Stackable compliant modules enable custom stiffness for flexible tools
Lego-Like Stiffness Configuration of Planar Compliant Modules for Task-Specific Flexible Interfaces
Robotics
Summary
Machines that gently touch or move objects often need parts that bend just right. The authors made small building blocks with springy shapes that snap together like Lego pieces. By changing their shape, size, and how they stack, they can control how stiff the combined part is for different jobs. They tested these pieces and showed they can create wrists that move safely and quickly with the right amount of flexibility. This helps build machines that can better adapt to different tasks by tuning their flexibility without redesigning everything.
What this means in practice
- •For robotics engineers: Create robotic joints with adjustable stiffness to safely interact with diverse environments and tasks without custom redesign.
- •For wearable device designers: Design wearable supports with task-specific flexibility, improving user comfort and device performance across different activities.
Authors
Siyue Yao, Xiaochi Xie, Shixuan Zhao, Yutong Li, Hao Li, Mark R. Cutkosky, Genliang Chen
Abstract
Compliant mechanisms provide compact and intrinsic structural compliance for regulating physical interactions between mechanisms and environments. However, different tasks demand distinct stiffness characteristics, often requiring task-specific optimization and redesign due to limited geometric design space and inherent coupling among multiple stiffness components. This paper presents a Lego-like stiffness configuration approach using stackable planar compliant modules. Three complementary module geometries are introduced, with their stiffness characteristics further regulated through beam width, plate thickness, and module orientation. A unified stiffness model is established for quantitative analysis of individual and composed modules. Further, a two-stage optimization method is presented to achieve desired stiffness profiles, combining a genetic algorithm for configuration and sequential quadratic programming for parameter refinement. Experimental verification shows deviations below 6.5% for simulated stiffness. A flexible wrist is further developed as a representative implementation, exhibiting distinct compliant and dynamic responses under different stiffness characteristics. An optimized modular composition realizes prescribed stiffness values and maintains compliant obstacle interaction during high-speed motion at 1 m/s, with a maximum tested angular compliance of approximately $15^\circ$. The proposed framework provides a systematic approach for constructing flexible interfaces with task-specific stiffness characteristics.