An Intelligent Self-Calibrating 4-DOF Parallel Robot for Precise Geometric Data Collection in Digital Manufacturing

摘要

Accurate capture of digital data from a manufactured part is an essential source of information about the quality of the produced part and the health of the corresponding manufacturing processes. The commonly known precise instruments for digitizing work-pieces on Coordinate Metrology Machine (CMM) are contact probes. Although, contact techniques confront difficulties, they lead to higher precisions comparing to non-contact methods. Ball-tip-radius error is one of the significant faults of contact methods. Conventional error compensating approaches of ball-tip-radius error often demand complicated and time consuming post-processes. Furthermore, considering the limitations of typical serial structure in commercial CMMs, adaptive accurate path planning is a very complex task. This paper presents an intelligent combination of a novel 4-DOF parallel mechanism implementing, a linear cost-effective contact probe, and an adaptive path planning method to automatically correct the probing direction. The implemented parallel structure has three translational DOF in X, Y and Z directions and one rotational DOF around X axis. A precise turn-table provides rotation of work-piece around the Z axis. The developed algorithm utilizes a data clustering approach and intelligently generates an automated adaptive probe placement and motion path. Validation process using simulation and actual measurement of free-form surfaces demonstrate highly reliable feasibility for eliminating the ball-tip-radius error resulting in high precision 3D data capturing process.