Improved three-point method for turning error and roundness error measurement

The invention relates to an improved three-point method for turning error and roundness error measurement. The method includes the following steps that: three displacement sensors are distributed at different angular positions so as to measure the radial run-out of a detection bar, and a high-frequency data acquisition system is utilized to record the measurement results of the sensors, and a three-point error separation technology is utilized to calculate the Fourier coefficients of harmonic waves of roundness error; the second sensor and/or third sensor is re-installed at different angles, the three-point method is repeated to perform measurement for many times, so that each Fourier coefficient can obtain a plurality of estimated values; a Fourier coefficient which is calculated through a transfer matrix of which the determinant is maximum is a most accurate Fourier coefficient estimated value; and the roundness error can be calculated through composite calculation based on the most accurate Fourier coefficient estimated value. With the method of the invention adopted, the accuracy of the estimation of each harmonic wave can be improved, and therefore, the accuracy of whole roundness error measurement can be improved.