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The problem of friction identification within the presliding and sliding regimes is addressed and three identification methods, designated as the LuGre (LG) method, the nonlinear regression (NLR) method, and dynamic nonlinear regression with direct application of the excitation (DNLRX) method, are postulated. The first employs the LG model structure, the second the basic Maxwell slip model structure, and the third an extended version of it. The Maxwell Slip model structure accounts for the presliding hysteresis with nonlocal memory, but is confined to providing constant sliding friction. This limitation is circumvented by the postulated extended version. In all methods identification is based upon signals obtained from a single experiment. The methods are successfully assessed via Monte Carlo experiments, as well as via a laboratory setup. The DNLRX is shown to achieve the best overall performance, followed by the NLR and LG methods. A simple DNLRX-based feedforward friction compensation scheme is also postulated and assessed. The results indicate that it is capable of yielding effective friction compensation.
Date of Publication: Jan. 2009