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Measurement System of Jaw Movements by Using BP Neural Networks Method and a Nonlinear LeastSquares Method
Xu ZHANG Masatake AKUTAGAWA Qinyu ZHANG Hirofumi NAGASHINO Rensheng CHE Yohsuke KINOUCHI
Publication
IEICE TRANSACTIONS on Information and Systems
Vol.E85D
No.12
pp.19461954 Publication Date: 2002/12/01 Online ISSN:
DOI: Print ISSN: 09168532 Type of Manuscript: PAPER Category: Medical Engineering Keyword: jaw movements, magnetic measurement, BP neural networks, nonlinear leastsquares method,
Full Text: PDF>>
Summary:
The jaw movements can be measured by estimating the position and orientation of two small permanent magnets attached on the upper and lower jaws. It is a difficult problem to estimate the positions and orientations of the magnets from magnetic field because it is a typical inverse problem. The back propagation neural networks (BPNN) are applicable to solve this problem in short processing time. But its precision is not enough to apply to practical measurement. In the other hand, precise estimation is possible by using the nonlinear leastsquare (NLS) method. However, it takes long processing time for iterative calculation, and the solutions may be trapped in the local minima. In this paper, we propose a precise and fast measurement system which makes use of the estimation algorithm combining BPNN with NLS method. In this method, the BPNN performs an approximate estimation of magnet parameters in short processing time, and its result is used as the initial value of iterative calculation of NLS method. The cost function is solved by GaussNewton iteration algorithm. Precision, processing time and noise immunity were examined by computer simulations. These results shows the proposed system has satisfactory ability to be applied to practical measurement.

