Various classes of signals controlling articulators in the mathematical model of speech production are investigated, namely: stepwise, continuous and discontinuous, piecewise-linear, piecewise-square, and spline signals. Input data for the inverse problem with respect to the control problem are trajectories of articulatory movements measured with the help of a X-ray microbeam system and cineradiography. The piecewise-linear discontinuous control yields the best approximation of articulatory movements, and the simulated efforts of the correspondent muscles prove to be physiologically attainable. The error of approximation is comparable with the errors in the trajectory measurements. The obtained functional class of controls and the additional con-straints on the values of the control parameters provide a stable and locally unambiguous solution to the dynamic inverse problem for the vocal tract. This justifies the inclusion of our model in a general speech production model.
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