A Unified MPC Framework for Whole-Body Dynamic Locomotion and Manipulation
This work addresses the challenge of coordinated locomotion and manipulation for multi-limbed robots, offering a practical solution for tasks like door opening, though it is incremental in building on existing MPC and optimal control methods.
The authors tackled the problem of whole-body planning for mobile manipulators by proposing a unified MPC framework that integrates dynamic locomotion and manipulation into a single multi-contact optimal control problem, enabling real-time onboard computation and demonstrating robustness in hardware experiments including pushing a heavy door.
In this paper, we propose a whole-body planning framework that unifies dynamic locomotion and manipulation tasks by formulating a single multi-contact optimal control problem. We model the hybrid nature of a generic multi-limbed mobile manipulator as a switched system, and introduce a set of constraints that can encode any pre-defined gait sequence or manipulation schedule in the formulation. Since the system is designed to actively manipulate its environment, the equations of motion are composed by augmenting the robot's centroidal dynamics with the manipulated-object dynamics. This allows us to describe any high-level task in the same cost/constraint function. The resulting planning framework could be solved on the robot's onboard computer in real-time within a model predictive control scheme. This is demonstrated in a set of real hardware experiments done in free-motion, such as base or end-effector pose tracking, and while pushing/pulling a heavy resistive door. Robustness against model mismatches and external disturbances is also verified during these test cases.