ORIGINAL POINT RETURN CONTROL METHOD FOR POSITION CONTROLLER

PURPOSE:To simplify the work and also to shorten the working time by performing the original point return jobs with the same operation regardless of the coincidence between the mechanical positive direction and the position information increasing direction with a position controller which controls the positions of members like the arms, etc., of an industrial robot in regard of an original point return control method that is carried out with application of a main power supply, etc. CONSTITUTION:A position where a Z pulse is detected for the first time is defined as an electrical original point (S1) while a prescribed member is moved in the prescribed direction after the operating position of a position detector is detected. Then the multi-revolution information is reset at a position moved in the prescribed direction from the original point at a proper angle (S2-S4). If the mechanical positive direction is coincident with the position information increasing direction under such conditions (S9), the position information on an encoder is directly used as the present position data ($10). Meanwhile the present position data are defined (S11, S13) by adding the value equivalent to one revolution to the position information on the encoder that undergoes the conversion of polarity when both preceding directions are adverse to each other (S9, S12).