Abstract:
A position detection system includes: a contactor including a tracing unit that traces and fits with a recess or a protrusion of an object; a slide member; a sliding unit that causes the slide member to slide in two directions; a moving unit that causes the contactor to move in a direction perpendicular to a plane so as to cause the tracing unit of the contactor to trace and fit with the recess or the protrusion of the object; a contactor detecting unit that detects a position of the contactor in the plane; and an object position detecting unit that detects the position of the object based on movement amount of the contactor before and after the slide member slides on the sliding unit to slide, when the tracing unit traces the recess or the protrusion.

Description:
RELATED APPLICATIONS 
     The present application claims priority to Japanese Application Number 2014-217683, filed Oct. 24, 2014, the disclosure of which is hereby incorporated by reference herein in its entirety. 
     BACKGROUND OF THE INVENTION 
     1. Technical Field 
     The present invention relates to a position detection system for detecting a position of an object having a recess or a protrusion. 
     2. Description of Related Art 
     As disclosed in Japanese Laid-open Patent Publication No. H05-241626, it has been common practice to determine an accurate position of an object by correcting detection data of the object acquired using a visual sensor or a camera. In Japanese Laid-open Patent Publication No. 2005-251086: an object is detected by a visual sensor provided on a robot; subsequently the visual sensor is moved by the robot; and an identical object is detected by the visual sensor thus moved. Further, in Japanese Laid-open Patent Publication No. 2005-251086, a determination is made as to whether the result of the detection by the visual sensor relates to an identical object. 
     However, when the object has a portion such for example as a recess or a protrusion that is difficult to detect by the visual sensor, an erroneous detection tends to occur. This may make it not possible to detect an accurate position of the object, thus lowering the operating efficiency. 
     The present invention has been made in view of such circumstances, and an object thereof is to provide a position detection system that is capable of accurately detecting a position of an object, even when the object has a recess or a protrusion. 
     SUMMARY OF THE INVENTION 
     In order to achieve the above object, according to a first aspect of the present invention, there is provided a position detection system for detecting a position of an object having a recess or a protrusion, the system including: a contactor including a tracing unit that traces and fits with the recess or the protrusion of the object; a slide member configured integrally with the contactor; a sliding unit that causes the slide member to slide in two directions perpendicular to each other; a moving unit that causes the contactor to move in a direction perpendicular to a plane defined between the two directions so as to cause the tracing unit of the contactor to trace and fit with the recess or the protrusion of the object; a contactor detecting unit that is in a fixed positional relationship with a base of the sliding unit and detects a position of the contactor in the plane; and an object position detecting unit that detects a position of the object based on the position of the contactor detected by the contactor detecting unit before and after the slide member slides on the sliding unit, when the tracing unit of the contactor traces the recess or the protrusion of the object. 
     According to a second aspect of the present invention, in the first aspect, when the moving unit causes the contactor to move in at least one direction of the two directions, the position of the object is detected based on the movement amount of the contactor by the moving unit and the movement amount of the contactor when the slide member slides on the sliding unit. 
     According to a third aspect of the present invention, in the first or second aspect, the contactor is a camera. 
     According to a fourth aspect of the present invention, in any one of the first to third aspects, the moving unit is a robot. 
     According to a fifth aspect of the present invention, in any one of the first to fourth aspects, the object has a recess, and the contactor is a cone fittable with the recess. 
     According to a sixth aspect of the present invention, in any of the first to fourth aspects, the object has a conical protrusion, and the contactor has a cylindrical portion fittable with the protrusion. 
     These and other objects, features, and advantages of the present invention will become more apparent from a detailed description of exemplary embodiments of the present invention illustrated in the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view illustrating a position detecting system based on the present invention. 
         FIG. 2  is a flow chart illustrating the operation of the position detection system illustrated in  FIG. 1 . 
         FIG. 3A  is a first perspective view for explaining the operation of the position detection system. 
         FIG. 3B  is a second perspective view for explaining the operation of the position detection system. 
         FIG. 3C  is a third perspective view for explaining the operation of the position detection system. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of the present invention will now be described with reference to the accompanying drawings. Throughout the drawings, like reference numerals are assigned to like elements. In order to facilitate understanding, the scale of the drawings is appropriately changed. 
       FIG. 1  is a perspective view illustrating a position detection system based on the present invention. As illustrated in  FIG. 1 , the position detection system  1  includes mainly a moving unit  11 , a contactor detecting unit  12 , and a control device  10  that controls the moving unit  11  and the contactor detecting unit  12 . Further, the control device  10  functions as an object position detecting unit that detects a position of an object as described hereinafter. 
     The moving unit  11  is a perpendicular articulated robot, for example, and instead may be another type of robot or another mechanism unit that can move in a vertical direction. Meanwhile, the contactor detecting unit  12  is a visual sensor or a camera. In the following, a description will be made on the assumption that the moving unit  11  is a robot and the contactor detecting unit  12  is a camera. 
     As illustrated, a base member  13  is attached to a distal end of the robot  11 . Further, the camera  12  is attached to a distal end of a bracket  14  fixed in such a manner as to extend substantially vertically with respect to the base member  13 . 
     Further, a sliding mechanism unit  20  is attached to the base member  13 . More specifically, mutually parallel two X-axis rails  21  of the sliding mechanism unit  20  are provided on the upper surface of the base member  13 . It is assumed that the positional relationship among the base member  13 , the bracket  14 , and the two X-axis rails  21  is such that they are fixed with respect to each other and are moved in unison when the robot  11  moves. Further, as illustrated, a first slider  23  of the sliding mechanism unit  20  is slidably located on the two X-axis rails  21 . 
     On the upper surface of the first slider  23  are provided mutually parallel two Y-axis rails  22  of the sliding mechanism unit  20 . These Y-axis rails  22  are perpendicular to the above-mentioned X-axis rails. A second slider  24  of the sliding mechanism unit  20  is slidably located on the two Y-axis rails  22 . 
     Further, a generally cylindrical contactor  30  is inserted and fixed in an opening provided at the center of the second slider  24 . Upper surface  31  of the contactor  30  is parallel with respect to the upper surface of the second slider  24 , and a target T is provided thereon. As can be seen from  FIG. 1 , the target T is located below the camera  12  in the range of view of the camera  12 . Preferably, both the X-direction defined by the X-axis rails  21  and the Y-direction defined by the Y-axis rails  22  lie in a horizontal plane. Thus the upper surface of the second slider  24  lies in a horizontal plane. 
     As illustrated in  FIG. 1 , the contactor  30  extends downwardly between the two Y-axis rails  22  and between the two X-axis rails  21 . An extension unit  32  extends from the lower surface of the contactor  30 , and a tracing unit  33  is provided on the distal end of the extension unit  32 . Preferably, the contactor  30 , the extension unit  32 , and the tracing unit  33  have a common center axis. 
     The extension unit  32  has a size greater than that of a recess formed on an object, which will be described hereinafter. The tracing unit  33  has a shape adapted to trace and fit with the recess of the object. In  FIG. 1 , for example, the extension unit  32  is of a cylindrical shape having a diameter greater than that of the recess, and the tracing unit  33  is of a conical shape such for example as a cone provided on the distal end of the extension unit  32 . 
       FIG. 2  is a flow chart illustrating the operation of the position detection system illustrated in  FIG. 1 . Further,  FIGS. 3A through 3C  are perspective views for explaining the operation of the position detection system. A description will now be made of the operation of the position detection system according to the present invention with reference to the drawings. 
     Prior to the operation of the position detection system  1 , the first slider  23  and the second slider  24  each are located at a predetermined initial position thereof. It is assumed, in this regard, that the first slider  23  and the second slider  24  will not be changed in position when the robot  11  is merely moved in the horizontal and/or vertical direction. 
     As illustrated in  FIG. 3A , the object W is of a generally cubic shape in which an opening W 0  is formed in the top face. A cylindrical recess extends from the opening W 0  through the interior of the object W. It is assumed that the following description applies to an object W of another shape having a similar recess as well. 
     Firstly, at step S 11  of  FIG. 2 , the control device  10  causes the robot  11  to move so that the base member  13  is made to approach above the object W. Since the robot  11  is operated in accordance with a simple program, in the present invention, the base member  13  can be made to approach above the object W easily and accurately. 
     As described above, the base member  13 , the bracket  14 , the camera  12 , and the two X-axis rails  21  are operated in unison so that when the base member  13  is moved, the camera  12  is also moved likewise. As such, as illustrated in  FIG. 3A , the contactor  30  is located generally above the object W. 
     The movements of the base member  13 , etc. at step S 11  may include both horizontal and vertical movements. Preferably, the distance between the contactor  30  and the object W illustrated in  FIG. 3A  is in a predetermined range. When the contactor  30  is located generally above the object W, the camera  12  picks up an image of the target T of the contactor  30 , and the image is stored in the control device  10 . 
     At step S 12 , the base member  13 , etc. are moved only downwardly toward the object W by the robot  11  as illustrated by an arrow mark in  FIG. 3A . In this manner, as illustrated in  FIG. 3B , the distal end of the tracing unit  33  enters the opening W 0  so that a part of the side surface of the tracing unit  33  contacts a part of the opening W 0 . 
     As the base member  13 , etc. are moved further downwardly by the robot  11 , the tracing unit  33  descends while tracing the opening W 0 . In response to this descending operation, the contactor  30  and the second slider  24  are moved slightly in at least one of the X-direction and the Y-direction along the X-axis rail  21  and the Y-axis rail  22 . As illustrated in  FIG. 3C , a part of the side surface of the tracing unit  33  fits with the opening W 0  over the entire circumference thereof. When the tracing unit  33  of the contactor  30  fits with the opening W 0 , the contactor  30  is prevented from moving any further in the X-direction and in the Y-direction. Then, the descending operation by the robot  11  is also ended. 
     Subsequently, at step S 13 , the target T of the contactor  30  is imaged by the camera  12 , and the image is stored in the control device  10 . Thereupon, the control device  10  compares the image imaged at step S 13  with the above-mentioned image and thus detects the movement amount of the contactor  30  in the X-direction and in the Y-direction. Finally, at step S 14 , the control device  10  detects a position of the object W in the X-Y plane based on the movement amount of the contactor  30  in the X-direction and in the Y-direction. 
     Alternatively, the control device  10  may process the image imaged at step S 13 , detect the movement amounts of the first slider  23  and the second slider  24  from their initial positions, and detect the position of the object W, with such movement amounts being the movement amounts of the contactor  30 . In such an instance, it is unnecessary for the camera  12  to pick up an image at step S 11 , and a single image processing suffices. 
     In this manner, in the present invention, the contactor  30 , which has traced and fitted with the object W, is detected, instead of the object W being detected directly by the camera  12 . When the tracing unit  33  of the contactor  30  fits with the opening W 0  of the object W, the contactor  30  is moved in the X-direction and in the Y-direction along the X-axis rail  21  and the Y-axis rail  22 . Thus, it is possible to indirectly grasp the position of the object W by detecting the movement amount of the contactor  30  using the camera  12 . 
     Consequently, in the present invention, it is possible to accurately detect the position of the object W even when the object W has a recess or a protrusion. In other words, in the present invention, it is possible to achieve a stable detection without being influenced by the feature of the object W, since the camera  12  does not detect the shape of the object W directly. As such, erroneous detection of the object W by the camera  12  decreases so that the operating efficiency is increased. 
     Meanwhile, at step S 11 , the robot  11  may move the base member  13  and the camera  12 , etc. in the horizontal direction. In this instance, the control device  10  stores the movement amount of the base member  13 , etc. moved in the X-direction and in the Y-direction by the robot  11 . Further, at step S 14 , the control device  10  detects the position of the object W using both the movement amount of the contactor  30  in the X-direction and in the Y-direction and the stored movement amount of the base member  13 , etc. in the X-direction and in the Y-direction. In such an instance, it will be appreciated that the object W can be detected over a wide range since the base member  13 , etc. are moved by the robot  11 . 
     In an unillustrated embodiment, the object has a protrusion, e.g., a conical protrusion. It is assumed, in this regard, that a recess, which is fittable with the protrusion and similar to that described above, is formed in the bottom surface of the extension unit  32  of the contactor  30 . In this instance, the shape of the recess is a shape corresponding to the bottom surface of the conical protrusion. Meanwhile, it is to be understood that the present invention encompasses a case in which the protrusion or the recess has a different cross-sectional shape and a case in which the recess or the protrusion is cylindrical. 
     ADVANTAGE OF THE INVENTION 
     In the first embodiment, the contactor is made to trace and fit with the object using the physical feature of the object. Then, the contactor detecting unit detects the contactor and indirectly grasps a position of the object. Thus, even with an object having a recess or a protrusion, it is possible to accurately detect a position of the object. Consequently, erroneous detection of the object by the contactor detecting unit decreases so that the operating rate is increased. 
     In the second embodiment, the object can be detected over a wide range when the contactor is moved by the moving unit. 
     In the third embodiment, the position of the contactor can be detected with ease via an analysis of an image acquired by imaging by the camera. 
     In the fourth embodiment, the object can be easily approached by operating the robot in accordance with a simple program. 
     In the fifth and sixth embodiments, it is possible, by a relatively simple structure, to cause the contactor to trace and fit with the object 
     While the present invention has been described using exemplary embodiments, those skilled in the art could understand that the above-described changes as well as various other changes, omissions, and additions are possible without departing from the scope of the present invention.