Safety-Critical Centralized Nonlinear MPC for Cooperative Payload Transportation by Two Quadrupedal Robots

2026-04-03

AI Summary

This work addresses the safety and stability challenges encountered by dual quadrupedal robots during cooperative heavy-load transportation in complex environments, where uncertainties in mass/inertia and external disturbances pose significant risks. To tackle these issues, the authors propose a safety-critical centralized nonlinear model predictive control (NMPC) framework. The robot–payload system is modeled as a discrete-time nonlinear differential-algebraic equation (DAE), explicitly retaining interaction forces and torques as optimization variables. Control barrier functions (CBFs) are integrated to enforce obstacle-avoidance constraints directly within the optimization. By efficiently handling holonomic constraints and the DAE structure, the method enables real-time solvability. Experimental validation on two Unitree Go2 robots demonstrates robust collaborative transport capabilities in cluttered environments, effectively mitigating the effects of parametric uncertainties and external disturbances.

Abstract

This paper presents a safety-critical centralized nonlinear model predictive control (NMPC) framework for cooperative payload transportation by two quadrupedal robots. The interconnected robot-payload system is modeled as a discrete-time nonlinear differential-algebraic system, capturing the coupled dynamics through holonomic constraints and interaction wrenches. To ensure safety in complex environments, we develop a control barrier function (CBF)-based NMPC formulation that enforces collision avoidance constraints for both the robots and the payload. The proposed approach retains the interaction wrenches as decision variables, resulting in a structured DAE-constrained optimal control problem that enables efficient real-time implementation. The effectiveness of the algorithm is validated through extensive hardware experiments on two Unitree Go2 platforms performing cooperative payload transportation in cluttered environments under mass and inertia uncertainty and external push disturbances.

Problem

• cooperative payload transportation
• safety-critical control
• quadrupedal robots
• collision avoidance
• nonlinear model predictive control

Innovation

• nonlinear model predictive control
• control barrier function
• differential-algebraic system
• cooperative manipulation
• quadrupedal robots