This paper presents a novel Graph Optimal Transport (Graph OT) framework for analyzing and aligning plant structures across different growth stages and transformations. Our method extends existing graph matching techniques by incorporating domain-specific botanical features and employing a multi-scale matching strategy that captures both local and global structural characteristics. The framework combines multiple feature representations, including node descriptors, spectral embeddings, Node2Vec embeddings, and relative positions, to construct an augmented cost matrix for optimal transport based matching. We evaluated our approach on a dataset of 50 distinct plant structures under various transformations, including rotation, deformation, and partial matching scenarios.

The results indicate that our Graph OT framework significantly outperforms traditional optimal transport (OT) methods, achieving node-matching accuracy scores of 0.75 for rotated,
0.74 for deformed structures, 0.67 for cut structures, and 0.71 for structures with skipped nodes. Our approach demonstrates particular robustness in handling complex transformations. This method provides a powerful tool for botany applications such as crop management, growth modeling, and automated pruning systems. ... Read more

Robot dexterous manipulation research has drawn more attention in recent years since the development of various learning methods makes it possible for robots to achieve dexterity at the human level. Many attempts have been made to integrate human knowledge into Reinforcement Learning (RL) processes for faster learning speed and better performance. Despite their successes in many aspects, there are two open problems that still need to be carefully considered: 1. The effect of demonstrations gradually vanishes during RL. 2. In most cases, only imperfect demonstrations are available to robots. In this work, we proposed a new learning framework - Interactive Behavioural Cloning for faster Reinforcement Learning (IBC-RL), which could alleviate problems in complex manipulation tasks with long horizons. Different demonstrations are shown to robots at different learning stages. Robots learn complex tasks step by step with interactive demonstrations from human teachers. The framework is evaluated with four dexterous manipulation tasks simulated with the Isaac Gym engine. Human teachers perform demonstrations by controlling the simulated robot hands through a hand-tracking system. The results of the experiments could demonstrate the efficiency of IBC-RL in guiding and accelerating the learning processes with imperfect demonstrations. ... Read more

Recent research has shown that a Learning from Demonstration (LfD) approach is useful for teaching robots flexible skills efficiently, and it opens the possibility for non-expert users to program these skills. When learning from demonstration data, learning frameworks should learn representations that are flexible and can generalize to unseen situations. Within the context of multi-reference frame skill learning, this work proposes a framework to learn such a representation without using task-specific heuristics or pre-segmentation of the demonstrations. Local policies are first learned by fitting the local dynamics with respect to each frame using Gaussian Processes (GP). A classifier that determines the relevance of each frame for every time step is then trained in a self-supervised manner. The uncertainty quantification capability of Gaussian Processes is exploited to improve the performance of the local policies and the self-supervised learning process of the classifier. The framework is validated through multi-frame tasks in simulation as well as on a robotic manipulator with a pick-and-place re-shelving task. Its performance is also compared to that of the Task-Parameterised Gaussian Mixture Model (TPGMM) with simulated and robotic data. In this comparison, the proposed model performs better according to metrics that quantify deviation from the goal at each reference frame and according to similarity measures between demonstrations and their corresponding reproductions. ... Read more

Grasping objects in a smooth humanlike motion, instead of the more typical pick-and-place approach, includes multiple aspects that need to be performed correctly for a successful grasp. These aspects involve moving the end-effector such that its surface makes and retains contact with the object while also coordinating the movement of the gripper to securely grasp the object. This work investigates how the intricate task of grasping may be learned from humans based on kinesthetic demonstrations. Due to the complexity of the task, these demonstrations are often slow and even slightly flawed, particularly at moments when multiple aspects (i.e. end-effector movement, orientation and gripper width) have to be demonstrated at once. Rather than training a person to provide faster demonstrations, non-expert users are provided with the ability to interactively modify the dynamics of their initial demonstration through teleoperated corrective feedback. This in turn allows them to teach motions outside of their own physical capabilities. In the end, the goal is to obtain a faster but reliable execution of the task.
The presented framework learns the desired movement dynamics based on the current Cartesian position with Gaussian Processes, resulting in a reactive, time-invariant policy. Using Gaussian Processes also allows online interactive corrections and active disturbance rejection through epistemic uncertainty minimization.
The experimental evaluation of the framework is carried out on a Franka-Emika Panda. Tests were performed to determine i) the framework's effectiveness in successfully learning how to grasp an object quickly, ii) ease of policy correction to environmental changes (i.e. different object shapes and mass), and iii) the framework’s usability for non-expert users. ... Read more

This work applies interactive imitation learning for the navigation of a mobile robot. The algorithm"Learning Interactively to Resolve Ambiguity in Sensor Policy Fusion" (LIRA-SPF) is introduced in the field of machine learning for robot navigation. This algorithm extends on existing methods by allowing the ambiguity-free fusion of existing single-sensor policy behavior using an active and interactive querying of the human expert. The ambiguous situations investigated in this work are due the possible perspective mismatch of each sensor: LIRA-SPF aims to detect these situations and save the correct solution in a new fused policy. As a consequence, we provide an alternative to training a new behavior again from scratch, leveraging the knowledge of existing expert behaviors and reducing the required teacher’s effort. The algorithm is tested with different supervised and unsupervised disambiguation strategies thanks to its modular implementation. This paper summarizes multiple simulated and real robot tests, showing the advantages of the proposed disambiguation module on state of the art approaches. In particular, the analysis underlines the necessity of less human-robot interaction during the training process. Finally the conclusions reveal the missing blocks of the approach and how this could be beneficial in the sensor fusion procedure. ... Read more