Abstract: Sensitivity analysis is used to quantify the contribution of the uncertainty of input variables to the uncertainty of systematic output responses. For tolerance design in manufacturing and assembly, sensitivity analysis is applied to help designers allocate tolerances optimally. However, different sensitivity indices derived from different sensitivity analysis methods will always lead to conflicting results. It is necessary to find a sensitivity index suitable for tolerance allocation to transmission mechanisms so that the sensitivity results can truly reflect the effects of tolerances on kinematic and dynamic performances. In this paper, a variety of sensitivity indices are investigated and compared based on hybrid simulation. Firstly, the hybrid simulation model of the crank-slider mechanism is established. Secondly, samples of the kinematic and dynamic responses of the mechanism with joint clearances and link length errors are obtained, and the surrogate model established using polynomial chaos expansion (PCE). Then, different sensitivity indices are calculated based on the PCE model and are further used to evaluate the effect of joint clearances and link length errors on the output response. Combined with the tolerance-cost function, the corresponding tolerance allocation schemes are obtained based on different sensitivity analysis results. Finally, the kinematic and dynamic responses of the mechanism adopting different tolerance allocation schemes are simulated, and the sensitivity index corresponding to the optimal response is determined as the most appropriate index.

Key words: Transmission mechanism; Sensitivity analysis; Tolerance allocation; Hybrid simulation; Polynomial chaos expansion (PCE)

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