A New Method for On-line Measurement of the Straightness Error of Machine Tools Using an Acceleration Sensor

Abstract

In order to improve the poor efficiency in the measurement of the geometric error of machine tools’ linear axes, this paper has presented a method to measure and restructure the geometric error of linear axes that is based on accelerometers. This method takes advantage of the phenomenon that when acceleration is measured under different measuring speeds, different frequencies and amplitudes are produced. The measurement data of the high signal-to-noise ratio for various velocities was fused together and the straightness error of the measured axis was obtained by integrating the acceleration twice. In order to remove the trend terms error in the integration, a zero phase IIR Butterworth filter was designed, which guarantees the signal’s phase invariance after filtering. The data was continued with the AR model to eliminate the endpoints’ effect in the filtering. The proposed method was verified by numerical values and experiments. The results showed that the proposed method has better robustness, a wider bandwidth and a higher efficiency than the methods of measuring by laser interferometer. It is also able to measure the geometric error of linear axes with an accuracy that reaches the micron scale.

Investigation on Modulation-Based Straightness Measurement

“…Air turbulences affect the stability of the beam with a random contribution which can be reduced by averaging, while the bending of the beam due to an orthogonal gradient of the air refractivity must be carefully evaluated and corrected [ 15 ]. An alternative approach worth mentioning is based on the analysis of the transverse accelerations measured when the axis is moving at constant speed [ 16 ]. The work in this paper measures the straightness of a machine path in space with respect to a laser beam by means of a sensor measuring the lateral position of the beam retroreflected by a target attached to the machine movable component.…”