Contact Planning for Multilegged Robots Under Constraints Through Parallel MCTS

Peng Xu
,
Liang Ding
Lei Ye
Lei Ye
,
Tengwei Pang
,
Tie Liu
,
Huaiguang Yang
,
Haibo Gao
,
Zongquan Deng
,
Joni Pajarinen
Parallel MCTS contact planning for multilegged robots under physical constraints. Research preview from the contact-planning project by Xu et al. (IEEE T-RO, 2025).
Abstract
This work formulates contact planning for multilegged robots as a constrained sequential decision problem over gait, footholds, and configuration. Multi-constraint reachability checks account for stability, collision avoidance, kinematics, joint torques, and contact conditions. A hash-driven parallel Monte Carlo tree search combines valueless-node pruning, depth-first backup, and virtual loss to search for feasible contact sequences within a limited planning budget. Evaluations cover sparse footholds and constrained terrain, with hexapod hardware demonstrations and humanoid simulation. The experiments study traversability, solution quality, physical feasibility, and planning speed.
Type
Publication
IEEE Transactions on Robotics, vol. 41, pp. 6102โ€“6122, 2025

Choosing contacts under physical constraints

The planner jointly reasons about gait, footholds, and robot configuration. Reachability checks incorporate stability, collision avoidance, kinematics, joint torque limits, and contact constraints so that a promising contact sequence also admits physically feasible transitions.

A hash-driven parallel MCTS framework shares search effort among workers. Valueless-node evaluation prunes trapped branches, depth-first backup supports longer-horizon decisions, and virtual loss balances parallel exploration. This combination targets useful solutions under a limited planning budget rather than exhaustive enumeration of contacts.

Evaluation across constrained scenes

The project studies sparse footholds and provides demonstrations on stairs, timber piles, tunnels, and discrete terrain, together with load and soft-terrain comparisons. Hexapod hardware experiments are complemented by humanoid simulation, testing how the contact-planning formulation transfers across robot structures.

Project and experiment videos ยท Code ยท Paper