Abstract:
An object handling method for determining the positions of the arm of a handling system with the aid of a location method which is based on a reference system predetermined by an associated location system. A handling system having a moveable arm. The arm is operational within a fixed reference system using a location system.

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to a method and to an apparatus for the handling of objects. 
     It is known to use a robot for the handling of objects. A robot having, for example, one gripping arm can be used for the loading and unloading and for the equipping of production apparatuses with workpieces to be processed. The robot can furthermore itself serve for assembly, such as for welding, since a robot arm can be provided with tools and can also carry out complicated manipulations. To move the robot arm in space, linear x, y and z transducers and incremental encoders are provided which are connected to a control computer. However, contamination of the transducers and incremental encoders by water or oil used in production halls and by chips which occur there can result in operational problems for the robot by which an accurate locating of the robot arm is no longer ensured. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide an improved apparatus and an improved method for the handling of objects with which the aforesaid disadvantages are at least very largely eliminated. 
     The object is satisfied by the features disclosed herein. 
     The object is in particular satisfied in that, in a method for the handling of objects in which at least one arm of a handling system for the handling of at least one object is moved in space relative to a reference system, in particular a fixed reference system, the locations of the arms are determined by a locating method with reference to the reference system fixed by the associated locating system. 
     The use of the locating method permits a very precise determination of the locations of the arm of the handling system without having to use transducers and incremental encoders which are prone to problems. At the same time, it is possible to steer to points in space much more precisely with the arm. This has the consequence that imprecise manipulations of the arm and—if the handling system is used in production—thus also the generation of rejects can be avoided. The location determination moreover takes place much faster due to the locating method than via the previously used transducers and incremental encoders. 
     At least one physical field, in particular an acoustic, optical and/or electromagnetic field, can be set up for the location of the arm. For this purpose, a plurality of transmitters are located in the space around the handling system as field sources of the physical field, for example sources for visible and/or invisible light, whose locations fix the reference system for the locating method. The arm is furthermore provided with at least one sensor for the physical field. Since the propagation speed of the physical field is known, the distance between the transmitters and the arm of the handling system can be precisely determined from the signal transit time. To determine the location of the arm as precisely as possible, it is favorable to distribute a high number of transmitters in the space. This permits the determination of the location of the arm with an accuracy of approximately up to ±1 μm. The handling system in accordance with the invention can moreover be set up substantially more easily than known handling apparatuses due to the use of the locating system. 
     It is particularly advantageous for a unidirectional locating system, in particular in the manner of the so-called global positioning system, GPS, to be used for the locating of the arm. A one-way distance measurement is carried out in this process by means of the transit time of the signals between the transmitters and corresponding sensors at the arm of the handling system. The measuring error can be kept small in this manner and the determination of the location of the arm can be carried out very precisely. 
     In an embodiment, a robot arm can be used as the arm. The advantages presented above can thus also be achieved with industrial robots. This is in particular of importance when using the robot at dangerous workplaces, for example in cooling ponds of nuclear power stations. The method in accordance with the invention and the associated handling system can also be used under water since the locating system works reliably under water unlike the linear transducers and incremental encoders of the known systems. 
     A gripping arm of a robot which takes up and/or moves the object can be used as the arm. This permits a variety of manipulations of the object so that, in a favorable case, only one robot can take over all necessary manipulations of the object in the space. 
     An exchangeable tool or a tool fixedly provided at the arm can furthermore be handled as the object in the space. The method in accordance with the invention thus permits not only the manipulation of objects, but also their processing, for example assembly and welding work. 
     It is advantageous for the relative orientation of the tool to the arm to be determined, in particular independently of the locating system. The operating point of the tool at an object to be worked can thereby be steered to very precisely. If the orientation determination should take place independently of the locating system, at least one sensor, for example a proximity sensor, independent of the physical field of the locating system is arranged in the tool and/or in the arm of the handling system. 
     In a further embodiment, the tool can be supplied with energy in a wireless manner, in particular inductively or by means of an accumulator. Control data of the tool can moreover be transmitted in a wireless manner, in particular inductively or by radio. The tool at the arm of the handling system can in this manner be exchanged simply in that a gripping element provided at the arm releases a first tool and takes up another tool, since the tools have an autonomous energy supply and/or an autonomous control. 
     It is furthermore of advantage for the locating system to be calibrated by self-calibration. This permits a recalibration of the locating system carried out at short time intervals. 
     Further advantageous embodiments of the invention are recited in the following FIGURE description and in the drawings. 
     The invention will be described in the following purely by way of example and with reference to the enclosed drawing. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an embodiment of an apparatus in accordance with the invention in a schematic representation. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The embodiment of the apparatus in accordance with the invention shown in  FIG. 1  includes a robot  10 , transmitters  12  distributed in the space around the robot and a control computer  14 . 
     The robot  10  is mounted on a work table  15  and has a gripping arm  16  at whose free end a grip  18  is provided. The grip  18  serves, on the one hand, to pick up tools  20  from a supply belt  22  and to place them on the work table  15  and to transfer them onto take-away belts  24  after their working. In addition, on the other hand, a tool can be taken up from the tool storage position  26  by the grip  18  and one of the workpieces  20  on the work table can be worked. 
     The transmitters  12  are arranged both in the space and on the measuring table  15 . They transmit an electromagnetic field, for example a radio signal, in particular a GPS signal. 
     A field sensor (not shown here) is provided in or at the grip  18  for the electromagnetic field generated by the transmitters  12 . The grip  18  furthermore has a transmitter and receiver element (not shown) which transmits the signals of the transmitters  12  received by the field sensor to a transmitter and receiver module  28  of the control computer  18 . 
     The tools taken up from the tool storage position  26  have a wireless energy supply (not shown here) and a transmitter and receiver element (likewise not shown) for wireless communication with the control computer  14 . Consequently, a tool can be used for the working of the workpiece  20  directly after having been taken up by the grip  18 . 
     The control computer  14  serves for the processing of the signals of the transmitters  12  and also for the calculation of the control signals for the transmitters  12 , for the robot  10  and for the tools from the tool storage position  26 . For this purpose, the transmitter and receiver module  28  of the control computer  14  receives the signals of the transmitters  12  and moreover transmits control signals to the transmitters  12 , to the robot  10  and to a tool taken up from the tool storage position  26 . The transmitter and receiver module  28  moreover receives the signals of the field sensor, which is provided for the detection of the electromagnetic field of the transmitters  12  at the grip  18 . 
     A proximity sensor, which is independent of the electromagnetic field of the transmitters  12 , is provided in the grip  18  for the fine positioning of a tool taken up by the grip  18 . The orientation of the tool relative to the grip  18  or to the gripping arm  16  can be measured using this proximity sensor. If the orientation of the tool to the grip arm  16  should not be ideal for a working of the workpiece  20 , it can be compensated simply by suitable movements of the gripping arm  16  or of its arm segments. For this purpose, the proximity sensor has a transmitter and receiver element (not shown) which is connected to the transmitter and receiver module  28  of the control computer so that the coordination of the movements of the gripping arm  16  can be carried out by the control computer  14  while taking account of the relative orientation of the tool to the gripping arm  16 . 
     For the working of a workpiece  20 , the first workpiece  20  on the supply belt  22  to be worked is taken up by the grip  18  of the robot  10  and placed on the work table  15 . The workpiece  20  is there fixed on the table, for example by an electromagnet. The grip  18  then grips a tool of the storage position  26  which is needed for the desired working of the workpiece  20 . Since the tool has its own energy supply and receives independent control signals, it can be used immediately after the grip has taken it up. The robot  10  now moves its gripping arm  16  to the workpiece  20 , while taking account of the relative orientation of the tool to the grip  18 , in order to process the workpiece  20  in a suitable manner. After the end of this working step, the tool  20  is transferred by the gripping arm  16 , after the gripping arm  16  has again positioned the tool on the tool storage position  26 , to one of the take-away belts  24  to then supply the workpiece  20  to a subsequent work step. 
     The movements of the gripping arm  16  required for the work step described are controlled by the control computer  14  in that it uses the signals of the transmitters  12  received by the field sensor of the grip  18  for the calculation of the location of the grip  18 . The distances between the field sensor and the transmitters  12  are determined from the product of the propagation speed of the electromagnetic field, which is known, and of the transit time of the respective signal. The current locations of the grip  18  relative to the transmitters  12  can thus be determined while the gripping arm  16  is in use. The locations of the gripping arm  18  in space can be determined very precisely in this manner and desired locations can moreover be steered to and set precisely. 
     The apparatus in accordance with the invention and the method in accordance with the invention above all permit a determination of the location of the gripping arm  18  or of the grip  16  with a precision of up to ±1 μm due to the use of the locating system or of the locating method. 
     Alternatively, light sources or sound sources, for example ultrasonic sources, can also be used as transmitters  12  for the electromagnetic field, alone or combined with one another. The field sensors at the gripping arm  16  can then consist of optical or acoustic interferometers which determine phase shifts for the determination of location. 
     A field sensor for the electromagnetic field of the transmitters  12  can be provided for the location determination not only in or at the gripping arm  16  and/or in or at the grip  18 , but also in the tools of the tool storage position  26 . 
     The handling system or handling method described can, for example, also be used under water in nuclear power stations.