Hierarchical Autoregressive Modeling With Multi-Scale Refinement for Robot Policy Learning

While autoregressive models demonstrate remarkable success in text and image generation, their application to robot policies suffers from weak holistic comprehension, cumulative errors, and limited multi-modal modeling capabilities, particularly in long-horizon tasks or multi-modal scenarios. This paper presents HAMR,, a novel Hierarchical Autoregressive framework with Multi-scale action Refinement that addresses these limitations through three key contributions: (1) a hierarchical architecture wherein high-level long-horizon motion features guide low-level fine-grained action generation, (2) a multi-scale action tokenization and generation mechanism that actively corrects previous prediction errors during inference, and (3) a lightweight diffusion-based decoder that enhances multi-modal modeling without compromising efficiency. HAMR achieves 12% and 15% improvements over state-of-the-art methods across 60+ tasks in simulation and real-world experiments, respectively, with a 25% improvement in perturbed experiments, demonstrating superior performance in both short- and long-horizon manipulation tasks.