POSITION MONITORING OF A KINEMATIC LINKAGE

Abstract

In order to detect when a kinematic linkage (1) leaves workspaces (WS) and/or enters safe spaces (SS), using, little computing power, and therefore doing so more quickly, at least a part of the kinematic linkage (1) is modeled with a number of kinematic objects (K1, K2, K3, K4), and a monitoring space (S) is specified, The number of kinematic objects (K1, K2, K3, K4) is modeled in less than two dimensions D<2. For each modeled kinematic object (K1, K2, K3, K4), a geometric variable of a monitoring space (S) is modified by a distance (d1, d2, d3, d4). Each distance (d1, d2, d3, d4) is derived from at least one geometric parameter (P1, P2, P3) of the modeled kinematic object (K1, K2, K3, K4), The position of each of the number of kinematic objects (K1, K2, K3, K4) is checked in relation to the modified monitoring spaces (S1, S2, S3, S4).

Claims

1.-15. (canceled)

16. A method for monitoring positions of kinematic linkage in relation to a predefined monitoring space, comprising: modeling at least a part of the kinematic linkage with a number of kinematic objects having fewer than two dimensions; for each kinematic object, modifying at least one geometric variable of the predefined monitoring space by a distance being derived from at least one geometric parameter of each respective kinematic object; and checking the positions of each of the kinematic objects in relation to respective modified monitoring spaces.

17. The method according to claim 16, wherein at least one of the kinematic objects is modeled in zero dimensions.

18. The method according to claim 16, wherein at least one of the kinematic objects is modeled in one dimension.

19. The method according to claim 16, wherein each kinematic object modeled in one dimension comprises two kinematic objects having zero dimensions, and a defined spacing between two zero dimension kinematic objects.

20. The method according to claim 16, wherein at least one kinematic object models a space outside the kinematic linkage.

21. The method according to claim 16, wherein the monitoring space is a line.

22. The method according to claim 16, wherein the monitoring space is an area.

23. The method according to claim 16, wherein the monitoring space is a body.

24. The method according to claim 16, wherein the predefined monitoring space comprises a safe space having a size, for each kinematic object, that is increased by the distance corresponding to the at least one geometric parameter of each respective kinematic object.

25. The method according to claim 16, wherein the predefined monitoring space comprises a workspace having a predetermined size, for each kinematic object, that is reduced by the distance corresponding to the at least one geometric parameter of each respective kinematic object.

26. The method according to claim 16, wherein the geometry of the monitoring space is adapted on the basis of an expected deviation between a computed position and a real position of the kinematic object.

27. A method for determining movement of kinematic linkage in relation to a predefined monitoring space, the method comprising: modeling at least a part of the kinematic linkage with a number of kinematic objects in less than two dimensions; modifying at least one geometric variable of the predefined monitoring space by a distance corresponding to at least one geometric parameter of a first one of the kinematic objects; and modifying at least one geometric variable of the predefined monitoring space by a distance being derived from at, least, one geometric parameter of a second one of the kinematic objects; checking a position of the first one of the kinematic objects in relation to the monitoring space as modified for the first kinematic object; and checking a position of the second one of the kinematic objects in relation to the monitoring space as modified for the second kinematic object.

28. The method according to claim 27, wherein the predefined monitoring space comprises a safe space having a size, for each kinematic object, that is increased by the distance corresponding to the at least one geometric parameter of each respective kinematic object.

29. The method according to claim 27, wherein the predefined monitoring space comprises a workspace having a size, for each kinematic object, that is reduced by the distance corresponding to the at least one geometric parameter of each respective kinematic object.

30. The method according to claim 27, wherein, for each additional kinematic objects, the method further comprises: modifying at least one geometric variable of the predefined monitoring space by a distance corresponding to at least one geometric parameter of each additional kinematic object; and checking a position of each additional kinematic object in relation to the monitoring space as modified for each additional kinematic object.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The present invention is explained in more detail below with reference to the Figures, which show exemplary, schematic and non-limiting advantageous embodiments of the invention.

[0021] FIG. 1 shows a modeled part of a robot arm;

[0022] FIGS. 2A-2D show a safe space with four kinematic objects;

[0023] FIGS. 3A-3E show a workspace with four kinematic objects.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0024] FIG. 1 shows a two-dimensional (to simplify the illustration) part of a robot arm (henceforth referred to as a robot arm) as part of a kinematic system 1—in this case, a serial kinematic linkage—wherein the dashed lines describe the spatial limit of the robot arm 1. The kinematic linkage 1, or a part thereof, is modeled according to the invention with zero dimensional (0d) or one-dimensional (1d) objects—that is, with a dimension D<2—in the following as kinematic objects. In the example of FIG. 1, the robot arm 1 is described by three point-shaped (0d) kinematic objects K1, K2, K3, which in this case represent the joint hubs of the robot arm 1. The modeled kinematic objects K1, K2, K3 could, of course, also describe objects under consideration which are located outside of the kinematic linkage, but which can still be considered part of the kinematic linkage. However, a simplified form of a wireframe model can also be used for modeling the kinematic linkage 1. In this way, line-shaped (1d) kinematic objects K4 are modeled, as shown in FIG. 1, by the connecting line between the first point-shaped kinematic object K1 and the second point-shaped kinematic object K2. A line-shaped (1d) kinematic object K4 preferably connects two point-shaped (0d) kinematic objects K1, K2 or K2, K3 in this case. In the embodiment in FIGS. 2b-c, the point-shaped modeled kinematic objects K1, K2, K3 are considered; in FIG. 2d, the line-shaped kinematic object K4 is considered.

[0025] The extension to a wireframe model is optional, as is a possible parameterization of the linear distance of two point-shaped kinematic objects K1, K2, K3. This parameterization and the extension to a wireframe model can be performed separately for each kinematic object K1, K2, K3, K4.

[0026] FIG. 1 also shows a prespecified safe space SS as the monitoring space S. The prespecified safe space SS is established, for example, from the installation location and the environment of the kinematic linkage 1 on site, and is defined in advance, and/or can be assumed to be prespecified. A safety function of a kinematic linkage 1 ensures that the kinematic linkage 1 (or a part thereof) does not penetrate into the safe space SS, or does not leave a defined. workspace WS of the kinematic linkage 1. The safety function is, for example, implemented in the controller of the kinematic linkage 1, but can also supplement the controller of the kinematic linkage 1 as an independent module. Fn the illustrated embodiment, the safe space SS is a rectangle with the side lengths r1, r2 and/or half side lengths r1/2, r2/2. In the case of a robot arm moved in three dimensions, the safe space SS could, of course, also be defined in three dimensions.

[0027] According to the prior art, to implement the safety function, the kinematic linkage 1 or a part thereof would be modeled as a three-dimensional object or a sum of three-dimensional objects, wherein an intersection of the object or the objects with the safe space would have to be computed. However, this monitoring is very computationally demanding.

[0028] According to the invention, therefore, at least a part of the kinematic linkage 1 is modeled as a number of kinematic objects K1, K2, K3, K4 which each have less than two dimensions (D<2)—that is, in the form of a wireframe model. The position and orientation of the kinematic Objects K1, K2, K3, K4 in the space is always unambiguously established from the known geometry and movement of the kinematic linkage 1, and can therefore be presumed to be known. After the safety function is generally integrated in the control system of the kinematics 1, or at least is connected to it, the safety function can always access the current positions and positions of the kinematic objects K1, K2, K3, K4.

[0029] In order to be able to monitor the safe space SS despite the modeling of the kinematic linkage 1 according to the invention, at this point a defined or parameterizable geometrical parameter P1, P2, P3, P4 is used according to the invention for each kinematic object K1, K2, K3, K4, and the prespecified safe space SS is thus modified. For example, a maximum diameter of the respective part of the kinematic linkage 1 is used as the parameter P1, P2, P3, P4 on the number of kinematic objects K1, K2, K3, K4 (the joint hubs, and/or a part of the robot arm). The kinematic linkage I (or a part thereof) is “scaled down” by the modeling, which is expressed by the parameters P1, P2, P3, P4. If, in return, the safe space SS/workspace WS is increased/decreased according to this parameter P1, P2, P3, P4, the modeling of the kinematic linkage 1 in the form of kinematic objects K1, K2, K3, K4 can be “compensated” to realize the safety function.

[0030] The geometric parameter P1, P2, P3, P4 can follow from, for example, a stored allocation table, which can be parameterized in advance using the known geometry of the kinematic linkage 1. For each modeled kinematic object K1, K2, K3, K4, a first, second and third distance d1, d2, d3, d4 are then computed and/or derived from the geometric parameter P1, P2, P3, P4. In a simple embodiment, the parameter P1, P2, P3, P4 can also correspond directly to the respective distance d1, d2, d3, d4, optionally with a predetermined safety margin. Thus, there is at least one characteristic parameter P1, P2, P3, P4 for the distance d1, d2, d3, d4, wherein the distance d1, d2, d3 d4 can be computed with d1=f(P1), d2=f(P2), d3=f(P3), d4=f(P4) via a given, known, or derivable function f(P1), f(P2), f(P3), f(P4). If, for example, the part of the kinematic linkage 1 has a rectangular cross-section with the side lengths a and b as further parameters, then the parameter of the maximum diameter results from the further parameters, in the form of the root of a.sup.2+b.sup.2. The distance d1, d2, d3 d4 then again results from the parameter of the diameter, via a relationship—for example by the distance d1, d2, d3 d4 corresponding to half the diameter. The distance d1, d2, d3, d4 modifies at least one geometric variable G (in this case, half the side lengths r1/2, r2/2) of the safe space SS for each kinematic object K1, K2, K3, K4 and thus leads to the modified safe spaces S1, S2, S3, S4. In the illustrated case, therefore, the geometric variable G in the form of half the side lengths r1/2, r2/2 (not shown explicitly in FIGS. 2A-2D for the sake of clarity) is modified by the distance d1, d2, d3, d4, wherein each side of the rectangle is modified by double the distance 2*d1, 2*d2, 2*d3, 2*d4, The distance d1, d2, d3, d4 can therefore be derived if needed and as desired from the parameter P1, P2, P3, P4, Likewise, if needed, the geometric quantity G to be modified can be selected—in this case, the half side lengths r1/2, r2/2, by way of example. The safe space SS is thus individually modified for each modeled kinematic object K1, K2, K3, K4, and a separate modified monitoring space S1, S2, S3, S4 (in this case, safe space) is assigned to each modeled kinematic object K1, K2, K3, K4. Therefore, in FIG. 2A, for the first modeled kinematic object K1, the half side lengths r1/2, r2/2 as the geometric variable G are increased by the first distance d1, which leads to the modified monitoring space S1. Likewise, in FIGS. 2B-2D, the half side lengths r1/2, r2/2, as the geometric variable G, for the second, third, and/or fourth kinematic objects K2, K3, K4, are respectively increased by the second, third, and/or fourth distance d2, d3, d4, which leads to the monitoring spaces S2, S3, S4.

[0031] At this point, for the safety function, the position and orientation of each monitored, modeled kinematic object K1, K2, K3, K4 in space is checked in relation to the modified monitoring space S1, S2, S3, S4 assigned in each case. If, in the example of FIGS. 2A-2D, a modeled kinematic object K1, K2, K3, K4 is situated in the modified monitoring space S1, S2, S3, S4, the monitored monitoring space of the kinematic linkage 1 (in this case, the safe space SS) has been violated, as is the case in FIG. 2C for the third kinematic object K3 in conjunction with the third modified monitoring space S3, and in FIG. 2D for the fourth kinematic object K4 in conjunction with the fourth modified monitoring space S4. For 1d objects as kinematic objects K1, K2, K3, K4, intersecting points of a straight line with an area or a space must be checked. For 0d objects, it is easy to check whether a point lies within an area or a space. Both checks can be carried out with very little computational power.

[0032] Of course, a plurality of distances d1, d2, d3, d4 per kinematic object K1, K2, K3, K4 can also be computed for the monitoring space S—for example, in the case of a rectangular monitoring space S, to differentially modify the side lengths r1, r2 and/or the half side lengths r1/2, r2/2. Likewise, the monitoring space S can represent a line (dimension one) or a body (dimension three) instead of the area (dimension two). In this case, the position of the number of kinematic objects K1, K2, K3, K4 must also be checked in relation to the monitoring space S, for example in the form of an intersection.

[0033] FIGS. 3A-3E illustrate an analogous method for a workspace WS as the monitoring space S. The workspace WS defines a space which the kinematic linkage 1, or a part thereof, is not permitted to leave. Therefore, the distances d1, d2, d3, d4 reduce the at least one geometric variable G—i.e., the half side lengths r1/2, r2/2 (not shown explicitly in FIGS. 3A-3E for clarity —in the illustrated embodiment. The position and orientation of each monitored, modeled kinematic object K1, K2, K3, K4 are checked in relation to the respectively modified monitoring space S1, S2, S3, S4 analogously to the safe space SS in FIGS. 2A-2D, although, in contrast, a space violation occurs when a modeled kinematic object K1, K2, K3, K4 is outside the modified monitoring space S1, S2, S3, S4, as shown in FIG. 3D for the third kinematic object K3 in relation to the modified monitoring space S3, and in FIG. 3E for the fourth kinematic object K4 in relation to the modified monitoring space S4.

[0034] Of course, a plurality of different monitoring spaces S can also be defined. By way of example, each kinematic object K1, K2, K3, K4, or several kinematic objects K1, K2, K3, K4, can have its/their own assigned monitoring space S. In this case, according to the invention, the associated monitoring space S for the respective kinematic object K1, K2, K3, K4 is again modified and checked for violation.