A two-step fast non-uniform knot placement algorithm applicable for noisy data is presented in this paper. The algorithm is started by evaluating the second derivative of the sampled data and, subsequently, by using the half-split approach, the best piecewise linear function is fitted to the computed derivative. In the second step, the fitted functions are adjusted to define the final knot for the B-spline fitting. The proposed method is subsequently validated on an experiment data with a known nominal surface. It is demonstrated that the proposed method offers a fast computational time that allow for online surface estimation.
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