Precise Mating Algorithm Using Articulated Robot Manipulators.

Abstract

In general, an articulated robotic manipulator is not suitable for precision assembly tasks because of its structural features. However, we can employ such an inaccurate robotic manipulator in some precise assembly tasks when the task algorithms or strategies are similar. We propose a new algorithm for precise mating tasks, which is derived on the assumption that an articulated robot manipulator (e. g., PUMA type) is employed. This algorithm consists of three stages, the searching stage, the axis fitting stage, and the twisting and inserting stage. To begin with, we introduce some valid parameters such as the allowable tilt angle (θa), the allowable initial insertion depth (ha), and the recovery angle (θ'). These parameters may provide some guidelines for constructing assembly task strategies and designing the end effector or additional assembly devices. As an effective method to avoid jamming or wedging that may happen in the initial insertion stage, we introduce the twisting and inserting stage. We experimented with accurate pegs and holes of which the clearance ratios (Cγ) are 0.0005∼0.0025 and the chamfer size 0∼0.5 mm. Experimental results are also shown to verify the reliability of the proposed algorithm.