Abstract
The author proposes a method of non-contact speed measurement similar to the so-called correlation method and to the model method that the author has proposed as the co-author. The irregular pattern on the surface of the moving strip is observed at two points along the direction of the velocity and the upperstream detected signal is supplied to a variable dead time mocel. The dead time is automatically adjusted so that the correlation of its input and output signals is equal to that of the two detected signals. Then, the dead time indicates the transport delay between the two points and the speed is measured from this.
The advantages of this method are as follows. First, as in the case of the model method, the variance in the measured value is suppressed independent of the length of the averaging interval when the patterns of the detected signals are identical. Secondly, the follow-up failure, which limits the application of a method of this type in practice, never occurs. This feature is an outstanding merit that the other methods do not possess.
On the other hand, examinations and experiments revealed the following difficulties in practical application of this method. One of them is that the auto-correlation of the irregurality must be known prior to the design of the detectors. And the other, that the difference of the patterns of the detected signals affects the accuracy of the measured speed more seriously than in the model method, because the gain of the measurement loop is lower.
The first of them was removed by an improvement of the measurement system to prepare for irregularities with fine components. The author concludes that the other difficulty will be overcome by jointly employing the model method, which necessitates a slight modification of the system.
