Abstract

In compliant Constant Force Mechanism (CFM) design, superior functionality often necessitates increased structural complexity. While the Incremental Complexity Design (ICD) method has facilitated the development of efficient topologies for Bidirectional compliant Constant Force Mechanisms (Bi-CFMs), its evolution has remained primarily empirical, limited by the absence of a comprehensive decision-making criterion that integrates functional performance, geometric cost, and mechanical risk. This study proposes a computational framework to identify complexity thresholds, utilizing a multi-objective optimization approach based on finite element analysis (FEA). This framework integrates functional performance (Energy Similarity Index SCF) with a Composite Complexity Index that encompasses geometric redundancy and mechanical risk. A sensitivity analysis revealed that Bi-CFM performance is highly sensitive to geometric boundary limitations. Consequently, optimization was conducted under varied constraints. Results show that through this computation-driven design framework, specific optimal complexity thresholds are established for different geometric constraints: 3 nodes for a 140 mm domain, 4 nodes for a 100 mm domain, and 7 nodes for a 60 mm domain. Such findings demonstrate that this threshold is dynamically coupled with the available spatial domain. This work provides a systematic strategy for Bi-CFM designers to balance functional performance and structural complexity, offering a robust foundation for lean design under diverse environmental conditions.

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