Authors: Yitong Chen, Fangbo Qin, Yang Wang, Ruihua Hu, Kui Zhang, Shan Yu
Organizations: Institute of Automation, Chinese Academy of Sciences, Beijing 100190, China. · School of Artificial Intelligence, University of Chinese Academy of Sciences, Beijing 100049, China. · State Key Laboratory of Brain Cognition and Brain-Inspired Intelligence Technology, Shanghai 200031, China. · Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, China.
Automated needle-loop hooking is a critical step in flexible microelectrode (FME) implantation. This paper presents MicroHookACT, an imitation learning-based visuomotor policy for automated 3D hooking under monocular microscopic vision. First, a unidirectional hooking strategy exploits defocus cues and optical-axis guidance to enable palpation-free precise alignment and contact-rich threading. Second, an action-supervised object attention module built on a frozen ViT backbone learns to focus on the micro-needle tip and micro-loop directly from human demonstrations, without requiring manual visual annotations for training. Third, attention-centered global coarse and local fine features are dynamically weighted according to predicted action progress, enabling a single ACT policy to adapt to changing defocus blur and visual requirements throughout the operation. In the experiments, visuomotor policies were trained on 60 human demonstrations and evaluated under five setups with varying difficulties. Our MicroHookACT framework achieved the highest overall success rate of 96.7% with an average execution time of 11.5 s. These results demonstrate the potential of visuomotor policy learning for micron-level control under varying operating conditions.
Figures & tables
Fig. 1: Monocular microscopic vision guided visuomotor policies. The green gradient region indicates the microscope’s depth of field, with darker shades representing positions closer to the focal plane.
Fig. 2: FME implantation setup and unidirectional hooking strategy. (a) Spatial relationship between micro-needle, FMEs, microscope, and brain cortex. The region of interest (ROI) view and optical axis of the camera are depicted with a dashed box and line, respectively. The green gradient region indicates the microscope’s depth of field (DoF), with darker shades representing positions closer to the focal plane. (b) A monocular view cannot distinguish which of the two micro-objects is closer to the camera. (c) The unidirectional needle-loop hooking strategy is divided into four stages, which are modeled with a single visuomotor policy.
Fig. 3: MicroHookACT framework.
Fig. 4: Experiment platform and evaluation setups.
Fig. 5: Action trajectory visualization. (a-e) Relative motion trajectories in {C} conditioned on the input frame. The movement direction reflects the correctness of the coarse approaching actions. (f) The motion trajectories of all demonstration and automated actions in {C} , whose endpoints are aligned.
Method
Standard
Hard Position
New Background
New Angle
New FME
Overall
Average Time(s)
MicroACT-3D [ 16 ]
8/10
1/5
0/5
2/5
4/5
15/30
16.1
HLF [ 14 ]
9/10
2/5
5/5
4/5
5/5
25/30
16.4
DINOv3ACT
5/10
0/5
3/5
4/5
3/5
15/30
11.7
Ours w/o Adapt.
8/10
1/5
5/5
3/5
3/5
20/30
12.8
Ours
10/10
5/5
5/5
5/5
4/5
29/30
11.5
TABLE I: Action Success Rates with Different Methods under Five Evaluation Setups.
Fig. 6: Visualization of object attention, ACGL features, progress prediction, and adaptive modulation. The six columns in (a–c) correspond to the six time steps in (d, e), with matching colored triangles indicating the correspondence.
Backbone
Attention Recall
Attention Focality
Resnet-18 (learnable)
0.99
0.21
Resnet-18 (frozen)
0.95
0.21
DINOv3-ViT (learnable)
0.99
0.02
DINOv3-ViT (frozen)
0.97
0.35
TABLE II: Evaluation of Object Attention across Vision Backbones
Precision assembly requires sub-millimeter corrections in contact-rich "last-millimeter" regions where visual feedback fails due to occlusion from the end-effector and workpiece. We present ReTac-ACT (Reconstruction-enhanced Tactile ACT), a vision-tactile imitation learning policy that addresses this challenge through three synergistic mechanisms: (i) bidirectional cross-attention enabling reciprocal visuo-tactile feature enhancement before fusion, (ii) a proprioception-conditioned gating network that dynamically elevates tactile reliance when visual occlusion occurs, and (iii) a tactile reconstruction objective enforcing learning of manipulation-relevant contact information rather than generic visual textures. Evaluated on the standardized NIST Assembly Task Board M1 benchmark, ReTac-ACT achieves 90% peg-in-hole success, substantially outperforming vision-only and generalist baseline methods, and maintains 80% success at industrial-grade 0.1mm clearance. Ablation studies validate that each architectural component is indispensable. The ReTac-ACT codebase and a vision-tactile demonstration dataset covering various clearance levels with both visual and tactile features will be released to support reproducible research.
Minchi Ruan, LiangQing Zhou, Hongtong Li +4
Beijing University of Posts and Telecommunications, Beijing, China · SunHDex Intelligent Technology (Beijing) Co. Ltd., Beijing, China · University of Hamburg, Hamburg, Germany
Current dexterous manipulation systems commonly rely on external or wrist-mounted cameras for visual feedback. However, such sensing setups are prone to occlusion and can limit performance on tasks requiring close-range, multi-view perception. In this work, we design a vision-enhanced fingertip module that brings clear visual perception directly to the fingertips and present FingerViP, a learning system that leverages fingertip visual perception for dexterous manipulation. Specifically, the fingertip module integrates miniature-camera sensing within compact-footprint hardware and is installed on each finger of a multi-fingered hand, which substantially improves visual perception by providing comprehensive, multi-view observations of objects and surrounding environment. Building on the integrated fingertip modules, we develop a diffusion-based whole-body visuomotor policy conditioned on a third-view camera and multi-view fingertip vision, enabling the robot to effectively learn complex manipulation skills directly from human demonstrations. To improve view-proprioception alignment and contact awareness in the policy observation representation, each fingertip visual feature is augmented with its corresponding camera-pose encoding and per-finger joint-current encoding. We validate the effectiveness of multi-view fingertip vision and demonstrate the robustness and adaptability of FingerViP across a range of challenging real-world tasks, including retrieving objects behind an occluding curtain, achieving a 56.6% relative improvement in average success rate over the baseline using an external third-view camera and a wrist-mounted camera. Videos, code, and hardware designs are available on our project page: https://fingervip.github.io/.
Zhen Zhang, Weinan Wang, Hejia Sun +4
The Chinese University of Hong Kong · The Hong Kong Polytechnic University
End-to-end visuomotor policies provide little opportunity for humans to understand or correct the policy's visual attention. We propose GuidedAttention, a visuomotor imitation learning framework that introduces interpretable and correctable visual attention as an explicit intermediate representation. Task-relevant attention keypoints are predicted from camera images and condition a diffusion-based action policy. Users can inspect and optionally correct selected keypoints once at rollout initialization, after which the corrected attention is automatically propagated throughout execution by a tracking module. Experiments in simulation and the real world demonstrate that GuidedAttention consistently improves robot manipulation performance, particularly under positional and appearance out-of-distribution (OOD) conditions. https://mmurooka.github.io/guided-attention-project-page
Masaki Murooka, Ryoichi Nakajo, Keisuke Shirai +4
CNRS-AIST JRL (Joint Robotics Laboratory), IRL, 1-1-1 Umezono, Tsukuba, Ibaraki 305-8560, Japan · Artificial Intelligence Research Center, National Institute of Advanced Industrial Science and Technology (AIST), 2-3-26 Aomi, Koto-ku, Tokyo 135-0064, Japan