A new multiprobe method of roundness measurements- W. Gao et al.

Abstract

This paper presents a new multiprobe method for roundness measurements
called the mixed method. In this method, displacements at two points on a
cylindrical workpiece and an angle at one of the two points are simultaneously
monitored by two probes. The differential output of the probes cancels
the effect of the spindle error, and deconvolving the differential data
yields the correct roundness error. The mixed method is compared to the
traditional 3-point method with respect to the transfer function and resolution.
Unlike the 3-point method, the mixed method can completely separate
the roundness error and the spindle error, and can measure high-frequency
components regardless of the probe distance. Resolution can also be improved
throughout the entire frequency domain by increasing angular separation
of the probes. An optical sensor specifically suited to the mixed
method is designed and used to make roundness measurements. A fiber
coupler and single-mode fibers are used in the sensor to divide a light beam
from a laser diode into two beams, resulting in a compact sensor with good
thermal drift characteristics. The displacement meter of the sensor is based
on the imaging system principle and has a resolution of O. 1 pm. The angle
meter is based on the principle of autocollimation and has a resolution of O.5
in. A measurement system is constructed to realize measurements of roundness
by using the optical sensor. Experimental results confirming the effectiveness
of the mixed method for roundness measurements are also presented
in this paper.