AI summary
Problem
Existing convex contact approximations suffer from nonphysical gliding artifacts, lack consistency, and cannot incorporate experimentally validated engineering-grade contact models, making robust simulation of complex robotic interactions difficult.
Approach
The authors enforce curl-free (irrotational) contact fields to derive convex potentials, introducing two new approximations—Lagged and Similar—that integrate arbitrary contact laws into a differentiable optimization framework.
Key results
- A general framework for generating convex approximations of complex contact models
- First convex formulation to incorporate Hunt & Crossley dissipation
- Lagged approximation completely eliminates the nonphysical gliding artifact
- Fully differentiable open-source implementation in Drake with robust interactive simulation
Why it matters
Enables accurate, stable, and efficient simulation of contact-rich robotic systems, directly benefiting controller design, sim-to-real transfer, and hardware optimization.
Abstract
We present Irrotational Contact Fields (ICF), a framework for generating convex approximations of complex contact models, incorporating experimentally validated models like Hunt & Crossley coupled with Coulomb’s law of friction alongside the principle of maximum dissipation. Our approach is robust across a wide range of stiffness values, making it suitable for both compliant surfaces and rigid approximations. We evaluate these approximations across a wide variety of test cases, detailing properties and limitations. We implement a fully differentiable solution in the open-source robotics toolkit, Drake. Our novel hybrid approach enables efficient computation of gradients for complex geometric models by reusing factorizations from contact resolution. We demonstrate robust simulation of robotic tasks at interactive rates, with accurately resolved stiction and contact transitions, supporting effective sim-to-real transfer.