Iranian Journal of Manufacturing Engineering

Iranian Journal of Manufacturing Engineering

Uncertain optimal design of a bio-capsule considering manufacturing and assembly tolerances uncertainty

Document Type : Original Article

Authors
Hassan Naseh
Hadiseh Karimaei
Mohammad Lesani Fadafan
Aerospace Research Institute of the Ministry of Science, Research and Technology, Tehran, Iran
10.22034/ijme.2025.536106.2111
Abstract
This paper presents an uncertain optimal design methodology for minimizing the total mass of a re-entry space capsule, taking into account geometric manufacturing and assembly tolerance uncertainties. Uncertain optimal design refers to the process of optimizing a design while considering the effects of uncertainties, ensuring that the final solution is both robust and stable. The proposed approach integrates multi-objective optimization with variance-based robustness analysis. Initially, the optimal design point is determined under deterministic conditions using a genetic algorithm. Subsequently, the design's robustness against potential parameter variations is assessed through an iterative process. If the initial design does not satisfy the robustness criteria, the algorithm iteratively updates the design constraints to identify a new optimal point until a robust solution is achieved. The multi-objective optimization framework is implemented using the All-At-Once (AAO) approach, and Latin Hypercube Sampling (LHS) is employed to explore the geometric uncertainty space and construct response surfaces for objective functions and constraints. Variance analysis quantifies the influence of geometric uncertainties on the optimal responses. Results show that the robust optimized capsule is 10.7% lighter than the baseline design, while exhibiting improved static stability margins. This mass reduction is accomplished through intelligent aerodynamic reshaping and the elimination of the need for balancing mass. Robustness evaluation confirms that all critical design functions maintain a minimum 2σ safety margin against geometric uncertainties, validating the reliability of the proposed design. The methodology effectively balances mass minimization with stability requirements, demonstrating particular relevance for aerospace applications where both performance and safety are paramount.
Keywords
Uncertainty-Based Design Optimization, Bio-Capsule, Geometric Uncertainties, Variance-Based Robustness Analysis
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Iranian Journal of Manufacturing Engineering
Volume 12, Issue 7 - Serial Number 93
September 2025
Pages 64-80