DEVELOPMENT OF LINEAR AND NONLINEAR HAND-ARM VIBRATION MODELS USING OPTIMIZATION AND LINEARIZATION TECHNIQUES

Hand-arm vibration (HAV) models serve as an effective tool to assess t he vibration characteristics of the hand-tool system and to evaluate t he attenuation performance of vibration isolation mechanisms. This pap er describes a methodology to identify the parameters of HAV models, w hether linear or nonlinear, using mechanical impedance data and a nonl inear programming based optimization technique. Three- and four-degree s-of-freedom (DOF) linear, piecewise linear and nonlinear HAV models a re formulated and analyzed to yield impedance characteristics in the 5 -1000 Hz frequency range. A local equivalent linearization algorithm, based upon the principle of energy similarity, is implemented to simul ate the nonlinear HAV models. Optimization methods are employed to ide ntify the model parameters, such that the magnitude and phase errors b etween the computed and measured impedance characteristics are minimum in the entire frequency range. The effectiveness of the proposed meth od is demonstrated through derivations of models that correlate with t he measured X-axis impedance characteristics of the hand-arm system, p roposed by ISO. The results of the study show that a linear model cann ot predict the impedance characteristics in the entire frequency range , while a piecewise linear model yields an accurate estimation.