Method for calibrating a SCARA robot

Abstract

A technique is provided for calibrating a SCARA type robot (10) comprised of a first rotatable link (20) and a second link (32), rotatably connected at one end to the first link, and carrying a tool (40) at the other end thereof. The calibration technique relies on the fact that SCARA robots are controlled using a kinematic model, which, when accurate, allows the links to be placed in both a first and second angular configuration at which the tool (40) carried by the second link remains at the same position. To calibrate the kinematic model, the links are placed in the first configuration to locate the tool above a fixed datum point (60). Then, the links are placed in the second angular configuration to nominally locate the tool again in registration with the datum point. The error in the kinematic model is computed from the shift in the position of the tool from the datum point when the links are switched from the first to the second angular configuration. The kinematic model is then compensated in accordance with the computed error. These steps are repeated until the error reaches zero, at which time the kinematic model of the SCARA robot is calibrated.

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