This paper, posted on arXiv, introduces a hierarchical control framework for teams of quadrupedal robots collaborating on a manipulation task. The approach is based on model predictive control and uses density functions as part of the control formulation.
The framework is designed for safe collaborative transport, where multiple robots push a shared object toward a desired location. The hierarchical structure helps manage the complexity of coordinating several robots, though the abstract does not give details on how the layers are divided.
As an arXiv announcement, the source does not include experimental results or comparisons. The work appears aimed at applications where legged robots must move large or heavy objects together without compromising safety.