A Velocity Vector Field Measurement System Based on Spatio-Temporal Image Derivative
Shigeru Ando · Transactions of the Society of Instrument and Control Engineers · 1986
This paper describes a structure and an algorithm of 2-D velocity field measurement system based on the spatio-temporal derivative method. This method, which has excellent simplicity and resolvability in nature, is too much susceptible to noise and has strict limitation in measurable range of velocity. At the expense of small degree of resolvability, the author proposes a computationaly efficient algorithm based on local least squares solution of the differential equalities. Parallel structure of this algorithm is realized in a hardware of the measurement system. Besides the noise susceptibility, its applications under overmuch velocity conditions confuse meaningless results with true ones. For automated judgement of reliability of the results, three evaluators, i.e., measurability, validity, and error variance, are derived to supply information for classifying the resultant velocity map into reliable velocity segments, overmuch velocity segments, and unmeasurable segments. The measuring conditions can be adjusted adaptively using this classifications. Experiments for performance test and applications of this system to the 2-D fluid flow velocity measurement are shown.