rocker plane up and down.

The crane has a hoist rope 4, which is guided around a deflection roller 11 at the tip of the boom. At the end of the hoisting rope 4, a load-receiving means 12 is arranged, with which a load 3 can be accommodated. The load-receiving means 12 and the load 3 are thereby by moving the hoisting rope 4th raised or lowered. The change of the position of the load receiving means 12 and the load 3 in the vertical direction is thus carried out by reducing or increasing the length I _{S of} the hoisting rope 4. For this purpose, a winch 13 is provided, which moves the hoist rope. The winch 13 is arranged on the superstructure. Furthermore, the hoist rope 4 is first guided by the winch 13 via a first deflection roller 6 at the top of the tower 2 to a deflection roller 14 at the top of the boom 5 and from there back to the tower 2, where it via a second guide roller 8 to a deflection roller 11 is guided on the jib tip, from where the hoist rope runs down to the load 3.

The load receiving means 12 and the load can be further moved by turning the tower 2 by the angle φ _D and by rocking up and down the boom 5 by the angle φ _A in the horizontal. Due to the arrangement of the winch 13 on the superstructure, the lifting and luffing of the jib 5 results in addition to the movement of the load in the radial direction, a lifting movement of the load 3. This must optionally be compensated by a corresponding control of the winch 13.

FIG. 2 shows an embodiment of a system according to the invention for detecting the load mass of a hanging on a hoist rope of a crane load. The input 20 of the system is signal 20, which is generated by a measuring arrangement for measuring the cable force in the hoist rope. This is supplied to the calculation unit 26 according to the invention for determining the load mass. As output signal 24, the calculation unit 26 supplies the exact load mass. In this case, the calculation unit has a compensation unit which at least partially compensates for the influences of the indirect determination of the load mass via the cable force. The compensation unit calculates the influences based on data on the crane state, which are transmitted from the crane state unit 25 to the calculation unit 26. In particular, the erecting or rocking angle or the upright or rocking angular velocity of the boom are used in the calculation unit. Furthermore, the rope length and / or the rope speed can enter the calculation unit, wherein these are determined in particular via the position and / or speed of the hoist winch 13.

The compensation unit is based on a physical model of the lifting system, by which the influences of the individual components of the lifting system on the cable force and the load mass can be calculated. As a result, the compensation unit can calculate these influences and at least partially compensate them.

In the exemplary embodiment, the compensation unit comprises three components which, however, could also be used independently of each other: The compensation unit initially comprises a deflection roller compensation 21 which compensates for the friction of the cable at the deflection rollers. Furthermore, the compensation unit comprises a rope mass compensation, which compensates for the influence of the rope weight on the cable force and thus on the load mass. The compensation unit further comprises a load mass observer 23, which takes into account dynamic disturbances of the signal due to the acceleration of the load mass or the hoist, and in particular those which arise due to the momentum of the system of hoisting rope and load.

The individual components of the system according to the invention will now be described in detail in more detail:

In the FIGS. 3a and 3b the hoist winch of the crane according to the invention is shown, on which a measuring arrangement 34 for measuring the cable force is arranged. The hoist winch 30 is rotatably mounted on two frame members 31 and 35 about a rotation axis 32. On the frame member 31, the Kraftmeßanordnung 34 is arranged as a torque arm. The frame member 31 is articulated about the axis 33 on the crane. On the opposite side of the frame member 31 is articulated via the Kraftmeßanordnung 34 on the crane. The force measuring arrangement 34 is rod-shaped and bolted via a Verbolzung 36 with the frame member 31 and a Verbolzung 37 with the crane. As Kraftmeßanordnung 34 comes here a Tension Load Cell used (TLC), ie a Kraftmeßlasche. Alternatively, as Kraftmeßanordnung eg a Kraftmeßbolzen or a load cell can be used.

Due to the arrangement of the force measuring arrangement 34 between the crane structure and the winch, the cable force F _S acts first on the winch and on the winch frame on the force measuring arrangement in which a force F _{TLC is} caused by the cable force F _S.

In order to calculate the cable force F _S from the force F _TLC measured by the force measuring arrangement 34, the geometry of the arrangement of the force measuring arrangement 34 on the winch must be taken into account. In this case, the mass of the winch itself is to be considered, which is supported on the force measuring arrangement 34 and thus counteracts the cable force.

In addition, it may be necessary to take into account that the force measuring arrangement 34 as in FIG. 3b shown only on one of the two frame members 31 and 35 is arranged. The frame member 35 is firmly bolted to the crane structure. At this frame member 35, the drive for the hoist winch is arranged.

The principle of measurement of the load mass on the basis of the cable force or on the basis of the force which is measured by the measuring arrangement 34 and the forces occurring are again in FIG. 4 summarized.

The hoist rope 4 runs from the winch 30 via deflection rollers 6, 14 and 8 to the guide roller 11 at the tip of the boom, from where the hoist rope 4 is guided to the load 3. The mass of the load 3 generates a force in the hoist rope 4, which introduces the hoist rope in the winch 30. The winch 30 is hinged to a winch frame and acts on this with a corresponding force. This introduces a force F _TLC into the force measuring assembly 34 which connects the frame member 31 of the winch frame to the crane structure. Due to the geometric relationships between hoist rope, hoist winch, winch frame and Kraftmeßanordnung Thus, it is possible to deduce the mass of the load from the force measured by the force measuring arrangement 34.

However, the arrangement of the measuring arrangement in a connecting element between crane structure and hoist rope, there are a number of influences, which would lead to significant inaccuracies in the determination of the load mass without compensation. The calculation unit according to the invention therefore has a corresponding compensation unit which compensates for these influences.

It should first be based on FIG. 5 the Umlenkrollenkompensation invention are described in more detail, are compensated by which friction effects on the pulleys. The hoist rope 4 is thereby deflected at the deflection rollers 6, 14, 8 and 11 in each case by a certain angle. This results in a number of frictional effects on the cable force. In this case, a frictional force arises on each deflection roller which, depending on the situation, in particular depending on the direction of rotation of the deflection roller, increases or decreases the force measured by the measuring arrangement.

This initially creates a rolling friction on the bearing of the pulley, which is determined according to the Striebeck curve. However, this rolling friction is relatively low and can therefore be neglected. The far greater influence has the bending of the hoist rope on the pulleys. In this case, the hoist rope is subject both during running and when leaving the deflection roller of a deformation which requires a corresponding deformation work. The size of this due to the deformation of the hoisting rope friction on the pulleys is determined essentially by the radius of the pulleys and by the cable force.

Measurements have shown that the total friction on each deflection roller is substantially linear to the cable force. The angular velocity of the pulleys, however, has only a very small influence on the friction. It is, however to note that the friction on each pulley depending on the direction of rotation of the pulley either added to the measured cable force or must be subtracted from this. When lifting the load while the frictional force of the pulleys counteracts the lifting force generated by the hoisting winch, so that the measured cable force increases by the frictional forces. When lowering the load by the hoist, however, the measured cable force decreases by a corresponding amount.

It should also be noted that the hoist rope between the tower top and the jib tip back and forth, wherein the two pulleys 6 and 8 are arranged on the tower top and the two pulleys 14 and 11 on the jib tip. Therefore, there is also a movement of the deflection rollers 8, 11, and 14, while the deflection roller 6 is not moved without movement of the lifting mechanism also when rocking and jogging the boom. Accordingly, a frictional force, which essentially corresponds to% of the frictional force during raising and lowering of the load via the hoisting mechanism, results during the rocking up and down of the jib.

The compensation unit according to the invention compensates for the influences resulting from the friction on the deflection rollers. For this purpose, the compensation unit determines the direction of rotation of the pulleys on the basis of the position and / or movement of the hoist and the boom. It must be considered that in a combined movement of the hoist and boom quite complex movement patterns of the pulleys can arise, so that not all pulleys with the same sign enter into the cable force. The Umlenkrollenkompensation is therefore advantageously based on the winch speed and the erection speed of the boom.

The calculation unit according to the invention further comprises a cable mass compensation which is now based on FIG. 6 is shown in more detail. As already described above, the weight force F _W 36 of the winch must first be taken into account when calculating the cable force from the measuring signal of the measuring arrangement 34, which is supported on the Kraftmeßanordnung 34. On the winch, however, the hoist rope is additionally at least partially wound up. The mass of the hoisting rope, which is wound on the hoist winch, is thus also supported on the force measuring arrangement 34. Therefore, the weight F _RW 37 of the wound on the winch hoist must be taken into account. This weight force can be determined, for example, based on the angle of rotation of the hoist winch.

Furthermore, the masses of the individual cable sections between the pulleys have an influence on the cable force and thus on the determination of the load mass. The cable sections 41 and 42 thereby increase the measured cable force by the mass of the cable, while the cable sections 43, 44 and 45 reduce the measured cable force. In the calculation of this influence must be considered in each case the length and the angle of the cable sections to the horizontal. It should be noted that only for the cable section 45 is a constant length and a constant angle. The section 41, however, is changed in length by raising and lowering the load. The sections 42-44 are in turn changed by rocking up and down the boom both in their length and in their orientation. The rope mass compensation is therefore based on the position of the boom and the hoist winch.

The Umlenkrollenkompensation and the rope mass compensation compensate thus substantially the influence of the arrangement of the measuring arrangement on the hoist winch. Alternatively to the arrangement of the measuring arrangement on the hoist winch is also conceivable to integrate a measuring arrangement in one of the deflection rollers, in particular in the deflection roller 8 on the jib tip. In this arrangement, the measuring arrangement, the compensation is again the principles presented above, but the friction effects and the effects of the cable mass must be adapted to the measured force by the other arrangement of the measuring device accordingly.

The system according to the invention not only takes into account the systematic influences which the arrangement of the measuring arrangement on a connecting element between Crane structure and hoisting rope on the determination of the load mass has, but also compensates for dynamic effects, which are due to the acceleration of load mass and / or hoist and the extensibility of the hoisting rope.

Due to the elasticity of the hoisting rope, the system of hoist rope and load essentially forms a spring-mass pendulum, which is excited by the hoist. This creates vibrations which are superimposed on the static component of the rope force signal which corresponds to the load mass. The load mass observer is based on a physical model of the spring-mass system of hoisting rope and load. The model is schematically in Fig. 7 played. By comparing the cable force resulting from this model with the measured cable force, the load mass observer 23 estimates the exact load mass, which enters into the physical model as a parameter.

An exemplary embodiment of the load mass observer according to the invention, which is implemented as an extended Kalman filter (EKF), will now be described in more detail below:

2 modeling hoist train

wobei l ₁, l ₂ und l ₃ die Teillängen von der Hubwinde zum Turm, vom Turm zum Auslegerkopf und vom Auslegerkopf zum Lastaufnahmemittel sind. Der Hubwerksstrang bestehend aus Hubwinde, Seil und Lastmasse wird im Folgenden vereinfacht als Feder-Masse-Dämpfer System modelliert und ist in Abbildung 7 dargestellt.The following section derives the dynamic model for the hoist harness. illustration 1 shows the complete construction of a mobile harbor crane (LHM). The load with the mass m _l is lifted by the crane by means of the lifting device and is connected to the lifting hoist via the rope with the total length l _s . The rope is deflected from the load handler via a respective deflection roller on the boom head and tower. It should be noted that the rope is not directly deflected from the boom head to the hoist winch, but that it is deflected from the boom head to the tower, back to the boom head and then over the tower to the hoist winch (see illustration 1 ). This results in the entire rope length too $$l_s\left(t\right)=l_1\left(t\right)+{3l}_2\left(t\right)+l_3\left(t\right).$$

where l ₁ , l ₂ and l _{3 are} the partial lengths from the hoist winch to the tower, from the tower to the boom head and from the boom head to the load handler. The hoist train consisting of hoist winch, rope and load mass is simplified in the following as a spring mass damper system and is modeled in Figure 7 shown.

mit der Erdbeschleunigung g, der Federkonstante c, der Dämpferkonstante d, der Lastposition z, der Lastgeschwindigkeit ż und der Lastbeschleunigung z. Die Seilgeschwindigkeit l̇_s folgt aus der Windengeschwindigkeit ϕ̇_w und dem Windenradius r_w zu $${\dot{l}}_s\left(t\right)=r_w{\dot{\varphi }}_w\left(t\right)\mathrm{.}$$

According to Newton's law of motion, the equation of motion for the spring-mass-damper system thus results $$m_l\ddot{z}\left(t\right)=m_{l}G-\underset{F_c}{\underset{\}}{\left(c\left(z\left(t\right)-l_s\left(t\right)\right)+d\left(\dot{z}\left(t\right)-{\dot{l}}_s\left(t\right)\right)\right)}}$$

with the gravitational acceleration g , the spring constant c, the damper constant d, the load position z, the load speed ż and the load acceleration z. The rope speed ls _s follows from the winch speed φ̇ _w and the winch radius r _w $${\dot{l}}_s\left(t\right)=r_w{\dot{\phi }}_w\left(t\right)\mathrm{,}$$

berechnet werden. Hierbei sind E_s und A_s das Elastizitätsmodul und die Querschnittsfläche des Seils. Da am Hafenmobilkran n_s parallele Seile die Last anheben (vgl. Abbildung 1) ergibt sich die Federsteifigkeit c des Hubwerksstrangs zu $$c=n_s{c}_s\mathrm{.}$$

The spring stiffness c _{s of} a rope of length l _s can by means of Hooke's law to $$c_s=\frac{e_s{A}_s}{l_s}$$

be calculated. Here, E _s and A _{s are} the elastic modulus and the cross-sectional area of the rope. Since the mobile harbor crane n _s parallel ropes the load lift (see FIG. illustration 1 ) gives the spring stiffness c of the hoist to $$c=n_s{c}_s\mathrm{,}$$

gegeben, wobei D das Lehrsche Dämpfungsmaß des Seils darstellt.The damper constant d of the hoist is through $$d=2D\sqrt{{\mathit{cm}}_l}$$

where D is the gauge damping measure of the rope.

wobei γ_l ein mittelwertfreies, weißes Rauschen darstellt.Since the main task of the load mass observer is the estimate of the actual load mass, a dynamic equation must be derived for the load mass. Within this work, the load mass m _{l is} modeled as a random-walk process, ie m _l is disturbed by an additive, mean-free, white noise. Thus, the following dynamic equation results for the load mass $${\dot{m}}_l={\gamma }_l.$$

where γ _{l represents} a mean-free white noise.

3 Observer Draft

und 2 $\mathrm{2}\frac{\mathrm{m}}{\mathrm{s}}$

und die Lastmasse zwischen 0 kg und 150 x 10³kg. Außerdem besitzen die beiden Parameter E_s und A_s auch sehr unterschiedliche Wertebereiche. Diese unterschiedlichen Wertebereiche können bei der Online-Schätzung des Beobachters zu numerischen Problemen führen. Zur Vermeidung dieser numerischen Probleme wird für den Beobachterentwurf ein neuer Parameter $$a_{\mathit{hw}}=\frac{E_s{A}_s{n}_s}{m_{\mathit{max}}}$$

eingeführt, wobei m_max die für den jeweiligen Krantyp maximal zulässige Hublast ist. Außerdem wird im Beobachter nicht direkt die Lastmasse m_l verwendet, sondern die normierte Lastmasse $\frac{m_l}{m_{\mathit{max}}}\mathrm{.}$

In this section, a link to the EKF | 3 | based observer. It should be noted that the value ranges of the individual variables are very different. The rope length l _s and the load position ż are usually between 100 m and 200 m, the rope speed l̇ _s and the load speed ż between $\mathrm{0}\frac{\mathrm{m}}{\mathrm{s}}$

and 2 $\mathrm{2}\frac{\mathrm{m}}{\mathrm{s}}$

and the load mass between 0 kg and 150 x 10 ³ kg. In addition, the two parameters E _s and A _s also have very different value ranges. These different ranges of values can lead to numerical problems in the online estimation of the observer. To avoid these numerical problems, the observer design becomes a new parameter $$a_{\mathit{hw}}=\frac{e_s{A}_s{n}_s}{m_{\mathit{Max}}}$$

introduced, where m _{max is} the maximum permitted lifting capacity for each crane type. In addition, not the load mass m _{l is} used directly in the observer, but the normalized load mass $\frac{m_l}{m_{\mathit{Max}}}\mathrm{,}$

About an incremental wind position be on the crane φ _w measured and the wind speed φ _w calculated. A force measuring sensor provides the cable force F _w measured at the winch. From the winch position and speed, the rope length and speed can be calculated by means of equation (3). When measuring the cable force on the winch F _w , it should be noted that not only the force due to the load mass is measured, but also the friction influences of the pulleys and the dead weight of the rope. However, these disturbances can be eliminated by a compensation algorithm and the actual spring force F _c (see equation (2)) can be calculated from the measured cable force on the winch F _w .

gewählt. Mit dem Zustandsvektor $x={\left[l_s,z,\dot{z},\frac{m_l}{m_{\mathit{max}}}\right]}^T$

kann das dynamische Modell, bestehend aus Gleichungen (2), (4), (5), (6), (7) und (8) in den Zustandsraum transformiert werden.For an observer design, the input quantities u and the output quantities (or measured quantities) y of the system must first be defined. For the present this problem the cable speed is the only system input L _s selected. The output variables are the cable length l _s and the normalized spring force $\frac{F_c}{{\mathit{m}}_{\mathit{Max}}}$

selected. With the state vector $x={\left[l_s,z,\dot{z},\frac{m_l}{m_{\mathit{Max}}}\right]}^T$

For example, the dynamic model consisting of equations (2), (4), (5), (6), (7), and (8) can be transformed into state space.

wobei $$\mathrm{f}\left(\mathrm{x}\right)=\left[\begin{array}{c}u\\ x_3\\ g-a_{\mathit{hw}}\frac{x_2-x_1}{x_1{x}_4}-2D\sqrt{a_{\mathit{hw}}}\frac{x_3-u}{{\mathit{sqrtx}}_1{x}_4}\\ 0\end{array}\right],$$

$$\mathrm{h}\left(\mathrm{x}\right)=\left[\begin{array}{c}{x}_1\\ a_{\mathit{hw}}\frac{x_2-x_1}{x_1}+2D\sqrt{a_{\mathit{hw}}\frac{x_4}{x_1}}\left(x_3-u\right)\end{array}\right],$$

$$u=l_s\mathrm{.}$$

The resulting system of first-order differential equations is $$\begin{array}{cc}\dot{\mathrm{x}}& =\mathrm{f}\left(\mathrm{x},u\right).x\left(0\right)={\mathrm{x}}_0.\hfill \\ \dot{\mathrm{y}}& =\mathrm{H}\left(\mathrm{x},u\right).\mathit{t}\ge 0.\hfill \end{array}$$

in which $$\mathrm{f}\left(\mathrm{x}\right)=\left[\begin{array}{c}u\\ x_3\\ G-a_{\mathit{hw}}\frac{x_2-x_1}{x_1{x}_4}-2D\sqrt{a_{\mathit{hw}}}\frac{x_3-u}{{\mathit{sqrtx}}_1{x}_4}\\ 0\end{array}\right].$$

$$\mathrm{H}\left(\mathrm{x}\right)=\left[\begin{array}{c}{x}_1\\ a_{\mathit{hw}}\frac{x_2-x_1}{x_1}+2D\sqrt{a_{\mathit{hw}}\frac{x_4}{x_1}}\left(x_3-u\right)\end{array}\right].$$

$$u=l_s\mathrm{,}$$

in jedem Zeitschritt minimiert [3], wobei x̂ _k für den aktuell geschätzten Zustand steht. In Gleichung (13) und im Folgenden gilt [●] _k = [●] (kΔt) mit der diskreten Abtastrate Δt. Da die Zustandsraumdarstellung (9) jedoch ein kontinuierliches System darstellt, wird das oben beschriebene System im Folgenden mit dem Euler-Vorwärts Verfahren [2] diskretisiert.As mentioned above, the observer is realized as an EKF. The EKF is an observer for non-linear discrete-time systems, which estimates the error covariance of the estimation error x _k - x _k $${\mathrm{P}}_k=e\left[\left({\hat{\mathrm{x}}}_k-{\mathrm{x}}_k\right){\left({\hat{\mathrm{x}}}_k-{\mathrm{x}}_k\right)}^{\mathit{{\rm T}}}\right]$$

in each time step minimizes [3], where x _{k stands} for the currently estimated state. In equation (13) and is [●] in the following _k = [●] (k At) with the discrete sampling rate Δ t. However, since the state space representation (9) represents a continuous system, the system described above is subsequently discretized by the Euler forward method [2].

For the state estimation, the EKF performs a prediction and a correction step in each time step. Within the prediction step, the state is predicted to the next time step based on the system equations (9) $$\begin{array}{cc}{\hat{\mathrm{x}}}_k^{-}& ={\hat{\mathrm{x}}}_{k-1}+\mathrm{\Delta }\mathit{t}\mathrm{f}\left({\hat{\mathrm{x}}}_{k-1},u_k\right).\hfill \\ {\hat{\mathrm{y}}}_k^{-}& =\mathrm{H}\left({\hat{\mathrm{x}}}_k^{-},u_k\right)\mathrm{,}\hfill \end{array}$$

wobei P _k-1 die Fehlerkovarianzmatrix zum Zeitschritt (k - 1)Δt ist, A _k die Transitionsmatrix des linearisierten Systems um den aktuellen Zustand und Q _k die zeitdiskrete Kovarianzmatrix des Systemrauschens. A _k wird näherungsweise durch die Taylor-Reihe der Matrixexponentialfunktion bis zum ersten Glied berechnet $${\mathrm{A}}_k=\mathrm{I}+\frac{\partial \mathrm{f}\left(\mathrm{x},u_k\right)}{\partial \mathrm{x}}{|}_{\mathrm{x}={\hat{\mathrm{x}}}_k^{-}},$$

In addition to the system states, the error covariance matrix is also predicted within the prediction step $${\mathrm{P}}_k^{-}={\mathrm{A}}_k{\mathrm{P}}_{k-1}{\mathrm{A}}_k^T+{\mathrm{Q}}_k.$$

where P _{k -1 is} the error covariance matrix at time step (k-1) Δ t , A _{k is} the transition matrix of the linearized system around the current state, and Q _{k is} the time discrete covariance matrix of the system noise. A _k is approximated by the Taylor series of the matrix exponential function up to the first term $${\mathrm{A}}_k=\mathrm{I}+\frac{\partial \mathrm{f}\left(\mathrm{x},u_k\right)}{\partial \mathrm{x}}{|}_{\mathrm{x}={\hat{\mathrm{x}}}_k^{-}}.$$

Fig. 8 shows once again the embodiment of the load mass observer in a block diagram. In addition to the force F _W measured on the winch, the length of the hoist rope I _S enters the load mass observer as measuring signals. The measured force is initially compensated as described above, first with respect to the rope weight and the friction effects and normalized with the maximum permissible load mass m _max . The load mass observer then estimates as x ₄ the normalized load mass, which is accordingly converted back into the load mass ml by multiplication with m _max . In addition, the load mass observer also estimates the cable length I _s , the position of the load z and the load speed ż , which can also be used for control purposes.

The present invention enables an accurate determination of the load mass, in which both the effects of the arrangement of the measuring device for measuring the cable force via a connecting element between the crane structure and the hoist such as at a moment supported the hoist winch or a pulley, as well as dynamic effects due to the extensibility of the hoisting rope, are taken into account. The load mass can be used either for control tasks or for data evaluation. In particular, the load mass for each stroke may be stored in a memory unit, e.g. stored in a database and so evaluated.

Claims (13)

1. A system for determining the load mass of a load (3) suspended at a hoist rope (4) of a crane, comprising:

   a measurement arrangement for measuring the rope force in the hoist rope (4); and

   a calculation unit (26) for determining the load mass on the basis of the rope force,

   characterized in that
   the calculation unit (26) has a compensation unit and a load mass observer which is based on a spring mass model of the rope (4) and of the load (3),
   wherein the calculation unit (26) describes the influence of the indirect determination of the load mass via the rope force in a dynamic model, calculates the load mass therefrom and at least partly compensates it.
2. A system in accordance with claim 1, wherein the compensation unit works on the basis of data on the position and/or movement of the crane, in particular on the basis of data on the position and/or movement of the hoisting gear, and/or data on the position and/or movement of the boom (5) and/or of the tower (2).
3. A system in accordance with either of claims 1 or 2 for a crane comprising a hoisting gear for raising and lowering the load (3) suspended at the hoist rope of the crane,
   wherein the hoist rope (4) is led from the measurement arrangement via at least one deflection pulley of the crane to the load (3), and/or wherein the measurement arrangement for measuring the rope force in the hoist rope is arranged at a deflection pulley or at the hoisting gear,
   wherein the compensation unit (26) at least partly compensates the effect of the arrangement of the measurement arrangement on the resulting load mass.
4. A system in accordance with claim 3, wherein the compensation unit includes a rope mass compensation which takes account of the unladen weight of the hoist rope and in particular the effect of a change of the rope length on raising and/or lowering the load in the calculation of the load mass,
   wherein the hoisting gear advantageously includes a winch (13) and the angle of rotation and/or the speed of rotation of the winch (13) is included in the rope mass compensation as an input parameter.
5. A system in accordance with claim 4, wherein the rope mass compensation takes account of the unladen weight of the hoist rope (4) wound on the winch (13).
6. A system in accordance with one of the claims 3 to 5, wherein the rope mass compensation takes account of a length and/or an alignment of hoist rope sections changing by the movement of the crane structure.
7. A system in accordance with one of the preceding claims, wherein the compensation unit includes a deflection pulley compensation which takes account of friction effects by the deflection of the hoist rope (4) about one or several deflection pulleys (6, 8, 11, 14).
8. A system in accordance with claim 7, wherein the deflection pulley compensation takes account of the direction of rotation and/or the speed of rotation of the deflection pulleys (6, 8, 11, 14), wherein the deflection pulley compensation advantageously calculates the direction of rotation and/or the speed of rotation of the deflection pulleys (6, 8, 11, 14) caused by the movement of the crane structure together with the movement of the hoisting gear.
9. A system in accordance with one of the claims 7 or 8, wherein the deflection pulley compensation calculates the friction effects in dependence on the measured rope force, in particular on the basis of a linear function of the measured rope force.
10. A system in accordance with one of the preceding claims, wherein the compensation unit takes account of the effect of the acceleration of the load mass and/or of the hoisting gear on the rope force in the determination of the load mass.
11. A system in accordance with claim 10, wherein the calculation unit takes account of the oscillation dynamics which arise due to the stretchability of the hoist rope (4) in the determination of the load mass.
12. A crane having a system for determining the load mass of a load (3) suspended at a hoist rope (4) in accordance with one of the preceding claims.
13. A method for determining the load mass of a load (3) suspended at a hoist rope (4) with a system in accordance with one of the claims 1-11, comprising the steps:

    measuring the rope force in the hoist rope (4),

    calculating the load mass on the basis of the rope force, with the influence of the determining of the load mass via the rope force being described and at least partly compensated in a model.

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