Automatic Reteach of Manipulators for Manufacturing Multiple Product Lines

Ordinarily, a robot workspace has insufficient room to allow the setup of multiple applications simultaneously. As a result, it is common practice to use modular fixtures which hold the workpiece while the robot performs one of the applications. When the product line is to be changed, the fixture is replaced. Doing this generally requires reprogramming the manipulator. When performing this reprogramming operation, several problems such as out of bound positions, and collisions with the fixture occur when the manipulator is near singular points. Although one might expect that these problems occur infrequently, this is not necessarily so. For example, using a Cartesian robot with a yaw, pitch, roll wrist the most "natural" pose for performing applications are frequently a t or very near the singular point. The transformation methods described in this paper were developed to handle some problems in reteach by performing inverse kinematics, according to application constraints, by allowing suboptimal solutions. The method has been applied with success on two manipulators assembling meshing gears.