Patent ID: 8099184

Claim:
A method to compensate for a combined load offset on a part positioner system that positions a part to be worked on by a robot comprising: providing said part positioner system that has a shoulder with a rotational shoulder drive that rotates a part holding assembly around a shoulder center line, said shoulder center line being a line along an axis of rotation of said rotational shoulder drive, said part holding assembly comprising a column having a column length disposed substantially perpendicular to said shoulder center line; providing a counter weight system for said column that has a counter weight pack that is moveable back and forth along at least a portion of said column length of said column by a linear actuator; loading said part to be worked on by said robot onto said part holding assembly to create a combined load of said part holding assembly and said part; driving said combined load using said rotational shoulder drive; measuring a test torque on said rotational shoulder drive during said driving of said combined load as a function of angular position of said rotational shoulder drive and power supplied to said rotational shoulder drive; calculating an updated position for said counter weight pack that substantially balances said combined load with respect to said shoulder center line as a function of said test torque; adjusting said counter weight pack by said linear actuator along said portion of said column length to said updated position; and, operating said part positioner system with a balanced combined total load to position said part to accommodate work operations of said robot.