Abstract
A controller controls a plurality of drives of a lifting device, wherein the controller is configured to perform a kinematic transformation of spatial position and orientation coordinates of a body and controls the drives based on the kinematic transformation. The drives can be electric drives. At least six drives are provided and regulated, so that their number exceeds the number of spatial position and orientation coordinates of the body. The lifting device is thus overdetermined.
Claims
1. A controller controlling a plurality of drives of a lifting device positioning a body, said controller being configured to perform a kinematic transformation of a spatial position and an orientation of the body, with the lifting device being overdetermined by having more drives than degrees of freedom of the body to be positioned, the controller further comprising an optimizing device for optimizing cable forces by at least one of minimizing a maximum cable force, by maximizing a minimal cable force, and by distributing the cable forces equally onto the cables.
2. The controller of claim 1, further comprising a closed-loop position controller having an input for the spatial position and an input for the orientation position.
3. The controller of claim 1, further comprising a first model for the body.
4. The controller of claim 1, further comprising a cable force calculator.
5. The controller of claim 1, further comprising a second model for a drive train.
6. The controller of claim 1, further comprising a feedforward control procedure.
7. A method for controlling a lifting device, comprising: performing a kinematic transformation of spatial position and orientation coordinates of a body to be lifted by at least six drives of a lifting device, controlling the at least six drives by way of closed-loop control, and with the kinematic transformation, computing from a desired speed curve of a trajectory of the body a rotational speed desired value curve of the drives.
8. The method of claim 7, wherein the at least six drives are electric drives operating on cables connected to the body, and wherein a distribution of forces operating on the cables is over-determined.
9. The method of claim 8, further comprising computing a cable force operating on the cables.
10. The method of claim 9, further comprising determining the cable force with a feedforward control procedure.
11. The method of claim 10, wherein the feedforward control procedure employs a load model and/or a drive train model.
12. The method of claim 10, wherein the lifting device is overdetermined by having more drives than degrees of freedom of the body to be positioned, the method further comprising using additional degrees of freedom for optimizing of the feedforward control procedure of the cable force.
13. The method of claim 7, further comprising controlling the position of the body in the spatial position and orientation coordinates of the body, and converting a manipulated variable for the load into drive coordinates by way of the kinematic transformation.
14. The method of claim 7, further comprising calculating the trajectory by adapting a maximum value of an acceleration of the body in dependence of a lifting height of the body.
15. The method of claim 7, further comprising calculating the trajectory by adapting a maximum value of an acceleration of the body in dependence of a position of a center of gravity of the body.
16. The method of claim 7, further comprising selecting or changing the trajectory so as to minimize a maximum cable force.
17. The method of claim 7, further comprising performing the kinematic transformation and controlling the at least six drives with a controller configured to perform a kinematic transformation of the body in dependence of a spatial position and an orientation position of the body, wherein the lifting device is overdetermined by having more drives than degrees of freedom of the body to be positioned.
18. A method for controlling a lifting device, comprising: performing a kinematic transformation of spatial position and orientation coordinates of a body to be lifted by at least six drives of a lifting device, controlling the at least six drives by way of closed-loop control, and controlling and adapting the drives in dependence on a lifting height or path dynamics of the body, with the lifting height effecting a change of the path dynamics.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
(1) The invention is further explained below in an exemplary manner with the aid of the FIGS. 1 to 7. Identical features are provided with identical reference numerals. Features of individual embodiments may be combined with one another. In detail in the drawings
(2) FIG. 1 shows a container bridge as an example for a lifting device;
(3) FIG. 2 shows a crane;
(4) FIG. 3 shows an open-loop control concept and closed-loop control concept;
(5) FIG. 4 shows an open-loop control concept with a cable force calculation;
(6) FIG. 5 shows forces on a spreader beam;
(7) FIG. 6 shows an optimized course and
(8) FIG. 7 shows a closed-loop control structure.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
(9) The illustration according to FIG. 1 illustrates a container bridge 1. The container bridge 1 has a plurality of supporting columns 2 by means of which the container bridge 1 is arranged on a ground 3. The supporting columns 2 may be moved on rails 4. The movement direction is orthogonal with respect to the illustration in FIG. 1, in other words into or out of the image plane. The supporting columns 2 support a crossbeam 5. The crossbeam 5 extends parallel with respect to the ground 3 and therefore likewise horizontally. The container bridge 1 furthermore has a crane trolley 6. The crane trolley 6 may be moved on the crossbeam 5 relative to the ground. The movement direction of the crane trolley 6 is horizontal and orthogonal with respect to the movement direction of the supporting columns 2. The crane trolley 6 is connected via a cable system 7 to a spreader beam 8. It is possible by means of extending or shortening the cable system 7 to lower or raise the spreader beam 8. Where applicable, a container 9 that is gripped by the spreader beam 8 is also lowered or raised together with the spreader beam 8. At each point in time, a respective prevailing load of the crane trolley 6 corresponds to the mass of the spreader beam 8 in addition to the mass of the container 9 that is gripped by the spreader beam 8. There may be differences between the load of the crane trolley 6 and the loading of said crane trolley. The load is the object that is moved by the crane trolley 6, in other words the spreader beam 8 with or without container 9. The loading of the crane trolley 6 is the weight force that is exerted by way of the load onto the crane trolley 6. If, by way of example the empty spreader beam 8 is moved by the crane trolley 6 and the mass of the spreader beam 8 is five tons, the load of the spreader beam 8 and the loading is 5 tons. A load transferring site 10, 11 is illustrated. The load transferring site 10, 11 may be by way of example a stationary load transferring site 10, in other words a load transferring site that cannot be moved on the ground 3. A typical example of a load transferring site 10 of this type is a storage area for a container 9. Alternatively, the load transferring site 10, 11 may be a mobile load transferring site 11, in other words a load transferring site that may be moved on the ground 3. A typical example of a load transferring site 11 of this type is an AGV (automated guided vehicle). Furthermore, the transferring system has a crane controller 12. The crane controller 12 is one example for a controller. The transferring system is controlled in an open-loop manner by the crane controller 12. The crane controller 12 is programmed using a computer program 13. The computer program 13 is stored in machine-readable form in particular in a storage device 14 of the crane controller 12. The computer program 13 comprises machine code 15 that may be processed by the crane controller 12. The processing of the machine code 15 by way of the crane controller 12 ensures that the crane controller 12 implements a control method for the transferring system. Apart from that, sensors 16 such as cameras are illustrated. It is possible using these sensors by way of example to determine the position of the load 8 that has a gap a from the trolley 6.
(10) The illustration according to FIG. 2 illustrates schematically in a side view a crane trolley 22 that is associated with a crane 20 as a further example for a lifting device. The crane 20 has a guiding rail 24 on which the crane trolley 22 is movably arranged along a movement axis 25. The crane trolley 22 comprises a crane trolley drive that provides a drive torque and renders possible a movement 23 along the movement axis 25. A load 30 is suspended on the crane trolley 22 via two or more lifting installation cables 26. The lifting installation cables 26 are respectively fastened to crane-trolley side suspension points 27 and to load-side suspension points 28. There is a bearing reaction in each of the crane trolley side suspension points 27, said bearing reaction comprising bearing reaction forces and/or bearing reaction torques depending upon the construction of the respective crane trolley side suspension point 27. Each of the lifting cable installations 26 is further allocated a lifting drive 31 via which the associated lifting installation cable 26 may be reeled on or reeled off. The procedure of reeling on or reeling off a lifting installation cable 26 reduces or increases the free length of said lifting installation cable. The load 30 is deflected 35, 32 from vertical by way of the movement 23 of the trolley crane 22. A distance 33 between a load reference point 29 and a crane trolley reference point 21 is produced by way of the deflection of the load 20. A pendulum movement 36 is possibly produced by means of the deflection of the load 30 and said pendulum movement may impede the placement of the load 30. The crane trolley 22 is provided with a controller 29 on which a computer program product 39 is stored in an executable manner. The computer program product is designed for the purpose of implementing at least one embodiment of the method in accordance with the invention. It is possible for signals of a measuring apparatus 38 to be taken into consideration using the computer program product.
(11) The Illustration as claimed in FIG. 3 illustrates an open-loop control concept and a closed-loop control concept. An open-loop control procedure and adjusting variable generating procedure 40 is illustrated, which outputs parameters in dependence upon a position p. The position relates in particular to a spatial position of a point (XC,YC,ZC) and an orientation (α,β,γ) of a body in the space with p=[XC,YC,ZC,α,β,γ].sup.T. It is possible for torques d=[d.sub.1, . . . , d.sub.m].sup.T 50 to be provided via a number of m drive trains having electric motors in order to by way of example guide a path 45 (the cable lifting installation) on the predetermined course. An optimized torque curve d.sub.ffw=[d.sub.ffw,1, . . . , d.sub.ffw,m].sup.T 46 is calculated on the open-loop control side with the aid of a mathematical model. For the feedforward control procedure of the rotational speed n.sub.desired=[n.sub.desired,1, . . . , n.sub.desired,m].sup.T with the aid of the kinematic transformation the desired speeds are transferred from the six-dimensional coordinate system of the load into the m-dimensional coordinate system of the drives. The desired value position p_desired thus moves into a closed-loop position control procedure 41. Afterwards, a kinematic transformation 43 is performed, whereupon this value is processed together with the desired rotational speed n.sub.desired in a closed-loop drive control procedure 44. The rotational speeds n.sub.desired and torques d.sub.ffw that are determined for example via a mathematical model in the feedforward control paths are connected to the respective comparators of the closed-loop control loops. The desired rotational speed n.sub.desired results from the first derivative of p_desired 47 and a subsequent kinematic transformation 42.
(12) The illustration according to FIG. 4 illustrates a further part of an open-loop control concept. A load model 51 is illustrated in addition to a trajectory generating procedure 77. A desired course is provided by means of the desired values of p 58, {dot over (p)} 57, {umlaut over (p)} 56. The forces F 61 that act upon the load are calculated using the six-dimensional movement equation 59 w=M(p){umlaut over (p)}+N({dot over (p)},p)+G(p)
(13) with:
(14) M(p) the mass matrix
(15) N({dot over (p)},p) the matrix of the centrifugal force and Coriolis force
(16) G(p) the matrix of the weight forces
(17) from the desired course (p,{dot over (p)},{umlaut over (p)}) 58, 57, 56, wherein a load model 51 is provided for this purpose. The force vector w 59 relates to the load coordinates. The forces 61 are provided via a cable force calculation 53. In the open-loop control concept, an optimized torque feedforward control procedure d.sub.ffw=[d.sub.ffw,1, . . . , d.sub.ffw,m].sup.T 62 is calculated with the aid of a mathematical load model for the m drive units. For this purpose, it is necessary to know the mass of the load and the position of the mass center point. An optimized torque feedforward control procedure d.sub.ffw is calculated for a given desired course (p,{dot over (p)},{umlaut over (p)}) in load coordinates with the aid of the mathematical model on the basis of a model 54 for the drive train. It is possible using the equilibrium condition A.sup.T(p)F=w to transform the six-dimensional force vector w into the cable force vector F. The cable force vector F=[F.sub.1, . . . , F.sub.m].sup.T includes the amount of cable force of each cable in the direction of the drive coordinates (cf. FIG. 5). The equilibrium condition is established with the aid of the geometric arrangement of the cables. The matrix A.sup.T(p) includes inter aa the m normalized cable force direction vectors and the position of the points of application of the force.
(18) The angular acceleration of the m drive trains 60 {umlaut over (φ)}=[{umlaut over (φ)}.sub.1, . . . , {umlaut over (φ)}.sub.m].sup.T results from a kinematic transformation 52 of the second derivation of p.sub.desired.
(19) FIG. 5 illustrates in an exemplary manner a definition of the force vectors for the equilibrium conditions in a simplified case that may be easily illustrated of a load suspension using 4 cables. The forces 71, 72, 73, 74 are illustrated on a spreader beam 63, which grips a container 64, having a reference coordinate system 68, a center of gravity SP 65 and a displacement 67 of the center of gravity with respect to the zero point of the reference coordinate system. More than 4 cables, such as 2 or more additional cables 81, 82 providing respective additional force vectors F.sub.5, F.sub.6 may be attached to the container or load, whereby the number of cables may exceed the degrees of freedom of the load.
(20) The illustration according to FIG. 6 illustrates an optimized course 75. By way of example, a shortest path 76 between a start point 69 and an end point 70 may be optimized in relation to maximum cable forces and the optimized course 75 results from said optimization procedure.
(21) The illustration according to FIG. 7 illustrates a closed-loop control structure and is based on FIG. 3. In FIG. 7, a feedback 79 of the position p is illustrated which is subtracted from the value 48 p.sub.desired and is used in the closed-loop position control procedure 41. The output of the closed-loop position control procedure is kinematically transformed 43 and is linked to the feedback 78 of an actual rotational speed n of the corresponding electric drive that is to be controlled in a closed-loop manner.
