Patent Publication Number: US-7720573-B2

Title: Robot control apparatus

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a robot control apparatus for controlling a robot using an imaging device, and more particularly to a robot control apparatus for controlling a robot using an imaging device in order to determine a relative position of a workpiece to the robot and correct a teaching point position of an operation program for the robot based on the determined relative positions. 
   2. Description of the Related Art 
   In the field of an industrial robot, an imaging device, such as a camera has been widely used as an eye for a robot. In the case where an imaging device is used for an industrial robot, it is common for the imaging device to be connected to an image processing unit separately provided from or integral with a robot control apparatus and the image processing device and an image display unit for displaying the image thereon are arranged integrally with or in the vicinity of the robot control apparatus. In a factory, it is common to surround the operating range of the robot with a protective fence or the like for the safety of an operator and to arrange the robot control apparatus and the image processing unit outside the protective fence at a sufficient distance from the robot. 
   As described above, where the image processing unit and the image display unit are installed is often far from the robot, and this poses a problem in that it is difficult to check an image picked up by the imaging device during a robot teaching operation or an adjustment operation of the image processing unit or the imaging device. In order to solve this problem, Japanese Unexamined Patent Publication No. 2000-135689, Japanese Unexamined Patent Publication No. 2001-191285 and Japanese Unexamined Patent Publication No. 2001-121458, for example, propose a portable teaching pendant having an image display and used for the operation of the robot or the image processing unit. The use of this teaching pendant makes it possible for the operator to display an image picked up by the imaging device on the teaching pendant. Therefore, an operator, manually operating the robot, can check the image on the teaching pendant during the robot teaching operation or the adjustment operation of the imaging device or the image processing unit. 
   The imaging device and the image processing unit (hereinafter collectively referred to as a visual sensor) of the industrial robot, as described above, function as an eye of the robot for doing a job and is continuously used while the robot is used. Therefore, once installed, the visual sensor is basically not removed from the robot. 
   However, in recent years, the visual sensor has been temporarily used only when installing the robot system. Japanese Unexamined Patent Publication No. 2005-149299, for example, discloses a teaching position correcting device in which in order to facilitate an operation for correcting teaching points in a robot operation problem at the time of relocation of a robot system, displacement of the relative positions between the installation place of the robot and the workpiece place, which may occur after the relocation of the robot system, is measured by a camera temporarily mounted on the robot to correct positions of teaching points in the robot operation program. The teaching position correcting device 100 disclosed in Japanese Unexamined Patent Publication No. 2005-149299, as shown in  FIG. 5 , includes an image processing unit 104 connected to a robot control apparatus 102, and a CCD camera 112 connected to the image processing unit 104 by a camera connecting cable 110. An image is picked up by a CCD camera 112 mounted on a working tool 114 of the robot 106 while an operator is operating a teaching pendant 108 connected to the robot control apparatus 102. The image thus picked up is processed by the image processing unit 104, so that three-dimensional positions of three reference marks 120 provided on a holding unit 118 for holding a workpiece 116 are measured to calculate a change in the position of the holding unit 118 relative to the robot 106 based on the positions of the reference marks 120 measured before and after relocation, and the positions of the teaching points defined in the robot operation program are corrected by the calculated change amount. 
   The image processing unit 104 used in the teaching position correcting device 100 disclosed in Japanese Unexamined Patent Publication No. 2005-149299 is similar to the image processing units disclosed in Japanese Unexamined Patent Publication No. 2000-135689, Japanese Unexamined Patent Publication No. 2001-191285 and Japanese Unexamined Patent Publication No. 2001-121458 and is installed in the vicinity of the robot control apparatus. Further, the CCD camera 112 is connected to the image processing unit 104. 
   On the other hand, the visual sensor constituted by the CCD camera 112 and the image processing unit 104, as disclosed in Japanese Unexamined Patent Publication No. 2005-149299, unlike a conventional visual sensor of the industrial robot, is not fixed to the robot 106, but used temporarily only to measure the positions of the reference marks 120 at the time of relocation, and one CCD camera 112 is generally used for a plurality of robots 106. Therefore, mounting and demounting the CCD camera 112 from the robot 106 and the robot control apparatus 102 is frequently carried out. 
   However, in starting a job on a robot 106 after finishing a job on another robot 106, the operator needs to move between the robot 106 and the robot control apparatus 102 installed at a distance from the robot 106 in order to reconnect the CCD camera 112 with the image processing unit 104 or the robot control apparatus 102. Especially on an actual production line, the robot 106 is surrounded by a protective fence for the safety of the operator, and the robot control apparatus 102 and the image processing unit 104 are arranged outside the protective fence. Therefore, the robot 106 and the robot control apparatus 102 are generally far from each other. Also, in some cases, the robot control apparatus 102 and the robot 106 are installed on different floors in a factory layout. Therefore, movement between the robot 106 and the robot control apparatus 102 imposes a heavy burden on an operator. 
   SUMMARY OF THE INVENTION 
   Accordingly, it is an object of the present invention to solve the aforementioned problem of the prior art and to reduce the burden on an operator in using one imaging device for a plurality of robots. 
   In order to achieve this object, according the present invention, there is provided a robot control apparatus, which includes a control apparatus body fixedly installed and connected to a robot and a portable teaching pendant connected to the control apparatus body to operate the robot through the teaching pendant, wherein the teaching pendant includes an imaging device connector for connecting an imaging device to the teaching pendant so as to enable the image picked up by the imaging device to be directly input to the teaching pendant through the imaging device connector. 
   The imaging device connector may be an imaging device connecting terminal for connecting a cable extending from the imaging device, and the image picked up by the imaging device may be transmitted through the cable and input to the teaching pendant. 
   Also, the imaging device connector may be a radio receiver for receiving a radio signal transmitted from the imaging device, and the image picked up by the imaging device may be transmitted wirelessly and input to the teaching pendant. 
   The teaching pendant may include an image processing unit for processing the image input to the teaching pendant, or the control apparatus body may include an image processing unit, so that the image input to the teaching pendant may be transmitted to and processed by the image processing unit of the control apparatus body. 
   Since the teaching pendant of the robot control apparatus according to the present invention includes an imaging device connector for connecting the imaging device such as a camera to the teaching pendant, the imaging device can be connected to the control apparatus body via the teaching pendant to make the imaging device usable, simply by connecting the imaging device to the teaching pendant. Therefore, in the case where an imaging device used temporarily when relocating a robot system is connected to another robot system and used in another robot system, the operator is not required to move between the robot and the control apparatus body installed at a place far from the robot in order to connect and demount the imaging device from the control apparatus body, thereby reducing the burden on the operator. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above and other objects, features and advantages of the present invention will be described in more detail below based on preferred embodiments of the present invention with reference to the accompanying drawings, in which: 
       FIG. 1  is a diagram showing a general configuration of a robot system including a robot control apparatus according to a first embodiment of the present invention; 
       FIG. 2  is a function block diagram of the robot control apparatus shown in  FIG. 1 ; 
       FIG. 3  is a diagram showing a general configuration of a robot system including a robot control apparatus according to a second embodiment of the present invention; 
       FIG. 4  is a function block diagram of a robot control apparatus according to a third embodiment of the present invention; and 
       FIG. 5  is a diagram showing a general configuration of the conventional robot system. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   The preferred embodiments of a robot control apparatus according to the present invention will be described below with reference to the accompanying drawings. 
   First, a robot control apparatus according to a first embodiment of the present invention will be described with reference to  FIGS. 1 and 2 .  FIG. 1  is a diagram showing a general configuration of a robot system  10  including a robot control apparatus  14  according to the first embodiment of the present invention. The robot system  10  includes a robot arm  12 , and a robot control apparatus  14  for controlling operation of the robot arm  12 . A working tool  16  is attached to the forward end of the robot arm  12 . In this embodiment, the working tool  16  is a welding gun for spot-welding, and the robot arm  12  conducts a welding job on a workpiece (not shown) such as a metal panel fixed to a holding unit (not shown) or the like (see  FIG. 5 ). Also, the working tool  16  attached to the robot arm  12  has a CCD camera mounted thereon as an imaging device, and the CCD camera is used to correct positions of teaching points in a robot operation program based on displacement of relative positions between the robot arm  12  and the workpiece which occur when relocating the robot system  10 . 
   The CCD camera  18 , upon completion of an operation for correcting the positions of the teaching points in the robot operation program for one robot system, can also be used in another robot system. For this purpose, the CCD camera  18  is mounted on the working tool  16  by an appropriate mounting means, such as a magnet or a clamp which allows the CCD camera  18  to be easily mounted and demounted from the working tool  16 . The CCD camera  18  is used, in this case, as the imaging device. However, other types of cameras may of course be used as the imaging device. 
   The robot control apparatus  14  includes a control apparatus body  20  fixedly arranged at a position far from the robot arm  12 , and a portable teaching pendant  22  connected to the control apparatus body  20  by a teaching pendant connecting cable  24 . The control apparatus body  20  includes a control processing unit  26  for generating an operation command to the robot arm  12  and the working tool  16 , and an image processing unit  28  for processing the image picked up by the imaging device such as the CCD camera  18 . The control processing unit  26  and the image processing unit  28  may be integrated with each other or may be separated from each other. An operator can operate the robot arm  12  and the image processing through the teaching pendant  22  from the vicinity of the robot arm  12  by carrying the teaching pendant  22 . 
   The teaching pendant  22  further includes a camera connecting terminal  30 , as an imaging device connector for connecting the imaging device such as the CCD camera  18  to the teaching pendant  22 , so that the camera connecting cable  32  extending from the CCD camera  18  can be directly connected to the teaching pendant  22 . The image picked up by the CCD camera  18 , after being sent to the teaching pendant  22  through the camera connecting cable  32 , is transmitted to the image processing unit  28  of the control apparatus body  20  from the teaching pendant  22  through the teaching pendant connecting cable  24  to execute predetermined processing, such as extraction of a predetermined shape and calculation of the position thereof. Also, the teaching pendant  22  includes a liquid crystal display (LCD)  60  as a display unit so as to make it function as a monitor of the image processing unit  28  as well. Thus, the image input from the CCD camera  18  and the processing results from the image processing unit  28  can be displayed thereon. 
   After relocation of the robot system  10 , the relative position relationship between the robot arm  12  and the holding unit (see  FIG. 5 ) for holding the workpiece may change. Therefore, it is necessary to mount the CCD camera  18  on the working tool  16 , detect positions of reference marks using the CCD camera  18 , and correct positions of the teaching points defined in the robot operation program based on the detected positions of the reference marks. However, in the case that a conventional robot control apparatus is used, the CCD camera  18  is connected to the image processing unit  28  of the control apparatus body  20  through the camera connecting cable  32 . Therefore, in the case that a single CCD camera  18  is used, in a plurality of the robot systems  10 , for correcting the positions of the teaching points in the robot operation program, the operator needs to move between the robot arm  12  and the control apparatus body  20  in order to connect the CCD camera  18  to another robot arm  12  and robot control apparatus  14  associated with it, which poses a great burden on the operator. 
   In contrast, the teaching pendant  22  of the robot control apparatus  14  according to this embodiment has the camera connecting terminal  30 , and the CCD camera  18  cannot be connected to the image processing unit  28  of the control apparatus body  20  arranged at a place far from the robot arm  12 , but to the teaching pendant  22  located in the vicinity of the robot arm  12 . Therefore, when the CCD camera  18  used in one robot arm  12  is connected to another robot arm  12 , the operator can connect the CCD camera  18  to the robot control apparatus  14  through the teaching pendant  22  and the teaching pendant connecting cable  24  to allow the CCD camera  18  to be used by the robot control apparatus  14  for another robot arm  12 , simply by mounting the CCD camera  18  on another robot arm  12  and connecting the camera connecting cable  32  of the CCD camera  18  to the teaching pendant  22  for another robot arm  12  arranged in the vicinity of another robot arm  12 . As a result, the operator is not required to move between the robot arm  12  and the control apparatus body  20  arranged at a place far from the robot arm  12  in order to connect the robot control apparatus  14  and the camera connecting cable  32 , thereby reducing the burden on the operator. 
   Next, with reference to  FIG. 2 , the robot control apparatus  14  according to the present invention will be described in more detail.  FIG. 2  is a function block diagram showing the control apparatus body  20  and the teaching pendant  22  of the robot control apparatus  14  shown in  FIG. 1 . The robot control apparatus  14  includes a main CPU  36  constituted by a microprocessor, memory such as ROM  38  and RAM  40 , a servo control circuit  42 , a communication interface  44  for communication with the teaching pendant  22 , a camera interface  46  for receiving an image signal from the CCD camera  18 , an image processing unit  28  and a servo amplifier  48 . Of these components, the ROM  38 , the RAM  40 , the servo control circuit  42 , the communication interface  44 , the camera interface  46  and the image processing unit  28  are connected in parallel to each other with a bus  50  connected to the main CPU  36 . The servo control circuit  42  generates an operation command signal for the robot arm  12  in accordance with a command from the main CPU  36 . This operation command signal, after being amplified by the servo amplifier  48 , is transmitted to the robot arm  12  to cause the robot arm  12  to operate based on the operation command signal. 
   The teaching pendant  22  includes a CPU  52  constituted by a microprocessor, memory such as ROM  54  and RAM  56 , a graphic controller  58 , a liquid crystal display  60  connected to the graphic controller  58  for displaying image information thereon, a key control circuit  62 , a communication interface  64  connected to the communication interface  44  of the control apparatus body  20  for providing signal communication, and a camera connecting terminal  30  for connecting the CCD camera  18  as an imaging device to the teaching pendant  22 . Of these components, the ROM  54 , the RAM  56 , the graphic controller  58 , the key control circuit  62  and the communication interface  64  are connected in parallel to each other with a bus  68  connected to the CPU  52 . On the other hand, the camera connecting terminal  30  is connected to the camera interface  46  of the control apparatus body  20  through the teaching pendant connecting cable  24  without through the bus  68  connected to the CPU  52 , so that an image signal from the CCD camera  18  can be relayed as it is to the camera interface  46 . The image signal output from the CCD camera  18  may be either an analog image signal typically conforming to NTSC or a digital image signal. Also, an appropriate cable such as a USB cable, IEEE1394 cable or Ethernet (registered trade mark) cable can be used as the camera connecting cable  32  for communication between the CCD camera  18  and the camera connecting terminal  30 . 
   In the embodiment shown in  FIG. 2 , the image signal from the CCD camera  18  is relayed as it is to the camera interface  46  through the camera connecting terminal  30 . However, in the case that the transmission distance of the teaching pendant connecting cable  24  is long or a high-quality image signal transmission is required, an A/D converting circuit for digitizing analog NTSC signals may be provided in the teaching pendant  22 , and digitized image signals may be transmitted to the control apparatus body  20  through the teaching pendant connecting cable. As an alternative, a signal amplification circuit may be provided in the teaching pendant  22 , and the signal from the CCD camera may be amplified by the teaching pendant  22  and then transmitted to the control apparatus body  20 . 
   Next, with reference to  FIG. 3 , a robot control apparatus according to a second embodiment of the present invention will be described.  FIG. 3  is a diagram showing a general configuration of a robot system  10 ′ including a robot control apparatus  14 ′ according to the second embodiment of the present invention. In  FIG. 3 , the same components as those of the robot system  10  shown in  FIG. 1  are designated by the same reference numerals, respectively. 
   The robot system  10 ′ according to this embodiment is different from the robot system  10  shown in  FIG. 1  in that an image signal is transmitted wirelessly between a CCD camera  70  and a teaching pendant  22 ′. A wireless CCD camera  70  is mounted on the working tool  16  of the robot arm  12  by an appropriate mounting means for facilitating mounting and demounting of the wireless CCD camera  70 . The wireless CCD camera  70  does not transmit the image signal to external circuits through the camera connecting cable  32 , but by a radio signal. Accordingly, the teaching pendant  22 ′ of the robot control apparatus  14 ′ is provided with a radio receiver  72  as an imaging device connector. The other components are similar to those of the robot system  10  shown in  FIG. 1  and will not be described in detail here. 
   As described above, in the robot system  10 ′ according to this embodiment, the image signal from the CCD camera  70  mounted on the working tool  16  is transmitted wirelessly to the radio receiver  72  of the teaching pendant  22 ′, and by wire from the teaching pendant  22 ′ to the control apparatus body  20  through the teaching pendant connecting cable  24 . As a result, the camera connecting cable  32  between the CCD camera  70  and the teaching pendant  22 ′ is eliminated, and therefore the operator is not exposed to danger of contacting the camera connecting cable  32  when the robot arm  12  moves, thereby leading to an advantage in that various operations can be facilitated. Generally, wireless communication is not suitable for long distance signal transmission, and is difficult to be used for signal transmission between the CCD camera  70  and the control apparatus body  20 . However, in the operation of correcting the positions of the teaching points, the operator generally operates the robot arm  12  in the vicinity of the robot arm  12  while carrying the teaching pendant  22 ′. Therefore, the distance between the CCD camera  70  and the teaching pendant  22 ′ is short, and a wireless communication system can be employed for signal transmission between the CCD camera  70  and the teaching pendant  22 ′. 
   Next, with reference to  FIG. 4 , a robot control apparatus according to a third embodiment of the present invention will be described.  FIG. 4  is a function block diagram showing a robot control apparatus  14 ″ according to the third embodiment of the present invention. In  FIG. 4 , the same components as those of the robot control apparatus  14  shown in  FIG. 2  are designated by like reference numerals, respectively. 
   The robot control apparatus  14 ″ according to this embodiment is different from the robot control apparatus  14  shown in  FIG. 2  in that an image processing unit  74  and a camera interface  76  are not included in a control apparatus body  20 ″, but in a teaching pendant  22 ″. The teaching pendant  22 ″ includes, as in the robot control apparatus  14  shown in  FIG. 2 , a CPU  52 , memory, such as ROM  54  and RAM  56 , a graphic controller  58 , a liquid display  60 , a key control circuit  62 , a communication interface  64  and a camera connecting terminal  30 , and further includes a camera interface  76  for taking image signals from the CCD camera  18 , and an image processing unit  74 . Of these components, the ROM  54 , the RAM  56 , the graphic controller  58 , the key control circuit  62 , the communication interface  64 , the image processing unit  74  and the camera interface  76  are connected in parallel to each other with the bus  68  connected with the CPU  52 . On the other hand, the camera connecting terminal  30  is not connected to the bus  68  connected to the CPU  52 , but to the camera interface  76 . Therefore, the image on the CCD camera  18  can be directly displayed on the liquid crystal display  60 , and not through the control apparatus body  20 ″. The other components of the configuration are similar to those of the robot control apparatus  14  shown in  FIG. 2 , and will not be described in detail here. 
   In the robot control apparatus  14 ″ according to this embodiment, the image signal input to the camera connecting terminal  30  is transmitted to the image processing unit  74  through the camera interface  76  and the bus  68  in the teaching pendant  22 ″ for image processing. As a result, information on the workpiece position (for example, the positions of the reference marks on the camera image) detected by image processing is sent from the teaching pendant  22 ″ to the control apparatus body  20 ″. The image picked up by the CCD camera  18  can of course be displayed on the liquid crystal display  60 . 
   Although the robot control apparatus according to the present invention has been described above with reference to the embodiments, the present invention is not limited to these embodiments. For example, in the robot control apparatus  14 ″ shown in  FIG. 4 , a wireless CCD camera can be used, and a radio receiver can be used in place of the camera connecting terminal.