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Stephan, Benedict; Dontsov, Ilja; Müller, Steffen; Groß, Horst-Michael
On learning of inverse kinematics for highly redundant robots with neural networks. - In: IEEE Xplore digital library, ISSN 2473-2001, (2023), S. 402-408

The inverse kinematic problem for redundant robots is still difficult to solve. One approach is learning the inverse kinematic model with artificial neural networks, while the key challenge is the ambiguity of solutions. Due to the redundancy in the robot's degrees of freedom, there are multiple or even unlimited valid joint states bringing the end effector to a desired position. We show to what extent this problem influences the achievable accuracy of supervised training approaches depending on the number of degrees of freedom. To overcome the difficulties, a new training scheme is proposed, which uses the analytically solvable forward kinematics model. The new unsupervised training method uses random sampling in the joint state space and is not dependent on ambiguous tuples of joint values and end effector poses. We analyze the effect of the sample density on the remaining position error and show that additional soft constraints can easily be integrated in the training scheme, which offers the possibility to consider obstacle avoidance directly in the inverse kinematic model. Evaluations have been done using different robot models with up to 20 degrees of freedom, while not only position, but also the end effector's orientation at the goal point is considered.



https://doi.org/10.1109/ICAR58858.2023.10406939
Seichter, Daniel; Stephan, Benedict; Fischedick, Söhnke Benedikt; Müller, Steffen; Rabes, Leonard; Groß, Horst-Michael
PanopticNDT: efficient and robust panoptic mapping. - In: 2023 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS), (2023), S. 7233-7240

As the application scenarios of mobile robots are getting more complex and challenging, scene understanding becomes increasingly crucial. A mobile robot that is supposed to operate autonomously in indoor environments must have precise knowledge about what objects are present, where they are, what their spatial extent is, and how they can be reached; i.e., information about free space is also crucial. Panoptic mapping is a powerful instrument providing such information. However, building 3D panoptic maps with high spatial resolution is challenging on mobile robots, given their limited computing capabilities. In this paper, we propose PanopticNDT – an efficient and robust panoptic mapping approach based on occupancy normal distribution transform (NDT) mapping. We evaluate our approach on the publicly available datasets Hypersim and ScanNetV2. The results reveal that our approach can represent panoptic information at a higher level of detail than other state-of-the-art approaches while enabling real-time panoptic mapping on mobile robots. Finally, we prove the real-world applicability of PanopticNDT with qualitative results in a domestic application.



https://doi.org/10.1109/IROS55552.2023.10342137
Scheidig, Andrea; Hartramph, Robert; Schütz, Benjamin; Müller, Steffen; Kunert, Kathleen S.; Lahne, Johanna; Oelschlegel, Ute; Scheidig, Rüdiger; Groß, Horst-Michael
Feasibility study: towards a robot-assisted gait training in ophthalmological rehabilitation. - In: 2023 International Conference on Rehabilitation Robotics (ICORR), (2023), insges. 6 S.

The idea of using mobile assistance robots for gait training in rehabilitation has been increasingly explored in recent years due to the associated benefits. This paper describes how the previous results of research and praxis on gait training with a mobile assistance robot in orthopedic rehabilitation can be transferred to ophthalmic-related orientation and mobility training for blind and visually impaired people. To this end, the specific requirements for such orientation and mobility training are presented from a therapeutic perspective. Using sensory data, it is investigated how the analysis of training errors can be automated and transferred back to the training person. These pre-examinations are the prerequisite for any form of robot-assisted mobile gait training in ophthamological rehabilitation, which does not exist so far and which is expected to be of great benefit to these patients.



https://doi.org/10.1109/ICORR58425.2023.10304760
Müller, Tristan; Müller, Steffen; Groß, Horst-Michael
Door manipulation as a fundamental skill realized on robots with differential drive. - In: IEEE Xplore digital library, ISSN 2473-2001, (2023), S. 338-345

In the context of assistive mobile service robotics for elderly living in nursing homes, but also for robots realizing autonomous transport in large public buildings in general, a fundamental challenge is to overcome closed doors on their way. We review the state of the art for autonomous door opening by mobile robots and present a modular framework for enabling various robots in this task. The necessary building blocks are introduced, and evaluation results for their application on two different robot platforms are presented. A common property of our platforms, which can be found on many commercial lowcost robots is the use of differential drives. This is limiting the maneuverability and is, therefore, an important constraint for the realization of door manipulation strategies. Furthermore, our method is not dependent on computationally expensive computer vision methods but utilizes the usually available laser-range scanner for localizing and analyzing the door to be manipulated.



https://ieeexplore.ieee.org/document/10363092
Fischedick, Söhnke B.; Richter, Kay; Wengefeld, Tim; Seichter, Daniel; Scheidig, Andrea; Döring, Nicola; Broll, Wolfgang; Werner, Stephan; Raake, Alexander; Groß, Horst-Michael
Bridging distance with a collaborative telepresence robot for older adults - report on progress in the CO-HUMANICS project. - In: IEEE Xplore digital library, ISSN 2473-2001, (2023), S. 346-353

In an aging society, the social needs of older adults, such as regular interactions and independent living, are crucial for their quality of life. However, due to spatial separation from their family and friends, it is difficult to maintain social relationships. Our multidisciplinary project, CO-HUMANICS, aims to meet these needs, even over long distances, through the utilization of innovative technologies, including a robot-based system. This paper presents the first prototype of our system, designed to connect family members or friends virtually present through a mobile robot with an older adult. The system incorporates bi-directional video telephony, remote control capabilities, and enhanced visualization methods. A comparison is made with other state-of-the-art robotic approaches, focusing on remote control capabilities. We provide details about the hard- and software components, e.g., a projector-based pointing unit for collaborative telepresence to assist in everyday tasks. Our comprehensive scene representation is discussed, which utilizes 3D NDT maps, enabling advanced remote navigation features, such as autonomously driving to a specific object. Finally, insights about past and concepts for future evaluation are provided to assess the developed system.



https://ieeexplore.ieee.org/document/10363093
Müller, Steffen; Stephan, Benedict; Müller, Tristan; Groß, Horst-Michael
Robust perception skills for autonomous elevator operation by mobile robots. - In: Proceedings of the 11th European Conference on Mobile Robots, (2023), insges. 7 S.

Autonomous mobile service robots with transportation tasks are often restricted to work on a single floor, since remote access to elevators is expensive to integrate for reasons of safety certification. Therefore, already ten years ago first robots have been enabled to use the human interface for riding an elevator. This requires a variety of perception and manipulation capabilities as well as social skills when it comes to interaction with other people who want to use the elevator too. We summarize the progress in solving the specific tasks of detecting and localizing the required buttons to press robustly. A deep-learning approach for detecting buttons in images is combined with a verification based on predefined knowledge on button arrangements in the elevator's control panels. Also perception of the elevator's state and our realization of the robot's elevator riding capabilities are discussed.



https://doi.org/10.1109/ECMR59166.2023.10256353
Fischedick, Söhnke Benedikt; Seichter, Daniel; Schmidt, Robin; Rabes, Leonard; Groß, Horst-Michael
Efficient multi-task scene analysis with RGB-D transformers. - In: IJCNN 2023 conference proceedings, (2023), insges. 10 S.

Scene analysis is essential for enabling autonomous systems, such as mobile robots, to operate in real-world environments. However, obtaining a comprehensive understanding of the scene requires solving multiple tasks, such as panoptic segmentation, instance orientation estimation, and scene classification. Solving these tasks given limited computing and battery capabilities on mobile platforms is challenging. To address this challenge, we introduce an efficient multi-task scene analysis approach, called EMSAFormer, that uses an RGB-D Transformer-based encoder to simultaneously perform the aforementioned tasks. Our approach builds upon the previously published EMSANet. However, we show that the dual CNN-based encoder of EMSANet can be replaced with a single Transformer-based encoder. To achieve this, we investigate how information from both RGB and depth data can be effectively incorporated in a single encoder. To accelerate inference on robotic hardware, we provide a custom NVIDIA TensorRT extension enabling highly optimization for our EMSAFormer approach. Through extensive experiments on the commonly used indoor datasets NYUv2, SUNRGB-D, and ScanNet, we show that our approach achieves state-of-the-art performance while still enabling inference with up to 39.1 FPS on an NVIDIA Jetson AGX Orin 32 GB.



https://doi.org/10.1109/IJCNN54540.2023.10191977
Aganian, Dustin; Köhler, Mona; Baake, Sebastian; Eisenbach, Markus; Groß, Horst-Michael
How object information improves skeleton-based human action recognition in assembly tasks. - In: IJCNN 2023 conference proceedings, (2023), insges. 9 S.

As the use of collaborative robots (cobots) in industrial manufacturing continues to grow, human action recognition for effective human-robot collaboration becomes increasingly important. This ability is crucial for cobots to act autonomously and assist in assembly tasks. Recently, skeleton-based approaches are often used as they tend to generalize better to different people and environments. However, when processing skeletons alone, information about the objects a human interacts with is lost. Therefore, we present a novel approach of integrating object information into skeleton-based action recognition. We enhance two state-of-the-art methods by treating object centers as further skeleton joints. Our experiments on the assembly dataset IKEA ASM show that our approach improves the performance of these state-of-the-art methods to a large extent when combining skeleton joints with objects predicted by a state-of-the-art instance segmentation model. Our research sheds light on the benefits of combining skeleton joints with object information for human action recognition in assembly tasks. We analyze the effect of the object detector on the combination for action classification and discuss the important factors that must be taken into account.



https://doi.org/10.1109/IJCNN54540.2023.10191686
Aganian, Dustin; Köhler, Mona; Stephan, Benedict; Eisenbach, Markus; Groß, Horst-Michael
Fusing hand and body skeletons for human action recognition in assembly. - In: Artificial Neural Networks and Machine Learning - ICANN 2023, (2023), S. 207-219

As collaborative robots (cobots) continue to gain popularity in industrial manufacturing, effective human-robot collaboration becomes crucial. Cobots should be able to recognize human actions to assist with assembly tasks and act autonomously. To achieve this, skeleton-based approaches are often used due to their ability to generalize across various people and environments. Although body skeleton approaches are widely used for action recognition, they may not be accurate enough for assembly actions where the worker’s fingers and hands play a significant role. To address this limitation, we propose a method in which less detailed body skeletons are combined with highly detailed hand skeletons. We investigate CNNs and transformers, the latter of which are particularly adept at extracting and combining important information from both skeleton types using attention. This paper demonstrates the effectiveness of our proposed approach in enhancing action recognition in assembly scenarios.



https://doi.org/10.1007/978-3-031-44207-0_18
Stephan, Benedict; Köhler, Mona; Müller, Steffen; Zhang, Yan; Groß, Horst-Michael; Notni, Gunther
OHO: a multi-modal, multi-purpose dataset for human-robot object hand-over. - In: Sensors, ISSN 1424-8220, Bd. 23 (2023), 18, 7807, S. 1-13

In the context of collaborative robotics, handing over hand-held objects to a robot is a safety-critical task. Therefore, a robust distinction between human hands and presented objects in image data is essential to avoid contact with robotic grippers. To be able to develop machine learning methods for solving this problem, we created the OHO (Object Hand-Over) dataset of tools and other everyday objects being held by human hands. Our dataset consists of color, depth, and thermal images with the addition of pose and shape information about the objects in a real-world scenario. Although the focus of this paper is on instance segmentation, our dataset also enables training for different tasks such as 3D pose estimation or shape estimation of objects. For the instance segmentation task, we present a pipeline for automated label generation in point clouds, as well as image data. Through baseline experiments, we show that these labels are suitable for training an instance segmentation to distinguish hands from objects on a per-pixel basis. Moreover, we present qualitative results for applying our trained model in a real-world application.



https://doi.org/10.3390/s23187807