Contact-Aware Safety in Soft Robots Using High-Order Control Barrier and Lyapunov Functions
Kiwan Wong, Maximilian Stölzle, Wei Xiao, Cosimo Della Santina, Daniela Rus, Gioele Zardini
AI summary
Problem
As soft robots evolve for greater precision and payload, they reintroduce injury risks that mechanical compliance alone cannot mitigate. Current control methods lack real-time, whole-body contact force enforcement that accounts for system dynamics, hindering safe deployment in human-centric settings.
Approach
The authors integrate a differentiable Piecewise Cosserat-Segment dynamics model with a novel convex-polygon distance metric (DCSAT) to enable real-time collision detection and resolution. These components are embedded into a High-Order Control Barrier and Lyapunov Function (HOCBF+HOCLF) optimization routine to guarantee safety while achieving task objectives.
Key results
- Principled HOCBF method enforcing global contact force constraints
- Adapted HOCBF+HOCLF framework for operational space regulation
- DCSAT: a fast, conservative, differentiable collision-detection metric
- Simulation validation showing safety-bounded contacts with precise task-space regulation
Why it matters
Provides a foundational, provably safe control strategy for deploying soft robots in demanding human-centric applications like medical procedures and collaborative manufacturing.
Abstract
Robots operating alongside people, particularly in sensitive scenarios such as aiding the elderly with daily tasks or collaborating with workers in manufacturing, must guarantee safety and cultivate user trust. Continuum soft manipulators promise safety through material compliance, but as designs evolve for greater precision, payload capacity, and speed, and increas- ingly incorporate rigid elements, their injury risk resurfaces. In this letter, we introduce a comprehensive High-Order Control Barrier Function (HOCBF) + High-Order Control Lyapunov Function (HOCLF) framework that enforces strict contact force limits across the entire soft-robot body during environmental interactions. Our approach combines a differentiable Piecewise Cosserat-Segment (PCS) dynamics model with a convex-polygon distance approximation metric, named Differentiable Conserva- tive Separating Axis Theorem (DCSAT), based on the soft robot geometry to enable real-time, whole-body collision detection, res- olution, and enforcement of the safety constraints. By embedding HOCBFs into our optimization routine, we guarantee safety, allowing, for instance, safe navigation in operational space under HOCLF-driven motion objectives. Extensive planar simulations demonstrate that our method maintains safety-bounded contacts while achieving precise shape and task-space regulation. This work thus lays a foundation for the deployment of soft robots in human-centric environments with provable safety and perfor- mance.