NTH

Learning Quality-Controllable Robot Policies with Iterative Hindsight Relabeling

AuthorsSinjae Kang, Dong Kyu Shin, Jaehong Kim, Kamin Lee, Hyoeun Kim, Kaixin Wang, Li Zhao, Seonghyeon Ye, Kimin Lee

AffiliationsKAIST · LGE · Microsoft Research

November 5, 2026 2 min read
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The one-line take

A robot policy learns to complete tasks while also adjusting qualities like speed and smoothness, improving through relabeled experience.

Key results

4
Quality bins

Equal-frequency labels condition the policy on requested execution quality.

1.5
Normalized Wasserstein distance

The rollout distribution exceeded this distance from the demonstration distribution, normalized by its interquartile range.

27.0%
Wine-task tilt reduction

Reduction in mean tray tilt compared with behavior cloning.

42.0%
Wine-task success rate

Final QCP success rate, up from 30.7% for behavior cloning.

36.6%
Conveyor end-effector speed increase

Increase compared with behavior cloning.

59.3%
Conveyor throughput increase

Increase compared with behavior cloning, reaching 13.0 cans per minute.

What the paper found

Quality-Controllable Policy, or QCP, lets a robot policy respond to requested execution qualities—such as speed or smoothness—rather than treating every successful demonstration as equally desirable. It conditions a flow-matching action-chunk policy on discrete quality labels, using 4 equal-frequency bins. Its key innovation, iterative hindsight relabeling, collects successful rollouts requested at the highest quality, labels them by the quality they actually achieved, recalculates the dataset’s quality bins, and retrains the policy. This expands the range of behavior beyond the demonstrations: on selected simulation metrics, the final rollout distribution shifted by more than 1.5 times the demonstrations’ interquartile range under a normalized Wasserstein distance. On a real wine-glass transport task, QCP reduced tray tilt by 27.0% and raised success from 30.7% to 42.0%. On a conveyor task, it increased end-effector speed by 36.6% and throughput by 59.3%, reaching 13.0 cans per minute. The method also jointly improved six quality attributes in RoboEval. For physical-robot experiments, the researchers fine-tuned the π0.5 vision-language-action model, conditioning it on quality instructions in the prompt.

Original abstract

Robot policy evaluation often relies on a binary success signal for task completion. In real-world deployment, however, desired execution behaviors are also defined by quality attributes such as execution speed and motion smoothness, which need to be dynamically controlled according to task requirements. To address this, we introduce Quality-Controllable Policy (QCP), a robot policy that enables inference-time control over both individual quality attributes and their combinations. To extend the controllable quality range beyond initial demonstrations, we further propose an iterative hindsight relabeling loop: QCP collects online rollouts under target quality labels, adds successful trajectories to the dataset, relabels the accumulated trajectories in hindsight according to their measured quality, and fine-tunes the policy. Experiments on Robomimic and RoboEval demonstrate that QCP consistently improves both task execution quality and success rates across iterations, producing successful rollouts that exceed the quality of the initial demonstrations. Finally, we validate QCP on real-world manipulation tasks, where controlling speed increases throughput in conveyor operations and controlling transport stability improves success when carrying wine glasses, demonstrating that quality-controllable policies yield practical gains in physical deployment.

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