Patent ID: 7356937

Claim:
A calibration method for calibrating a parallel kinematic mechanism which is provided with: a base supported on a support platform; an end effecter; a plurality of driver shafts connecting the base and the end effecter via a plurality of joints provided in the base and the end effecter, respectively; and a numerical control device for controlling the posture of the end effecter by manipulating coordinates of each driver shaft using the kinematics or the inverse kinematics; the calibration method comprising: a setting step of setting an adjustment tool attached to the end effecter in a specified number of different predetermined known postures in a reference coordinate system provided outside the parallel kinematic mechanism, an axis of the adjustment tool being in agreement with an axis of the end effecter, the adjustment tool including a measurement device, a coordinate adjustment unit and an orientation adjustment unit, the setting being performed based on a measurement of the measurement device, the setting step further including setting the adjustment tool in such a position as to specify the position of the adjustment tool based on coordinates of a reference hole formed at a predetermined position in the reference coordinate system and measurements of the coordinate adjustment unit to determine a spatial coordinate, the reference hole having a cylindrical inner peripheral surface around an axis of the reference hole perpendicularly intersecting a reference surface, and the setting step also including setting the adjustment tool in such a position as to specify two orientation angle coordinates expressing an orientation of the axis of the end effecter based on relative distance between the reference surface and a rotation plane of the orientation adjustment unit being rotated about the axis of the end effecter to determine the two orientation angle coordinates, and adjust the orientation of the end effecter so that a reference side of the end effecter becomes parallel to a predetermined line, and determine orientation angle coordinates of the end effecter about the axis of the end effecter; a recording step of recording actual coordinates of each driver shaft manipulated by the numerical control device in accordance with the inverse kinematics each time the adjustment tool is placed in the posture; and a calculating step of calculating kinematic parameters necessary for the kinematics of the parallel kinematic mechanism based on original coordinates of the postures of the driver shafts and the recorded actual coordinates of the driver shafts.