Method and system for calculating misalignment of rotational body

A system for calculating misalignment of a rotational body, comprising:

• an input part that sets at least four or more measurement points in one turn of the rotational body;
• a deflection amount detection part that derives radial displacement amounts of the rotational body for the at least four or more measurement points along an outer surface in a circumferential direction of the rotational body based on measured values measured by a displacement gauge;
• a storage part that stores the radial displacement amounts derived by the deflection amount detection part and measured angles at the measurement points;
• and
• a calculation part that calculates misalignment data of a most probable circle of the rotational body based on data stored in the storage part,
• wherein the calculation part
• selects three arbitrary points among all the measurement points stored in the storage part to calculate a circle from the radial displacement amounts and the measured angles,
• calculates circle values for all the measurement points from the calculated circle,
• calculates differences between the calculated circle values and the radial displacement amounts as error amounts at the measurement points,
• sums the error amounts to derive a total error amount,
• repeats circle calculation for different combinations of three measurement points among all the measurement points and calculates a total error amount for each calculated circle,
• selects a calculated circle with a minimum total error amount among obtained total error amounts for all combinations as the most probable circle, and
• calculates deviation between the center of the most probable circle and the center of rotation of the rotational body as misalignment data of the most probable circle.