Forward slip measurements in cold rolling by laser Doppler velocimetry: uncertainty analysis and accuracy improvement

Accurate determination of the relative motion between the work rolls and the strip, known as forward slip, is required in the metal rolling process. Laser Doppler velocimetry (LDV) is one of the promising methods to measure this small relative speed in cold rolling. In this paper, the accuracy of forward slip measurements in cold rolling is addressed. The uncertainty of the LDV system designed for forward slip measurement is analysed. It is demonstrated that with small slips, a high accuracy is difficult to achieve, although both the roll and the strip speeds are measured with a reasonably high accuracy. A method for further improving the accuracy of the LDV system is proposed and tests made on an experimental rolling mill are described.