Towards Simulation-Based Optimization of Compliant Fingers for High-Speed Connector Assembly
and Kevin Haninger
AI summary
Problem
Designing compliant robotic fingers for contact-rich manipulation traditionally relies on slow hardware iteration or simplified models that cannot capture complex task dynamics. This paper addresses the need for scalable, simulation-based tools to optimize mechanical compliance for specific assembly objectives.
Approach
The authors develop a MuJoCo-based simulation pipeline to model structured compliant fingers and evaluate their performance across four NIST benchmark assembly tasks, optimizing 3D-printed infill parameters to maximize the successful insertion tolerance window.
Key results
- Optimized finger stiffness increased the tolerable insertion range by up to 2.29×
- Simulation accurately predicted failure modes for simple tasks but showed significant sim2real gaps for complex geometries
- Optimal stiffness trends were highly task-specific, varying between high and low stiffness depending on the assembly scenario
- Achieved 100% failure prediction accuracy in simple peg-in-hole tasks, dropping to 27.3% for complex connectors
Why it matters
Offers roboticists and mechanical designers a validated, scalable pipeline to optimize compliant end-effectors for high-speed assembly, reducing reliance on costly physical prototyping.
Abstract
Mechanical compliance is a key design parameter for dynamic contact-rich manipulation, affecting task success and safety robustness over contact geometry variation. Design of soft robotic structures, such as compliant fingers, requires choosing de- sign parameters which affect geometry and stiffness, and therefore manipulation performance and robustness. Today, these param- eters are chosen through either hardware iteration, which takes significant development time, or simplified models (e.g. planar), which can’t address complex manipulation task objectives. Im- provements in dynamic simulation, especially with contact and friction modeling, present a potential design tool for mechanical compliance. We propose and investigate feasibility of a simulation- based design tool for compliant mechanisms which allows design with respect to task-level objectives, such as success rate. This is applied to optimize design parameters of a structured compliant finger to reduce failure cases inside a tolerance window in insertion tasks. The improvement in robustness is then validated on a real robot using tasks from the benchmark NIST task board. The finger stiffness affects the tolerance window: optimized parameters can increase tolerable ranges by a factor of 2.29, with workpiece varia- tion up to 8.6 mm being compensated. However, the trends remain task-specific. In some tasks, the highest stiffness yields the widest tolerable range, whereas in others the opposite is observed, moti- vating need for design tools which can consider application-specific geometry and dynamics. While the task simulation demonstrates a high accuracy for simple scenarios, achieving a 100% failure mode prediction, tasks with higher geometric complexity yield significant discrepancies between simulation and real-life, resulting in lower rates of 27.3% due to excessive simplifications of the simulated task. Failure during insertion can be modeled with a small sim2real gap, whereas failure during search and in-hand slip demonstrated a higher sim2real gap.