High Precision Robust Automatic Alignment Method for Rotating Shaft

Rotating Shaft is widely used in various high precision instruments on scientific and industrial metrology. This paper proposes a high precision and robust method to automatically align a rotating shaft perpendicular to the horizontal plane. Firstly, an alignment model consisting of a dual-axis inclinometer and four motors is designed. Then the rotating shaft tilt angle between the practical and the ideal shaft is projected to two orthogonal planes, and generates a rotation angle in each plane. The two rotation angles are calculated by differential measurement method based on the inclinometer outputs, and then the relationship of shaft tilt angle against inclinometer outputs is obtained. According to these two rotation angles, the relative heights of the three supporting points of the platform attached to the rotating shaft are calculated. Employing an angle closed loop strategy; the rotating shaft tilt angle is aligned by three linear stepping motors. Experiment results show an alignment precision of 0.003º is achieved using an inclinometer with the resolution of 0.0005º and a linear stepping motor with the regulation precision of 0.89 μm. The proposed method is suitable for a wide variety of precision machines that require the use of rotating shaft.