arXiv:2608.00391cs.ROcs.AI2026-08

提出刷新机制,解决视觉-语言-动作模型跳过令牌时的累积误差问题。

The Gate, Not the Cache: Gate Provenance Bounds the Closed-Loop Reliability of Training-Free VLA Token Skipping

论文配图:The Gate, Not the Cache: Gate Provenance Bounds the Closed-Loop Reliability of Training-Free VLA Token Skipping
图 1 · 摘自论文原文
  • 用无跳过的完整前向计算生成干净门控信号,避免错误传播。
  • 在90%跳过率下,任务成功率从0.31恢复至0.98,显著提升可靠性。
  • 适用于多种主流加速方法,适合部署于物理机器人系统的实时控制场景。

Token skipping 是一种广泛使用的训练无关加速方法,通过在每个控制步跳过大部分视觉令牌来提升视觉-语言-动作(VLA)模型效率。然而,当下一阶段的门控信号来自先前被加速的前向传播时,被跳过的令牌也最不可见,导致误差在控制步骤间累积,最终任务失败。本文研究了该类方法依赖的复用与删除两种机制,发现当门控信号来自自身加速前向时,在 LIBERO-Object 上跳过率为 0.9 时,复用与删除机制性能分别降至 0.68 和 0.31,远低于密集模式下的 1.00,且行为级检测器无法察觉。关键差异不在于机制本身,而在于门控信号是否干净——即由未跳过的完整前向计算得出。为此,提出执行空闲刷新:在机器人执行当前动作块期间,非关键路径上运行一次密集前向,为下一阶段提供干净门控与全新键值缓存。由于现有检测器无法可靠识别故障,刷新采用无条件执行策略。实验表明,两种机制均恢复至 0.98 的成功率,保持跳过加速的同时保留密集信息。将该刷新机制集成至两类先进缓存与剪枝方法中,在两个 VLA 策略、四个 LIBERO 套件和四个 SIMPLER 任务中,修复所有因自采门控导致的崩溃。仿真与真实机器人测试显示,服务延迟比密集模式降低 18–22%。

原文摘要 · Abstract (English)

Token skipping is a widely used training-free way to accelerate vision--language--action (VLA) models by bypassing computation for most visual tokens at each control step according to a gate. When the next gate is harvested from the previous accelerated forward, however, the tokens skipped at one step are also the ones least visible to the next gate, and the damage can compound across control steps until the task fails. We study the two mechanisms this class is built on, reuse and deletion, crossing each against where its gate signal comes from on identical episodes. At a skip ratio of 0.9 on LIBERO-Object, both collapse when the gate comes from the model's own accelerated forwards, to 0.68 under reuse and to 0.31 under deletion against a dense 1.00, and the collapse is invisible to the action-level detectors we evaluate. What separates collapse from dense-level operation is not the mechanism but whether the gate is clean, computed by a forward that skipped nothing. We therefore propose actuation-slack refresh, one dense pass run while the robot executes its current action chunk, off the critical path, that hands the next step a clean gate and a fresh KV base. Since the measured detectors do not reliably reveal the failure, the refresh is unconditional rather than triggered. Both mechanisms then recover to 0.98, keeping the speed of skipping and the information of a dense pass. We then integrate the refresh into state-of-the-art caching and pruning methods across two VLA policies, 4 LIBERO suites, and 4 SIMPLER tasks, where it repairs every collapse caused by using a self-harvested gate. Serve latency drops 18--22\% below dense, measured both in simulation and on a physical robot. Where the gate signal comes from, not how tokens are skipped, decides closed-loop reliability for accelerated VLAs.

VLA加速推理机器人控制门控机制

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