FI90965C - Crane control method - Google Patents

Description

90965

Crane control method

The invention relates to an acceleration or speed controlled method of controlling a crane or similar device, which method is used, for example, in controlling a bridge crane, comprising controlling a crane from a load-carrying crane control system by control sequences consisting of speed steps, where speed steps describe control system time intervals.

A crane is a commonly used tool for handling piece goods in conditions where it is not possible to transport the piece to be worked along the floor surface or the ground. Cranes are used, for example, in 15 ports, warehouses and industry to move pieces. Cranes based on open control, i.e. cranes without feedback, and their control methods are based on knowing the suspension height of the center of gravity of the load suspended on the crane and the oscillation time of the 20 mathematical pendulums calculated on the basis thereof. Control methods based on a mathematical pendulum are relatively simple and useful in practical solutions. However, a change in the lifting height of the load in the crane during the acceleration or braking sequence of the crane causes undesired oscillation, whereby the crane cannot be controlled as desired.

To overcome the above-mentioned drawback, a method is known from DE 3714570 A1, in which the change in the lifting height of a load during the acceleration of a crane is determined in advance and the load lifting height is calculated. However, a disadvantage of the method is the requirement to know the change in lifting height even before the start of the 35 acceleration sequences.

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It is also previously known to change the speed sequence by changing the control interval used by the control system by the control device so that the ratio of the control interval to the oscillation time of the mathematical pendulum remains constant. Changing the control interval 5 in a digital control system is problematic and in practice it would be most natural to try to keep the control interval constant in real-time implementations.

An iterative method is also known from DE-3228302, in which a speed-10 path is calculated and formed, after which it is in a non-oscillating end state. With each calculation step, the calculation program tests whether the load has reached a non-oscillating end state. The method is based on an inverse dynamic model and solving the partial differential equation formed from it. The method does not show 1 5 how the scaling of the control caused by the change in the lift height known per se is taken into account and how it can be used to eliminate the detrimental effect of the random change in the lift height.

The object of the present invention is to provide a control method which eliminates the drawbacks contained in the prior art and known solutions. This is achieved by the method according to the invention, the characteristic features of which are given in the claim.

The method according to the invention is based on the idea that the characteristics of the crane control system are improved by scaling the crane control on the basis of the change in the lifting height of the load.

The crane control method according to the invention achieves significant advantages, the most important advantage of which is the improvement of the characteristics of the control system assisted by the crane operator. The method does not require changing the adjustment range used and this makes the method easier to implement with a digital control system. The method also does not require prior knowledge of the change in lifting height 35 and is thus ideally suited to assist the person operating the crane. The invention also makes it possible to easily control the effect of changes in load lifting heights during crane acceleration and braking on the acceleration and braking sequences which eliminate the load oscillation.

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The advantages of the method are particularly significant when it is desired to simultaneously increase or decrease the load while accelerating or braking the speed of the crane. With the method according to the invention, the error between the actual crane system and the control based on the ideal mathematical model can be eliminated.

When the acceleration and velocity sequences produced by the control system are more accurately based on the mathematical pendulum underlying the system, it is then possible to provide control of the hoist in a more precise manner and with less load fluctuations interfering with the hoisting event. The method is also computationally easy to implement.

The invention will now be described in more detail with reference to the accompanying drawings, in which "* Fig. 1 schematically shows a bridge crane, Fig. 2 shows an evenly discrete speed sequence, Fig. 3 shows a flow chart of a method according to the invention, Fig. 4 shows a flow chart of a preferred embodiment of the method, Fig. Fig. 5 shows a calculation of a discrete speed vector when increasing a load during acceleration, Fig. 6 shows a calculation of a discrete speed vector when a load is calculated during acceleration, Fig. 7 shows a change in an acceleration speed vector, Fig. 8 shows a more detailed description of a flow chart according to a preferred embodiment of the invention.

The method according to the invention is suitable for bridge cranes, reversible cranes, multi-purpose cranes and other similar devices.

According to Figure 1, the crane carriage 1 is adapted to be movable along the bridge beam 35 3 of the bridge crane 2. The bridge beam 3 is further adapted to be movable relative to the end beams 4 and 5 at the ends of the bridge beam 3. A cable, rope or other suitable suspension is suspended from the crane carriage 1 , at the 4 end of which is a hook 7 or similar device. A load 8 is placed on the hook 7 by means of lifting straps 7a. The lifting height 1 of the load is considered to be lowered from the location of the hook 7. Each varying lifting height lj 5 (j = 1, 2, ...) of the load 8 corresponds to the oscillation time T characteristic of each value of the lifting height 1_, whereby the oscillation time T of the system according to formula (1) is T = 2n (l / g) 1/2, (1) 10 where g = acceleration due to gravity.

The velocity sequence 9 shown in Fig. 2 consists of a plurality of evenly discreted velocity steps 10, which velocity steps (velocity converter) are denoted by reference numeral 15a 10. The velocity step 10, i.e. the velocity change dV in each control interval dt, can be calculated by formula (2), dV = VBax / (T / dt), (2) 20 where Vaax = maximum speed (m / s) dV = speed change at each control interval (m / s) dtt = i - th control interval (s).

The speed is increased until the maximum speed VBax is reached and the adjustment intervals dt * sum the oscillation time T. The crane 2 is controlled by control sequences 9 as shown in Fig. 2 from the control system 11. Fig. 2 shows two speed sequences v (t) in the time plane. The different velocity sequences are denoted by the letters 9a and 9b. The control devices 14 of the crane-30 carriage 1 or the drive devices 15 of the bridge beam 3 are subjected to a control command according to the desired control sequence 9, i.e. a speed instruction, whereby the crane carriage 1 is set to move according to the control sequence 9 either in the direction of the bridge beam 3 or with the bridge beam 3.

According to the method 590965 according to the invention shown in Fig. 3, when the lifting height 1 of the load 8 in the crane 2 changes, the speed steps 10 of the control sequence 9 are changed so that the speed step 10 is extended when the load 8 is lifted and the speed step 10 is lowered, then the speed step 10 is reduced. the instruction is transmitted to the crane drives 14, 15.

Figure 5 shows the calculation of the discrete velocity vector when the load 8 is lifted during acceleration. According to the above formula (1), when lifting a load 8, i.e., as the lifting height 1 decreases, the specific oscillation time T decreases and then the value of the control interval dt increases with respect to the specific oscillation time T, whereby the term T / dt the change in velocity dV increases. The velocity curve v (t) moves forward from 15 points v (Tt) to the point v (Tt + Tdt), whereby the velocity curve leads to the point v (Tsua).

Figure 6 shows the calculation of the discrete velocity vector when the load 8 is calculated during acceleration. According to the above formula (1), when calculating the load 8, i.e., as the load lifting height 1 increases, the specific oscillation time T increases and then the value of the control interval dt decreases with respect to the specific oscillation time T, increasing the term T / dt in formula (2) and further decreasing .

Figure 7 shows the change in the acceleration velocity trajectory. The graph marked with the letter a in Fig. 7 shows the change of the velocity trajectory when the load 8 is lifted, whereby the velocity step 10 thus increases. In Fig. 7, the graph denoted by the letter b shows the speed trajectory variable-30 from which when calculating the load 8, whereby the speed step decreases.

According to the flow chart illustrating the preferred embodiment of the invention shown in Fig. 4, the speed steps 10 are changed so that before passing the new speed step 10 to the crane 2 drives 14, 15 the time Tt of the oscillation time T is added together at the measured load height 1 after which the time sum corresponding to the time sum TSUB = Tt + Tdt formed as described above is determined by the velocity curve v (t). Thus, when forming the term Tdt, it is calculated how much of the control interval dt used is the characteristic oscillation time T of the mathematical pendulum calculated at the height 1 of the load 8 measured at that time. The speed 10 kel 10 obtained as described above forms a speed reference for the crane 2 actuators 14, 15.

Figure 8 shows a more detailed flow chart of a preferred embodiment of the invention. In Fig. 8, the elapsed part Tt of the oscillation time T is initially stored in the variable x, after which the part of the oscillation time Tdt corresponding to the control interval dt is calculated at the measured load height and added to the variable x, whereby the content x becomes sum = Tt + Tdt. Next, the velocity curve v (t) reads the time t = the velocity v (TeuB) corresponding to Teu. If the value of the speed obtained in this way is less than the maximum speed VB (1X), then the crane drives 14, 15 are given a new speed reference v (Teuill).

According to a preferred embodiment of the invention, the speed step 10, i.e. the speed change dV, is calculated for each control interval dt according to the lifting height 1 of the separately measured load 8.

The method according to the invention is suitable for both acceleration and speed controlled cranes. Thus, instead of the speed step 10, the term change in speeds 30 could also be used above to describe the change in speed dV in each control interval. In this case, the speed step would describe the acceleration. Acceleration-based control is possible with current motor drives.

Although the invention has been described above with reference to the examples according to the accompanying drawings, it is clear that the invention is not limited thereto, but can be modified in many ways within the scope of the inventive idea set forth in the appended claims.

Claims (2)

1. Nosturin tai vastaavan laitteen kiihtyvyys- tai nopeusohjattu ohjausmenetelmä, jota menetelmää hyväksi-5 käytetään esimerkiksi siltanosturin (2) ohjaamisessa, joka menetelmä käsittää taskkaa (8) kuljettavan ) muodostuvilla ohjausse-kvensseillä (9), missä nopeusaskeleet kuvaavat ohjaus-10 järjestelmän (11) sätövälin aikana tapahtuvia nopeuden muutoksia (dV), jossa menetelmässä nosturissa (2) olevan task (8) 10) the site, one task (8) nostettaessa nopeusaskelta (10) pidennetään, 15 yes one taskkaa (10) laskettaessa nopeusaskelta (10) lyhennetään, young jälkeen nopeusaskel (10) velitetään nosturin (2) käyttölaitteett (14) , one nopeus skeleton (10) scale scale huomioidaan site, one and another nopeus skeleton (10) antamista nosturin 20 (2) käyttölaitte ille (14, 15) tarkasteluajanhetkeen (t) mennessä kulunut osa (Tt) dimensiottomasta heilahdusajas-ta (T) lasketaan yhteen mitatulla taskan (8) corkeudella (1) sätöväliä (dt) vastaavan heilahdusajän (T) osan (T4) chance jälkeen saatua aikasummaa (T ^, T, + TA) vastaava nopeusaskel (10) määritetään nopeuskäyrältä v (t). 90965 1. A control method controlled by the acceleration or speed of a crane or equivalent device, which method is used, for example, for the control of a bridge crane (2), which method consists of the control of the crane (2) which carries a load (8) with a control system (11) having control sequences (9) formed by speed steps (10), wherein the speed steps describe 10 speed changes (dV) occurring during a control interval at the control system (11), in which method, when the lift height (1) of the load (8) ) hanging from the crane (2) changes, the speed steps (10) of the control sequence (9) are scaled so that as the load (8) is lifted, the speed step (10) is extended and that as the load (8) is lowered, the speed step (10) is shortened. whereafter the speed step (10) is conveyed to the drive devices (14, 15) of the crane (2), characterized in that the scaling of the speed steps (10) is taken into account so that before a new speed step (10) is given to the drive device of the crane (2) (14, 15) the part (Tt) of the dimensionless oscillation time (T) that elapses at the time of reflection (t) is added to a part (TA) of the oscillation time corresponding to the control interval (dt) of the load (8) measured Height (1), after which the rate step (10) corresponding to the obtained time sum T, + TA) is determined on the velocity curve v (t).