Self-calibration system for robot mechanisms

A method for automatically calibrating a robot capable of movement in two axes and installed in a robot chamber, the robot being capable of moving a substrate support angularly and radially with respect to an axis, the method comprising the steps of:

• moving the robot to an angular position such that the substrate support is positioned adjacent to a fixed sensor in the robot chamber;
• moving the substrate support angularly across the fixed sensor;
• detecting when at least one edge of the substrate support trips the fixed sensor, and recording an angular position of the robot;
• computing the difference between the angular position of the robot recorded in the immediately preceding recording step and a predicted robot angular position at which the fixed sensor should be tripped;
• applying the difference value computed in the prior immediately computing step to calibrate the robot in angular position;
• moving the substrate support such that a front edge of the substrate support is adjacent to the fixed sensor;
• moving the substrate support radially out across the fixed sensor;
• detecting when at least one feature of the front edge of the substrate support trips the fixed sensor and recording a radial position of the robot;
• computing the difference between the radial position of the robot recorded in the immediately preceding recording step and a predicted robot radial position at which the fixed sensor should be tripped;
• and
• applying the difference value computed in the immediately prior computing step to calibrate the robot in radial position.

Apparatus for automatically calibrating a robot capable of movement in two axes and installed in a robot chamber, comprising:

• a robot mechanism installed in a robot chamber and including a movable workpiece support and means for moving the workpiece support in at least two dimensions;
• a sensor fixed to the robot chamber in a known position;
• means for moving the workpiece support to a position adjacent to the sensor;
• means for next moving the workpiece support along a first position axis and across the sensor;
• means for detecting when at least one feature of the workpiece support trips the sensor, and recording a robot position in the first position axis;
• means for computing the difference between the robot position in the first position axis recorded in the immediately preceding means for detecting and recording, and a predicted robot first-axis position at which the sensor should be tripped;
• means for applying the difference value computed in the means for computing, to calibrate the robot in the first position axis;
• means for next moving the workpiece support along a second position axis and across the sensor;
• means for detecting when at least one feature of the workpiece support trips the sensor, and recording a robot position in the second position axis;
• means for computing the difference between the robot position in the second position axis recorded in the immediately preceding means for detecting and recording, and a predicted robot second-axis position at which the sensor should be tripped;
• and
• means for applying the difference value computed in the immediately preceding means for computing, to calibrate the robot in the second position axis.

Apparatus for automatically calibrating a robot capable of movement in two axes and installed in a robot chamber, the apparatus comprising:

• means for moving a substrate support in the robot to a selected angular position and a selected radial position with respect to a fixed axis;
• a sensor fixed in the robot chamber, and capable of detecting the presence of the edge of an object moved across the sensor;
• and
• calibration control means, including:
• means for moving the substrate support to an angular position adjacent to the sensor;
• means for moving the substrate support angularly across the sensor;
• means for detecting when at least one edge of the substrate support trips the sensor, and recording an angular position of the robot;
• means for computing the difference between the angular position of the robot recorded in the immediately preceding means for detecting and recording, and a predicted robot angular position at which the sensor should be tripped, and applying this difference value to calibrate the robot in angular position;
• means for moving the substrate support such that a front edge of the substrate support is adjacent to the sensor;
• means for moving the substrate support radially out across the sensor;
• means for detecting when at least one feature of the front edge of the substrate support trips the sensor and recording a radial position of the robot;
• and
• means for computing the difference between the radial position of the robot recorded in the immediately preceding means for detecting and recording, and a predicted robot radial position at which the sensor should be tripped, and applying this difference value to calibrate the robot in radial position.