Enabling Safe, Active and Interactive Human-Robot Collaboration via Smooth Distance Fields

1Technical University of Applied Sciences Würzburg-Schweinfurt
2University of Technology Sydney
Code

Abstract

Human-Robot Collaboration (HRC) scenarios demand computationally efficient frameworks that enable natural and safe actions and interactions in shared workspaces. To address this, we propose a novel framework that utilises interactive Gaussian Process (GP) distance fields applying Riemannian Motion Policies (RMP) for key HRC functionality. Unlike traditional Euclidean distance field methods, our framework provides continuous and differentiable distance fields resulting in smooth collision avoidance, efficient updates in dynamic scenes and readily available surface information such as normal vectors and curvature. By leveraging RMPs, our framework supports fast, reactive motion generation, utilising both the distance and gradient fields generated by the GP model. In addition, we propose a Hessian-based normal vector estimation technique that elegantly leverages the GP’s second-order derivative information which we utilise for object manipulation. We demonstrate the versatility of our CPU-only system in common HRC scenarios where a collaborative robot (cobot) interacts safely and naturally with a human and performs grasping actions in a dynamic environment. Our framework offers an open-source, comprehensive and low-computational resource solution for HRC, making it an ideal tool for conducting a wide range of user studies. By providing a continuous and differentiable distance field and combining motion generation, obstacle avoidance, and object manipulation within a single system, we aim to broaden the scope and accessibility of HRC research in real dynamic environments.

System diagram of our proposed framework.

Proposed Framework

System diagram of our proposed framework.

The Figure shows proposed system architecture, where IDMP takes as input the depth sensor's data and pose. These inputs are used to generate the local Frustum Field which determines the implicit semantics of the scene and is then used to fuse the new observation with the global GPDF. Our RMP policy queries distance and gradient information from the fused global GPDF to generate accelerations which are passed to a controller for execution on the robot. The key aspect of the IDMP framework is that it uses a Frustrum Field to fuse and identify the dynamic regions locally before passing the information to the Fused Field that contains the global information. The following figures are showing the internal update process of IDMP. The background displays the distance field within the sensor's field of view generated by the frustum GPDF. While the fused GPDF is trained on all points from the internal global map, the frustum GPDF only utilizes the latest observations, capturing changes in the scene. By querying the frustum GPDF with the fused GPDF's training points, we can directly retrieve implicit semantics based on distance metrics. Training points in the fused GPDF are classified as static if their queried distance in the frustum GPDF is below a certain threshold, indicating the object has not moved. Training points are classified as dynamic when this distance exceeds the sensor noise threshold, indicating that the object has moved. For the final case we query newly observed sensor points with the fused GPDF. Those points with distances greater than a certain threshold are classified as new and are fused into the global GPDF.

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Quantitative Results

We evaluate our method in a mock human-robot interaction scene where the robot is tasked to cycle between two waypoints. During the execution, a human enters the workspace and places their arm in the way of the robot. We compare the behaviour of our framework against an occupancy-based reactive method implemented in ROS package MoveIt. This baseline method builds an Octomap which is continuously updated with the sensor input. A trajectory is then planned using the Bi-directional Fast Marching Tree (BFMT*). During execution the trajectory is checked for possible collisions which then triggers replanning.

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As can be seen in the following Table the trajectories produced by our method result in much smoother trajectories. Notably the mean squared jerk and change in curvature were approximately 2x and 3x lower, respectively, than the baseline.

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Videos

BibTeX

@inproceedings{10.5555/3721488.3721544,
author = {Ali, Usama and Sukkar, Fouad and Mueller, Adrian and Wu, Lan and Le Gentil, Cedric and Kaupp, Tobias and Vidal Calleja, Teresa},
title = {Enabling Safe, Active and Interactive Human-Robot Collaboration via Smooth Distance Fields},
year = {2025},
booktitle = {Proceedings of the 2025 ACM/IEEE International Conference on Human-Robot Interaction},
pages = {439–446},
numpages = {8},
location = {Melbourne, Australia},
}