Project Showroom

Selected project narratives with key contributions and playable demos where available.

Granular and Deformable Object Manipulation

DDBot: Differentiable Physics-Based Digging Robot for Unknown Granular Materials

IEEE Transactions on Robotics, 2025 (vol. 42, pp. 152-169)

Yang X., Wei M., Ji Z., Lai Y.-K.

DDBot combines a GPU-accelerated differentiable granular simulator with gradient-based optimisation. It identifies unknown material properties and optimises digging strategy without prior material knowledge, then transfers zero-shot to real robots.

Key contributions

  • First-order gradient optimisation for differentiable granular simulation
  • Efficient convergence (5-20 min) for both system identification and skill optimisation
  • High-precision zero-shot deployment on sand and soil
  • Parallel simulation with automatic differentiation

Differentiable Physics-Based System Identification for Robotic Manipulation of Elastoplastic Materials

International Journal of Robotics Research (IJRR), 2025

Yang X., Ji Z., Lai Y.-K.

DPSI estimates physically interpretable material parameters from one real robot interaction and incomplete point clouds, enabling accurate long-horizon simulation and manipulation planning for elastoplastic materials.

Key contributions

  • Material parameter estimation from a single real-world interaction
  • Works with incomplete and occluded 3D point cloud observations
  • Interpretable physics parameters (e.g., modulus, friction, yield stress)
  • High-fidelity simulation-to-real alignment for long-horizon planning
  • Fully open-sourced workflow

AutomaChef: A Physics-Informed Demonstration-Guided Learning Framework for Granular Material Manipulation

IEEE Transactions on Neural Networks and Learning Systems (TNNLS), 2025

Wei M., Yang X., Lai Y.-K., Tafrishi S.A., Ji Z.

AutomaChef uses differentiable simulation to generate expert demonstrations through optimisation, then uses those demonstrations to train manipulation policies for granular transport with real-world transfer.

Key contributions

  • Differentiable granular simulator implemented with Taichi
  • Demonstrations generated automatically via gradient optimisation
  • Outperforms standard RL, imitation learning, and prior task-specific methods
  • Successful real-world granular transport deployment

Celebi's Choice: Causality-Guided Skill Optimisation for Granular Manipulation via Differentiable Simulation

IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS), 2025

Wei M., Yang X., Yan J., Lai Y.-K., Ji Z.

Celebi integrates causal inference into differentiable optimisation for granular manipulation, adaptively adjusting gradient step sizes to improve optimisation stability and convergence speed.

Key contributions

  • Causality-enhanced gradient optimisation for granular skill learning
  • Differentiable granular interaction simulation environment
  • Differentiable skill-to-action mapping for trajectory optimisation
  • Adaptive step-size control improves stability and convergence

Affordance and Reinforcement Learning for Rigid Object Manipulation

GAM: General Affordance-Based Manipulation for Contact-Rich Object Disentangling Tasks

Neurocomputing, 2024 (vol. 578, 127386)

Yang X., Wu J., Lai Y.-K., Ji Z.

GAM learns where and how to act in contact-rich disentangling tasks, combining affordance prediction with goal-conditioned reinforcement learning to handle diverse object configurations.

Key contributions

  • General affordance prediction without task-specific engineering
  • Generalises to diverse and unseen disentangling configurations
  • Combines affordance learning and goal-conditioned RL
  • Validated in real and simulated contact-rich scenarios

Abstract Demonstrations and Adaptive Exploration for Efficient and Stable Multi-Step Sparse Reward Reinforcement Learning

International Conference on Automation and Computing (ICAC), 2022

Yang X., Ji Z., Wu J., Lai Y.-K.

A2E improves sparse-reward long-horizon robotic learning by combining abstract sub-task demonstrations with adaptive exploration that changes as each sub-task is mastered.

Key contributions

  • Task decomposition into ordered sub-task sequences with abstract demonstrations
  • Adaptive exploration strategy across mastered and weak sub-tasks
  • Validated on grid-world and real robotic manipulation benchmarks
  • Improves both sample efficiency and training stability

Efficient Hierarchical Reinforcement Learning for Mapless Navigation with Predictive Neighbouring Space Scoring

IEEE Transactions on Automation Science and Engineering (TASE), 2023

Gao Y., Wu J., Yang X., Ji Z.

This work introduces Predictive Neighbouring Space Scoring to generate compact sub-goals in hierarchical RL for mapless navigation, reducing complexity compared with end-to-end learning from raw observations.

Key contributions

  • Predictive Neighbouring Space Scoring (PNSS) for compact sub-goal generation
  • Hierarchical RL with high-level goal selection and low-level control
  • Lower learning complexity than end-to-end raw-sensor approaches
  • Validated on challenging mapless navigation tasks

Recent Advances of Deep Robotic Affordance Learning: A Reinforcement Learning Perspective

IEEE Transactions on Cognitive and Developmental Systems (TCDS), 2023

Yang X., Ji Z., Wu J., Lai Y.-K.

A survey of deep robotic affordance learning from an RL perspective, including taxonomy, limitations, and future directions focused on action-consequence prediction.

Key contributions

  • Taxonomy of deep robotic affordance learning from RL perspective
  • Connects affordance theory and modern deep RL
  • Identifies open challenges in representation and deployment
  • Proposes action-consequence prediction as a future direction

Hierarchical Reinforcement Learning with Universal Policies for Multi-Step Robotic Manipulation

IEEE Transactions on Neural Networks and Learning Systems (TNNLS), 2021

Yang X., Ji Z., Wu J., Lai Y.-K., Wei C., Liu G., Setchi R.

The Universal Option Framework (UOF) decomposes long-horizon tasks into reusable sub-goals with universal low-level policies for efficient sparse-reward manipulation learning.

Key contributions

  • Hierarchical decomposition of long-horizon tasks into reusable sub-goals
  • Universal low-level policies generalise across sub-task instances
  • Efficient learning under sparse rewards
  • Demonstrated on challenging multi-step manipulation tasks

An Open-Source Multi-Goal Reinforcement Learning Environment for Robotic Manipulation with PyBullet

Towards Autonomous Robotic Systems (TAROS), 2021

Yang X., Ji Z., Wu J., Lai Y.-K.

An open-source PyBullet re-implementation of robotic multi-goal benchmarks with extra APIs and long-horizon tasks, removing dependency on commercial simulators.

Key contributions

  • Open-source alternative to MuJoCo-based benchmark environments
  • Added APIs for joint control, image observations, and cameras
  • Introduced long-horizon sparse-reward benchmark tasks
  • Validated parity against original benchmark behavior

Related Open-Source Resources