Abstract:
A method and device for determining the position of the object with a light source. The light source illuminates light with a specific range of wave length. The optical band-pass filter lets pass only the light from the light source for the most part. And the camera only sees the light from the light source which is mounted on the object. The arithmetic unit calculates the position of the light source from the data of the cameras. The position is known of the light source on the object and therefore it is possible to determine the position of the object over the position of the light source.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The invention relates to a method and device for determine the position of an object. The exact determining the position of objects in the industrial production is a vary useful and necessary condition. The acknowledgment the coordinates of the tools and components provide increasing quality of products and decreasing production costs. For example at tightening joint screws of cylinder head must follow the right sequence to avoid stress in the cylinder head and clamp the cylinder head seal uniformly. A screw joint which has not been acceptably tightened can cause a break down of safety critical parts of a motor car. 
         [0002]    At the moment there are several possibilities to determine the position of an object: 
         [0003]    Mechanical, for example through turn sensors or distance sensors. The object is mounted on a movable arm. The Disadvantage of this system is that a movable arm is fixed on a device and the freedom of movement is limited. 
         [0004]    Position determination through delay time, for example Global Positioning System or ultrasound. The disadvantage of a system based on radiowave is bad accuracy (circa 50 cm) and therefore is not sufficient. A ultrasound positioning system is disturbed by sound of pneumatic machines that are used in a production. 
         [0005]    Position determination through a optical method with a camera. The camera searches for a pattern or an object that is deposited in the memory of the system. 
         [0006]    This system is very disturbed for example by bad contrast, bad lightening and radiation of other light sources. 
         [0007]    It is an object of the invention to provide a method and device for determining the position of an object precise and undisturbed. It increase the quality on objects assembled by screw joints through force the operator for removal an unacceptable tightened screw joint before he move to the next screw joint or object. 
         [0008]    Further objects and advantages of the invention will appear from the following specifications and claims. 
         [0009]    A preferred embodiment of the invention is described below with references to the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]      FIG. 1  shows a schematic view of an object with a light source which position will determine through a light sensor/image sensor with an optical band-pass filter and an optical lens. 
           [0011]      FIG. 2  shows a schematic 3D plane view of an object with a light source and the light sensor/image sensor, the optical band-pass filter and the optical lens are shown as a plane. 
           [0012]      FIG. 3  shows a similar view as  FIG. 2  but illustrates two systems comprises light sensor/image sensor, optical band-pass filter and optical lens as a plane for determining the position of the object in space. 
           [0013]      FIG. 4  shows a schematic view of a workpiece carrier carrying an object with screw joints to be tightened by a power wrench with position indicating means. 
       
    
    
     DETAILED DESCRIPTION 
       [0014]    The schematic arrangement shown in  FIG. 1  comprises an object  1  with a light source  2 , an optical band-pass filter  3 , an optical lens  4 , a light sensor/image sensor  5 , a front view of the light sensor/image sensor  9 , a pixel  10  on the light sensor/image sensor, a light beam  6  from the light source and a light beam  7  from other light source that is unwanted. Number  8  shows the side view of the optical band-pass filter  3 , optical lens  4  and the light sensor/image sensor  5 . 
         [0015]    The arrangement in  FIG. 1  describes the method of the invention for sense the light from the light source  2  to determine the position of the object  1 . The light beam  6  from the object  1  passes the optical band-pass filter  3 , the optical lens  4  and meets the light sensor/image sensor  9 . The pixel  10  that is illuminated from the light beam  6  appear as a bright pixel. All pixels that are illuminated from the light beam  6  together add up to a bright flaw. The unwanted light beam  7  can not pass the optical band-pass filter and therefore comes the bright flaw  10  on the light sensor/image sensor only from the light source  2  from the object  1 . The bandwidth of the light source  2  and the bandwidth of the optical band-pass filter  3  is attuned to each other. 
         [0016]    In  FIG. 2  there is illustrated the schematic arrangement in form of planes. 
         [0017]    The arrangement in  FIG. 2  comprises an object  12  with a light source  13 , a plane  11  of the object  12 , an optical band-pass filter  15 , an optical lens  16 , a light sensor/image sensor  17 , a pixel  18  on the light sensor/image sensor  17 , a light beam  14  from the light source  13  and a light beam  20  from other light source  19  that is unwanted. 
         [0018]    The arrangement in  FIG. 2  describes the method of the invention for sense the light from the light source  13  to determine the position of the object  12 . The light beam  14  from the light source  13  passes the optical band-pass filter  15 , the optical lens  16  and meets the light sensor/image sensor  17 . The pixel  18  that is illuminated from the light beam  14  appear as a bright pixel. All pixels that are illuminated from the light beam  14  together add up to a bright flaw. The unwanted light beam  20  can not pass the optical band-pass filter  15  and therefore comes the bright flaw on the light sensor/image sensor  17  only from the light source  13  on the object  12 . The bandwidth of the light source  13  and the bandwidth of the optical band-pass filter  15  is attuned to each other. 
         [0019]    In  FIG. 3  there is illustrated the schematic arrangement in form of planes which comprises two systems for determine the position of an object in space. 
         [0020]    The schematic arrangement comprises an object  21  with a light source  22 , two planes from two views  28 ,  29  of the object  21 , an optical band-pass filter  23 ,  30 , an optical lens  24 ,  31 , a light sensor/image sensor  25 ,  32 , a pixel  27 ,  33  on the light sensor/image sensor  25 ,  32 , a light beam  46 ,  47  from the light source  22  and a light beam  48 ,  49  from other unwanted light source  26 . 
         [0021]    The arrangement in  FIG. 3  describes the method of the invention for sense the light from the light source  22  to determine the position of the object  21  in space. The light beam  46 ,  47  from the light source  22  passes the optical band-pass filter  23 ,  30 , the optical lens  24 ,  31  and meets the light sensor/image sensor  25 ,  32 . The pixel  27 ,  33  that is illuminated from the light beam  46 ,  47  appear as a bright pixel. All pixels that are illuminate from the light beam  46 ,  47  together add up to a bright flaw. The unwanted light beam  48 , 49  can not pass the optical band-pass filter  23 ,  30  and therefore comes the bright flaw on the light sensor/image sensor  25 ,  32  only from the light source  22  on the object  21 . The bandwidth of the light source  22  and the bandwidth of the optical band-pass filter  23 ,  30  is attuned to each other. Under consideration of geometrical context it is possible from the information of the light sensor/image sensor  25 ,  32  to determine/calculate the position of the object  21  in space. 
         [0022]    In  FIG. 4  there is illustrated an embodiment of the invention that provides a device to control a power wrench  38  that each screw joint  40 , 41  is tightened with the right parameters. The power wrench  38  is provided with an identity providing means in the form of a light source  39  which is recognised by two stationary position scanning cameras  34 ,  35  with optical band-pass filter  36 ,  37 , wherein the light source  39 , the cameras  34 , 35 , the optical band-pass filters  36 ,  37  and control unit/calculation unit  44  form a position sensing system. The cameras  34 , 35  with the optical band-pass filter  36 , 37  are connected to the control unit/calculation unit  44  and arranged to transfer the signals for calculation the actual position of the power wrench  38 . The control unit/calculation unit  44  is connected to the control unit  45  of the power wrench  38  and they communicate with each other. 
         [0023]    The position sensing system is arranged to indicate continuously the position of the power wrench  38  during operations on the workpiece  42  that lies on the workpiece carrier  43 . 
         [0024]    The control unit  45  of the power wrench  38  is programmed with target torque levels, angle and/or spend time as well as limit value for each tightening operation for each screw joint  40 ,  41 . The control unit/calculation unit  44  is programmed with the right sequence of tightening screw joints  40 ,  41 . That means that each tightening operation will monitor by the control unit  45  and control unit/calculation unit  44  and they together will provide an OK or NOK indicating telling whether the tightening result of each screw joints  40 , 41  is acceptable or not. 
         [0025]    If a non-acceptable tightening result is occurred it is possible to program the control unit  45  of the power wrench  38  so, that for example the power wrench  38  can be locked until the non-acceptable tightening screw joint is corrected before moving to the next screw joint or to the next workpiece. Other possibilities for programming the control unit  45  are thinkable and are not limited after a non-acceptable tightening screw joint. 
         [0026]    An important advantage provided by the method and device according to the invention is that no-preprogramming of screw joint positions is necessary. 
         [0027]    It is to be observed that the embodiment of the invention are not limited to the above described examples but may be freely varied within the scope of the claims. For instance, the above mentioned method to communicate signals by wire between the control unit of the power wrench and the control unit/calculation unit of the position sensing system may be carried out by any available communication system and by wireless communication too. All communications by wire can replace through wireless communications. The control unit of the power wrench and the control unit/calculation unit of the position sensing system can be integrated to one control unit.