Real-world robot learning

HiFun: A Hierarchical Framework for Efficient
Functional Dexterous Manipulation Learning

Accepted to CoRL 2026

Linyi Huang1Guowei Huai1Weibin Liu1Shulong Jiang1Ping Tan2Hui Zhang3Jie Song1,2

1 HKUST (Guangzhou)2 HKUST3 ETH Zurich

Overview

3 min · Playback speeds are marked in the video. Download video ↓

The full picture

Abstract

While multi-fingered dexterous robot hands have the potential to provide human-level dexterity, using them for functional manipulation remains difficult because task success depends on precise contact, coordinated arm-hand motion, and reactive recovery from execution errors. Precise contact depends on complex contact dynamics that are difficult to model accurately in simulation, motivating real-world learning. However, real-world demonstrations in the full arm-hand control space are costly and noisy because each trajectory must coordinate arm motion with high-DoF multi-finger contact. Small execution deviations can further cause slipped contact or premature force application, making recovery from off-nominal contact states important for robust execution.

To deal with these challenges, we propose HiFun, a hierarchical real-world RL framework for functional dexterous manipulation tasks. Our key insight is to decouple the control complexity into a functional hand skill for precise contact execution and an arm-hand coordination policy for arm control and hand-skill activation. This design enables effective real-time human intervention for reactive recovery learning and efficient data collection with Dynamic Movement Primitive (DMP) augmentation. Across six real-world tasks on two dexterous hands, HiFun achieves 98.3% average success within one hour of online training and remains robust to dynamic disturbances.

01 / From challenges to design

Challenges & Insights

HiFun structures what the robot explores, how actions are evaluated, and how human guidance enters learning.

01 / Challenge

High-dimensional exploration

Direct arm–hand RL must discover arm motion, coordinated finger contacts, and activation timing in a coupled action space. Successful contact sequences occupy only a small part of that space.

HiFun insight

Explore through contact-aware skills.

Learn finger execution separately, then let the coordination policy explore 6D arm motion and hand-skill activation.

Contact-aware execution, through a hand skill. Key turning and thin-handle retrieval illustrate precise contact and recovery. The hand skill executes finger contacts; coordination controls arm motion and activation. See the coordination comparison ↓

02 / Challenge

Ambiguous credit assignment

The same unsuccessful outcome can result from poor arm alignment or mistimed hand-skill activation. A terminal success signal alone does not distinguish these causes.

HiFun insight

Separate alignment and activation value learning.

Use distinct navigation and modulation targets, with action-subspace gradient routing, to guide arm motion and skill timing.

Method overview

Experimental evidence

Separate value heads, better activation placement. Left: the multi-head critic in the original method overview. Right: Appendix Fig. 4A on Angle-Spreader Retrieval. Blue = HiFun; orange = without multi-head critic. Inspect the multi-head critic evidence ↓

03 / Challenge

Difficult finger-level intervention

Real-time correction of many coupled finger joints is difficult to deliver consistently, especially when human and robot hand morphologies differ.

HiFun insight

Make the skill the intervention interface.

Operators correct arm placement and skill activation through the learned hand skill, reducing the need to teleoperate individual finger joints.

Full-DoF HIL-SERL
7 s
HiFun
7 s
Explore arm motion and skill activation. HiFun delegates finger execution to a learned hand skill. This avoids direct full-DoF arm-hand exploration and enables more efficient real-world learning. Explore the skill-level interface ↓

04 / Challenge

Heterogeneous human supervision

Human corrections can be noisy, delayed, or hesitant. Their usefulness also depends on what the current policy would do in the same state.

HiFun insight

Imitate according to estimated advantage.

IAW weights each correction relative to the current policy action, giving stronger imitation weight to corrections with higher critic-estimated advantage.

Method overview

Judge a correction by the improvement it offers. A critic trained on real-world outcomes predicts the return of each candidate action. Comparing the intervention with the current policy action in the same state estimates how much the correction improves on the robot’s own behavior. IAW gives higher-advantage corrections more imitation weight and limits the influence of low-advantage corrections, focusing learning on guidance expected to improve execution. See the intervention-weighting ablation ↓

Learning contact skills and when to use them.

25 seconds · real robot executions · edited excerptsRecovery includes an additional key-turning example.
295/300

successful evaluation trials

6

functional manipulation tasks

2

dexterous hand embodiments

≤60 min

online HIL per task*

98.3% mean success. 50 trials per task within the trained workspace. Online HIL is one training stage; the full pipeline averages approximately 109 min/task. Evaluation details ↗

02 / What makes these tasks hard

Precise contact · Arm–hand coordination · Reactive recovery

Precise tool use, contact-rich rotation, and constrained-space manipulation require precise fingertip placement and force regulation, synchronized arm–hand motion, and recovery after small errors. Here, a narrow opening blocks direct grasping. The robot must lever the exposed handle into reach, form a precision grasp, and extract it without slipping, trapping the tool, or colliding with the opening.

Thin-Handle Retrieval · Sharpa hand · source timing preserved
  1. 01

    Establish contact

    Place the fingers on the exposed, task-relevant part of the handle.

  2. 02

    Create clearance

    Synchronize arm motion and multi-finger levering to bring the handle within reach.

  3. 03

    Secure the tool

    Transition to a precision grasp without losing contact.

  4. 04

    Complete the retrieval

    Maintain coordinated arm motion and finger contact to avoid trapping or collision at the opening.

Task challengeSmall contact errors can break an entire manipulation sequence. Recovery must be learned alongside precise contact and coordination.

03 / Experimental evidence

Evidence behind the design

Three views of the evidence: adapting finger contact, learning arm–skill coordination, and using corrections selectively.

01

Contact-aware hand skills

The fingers can recover a lost contact.

A collision rotates the key and breaks thumb contact. The residual hand skill adjusts the fingers to restore contact without arm re-alignment.

Contact lost → finger adjustment → contact restored. Submitted supplementary video, 0:27–0:34. Key turning is an additional skill example, outside the six-task main evaluation.
From collision to restored thumb contact: the reference rewinds and the residual skill adjusts finger execution. Swipe or use the arrow keys to inspect all five frames. Click the figure to enlarge.
19/20

Unseen tool orientations

Fixed-arm Angle-Spreader skill. Toolbox yaw 0–30°; tool pitch/roll 0–20°.

18/20

Unseen drill orientations

Fixed-arm Bit Removal skill, with drill yaw up to 30°.

18/20

External contact disturbances

Fixed-arm Angle-Spreader skill under strong wrench perturbations.

These experiments support local recovery around a demonstrated contact structure. Additional evaluation, rebuttal ↗

02

Skill-conditioned coordination

A hand skill still needs the right timing.

Giving a baseline access to the same learned skill improves performance. Learning where to align the arm and when to activate that skill closes a further gap.

Mean task successFour Sharpa tasks · matched training budget

Separate from the six-task 98.3% headline result. Rebuttal comparison ↗

03

Value-guided learning

Learn activation timing.
Weight useful corrections.

Separate value heads train spatial alignment and skill activation. Intervention advantage weighting (IAW) gives more imitation weight to corrections with higher estimated value than the current policy action.

Multi-head critic

Activation closer to the target

4.58 cmwithout multi-head
2.00 cmHiFun

95th-percentile TCP-to-target error at activation, measured on Angle-Spreader Retrieval.

Intervention advantage weighting

Selective imitation improves success

100%HiFun
60%Uniform
intervention BC
40%No intervention
BC loss

The same success rates are reported on each of Angle-Spreader Retrieval and Bit Removal.

Inspect the component evidence
Original Appendix Fig. 4. IAW estimates usefulness through a critic; it does not directly observe the true quality of a human correction.

Main paper, Table 2 ↗ · Appendix D.3 ↗

04 / Method

Two levels.
One physical interaction.

A learned hand skill executes precise contact. A coordination policy controls arm motion and hand-skill activation through a compact interface.

Observation

RGB images · arm–hand state · contact feedback

πskill

How to contact

Kinesthetic reference + residual RL

Contact-aware finger commands
Weights frozen during coordination learning;
execution remains feedback-conditioned.
πcoord

Where / when to activate

Learned arm–hand coordination

6D arm motion Δx + activation α
Arm motion and skill activation are learned;
a fixed move–stop–act sequence is not imposed.
Coordinated arm–hand execution

The activation value blends the hand-skill command with the neutral hand configuration.

Training stages and complete framework
  1. Acquire a contact-aware hand skill. Start with a kinesthetic reference and refine finger execution with residual RL on the real robot.
  2. Warm-start coordination. Generate 100 physical DMP rollouts from an arm-and-activation demonstration, then pretrain the coordination policy.
  3. Refine with online interaction. Use skill-level human corrections, separate value heads and intervention advantage weighting.
Main paper, Fig. 2. The hand skill is also the human operator’s intervention interface. Read the method ↗

05 / Real-world evaluation

Six tasks.
Functional outcomes, measured.

Each task is evaluated over 50 trials with randomized object poses inside the trained workspace. Success requires completing the functional outcome.

A / Precise tool use · Sharpa

Power-Drill Actuation

Tighten the target screw while maintaining alignment and actuating the trigger.

B / Constrained space · Sharpa

Angle-Spreader Retrieval

Establish fingertip contact and fully extract the tool from its constrained tray.

C / Constrained space · Sharpa

Thin-Handle Retrieval

Lever an exposed handle into reach, form a precision grasp and fully extract it.

D / Contact-rich rotation · Sharpa

Power-Drill Bit Removal

Maintain multi-finger contact while loosening the chuck, then remove the drill bit.

Across hand embodiments

One framework, different dexterous hands

HiFun deploys on both Sharpa and XHand. On XHand, it performs precise pipette dispensing and retrieves a thin tool from a constrained space.

E / Precise tool use · XHand

Pipette Dispensing

Three vial positions, one dispensing skill. Align the tip with each vial and dispense liquid without collision or leakage.

F / Constrained space · XHand

Thin-Shaft Tool Retrieval

1.5×

Use a fingertip contact sequence to fully retrieve a thin shaft embedded in foam.

Beyond nominal rollouts

Recovery and local transfer

HiFun adjusts its approach after a tray moves and reuses a learned hand skill across different tool sizes.

Changed object placement. A moved tray requires coordination to adapt the approach.
7.5 cm → 6.5 cm / 5.5 cm. The same hand skill transfers to smaller tool variants.

Long-horizon manipulation

Multiple skills, one policy

Here, HiFun runs on XHand in a longer functional sequence. The policy turns the key, grasps the drill, and places it into the drawer by coordinating different hand skills. This shows that HiFun can deploy across dexterous hands and integrate multiple skills in one policy.

1.3×
Turn the key → grasp the drill → place it in the drawer. Coordinated execution on XHand.

06 / Learning cost & autonomy

What does the training budget include?

Online HIL fine-tuning averages 46.2 minutes per task. Including hand-skill learning and preparation, the reported full pipeline averages approximately 109 minutes per task.

~109 min/task

Reported full-pipeline average

Training-cost clarification ↗
Kinesthetic reference<5 min
Hand-skill residual RL~30 min
Reward-classifier data8.8 min avg.
Automated DMP rollouts18.8 min avg.
Online HIL coordination46.2 min avg.

Human guidance decreases during training.

Intervention rate complements success: it measures how much human correction is still needed. The original curves below show intervention rate and cycle time across the six tasks.

Original Appendix Fig. 3. Running averages over 20 episodes. The original figure uses orange for HiFun and blue for HIL-SERL. Source ↗

07 / Explore the work

From the behavior
to the details.

Read the method and evaluation, watch the overview video, or explore the additional evidence introduced during review.

Scope and next directions

HiFun relies on task-relevant hand skills learned around kinesthetic priors. New contact structures may require additional priors or adaptation. The current evaluation establishes functional execution within trained workspaces and local contact variations, rather than language-conditioned or open-ended task generalization.

Reusable hand-skill libraries and integration with high-level task-selection models are research directions. They are not evaluated capabilities of the current system.

Main paper, Limitations ↗

Citation

@inproceedings{huang2026hifun,
  title = {HiFun: a Hierarchical Framework for Efficient
           Functional Dexterous Manipulation Learning},
  author = {Huang, Linyi and Huai, Guowei and Liu, Weibin and
            Jiang, Shulong and Tan, Ping and Zhang, Hui and Song, Jie},
  booktitle = {Conference on Robot Learning (CoRL)},
  year = {2026}
}

Research figure