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Johannes Meyer

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4 papers

1 author row

IROS Conference 2020 Conference Paper

Improving Unimodal Object Recognition with Multimodal Contrastive Learning

Johannes Meyer
Andreas Eitel
Thomas Brox
Wolfram Burgard

Robots perceive their environment using various sensor modalities, e. g. , vision, depth, sound or touch. Each modality provides complementary information for perception. However, while it can be assumed that all modalities are available for training, when deploying the robot in real-world scenarios the sensor setup often varies. In order to gain flexibility with respect to the deployed sensor setup we propose a new multimodal approach within the framework of contrastive learning. In particular, we consider the case of learning from RGB-D images while testing with one modality available, i. e. , exclusively RGB or depth. We leverage contrastive learning to capture high-level information between different modalities in a compact feature embedding. We extensively evaluate our multimodal contrastive learning method on the Falling Things dataset and learn representations that outperform prior methods for RGB-D object recognition on the NYU-D dataset. Our code and details on the used datasets are available at: https://github.com/meyerjo/MultiModalContrastiveLearning.

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IROS Conference 2020 Conference Paper

Modality-Buffet for Real-Time Object Detection

Nicolai Dorka
Johannes Meyer
Wolfram Burgard

Real-time object detection in videos using lightweight hardware is a crucial component of many robotic tasks. Detectors using different modalities and with varying computational complexities offer different trade-offs. One option is to have a very lightweight model that can predict from all modalities at once for each frame. However, in some situations (e. g. , in static scenes) it might be better to have a more complex but more accurate model and to extrapolate from previous predictions for the frames coming in at processing time. We formulate this task as a sequential decision making problem and use reinforcement learning (RL) to generate a policy that decides from the RGB input which detector out of a portfolio of different object detectors to take for the next prediction. The objective of the RL agent is to maximize the accuracy of the predictions per image. We evaluate the approach on the Waymo Open Dataset and show that it exceeds the performance of each single detector.

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ICRA Conference 2014 Conference Paper

Online marker labeling for fully automatic skeleton tracking in optical motion capture

Johannes Meyer
Markus Kuderer
Jörg Müller 0004
Wolfram Burgard

Methods to accurately capture the motion of humans in motion capture systems from optical markers are important for a large variety of applications including animation, interaction, orthopedics, and rehabilitation. Major challenges in this context are to associate the observed markers with skeleton segments, to track markers between consecutive frames, and to estimate the underlying skeleton configuration for each frame. Existing solutions to this problem often assume fully labeled markers, which usually requires labor-intensive manual labeling, especially when markers are temporally occluded during the movements. In this paper, we propose a fully automated method to initialize and track the skeleton configuration of humans from optical motion capture data without the need of any user intervention. Our method applies a flexible T-pose-based initialization that works with a wide range of marker placements, robustly estimates the skeleton configuration through least-squares optimization, and exploits the skeleton structure for fully automatic marker labeling. We demonstrate the capabilities of our approach for online skeleton tracking and show that our method outperforms solutions that are widely used and considered as state of the art.

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IROS Conference 2010 Conference Paper

Vision based victim detection from unmanned aerial vehicles

Mykhaylo Andriluka
Paul Schnitzspan
Johannes Meyer
Stefan Kohlbrecher
Karen Petersen
Oskar von Stryk
Stefan Roth 0001
Bernt Schiele

Finding injured humans is one of the primary goals of any search and rescue operation. The aim of this paper is to address the task of automatically finding people lying on the ground in images taken from the on-board camera of an unmanned aerial vehicle (UAV). In this paper we evaluate various state-of-the-art visual people detection methods in the context of vision based victim detection from an UAV. The top performing approaches in this comparison are those that rely on flexible part-based representations and discriminatively trained part detectors. We discuss their strengths and weaknesses and demonstrate that by combining multiple models we can increase the reliability of the system. We also demonstrate that the detection performance can be substantially improved by integrating the height and pitch information provided by on-board sensors. Jointly these improvements allow us to significantly boost the detection performance over the current de-facto standard, which provides a substantial step towards making autonomous victim detection for UAVs practical.

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