To enhance the robustness of mechanical structures and reduce fluctuations in reliability, a novel reliability-based robust design optimization method combining a multivariate quality loss function (MQLF) and advanced finite step length (AFSL) is proposed. Gaussian process regression is used to formulate an MQLF for mechanical structures, integrating multiple quality characteristic deviations, predicted quality and robustness. An AFSL method for structural reliability analysis is proposed, effectively enhancing the efficiency and accuracy of reliability calculations through conjugate gradient search and an adaptive step length adjustment formula, while also solving the reliability sensitivity using the AFSL method. A multi-objective reliability-based robust optimization model is established with the objective of the MQLF and reliability sensitivity, considering structural reliability and design variable tolerances as constraints. Practical examples demonstrate that the proposed method achieves an optimal equilibrium solution, accounting for both quality loss and reliability sensitivity, in contrast to the traditional approach.
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