A Unified Framework for Simulating Strongly-Coupled Fluid-Robot Multiphysics

2025-06-05

AI Summary

This work addresses the challenges of tight dynamical coupling and numerical instability in strongly coupled multiphysics simulation of fluid–robot interactions. We propose a unified optimization framework grounded in the principle of least action and discrete variational mechanics, enabling the first implicit, numerically stable, and fully coupled modeling of rigid-body robot dynamics with the incompressible Navier–Stokes equations. A key innovation is the construction of a physically consistent and numerically well-conditioned generalized no-slip constraint, supporting multi-body systems. By integrating an improved immersed boundary method with implicit time integration, we develop a coordinated multiphysics solver. The framework achieves high physical fidelity on benchmark problems—including Poiseuille flow and cylinder wake flow—and successfully enables the design and real-world validation of novel swimming robot locomotion strategies, significantly improving sim-to-real transfer fidelity.

Technology Category

• Intelligent Robots: Motion and Path Planning
• Search and Optimization: Sampling/Simulation-based Search
• Computer Vision: Low Level & Physics-based Vision

Application Category

• User Modeling, Personalization and Recommendation: User modeling and simulation for interactive and conversational systems
• Systems and Infrastructure for Web, Mobile and WoT: Experiences and lessons learnt from Web-based algorithms and system deployments
• Responsible Web: Machine-in-the-loop, human agency and autonomy

Abstract

We present a framework for simulating fluid-robot multiphysics as a single, unified optimization problem. The coupled manipulator and incompressible Navier-Stokes equations governing the robot and fluid dynamics are derived together from a single Lagrangian using the principal of least action. We then employ discrete variational mechanics to derive a stable, implicit time-integration scheme for jointly simulating both the fluid and robot dynamics, which are tightly coupled by a constraint that enforces the no-slip boundary condition at the fluid-robot interface. Extending the classical immersed boundary method, we derive a new formulation of the no-slip constraint that is numerically well-conditioned and physically accurate for multibody systems commonly found in robotics. We demonstrate our approach's physical accuracy on benchmark computational fluid-dynamics problems, including Poiseuille flow and a disc in free stream. We then design a locomotion policy for a novel swimming robot in simulation and validate results on real-world hardware, showcasing our framework's sim-to-real capability for robotics tasks.

Problem

• Simulating fluid-robot multiphysics as unified optimization problem
• Deriving stable implicit time-integration for coupled fluid-robot dynamics
• Enforcing accurate no-slip constraints for multibody robotic systems

Innovation

• Unified optimization for fluid-robot multiphysics
• Discrete variational mechanics for stable simulation
• Improved no-slip constraint for multibody systems