Horizontal articulated robot and return-to-origin method thereof

A horizontal articulated robot used for transferring a work, comprising:

• a base;
• a base side link rotatably connected to the base;
• an arm section side link coupled to the base side link;
• an arm section freely rotatably connected to the arm section side link;
• a hand section freely rotatably connected to the arm section to hold the work;
• a storage configured to store at least teaching data;
• and
• a computation unit which calculates a transfer path on a basis of the teaching data to control drive of the base side link, the arm section, and the hand section,
• wherein the base side link and the arm section side link constitute a link mechanism configured to control in such a manner that a movement locus of a center point of a coupling shaft of the arm section side link and the arm section becomes a predetermined straight line,
• wherein with a center of rotation of the base side link with respect to the base as an origin, a specified via point is specified for each quadrant of an XY orthogonal coordinate system in which one of two opposite directions parallel to the predetermined straight line is an X-axis positive direction,
• wherein the computation unit continuously executes recording of coordinates of the horizontal articulated robot during transfer operation and return-to-origin operation,
• wherein when a return-to-origin request is input, the computation unit determines whether or not a current coordinate of the horizontal articulated robot when the return-to-origin request is input is within a predetermined range from a latest recorded coordinate,
• wherein when the current coordinate is within the predetermined range, the computation unit calculates a locus for the return-to-origin operation and moves the horizontal articulated robot in a returning direction to a return-to-origin position,
• wherein when the current coordinate is not within the predetermined range, the computation unit calculates past transfer paths based on past teaching data stored in the storage, and determines whether or not there is any calculated transfer path close to the current coordinate among the past transfer paths, and if there is the calculated transfer path close to the current coordinate, the computation unit moves the horizontal articulated robot to the calculated transfer path, and then moves the horizontal articulated robot to the return-to-origin position, and
• wherein if there is no calculated transfer path close to the current coordinate among the past transfer paths, the computation unit determines whether or not the hand section is positioned outside of a turn safe area, and when the hand section is positioned outside of the turn safe area, the computation unit pulls in the hand section to an inside of the turn safe area and then moves the horizontal articulated robot to the return-to-origin position through the specified via point specified for each quadrant of the XY orthogonal coordinate system.