Seam welding apparatus, seam welding method, robot control device, and robot control method

A seam welding apparatus that performs seam welding on layered steel plates, the seam welding apparatus comprising:

• an articulated robot capable of setting a predetermined tolerance for a joint;
• and
• a welding device attached to the robot and revolvable about a revolving axis of the robot,
• the welding device comprising:
• a pair of rotation electrodes for seam-welding the layered steel plates while applying pressure, the pair of rotation electrodes being rotatably supported by the welding device about respective rotation axes orthogonal to the revolving axis;
• an electrode supporting frame that supports the rotating electrodes;
• a supporting frame that rotatably supports the electrode supporting frame so that it is possible to change a direction of running when the rotating electrodes run on the steel plates;
• a revolving means configured to revolve the electrode supporting frame provided on the supporting frame;
• an optical distance measuring device provided on the supporting frame or the electrode supporting frame, the optical distance measuring device including:
• a laser emission part disposed to face an edge of one of the layered steel plates, the laser emission part being configured to emit light toward the edge;
• a light position detecting device configured to receive the light emitted from the laser emission part that reflects from the edge so as to detect a position of the received light reflected from the edge, the light position detecting device comprising a plurality of light receiving elements that are arranged in a row in an extending direction of the edge and receive different reflected lights corresponding to positions at which the light reflects from the edge of one of the layered steel plates;
• a light projecting lens;
• and
• a light receiving lens,
• wherein the laser emission part, the light position detecting device, the light projecting lens, and the light receiving lens are provided at fixed positional relationships with respect to each other, and
• the optical distance measuring device is configured to geometrically measure, based on which light receiving element of the plurality of light receiving elements of the light position detecting device receives the different reflected lights, a distance from the optical distance measuring device to the edge in a direction parallel to the rotation axes of the pair of rotation electrodes;
• and
• a controller configured to:
• set a target position of the welding device to set a target distance from the optical distance measuring device to the edge when the welding device is in the target position;
• calculate a deviation of the distance measured by the optical distance measuring device from the target distance while the pair of rotation electrodes is running on the layered steel plates to perform seam welding;
• and
• control the revolving means to adjust a running direction of the rotation electrodes so that the deviation comes into zero when a distance actually measured by the optical distance measuring device deviates from the target distance.

A robot control system comprising:

• a processor;
• a robot having an end effector revolvable about a revolving axis of the robot, the end effector including a pair of rotation electrodes for seam-welding two overlapped steel plates while applying pressure, the pair of rotation electrodes being rotatably supported by the end effector about respective rotation axes orthogonal to the revolving axis;
• and
• an optical measuring device that is provided on the end effector,
• the optical measuring device including:
• a laser emission part disposed to face an edge of one of the two overlapped steel plates, the laser emission part being configured to emit light toward the edge;
• a light position detecting device configured to receive the light emitted from the laser emission part that reflects from the edge so as to detect a position of the received light reflected from the edge, the light position detecting device comprising a plurality of light receiving elements that are arranged in a row in an extending direction of the edge and receive different reflected lights corresponding to positions at which the light reflects from the edge of one of the two overlapped steel plates;
• a light projecting lens;
• and
• a light receiving lens,
• wherein the laser emission part, the light position detecting device, the light projecting lens, and the light receiving lens are provided at fixed positional relationships with respect to each other, and
• the optical measuring device is configured to geometrically measure, based on which light receiving element of the plurality of light receiving elements of the light position detecting device receives the different reflected lights, a distance from the optical measuring device to the edge in a direction parallel to the rotation axes of the pair of rotation electrodes,
• wherein the processor is configured to:
• set a target position of the end effector to set a target distance from the optical measuring device to the edge when the end effector is in the target position;
• calculate an error of the distance measured by the optical measuring device from the target distance while the pair of rotation electrodes is running on the two overlapped steel plates to perform seam welding;
• and
• rotate the end effector about the revolving axis of the robot so as to adjust a running direction of the pair of rotation electrodes so that the error comes into zero.