ADVANCES IN PROCESSING OF SURFACE MYOELECTRIC SIGNALS .2.

The paper focuses on the analysis of myoelectric evoked potentials and their progressive scaling, as well as morphological changes using ort hogonal basis functions with essentially finite time support; and the compression of the information content using principal component analy sis. The application of the Hermite-Rodriguez and the associated Hermi te functions is discussed as a means to provide compact information ab out the shape of the M-wave or of the power spectral density function of either voluntary or electrically elicited myoelectric signals; a me ans to estimate scaling factors; and a means to describe and classify nonstationarities. The principal component analysis shows the possibil ity of a compression ratio of at least 10:1 in the storage of M-wave s equences. The paper also describes three methods for the estimation of delay between similar signals, and therefore for estimation of conduc tion velocity. They are based on normalised integrals, Fourier transfo rm matching and matching in the time domain. In particular conditions they provide different results for the same pair of signals. The conce pt of delay and the performance of these methods are reviewed and disc ussed. The paper is not exhaustive. It has the main objective of makin g the reader aware of the wealth of methods available for nonstationar y myoelectric signal analysis and conduction velocity estimation, and of the need to use them with knowledge of their respective advantages, disadvantages, peculiarities and limitations.