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ACRoCo: An Action-Constrained Multi-Robot Collaboration Framework Based on Large Language Models

ACRoCo is an innovative multi-robot collaboration framework that converts open-ended LLM planning into constrained decisions via action legality masks, and optimizes collaborative behaviors by combining MAPPO training and hybrid LLM+RL strategies.

多机器人协作大语言模型强化学习MAPPO机器人控制LLM多智能体系统动作约束开源项目
Published 2026-05-29 16:12Recent activity 2026-05-29 16:19Estimated read 8 min
ACRoCo: An Action-Constrained Multi-Robot Collaboration Framework Based on Large Language Models
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Section 01

Introduction / Main Floor: ACRoCo: An Action-Constrained Multi-Robot Collaboration Framework Based on Large Language Models

ACRoCo is an innovative multi-robot collaboration framework that converts open-ended LLM planning into constrained decisions via action legality masks, and optimizes collaborative behaviors by combining MAPPO training and hybrid LLM+RL strategies.

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Section 02

Original Authors and Source

  • Original Author/Maintainer: flybbits
  • Source Platform: GitHub
  • Original Title: ACRoCo: Action-Constrained Dialectic Multi-Robot Collaboration with Large Language Models
  • Original Link: https://github.com/flybbits/ACRoCo
  • Source Publication/Update Time: 2026-05-29T08:12:35Z
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Section 03

Introduction: A New Paradigm for Multi-Robot Collaboration

In the field of multi-robot systems, how to enable multiple agents to collaborate efficiently to complete complex tasks has always been a core challenge. Traditional methods often rely on predefined rules and fixed behavior patterns, making it difficult to adapt to dynamically changing environments. In recent years, Large Language Models (LLMs) have demonstrated strong reasoning and planning capabilities, bringing new possibilities to robot control. However, there is an important issue when directly applying LLMs to robot control: the output of LLMs is often open-ended natural language descriptions, while robot execution requires precise and verifiable action instructions.

ACRoCo (Action-Constrained Dialectic Multi-Robot Collaboration) is an innovative framework designed to resolve this contradiction. It cleverly converts open-ended LLM planning into action-constrained decisions, filtering unreachable or invalid actions through legality masks to achieve safe and reliable multi-robot collaboration.

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Section 04

From Open-Ended Planning to Constrained Decision-Making

The core insight of ACRoCo is: instead of letting LLMs directly generate action instructions, it is better to let LLMs choose within a predefined legal action space. This design brings several significant advantages:

First, safety is guaranteed. Through legality masks, the system can automatically exclude dangerous or unexecutable actions before strategy selection, avoiding robots from executing instructions that may cause damage or danger.

Second, interpretability is greatly improved. Since the action space is clearly defined, each decision can be traced back to a specific set of legal actions, facilitating debugging and optimization.

Finally, training efficiency is significantly enhanced. Constraining the action space reduces the strategy search space, allowing reinforcement learning algorithms to converge to optimal strategies faster.

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Section 05

Factorized Legality Mask Mechanism

ACRoCo adopts an elaborate factorized design to handle action legality. Each agent's action is decomposed into two key dimensions: verb/object and target. The system calculates legality masks for each dimension separately and then performs joint filtering.

This factorized design's advantage lies in its ability to flexibly handle different types of constraints. For example, in some scenarios, an object may be unreachable for all agents; in others, specific agents may be unable to perform certain types of actions. By separating these two dimensions, the system can control action selection more precisely.

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Section 06

Primitive-Aware Architecture

To align strategy actions with executable motion phases, ACRoCo introduces a primitive-aware architecture. Macro actions are composed of reusable primitives, including:

  • REACH: Move to the target position
  • GRASP: Grab an object
  • LIFT: Lift an object
  • TRANSLATE: Translational movement
  • RELEASE: Release an object
  • PUSH: Push an object
  • WAIT: Wait

These primitives form the basic vocabulary of robot actions. By combining these primitives, the system can construct complex macro actions while maintaining consistency with underlying motion control.

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Section 07

Hierarchical Phase-Adaptive Reward

ACRoCo designs an innovative reward mechanism that mixes semantic-level rewards and physical-level rewards according to the execution phase. In the decision phase, the system focuses more on semantic-level goal achievement; in the execution phase, it focuses more on physical-level action quality.

This phase-adaptive reward design solves a classic problem in multi-robot collaboration: how to establish an effective feedback loop between high-level planning and low-level execution. By dynamically adjusting reward weights, the system can optimize different goals in different phases, thereby improving overall performance.

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Section 08

MAPPO and CTDE Training

In multi-agent training, ACRoCo uses the MAPPO (Multi-Agent PPO) algorithm and the CTDE (Centralized Training with Decentralized Execution) paradigm. This combination ensures both information sharing and coordinated optimization during training, as well as distributed decision-making capabilities during execution.

The CTDE paradigm is particularly suitable for practical deployment scenarios: during training, the system can use global information to learn optimal collaborative strategies; during execution, each agent only needs local observations to make decisions, reducing requirements for communication bandwidth and latency.