Abstract:
For operating a positioning device of a multi-axes processing device having at least one processing for improving its positioning accuracy, a position change of the processing device and the associated processing head is controlled with a computer, work poses of the processing device and the associated processing head controlled by a computation and control unit of the processing device are detected, and the work poses are adjusted if necessary.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The present invention relates to a method of and apparatus for operating a work robot.  
           [0002]    More particularly, it relates to a method for improving the positioning accuracy of a multi-axes operating device, as well as to an apparatus for performing this method.  
           [0003]    It is known from practice to provide processing devices, such as for example work robots which are driven into a corresponding work pose in a computerized manner. The disadvantage of such an adjustment of processing devices is that the positioning inaccuracies, caused for example by geometrical inaccuracies, transmission clearances and elasticity, are unavoidable. Such inaccuracies however must be avoided or at least approximately avoided when a high precision in the processing of workpieces is required.  
         SUMMARY OF THE INVENTION  
         [0004]    Accordingly, it is an object of the present invention to provide a method and an apparatus for operating a work robot, which avoid the disadvantages of the prior art.  
           [0005]    More particularly, it is an object of the present invention to provide a method of operating a work robot, with which it is possible to exactly adjust the work pose of robots by a computer, so as to eliminate the disadvantages of the prior art.  
           [0006]    In keeping with these objects and with others which will become apparent hereinafter, one feature of the present invention resides, briefly stated in a method which has the steps of controlling a position change of the processing device and a processing head associated therewith with a computer; detecting work poses of the processing device and the associated processing head by a computation and control unit of the processing device; and post adjusting the work poses if necessary.  
           [0007]    When the method is performed in accordance with the present invention, it has the advantage that gradually occurring deviations between the nominal variables to be reached by the processing device and the actual reached actual variables are tested in regular periods and in some cases can be post-adjusted, so that the work quality of the processing device remains approximately unchangeably high.  
           [0008]    The testing and in some cases the post adjustment can be performed in a simple and arbitrarily frequently repeatable manner when the coordinates of the work region of the at least one processing head are compensated on reference coordinates of a calibration region.  
           [0009]    In accordance with a further feature of the present invention, in order to be able to take into consideration longitudinal changes in directions x-y-z which are difficult to determine due to the great number of turning axes, the work region and the calibration region are arranged relative to one another so that the processing device and at least one processing head associated with it during running through the processing region and the calibration region assume substantially the same work pose. In this way an expensive software which takes into consideration length changes depending of the corresponding turning angles by means of a mathematical filter, is dispensed with.  
           [0010]    In accordance with a further feature of the present invention, the coordinates of the work region in a co-moved coordinate system and reference coordinates of the calibration region for at least one work pose are defined in a stationary global coordinate system. Such an approach has first of all the advantage that the calibration region which receives the reference coordinates can be protected from environmental influences as well as temperature fluctuations, so that in a simple manner a change of the reference coordinates provided for calibration of the processing device can be avoided.  
           [0011]    Since the coordinates of the work region and the reference coordinates of the calibration region are provided in the computer of the processing device, it is therefore in a simple manner guaranteed that additional control and regulating means can be dispensed with. In addition it has the advantage that the processing device on the one hand can assume its work poses in any positions in space and there corresponding handlings can be performed in accordance with the coordinates of the work region. On the other hand the coordinates of the work region and the reference coordinates in the calibration region can be determined simply with respect to one another without complicated software support.  
           [0012]    With relatively constant outside conditions, it can be advantageous based on the regulation technique simplification when the calibration process is performed only in dependence on time in regular or irregular intervals. In connection with this, substantially only bearing clearance-dependent and transmission clearance-dependent inaccuracies are compensated. In accordance with an advantageous further embodiment of the invention, the calibration process can be performed also in dependence on a predetermined parameters such as for example time, temperature changes and impact loads. This is especially advantageous when the calibration process can be adjusted more precisely and faster to changing outer conditions, such as for example during temperature fluctuations or after collision-caused impact loads.  
           [0013]    An important feature of the present invention is that the work region can include a plurality of work points and the calibration region represents a selection of these work points as reference points, whereby the work points which are not represented in the calibration region by reference points can be determined by interpolation in a computerized manner. This provides a special advantage for the invention, since complicated mathematical models can be dispensed with when the robot during the calibration assumes the same or similar poses as during work in the working region.  
           [0014]    In an arrangement for improving the position accuracy in accordance with the present invention, the calibration region which represents the work region can be formed in a structurally simple manner by a caliber plate with a plurality of reference points, wherein the reference points can be also a selection of the work points defined in the work region. It is advantageous when the position of the caliber plate is adapted to the position of the work region in such a way that the processing device and the at least one processing head associated with it assume substantially the same work poses in the region of the caliber plate and the work region.  
           [0015]    In case of alternating processing steps within a work pose of the processing device, it is advantageous when the reference points are applied on the caliber plate as a flat grid and the actual work coordinates of the processing device located between them are determined by interpolation, so that a gap-less representation of the total defined work region is obtained.  
           [0016]    For positioning the caliber plate at a protected location so that the environmental factors (temperature, dirt, vibrations, etc.) which negatively influence the calibration surface can be substantially eliminated, the distance of the caliber plate to the work region in horizontal and/or vertical direction is changeable, wherein the relative position to the work pose of the processing device can be substantially maintained.  
           [0017]    In accordance with a further advantageous embodiment of the present invention, the reference points of the caliber plate can be formed as openings or pins which are sensed by a sensor connected with a computer of the processing device. Alternatively, in a structurally simplified manner it is possible to form the reference points of the caliber plate as reflecting points which are sensed by a measuring sensor connected with the computer of the processing device.  
           [0018]    In accordance with still a further feature of the present invention, an especially structurally simple solution is provided when the measuring sensor is a component of the work head of the processing device.  
           [0019]    The novel features which are considered as characteristic for the present invention are set forth in particular in the appended claims. the invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0020]    [0020]FIG. 1 is a front view of a work robot in accordance with the present invention;  
         [0021]    [0021]FIG. 2 is a side view of the work robot of FIG. 1 in accordance with the present invention; and  
         [0022]    [0022]FIG. 3 is a view showing a detail of the work robot of FIG. 1, in accordance with the present invention.  
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0023]    [0023]FIG. 1 illustrates a processing device  2  which is formed as a work robot  1 . It has a plurality of segments  3 ,  4 ,  5 , which form a work support and are movable in a known manner around a plurality of horizontal and vertical turning axes  6 ,  7 ,  8 . At least one of the segments which form the work support carries a horizontal turning axis  9  on its front-side end. A processing head  10  is arranged on the segment  5  turnably about the horizontal turning axis  9 . The work robot  1  is fixed at its lower side on a carriage  11  which is arranged displacably in direction of the arrow  12  on a carriage guide  13 . The work robot  1  is provided in a known manner with a computation and control unit  13  which primarily performs the control of the different turning axes  6 ,  7 ,  8 ,  9  and the displacement of the work robot  1  along the carriage guide  13 . In addition, a measuring system  16  which is formed in accordance with the present is associated with the processing head  10  in the region of a work unit  15  which can be formed for example as a drill.  
         [0024]    The work robot  11  is displaceable along the carriage guide in one or several so-called work regions  17 - 20 . In the simplest case, the work regions  17 - 20  are formed by workpiece surfaces to be processed, while the processing head  10  of the work robot  1  in these work regions  17 - 20  for example produces openings in the workpiece surfaces. For forming the openings at desired locations in the corresponding working regions  17 - 20  by the work unit  15  formed as a drill, these desired positions are stored as coordinates K of the work regions  17 - 20  in the computing and control unit  14 . The coordinates K are identified on a coordinate system  21  which moves together and determines the corresponding work regions  17 - 20 . Furthermore, the work robot  1  can move by the carriage guide  30  in a calibration region  22  which can be formed by a caliber plate  23 . So called reference coordinates RK related to a stationary global coordinate system  24  are associated with the calibration region  22  and also can be stored in the computation and control unit  14 .  
         [0025]    The reference coordinates RK of the calibration region  22  in accordance with the present invention correspond to the coordinates K of the work region  17 - 20 , wherein the former are drawn to a stationary global coordinate system  24  and the latter are drawn to co-moving coordinate system  21 . Both the coordinates K of the co-moving coordinate system  21  and the reference coordinates RK can be either fictitiously selected reference points  25  of the work regions  17 - 20  in the calibration region  22 , or directly concrete positions  27  for example of openings  28  introduced in the work piece surfaces. Since the processing device  2  formed as the work robot  1  is movable over the carriage guide  13  between the work regions  17 - 20  and the calibration region  22 , with the computation and control unit  14  controlling these position changes, the processing device  2  and in particular the processing head  10  associated with it can cover both the work regions  17 - 20  and also calibration region  22 .  
         [0026]    Since the relevant coordinates K of the work regions  17 - 20  and the reference coordinates RK of the calibration region  22  are stored in the computation and control unit  14 , the computation and control unit  14  can move the processing device  2  both in the work regions  17 - 20  and also in the calibration region  22  in accordance with the coordinates K of the work region  17 - 20  or the reference coordinates RK of the calibration region  22 . Thereby, it is possible to drive the processing device  2  in accordance with the inventive method so that the work poses  26  of the processing device  2  and the processing head  10  associated with it can be tested and when necessary can be adjusted. This is especially important since due to different outside influences and different increase of movement deviations of the processing device  2  the coordinates K of the work regions  17 - 20  defined by the computation and control unit  14  can no longer be correctly controlled, so that for example openings produced in the workpiece can gradually deviate from their nominal positions.  
         [0027]    The post adjustment of the processing device  2  is performed finally in such a manner that the work poses  26  which are controlled by the computation and control unit  14  in the work regions  17 - 20  in dependence on the corresponding coordinates K can be compared with the nominal work poses  26 ′ determined by the reference coordinates RK of the calibration region  22 , and when the actual poses  26  no longer correspond to the nominal work poses  26 ′, they are post-adjusted in accordance with the nominal work poses  26 ′. For this purpose the processing device  2  is moved into the calibration region  22 , in which the nominal work poses  26 ′ determined by the reference coordinates RK are taken in and the coordinates K of the work regions  17 - 20  provided in the computation and control unit  14  are corrected in accordance with these reference coordinates RK, which finally corresponds to a post-adjustment of the actual work poses  26  of the processing device  2  and the processing head  10  associated with it.  
         [0028]    In accordance with the shown embodiment of the invention, the calibration region  22  and the work regions  17 - 20  occupy the same similar position in space, wherein this same position in accordance with the present position is limited to the inclination of the calibration region  22  and the work regions  17 - 20  in horizontal and vertical directions. It is thereby guaranteed that the processing device  2  and the processing head  10  associated with it assume during running through the working regions  17 - 20  and also during running the calibration region  22  the same work poses  26 . For protecting the calibration region  22  from the disturbing environmental influences such as for example vibrations, temperature fluctuations, and dirtying, the calibration region  22 , in deviation from the shown arrangement, can be displaced in vertical or horizontal directions relative to the work regions  17 - 20  but arranged approximately on the same inclination in horizontal and vertical directions. For designing the position of the work regions  17 - 20  flexible, the coordinates K of the work regions  17 - 20 , as mentioned above, are defined in a co-moving coordinate system  21 , while the reference coordinates RK of the stationary calibration region  22  are defined in a stationary so-called global coordinate system  24 .  
         [0029]    The deviations of the actual work poses  26 ′ from the nominal work poses  26  depend on a plurality of influence factors. The important outer influences, in addition to the environmental temperature, include first of all impact loads which are caused by collisions with bodies reaching the movement region of the processing device  2 . In addition, friction-related wear of the processing device leads to the situation that the clearance in the various bearings is increased which significantly influences the movement course of the processing device  2  and thereby reaching the work positions of the work unit  15  which are determined by the different coordinates K, RK. Since the wear significantly depends on the movement of the processing device  2 , it is desirable to perform the inventive method in dependence on time in regular or irregular intervals, which can mean preferably operation hours or fixed time intervals. Furthermore, it can be also desirable to perform the inventive method always when the processing device had increased impact loads, for example due to collisions or the processing device  2  is subjected to high temperature fluctuations. The temperature fluctuations can be determined on the one hand by variations of the environmental temperature and on the other hand by the operation-caused heating of the processing device  2 .  
         [0030]    For performing the inventive method in a short time for efficiency purposes, the reference coordinates RK can represent only a part of the work points  27 ,  28  determined by the coordinates K of the work regions  17 - 20 , so that the adjusting processing is limited to this selection of the work points  27 ,  28 . For example, with interpolation it is possible to determine in a computerized way a plurality of further work points  27 ,  28  in the computation and control unit  14  in a faster and precise manner without the need of a position change of a processing device  2 .  
         [0031]    As mentioned above, the calibration region  22  is formed by a caliber plate  23  and the horizontal and vertical inclination of the caliber plate  23  correspond to the horizontal and vertical inclinations of the work regions  17 - 20 . Therefore the processing device  2  with the processing head  2  associated therewith assumes approximately the same work poses  26  in the region of the caliber plate  23  as well as in the work regions  17 - 20 .  
         [0032]    As illustrated, the caliber plate  23  can be provided by a grid of reference points  29 , wherein the work points  27 ,  28  which do not coincide with the reference points  29  can be determined by interpolation. The arrangement of a grid of reference points  29  has in particular the advantage that great work regions  17 - 20  can be represented by a single calibration unit  22 . The calibration process can be limited depending on the work points  27 ,  28  to completely predetermined regions  30  of the calibration region  22 , so that it is always guaranteed that with work points  26 ,  28  which are significantly spaced from one another, the processing device  2  during the calibration process assumes the work poses  26  which correspond to the work poses in the work regions  17 - 20 .  
         [0033]    In accordance with a further embodiment of the present invention, the caliber plate  22  is displaceable in horizontal and vertical directions without an inclination change. Therefore on the one hand it is usable on different processing devices  1 ,  2  and in addition can be utilized in a favorable outside conditions on the same processing device  1 ,  2  for example in a protected position. For providing the possibility of adapting the caliber plate  23  further to differently positioned work regions  17 - 20 , the caliber plate  23  can be changed in its inclination in correspondence with directions of arrows  31 ,  32 . The inclination change is performed so that the new work regions  17 - 20  and the new calibration region  22  have again the same inclination, so that the processing device  2  and the processing head  10  associated with it assume approximately the same work poses  26   m  both during running over the work regions  17 - 20  and during running over the calibration region  22 .  
         [0034]    The reference points  22  in the simplest case can be provided as openings  34  or socket pins  35 . Thereby the sensor  33 , which is connected with the computation and control unit  33  and arranged in the processing head  10  of the processing device  2 , can scan the reference points  29  in a simple manner. The reference points  22  can be also formed by reflecting points  36  on the caliber plate  23  to keep the expenses for providing the reference points  29  and the caliber plate  23  as low as possible. The reflecting points  36  can be detected for example by an optical sensor  33 .  
         [0035]    It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of constructions differing from the types described above.  
         [0036]    While the invention has been illustrated and described as embodied in method of and apparatus for operating a work robot, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.  
         [0037]    Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of the invention.  
         [0038]    What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims.