Improving rotation behaviour of robotic structures for micro-assembly

Serial micro-assembly requires high precision robots able to produce translations and rotations to position and orient objects during assembly. In micro-scale, the translation ranges required are typically up to the millimeter and can be obtained with smart devices (piezomotor, etc.). In the other hand, the rotation ranges stay identical to the macroscale (eg. 90°) and require standard guidings like ball bearings which induce disturbances on the linear position. Thus the ability to produce high precision robots where translations and rotations are decoupled is currently one of the major stake in micro-assembly. This paper deals with an original modeling of the coupling between rotation and linear position. The geometrical model is presented and two calibration methods are discussed. Our method were tested on a 3 DOF planar robotic systems and the coupling was reduced by 93%.