Automatic maintenance of robot programs

After writing programs for a production robot, an operator must manually teach hundreds or thousands of poses. Teaching poses is extremely time consuming and, unfortunately, periodic reteaching is necessary. The need to reteach is commonly due to: wear, repair, slight movements of workpieces, or replacement of the robot and its tools. Our experience has shown that conventional methods of adjusting pose data’ do not work reliably. This paper discusses an automatic reteach method. The method has been tested on a production robot in a laboratory environment. In spite of changes in the robot and environment, we want constant shaped and sized tools to arrive consistently at taught work locations within desired tolerances. This means tool pose relative to the work piece is invariant. To assure this invariance, we establish a coordinate frame on the work piece and identify the tool locations relative to this frame. We apply a calibration algorithm to the pose data to accomplish our goal. This paper demonstrates an automatic, economic implementation of kinematic calibration on an industrial manipulator. The method is retrofit to a manufacturing system and does not require real time solution of the calibrated inverse kinematic problem. As a result, the method applies to most manipulators in use today.