Reinforcement / Imitation Learning

• Scan Diffusion Policy

  We propose a data-efficient 3D scanning framework that uses Diffusion Policy to imitate human-like scanning strategies. To enhance robustness and generalization, we adopt the Occupancy Grid Mapping instead of direct point cloud processing, offering improved noise resilience and handling of diverse object geometries. We also introduce a hybrid approach combining a sphere-based space representation with a path optimization procedure that ensures path safety and scanning efficiency.
  
  

  • I. Hirako, R. Hakoda, Y. Liu, M. Hwang, Y. Sato and T. Oishi1, "ScanDP: Generalizable 3D Scanning with Diffusion Policy," Proc. International Conference on Intelligent Robots and Systems, 2026.

  Symmetry-aware Policy Network

  We propose a symmetry-assisted, general-purpose DRL framework for morphologically symmetric robots that enables stable and robust learning. The framework models the environment as a symmetric Markov decision process (MDP) and constructs a full-body policy from a single-sided base policy using symmetry operators. We further propose a symmetric PPO objective with a coupled importance-sampling ratio. This objective aligns the policy optimization process with the imposed symmetry and serves as a principled alternative to MAPPO-style multi-agent formulations.
  
  

  • R. Hakoda, Y. Liu, M. Hwang, Y. Sato, J. Takamatsu, K. Ikeuchi, and T. Oishi, "Morphological symmetry-aware generalized policy network for deep reinforcement learning," Frontiers in Robotics and AI, 13:1816301, 2026.

SLAM and Navigation

• Pose-Graph Topological Integrity

  We introduce the pose-graph topological integrity, an approach designed to assess the correctness of pose graphs in simultaneous localization and mapping. Traditional map quality assessment methods cannot capture the inconsistencies between the constructed map and the actual environment. The proposed approach utilizes heat kernel signatures to directly quantify topological inconsistencies between the pose graph and support graph derived from free-space constraints. This enables a multi-scale and per-vertex evaluation of topological integrity.
  
  

  • S. Xie, K. Sakurada, R. Ishikawa, M. Onishi and T. Oishi, "PGTI: Pose-Graph Topological Integrity for Map Quality Assessment in SLAM," Robotics. 2025; 14(12):189. [code]

  Structure Aware Loop Closure for SLAM

  This study provides a spherical harmonics (SH) based fast structural representation (SH-FS) in visual SLAM using sparse point clouds, which extracts the structure information from sparse points into single vector. SH-FS was applied in conventional feature-based loop closing process. Furthermore, a structure-aware loop closing method in visual SLAM was proposed to improve the robustness of SLAM systems.
  
  

  • S. Xie, R. Ishikawa, K. Sakurada, M. Onishi and T. Oishi, "Fast Structural Representation and Structure-aware Loop Closing for Visual SLAM," IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS), pp. 6396-6403, 2022. [video] [code]

  Drone-Rover relative pose estimation

  To take advantage of the drone's wide field of view, we developed a drone pose estimation system from the ground vehicle. In this system, the relative pose is obtained by direct measurement by LiDAR and indirect measurement of the camera's vanishing directions.
  
  

  • J. Hausberg, R. Ishikawa, M. Roxas. T. Oishi, "Relative Drone - Ground Vehicle Localization using LiDAR and Fisheye Cameras through Direct and Indirect Observations," arXiv:2011.07008, 2020. [video]

  Robot navigation by SLAM-device

  We proposed a concept to attach the SLAM-device onto a robot and quickly realize the robot navigation in 3D space. The proposed method calibrates SLAM-device and robot itself by using the relative poses obtained by several robot movements and clarified the efficient ones for the calibration according to the DoF of the robot. Furthermore, the relative pose is dynamically refined so that the contact between the environment and the robot maintains the geometric consistency.
  
  

  • R. Ishikawa, T. Oishi, K. Ikeuchi, "Dynamic Calibration between a Mobile Robot and SLAM Device for Navigation," The 28th IEEE International Conference on Robot and Human Interactive Communication, 2019. [ src (HoloLensRobotNav)] [ src (HoloLens Robot ROSPackage)] [video(long)] [video(short)]

Sensor

• Agricultural support robot

  Pesticide spraying is essential for growing crops, but food safety and cost are significant issues. We have, therefore, developed a system to detect and remove worms using a quadruped robot capable of moving over uneven terrain.
  
  

  • S. Balasooriya, Y. Sato, T. Oishi, "Autonomous Robotic Platform for Proximal Data Collection Amongst Foliage Utilizing an Anisotropically Flexible Manipulator," The 2024 16th IEEE/SICE International Symposium on System Integration (SII), Ha Long, Vietnam, 2024.
    
    
  • H. Hansen, Y. Liu, R. Ishikawa, T. Oishi, Y. Sato, "Quadruped Robot Platform for Selective Pesticide Spraying," 18th International Conference on Machine Vision Applications (MVA), Hamamatsu, Japan, 2023. pp. 1-6.
    
    

Image processing

• Event Camera Tracking

  We propose two event-camera-based tracking methods for robotic object manipulation. One method achieves very fast object tracking by leveraging distance fields. The other employs a unified camera projection model for different lens types and an error function and optimization method that account for motion blur.
  
  

  • Y. Kang, R. Ishikawa, G. Caron, T. Oishi, "Event-based 6-DoF object tracking with distance field reaching 130 Hz," IEEE Robotics and Automation Letters, 2026.

  • Y. Kang, G. Caron, R. Ishikawa, A. Escande, K. Chappellet, R. Sagawa, T. Oishi, "Direct 3D model-based object tracking with event camera by motion interpolation," 2024 IEEE International Conference on Robotics and Automation (ICRA), Yokohama, Japan, 2024, pp. 2645-2651.

  RIND edge detection

  This study proposes a learning-based method to detect four different types of edges in 2D images. The network architecture is based on the SWIN Transformer and is capable of extracting fine edges by using Dice loss.
  
  

  • L. Miao, R. Ishikawa, and T. Oishi, "SWIN-RIND: Edge Detection for Reflectance, Illumination, Normal and Depth Discontinuity with Swin Transformer," British Machine Vision Conference (BMVC), 2023. [video] [code]

Depth Estimation

• Non-Learning Stereo-Aided Depth Completion

  We propose a non-learning depth completion method for a sparse depth map captured using a LiDAR sensor guided by a pair of stereo images. The proposed selective stereo matching (SSM) method searches the most appropriate depth value for each image pixel from its neighborly projected LiDAR points based on an energy minimization framework. This depth selection approach can handle any type of mis-projection. Moreover, SSM has an advantage in terms of long-range depth accuracy because it directly uses the LiDAR measurement rather than the depth acquired from the stereo.
  
  

  • Y. Yao, R. Ishikawa, and T. Oishi, "Stereo-LiDAR Fusion by Semi-Global Matching with Discrete Disparity-Matching Cost and Semidensification," in IEEE Robotics and Automation Letters, vol. 10, no. 5, pp. 4548-4555, May 2025. [code] [bib]

  • Y. Yao, R. Ishikawa, S. Ando, K. Kurata, N. Ito, J. Shimamura, T. Oishi, "Non-Learning Stereo-Aided Depth Completion Under Mis-Projection via Selective Stereo Matching," in IEEE Access, vol. 9, pp. 136674-136686, 2021.

  Depth upsampling

  We proposed methods for estimating a dense depth map from a sparse LIDAR point cloud and images. Our unsupervised approach is a real-time dense depth completion from sparse depth maps guided by a single image. Our method generates smooth depth maps while preserving discontinuity between different objects. The key idea is a Binary Anisotropic Diffusion Tensor (B-ADT) which can eliminate smoothness constraint at intended positions and directions by applying variational regularization.
  
  

  • Y. Yao, M. Roxas, R. Ishikawa, S. Ando, J. Shimamura, and T. Oishi, "Discontinuous and Smooth Depth Completion with Binary Anisotropic Diffusion Tensor," IEEE Robotics and Automation Letters, vol. 5, no. 4, pp. 5128-5135, Oct. 2020. arXiv:2006.14374

  Semantically-guided depth upsampling

  Another approach relies on a directionally biased propagation of known depth to missing areas based on semantic segmentation. Additionally, we classify different object boundaries as either occluded or connected to limit the extent of the data propagation. At the regions with inevitably missing point cloud data, we depend on estimated depth using motion stereo.
  
  

  • A. Hirata, R. Ishikawa, M. Roxas, T. Oishi, "Real-Time Dense Depth Estimation using Semantically-Guided LIDAR Data Propagation and Motion Stereo," IEEE Robotics and Automation Letters, vol. 4, no. 4, pp. 3806-3811, Oct. 2019. [video] [ src (MATLAB for accuracy comparison)]

  Fish-eye depth estimation

  We propose a real-time dense 3D mapping method for fisheye cameras without explicit rectification and undistortion. We extend the conventional variational stereo method by constraining the correspondence search along the epipolar curve using a trajectory field induced by camera motion. We also propose a fast way of generating the trajectory field without increasing the processing time compared to conventional rectified methods.
  
  

  • M. Roxas and T. Oishi, "Variational Fisheye Stereo," IEEE Robotics and Automation Letters, vol. 5, no. 2, pp. 1303-1310, April 2020. arXiv:1909.07545 [ src] [video(result)] [video(presentation)]

Teleoperation

• Teleoperation of humanoid robot

  We proposed a method to generate robot motions for vision-based teleoperation systems. Task Model performs recognition and transmission of human motions and can simultaneously solve the issues of the structural differences between the human and the humanoid robot and time delays. We also developed a method of articulation modeling using an RGB-D sensor. The articulation parameters are estimated by a fusion of hand motion and point-cloud alignment.
  
  

  • L. Fu, R. Ishikawa, Y. Sato and T. Oishi, "CAPT: Category-level Articulation Estimation from a Single Point Cloud Using Transformer," International Conference on Robotics and Automation (ICRA 2024), 2024.
  • R. Hartant, R. Ishikawa, M. Roxas, T. Oishi, "Hand-Motion-guided Articulation and Segmentation Estimation," The 29th IEEE International Conference on Robot and Human Interactive Communication (RO-MAN), Naples Italy, 2020, arXiv:2005.03691. [src] [video]
    
    

  • M. Ogawa, K. Honda, Y. Sato, T. Oishi and K. Ikeuchi, "Development of interface for teleoperation of humanoid robot using task model method," Proc. 2016 IEEE/SICE International Symposium on System Integration, Dec. 2016, Sapporo, Japan.
    
    M. Ogawa, K. Honda, Y. Sato, S. Kudoh, T. Oishi, K. Ikeuchi, "Motion Generation of the Humanoid Robot for Teleoperation by Task Model," Proc. 24th IEEE International Symposium on Robot and Human Interactive Communication (RO-MAN), pp. 71-76, Sept. 1, 2015, Kobe Japan.

City modeling

• Global positioning in urban environment

  • A. Kumar, Y. Sato, T. Oishi and K. Ikeuchi, "Identifying Reflected GPS Signals and Improving Position Estimation Using 3D Map Simultaneously Built with Laser Range Scanner," 13th ITS Asia-Pacific Forum, Auckland, New Zealand, April 2014.

• Large structure modeling

  • L. Xue, S. Ono, A. Banno, T. Oishi, Y. Sato, K. Ikeuchi, "Global 3D Modeling and its Evaluation for Large-Scale Highway Tunnel using Laser Range Sensor," In Proc. 19th ITS World Congress Vienna, Oct. 2012, Austria. (Best Paper Award)

• Object detection

  • Z. Wang, M. Kagesawa, S. Ono, A. Banno, T. Oishi, K. Ikeuchi, "Detection of Emergency Telephone Indicators in a Tunnel Environment," International Journal of Intelligent Transportation Systems Research, Jan. 2014.

• Historical Analysis of ITS

  • K. Koide, T. Oishi and K. Ikeuchi, "Historical Analysis of the ITS Progress of Japan," International Journal of Intelligent Transportation Systems Research, pp. 1-10, 2015.