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Emperical Interference

Haptic Intelligence

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Perceiving Systems

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Bioinspired Autonomous Miniature Robots

Dynamic Locomotion

Embodied Vision

Human Aspects of Machine Learning

Intelligent Control Systems

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Locomotion in Biorobotic and Somatic Systems

Micro, Nano, and Molecular Systems

Movement Generation and Control

Neural Capture and Synthesis

Physics for Inference and Optimization

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Haptic Intelligence Miscellaneous AiroTouch: Naturalistic Vibrotactile Feedback for Telerobotic Construction-Related Tasks Gong, Y., Tashiro, N., Javot, B., Lauer, A. P. R., Sawodny, O., Kuchenbecker, K. J. Extended abstract (1 page) presented at the ICRA Workshop on Communicating Robot Learning across Human-Robot Interaction, London, UK, May 2023 (Published) BibTeX

Empirical Inference Article Better Together: Data Harmonization and Cross-StudAnalysis of Abdominal MRI Data From UK Biobank and the German National Cohort Gatidis, S., Kart, T., Fischer, M., Winzeck, S., Glocker, B., Bai, W., Bülow, R., Emmel, C., Friedrich, L., Kauczor, H., Keil, T., Kröncke, T., Mayer, P., Niendorf, T., Peters, A., Pischon, T., Schaarschmidt, B., Schmidt, B., Schulze, M., Umutle, L., et al. Investigative Radiology, 58(5):346-354, May 2023 (Published) DOI BibTeX

Autonomous Learning Empirical Inference Conference Paper Bridging the Gap to Real-World Object-Centric Learning Seitzer, M., Horn, M., Zadaianchuk, A., Zietlow, D., Xiao, T., Simon-Gabriel, C., He, T., Zhang, Z., Schölkopf, B., Brox, T., Locatello, F. In Proceedings of the Eleventh International Conference on Learning Representations, The Eleventh International Conference on Learning Representations (ICLR), May 2023 (Published)
Humans naturally decompose their environment into entities at the appropriate level of abstraction to act in the world. Allowing machine learning algorithms to derive this decomposition in an unsupervised way has become an important line of research. However, current methods are restricted to simulated data or require additional information in the form of motion or depth in order to successfully discover objects. In this work, we overcome this limitation by showing that reconstructing features from models trained in a self-supervised manner is a sufficient training signal for object-centric representations to arise in a fully unsupervised way. Our approach, DINOSAUR, significantly out-performs existing object-centric learning models on simulated data and is the first unsupervised object-centric model that scales to real world-datasets such as COCO and PASCAL VOC. DINOSAUR is conceptually simple and shows competitive performance compared to more involved pipelines from the computer vision literature.
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Empirical Inference Conference Paper Disentanglement of Correlated Factors via Hausdorff Factorized Support Roth, K., Ibrahim, M., Akata, Z., Vincent, P., Bouchacourt, D. The Eleventh International Conference on Learning Representations (ICLR), May 2023 (Published) URL BibTeX

Autonomous Learning Conference Paper Efficient Learning of High Level Plans from Play Armengol Urpi, N., Bagatella, M., Hilliges, O., Martius, G., Coros, S. In International Conference on Robotics and Automation, May 2023 (Accepted)
Real-world robotic manipulation tasks remain an elusive challenge, since they involve both fine-grained environment interaction, as well as the ability to plan for long-horizon goals. Although deep reinforcement learning (RL) methods have shown encouraging results when planning end-to-end in high-dimensional environments, they remain fundamentally limited by poor sample efficiency due to inefficient exploration, and by the complexity of credit assignment over long horizons. In this work, we present Efficient Learning of High-Level Plans from Play (ELF-P), a framework for robotic learning that bridges motion planning and deep RL to achieve long-horizon complex manipulation tasks. We leverage task-agnostic play data to learn a discrete behavioral prior over object-centric primitives, modeling their feasibility given the current context. We then design a high-level goal-conditioned policy which (1) uses primitives as building blocks to scaffold complex long-horizon tasks and (2) leverages the behavioral prior to accelerate learning. We demonstrate that ELF-P has significantly better sample efficiency than relevant baselines over multiple realistic manipulation tasks and learns policies that can be easily transferred to physical hardware.
Arxiv Website Poster BibTeX

Empirical Inference Conference Paper Flow Annealed Importance Sampling Bootstrap Midgley*, L. I., Stimper*, V., Simm, G. N. C., Schölkopf, B., Hernádez-Lobato, J. M. The Eleventh International Conference on Learning Representations (ICLR), May 2023, *equal contribution (Published) arXiv URL BibTeX

Empirical Inference Conference Paper Generalizing and Decoupling Neural Collapse via Hyperspherical Uniformity Gap Liu, W., Yu, L., Weller, A., Schölkopf, B. The Eleventh International Conference on Learning Representations (ICLR), May 2023 (Published) URL BibTeX

Empirical Inference Conference Paper How robust is unsupervised representation learning to distribution shift? Shi, Y., Daunhawer, I., Vogt, J. E., Torr, P., Sanyal, A. The Eleventh International Conference on Learning Representations (ICLR), May 2023 (Published) URL BibTeX

Physics for Inference and Optimization Article Hypergraphx: a library for higher-order network analysis Lotito, Q. F., Contisciani, M., De Bacco, C., Di Gaetano, L., Gallo, L., Montresor, A., Musciotto, F., Ruggeri, N., Battiston, F. Journal of Complex Networks, 11, May 2023 (Published) Preprint Code DOI BibTeX

Empirical Inference Conference Paper Identifiability Results for Multimodal Contrastive Learning Daunhawer, I., Bizeul, A., Palumbo, E., Marx, A., Vogt, J. E. The Eleventh International Conference on Learning Representations (ICLR), May 2023 (Published) URL BibTeX

Empirical Inference Conference Paper Investigating the Impact of Action Representations in Policy Gradient Algorithms Schneider, J., Schumacher, P., Häufle, D., Schölkopf, B., Büchler, D. Workshop on effective Representations, Abstractions, and Priors for Robot Learning (RAP4Robots) @ ICRA 2023, May 2023 (Published) arXiv Poster BibTeX

Empirical Inference Ph.D. Thesis Learning with and for discrete optimization Paulus, M. ETH Zurich, Switzerland, May 2023, CLS PhD Program (Published) BibTeX

Perceiving Systems Empirical Inference Conference Paper MeshDiffusion: Score-based Generative 3D Mesh Modeling Liu, Z., Feng, Y., Black, M. J., Nowrouzezahrai, D., Paull, L., Liu, W. The Eleventh International Conference on Learning Representations (ICLR), ICLR, May 2023 (Published)
We consider the task of generating realistic 3D shapes, which is useful for a variety of applications such as automatic scene generation and physical simulation. Compared to other 3D representations like voxels and point clouds, meshes are more desirable in practice, because (1) they enable easy and arbitrary manipulation of shapes for relighting and simulation, and (2) they can fully leverage the power of modern graphics pipelines which are mostly optimized for meshes. Previous scalable methods for generating meshes typically rely on sub-optimal post-processing, and they tend to produce overly-smooth or noisy surfaces without fine-grained geometric details. To overcome these shortcomings, we take advantage of the graph structure of meshes and use a simple yet very effective generative modeling method to generate 3D meshes. Specifically, we represent meshes with deformable tetrahedral grids, and then train a diffusion model on this direct parametrization. We demonstrate the effectiveness of our model on multiple generative tasks.
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Empirical Inference Conference Paper Meta-learning Adaptive Deep Kernel Gaussian Processes for Molecular Property Prediction Chen, W., Tripp, A., Hernández-Lobato, J. M. The Eleventh International Conference on Learning Representations (ICLR), May 2023 (Published) URL BibTeX

Empirical Inference Movement Generation and Control Conference Paper On the Use of Torque Measurement in Centroidal State Estimation Khorshidi, S., Gazar, A., Rotella, N., Naveau, M., Righetti, L., Bennewitz, M., Khadiv, M. IEEE International Conference on Robotics and Automation (ICRA), 9931-9937, May 2023 (Published) DOI BibTeX

Autonomous Learning Conference Paper Pink Noise Is All You Need: Colored Noise Exploration in Deep Reinforcement Learning Eberhard, O., Hollenstein, J., Pinneri, C., Martius, G. In Proceedings of the Eleventh International Conference on Learning Representations (ICLR), The Eleventh International Conference on Learning Representations (ICLR), May 2023
In off-policy deep reinforcement learning with continuous action spaces, exploration is often implemented by injecting action noise into the action selection process. Popular algorithms based on stochastic policies, such as SAC or MPO, inject white noise by sampling actions from uncorrelated Gaussian distributions. In many tasks, however, white noise does not provide sufficient exploration, and temporally correlated noise is used instead. A common choice is Ornstein-Uhlenbeck (OU) noise, which is closely related to Brownian motion (red noise). Both red noise and white noise belong to the broad family of colored noise. In this work, we perform a comprehensive experimental evaluation on MPO and SAC to explore the effectiveness of other colors of noise as action noise. We find that pink noise, which is halfway between white and red noise, significantly outperforms white noise, OU noise, and other alternatives on a wide range of environments. Thus, we recommend it as the default choice for action noise in continuous control.
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Perceiving Systems Ph.D. Thesis Reining in the Deep Generative Models Ghosh, P. University of Tübingen, May 2023 (Published)
This thesis studies controllability of generative models (specifically VAEs and GANs) applied primarily to images. We improve 1. generation quality, by removing the arbitrary prior assumptions, 2. classification by suitably choosing the latent space distribution, and 3. inference performance by optimizing the generative and inference objective simultaneously. Variational autoencoders (VAEs) are an incredibly useful tool as they can be used as a backbone for a variety of machine learning tasks e.g., semi-supervised learning, representation learning, unsupervised learning, etc. However, the generated samples are overly smooth and this limits their practical usage tremendously. There are two leading hypotheses to explain this: 1. bad likelihood model and 2. overly simplistic prior. We investigate these by designing a deterministic yet samplable autoencoder named Regularized Autoencoders (RAE). This redesign helps us enforce arbitrary priors over the latent distribution of a VAE addressing hypothesis (1) above. This leads us to conclude that a poor likelihood model is the predominant factor that makes VAEs blurry. Furthermore, we show that combining generative (e.g., VAE objective) and discriminative objectives (e.g., classification objective) improve performance of both. Specifically, We use a special case of an RAE to build a classifier that offers robustness against adversarial attack. Conditional generative models have the potential to revolutionize the animation industry, among others. However, to do so, the two key requirements are, 1. they must be of high quality (i.e., generate high-resolution images) and 2. must follow their conditioning (i.e., generate images that have the properties specified by the condition). We exploit pixel-localized correlation between the conditioning variable and generated image to ensure strong association between the two and thereby gain precise control over the generated content. We further show that closing the generation-inference loop (training them together) in latent variable models benefits both the generation and the inference component. This opens up the possibility to train an inference and a generative model simultaneously in one unified framework, in the fully or semi supervised setting. With the proposed approach, one can build a robust classifier by introducing the marginal likelihood of a data point, removing arbitrary assumptions about the prior distribution, mitigating posterior-prior distribution mismatch and completing the generation inference loop. In this thesis, we study real-life implications of each of the themes using various image classification and generation frameworks.
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Empirical Inference Article Staying and Returning dynamics of young children’s attention Kim, J., Singh, S., Vales, C., Keebler, E., Fisher, A. V., Thiessen, E. D. Developmental Science, 26(6), May 2023 (Published) DOI BibTeX

Empirical Inference Conference Paper Structure by Architecture: Structured Representations without Regularization Leeb, F., Lanzillotta, G., Annadani, Y., Besserve, M., Bauer, S., Schölkopf, B. The Eleventh International Conference on Learning Representations (ICLR), May 2023 (Published) URL BibTeX

Haptic Intelligence Miscellaneous Surface Perception through Haptic-Auditory Contact Data Khojasteh, B., Shao, Y., Kuchenbecker, K. J. Workshop paper (4 pages) presented at the ICRA Workshop on Embracing Contacts, London, UK, May 2023 (Published)
Sliding a finger or tool along a surface generates rich haptic and auditory contact signals that encode properties crucial for manipulation, such as friction and hardness. To engage in contact-rich manipulation, future robots would benefit from having surface-characterization capabilities similar to humans, but the optimal sensing configuration is not yet known. Thus, we developed a test bed for capturing high-quality measurements as a human touches surfaces with different tools: it includes optical motion capture, a force/torque sensor under the surface sample, high-bandwidth accelerometers on the tool and the fingertip, and a high-fidelity microphone. After recording data from three tool diameters and nine surfaces, we describe a surface-classification pipeline that uses the maximum mean discrepancy (MMD) to compare newly gathered data to each surface in our known library. The results achieved under several pipeline variations are compared, and future investigations are outlined.
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Dynamic Locomotion Article Virtual pivot point in human walking: always experimentally observed but simulations suggest it may not be necessary for stability Schreff, L., Haeufle, D. F. B., Badri-Spröwitz, A., Vielemeyer, J., Müller, R. Journal of Biomechanics, 153, May 2023 (Published)
The intersection of ground reaction forces near a point above the center of mass has been observed in computer simulation models and human walking experiments. Observed so ubiquitously, the intersection point (IP) is commonly assumed to provide postural stability for bipedal walking. In this study, we challenge this assumption by questioning if walking without an IP is possible. Deriving gaits with a neuromuscular reflex model through multi-stage optimization, we found stable walking patterns that show no signs of the IP-typical intersection of ground reaction forces. The non-IP gaits found are stable and successfully rejected step-down perturbations, which indicates that an IP is not necessary for locomotion robustness or postural stability. A collision-based analysis shows that non-IP gaits feature center of mass (CoM) dynamics with vectors of the CoM velocity and ground reaction force increasingly opposing each other, indicating an increased mechanical cost of transport. Although our computer simulation results have yet to be confirmed through experimental studies, they already indicate that the role of the IP in postural stability should be further investigated. Moreover, our observations on the CoM dynamics and gait efficiency suggest that the IP may have an alternative or additional function that should be considered.
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Empirical Inference Conference Paper DCI-ES: An Extended Disentanglement Framework with Connections to Identifiability Eastwood*, C., Nicolicioiu*, A. L., von Kügelgen*, J., Kekić, A., Träuble, F., Dittadi, A., Schölkopf, B. The Eleventh International Conference on Learning Representations (ICLR), May 2023, *equal contribution (Published) URL BibTeX

Haptic Intelligence Miscellaneous OCRA: An Optimization-Based Customizable Retargeting Algorithm for Teleoperation Mohan, M., Kuchenbecker, K. J. Workshop paper (3 pages) presented at the ICRA Workshop Toward Robot Avatars, London, UK, May 2023 (Published)
This paper presents a real-time optimization-based algorithm for mapping motion between two kinematically dissimilar serial linkages, such as a human arm and a robot arm. OCRA can be customized based on the target task to weight end-effector orientation versus the configuration of the central line of the arm, which we call the skeleton. A video-watching study (N=70) demonstrated that when this algorithm considers both the hand orientation and the arm skeleton, it creates robot arm motions that users perceive to be highly similar to those of the human operator, indicating OCRA would be suitable for telerobotics and telepresence through avatars.
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Perceiving Systems Article Fast-SNARF: A Fast Deformer for Articulated Neural Fields Chen, X., Jiang, T., Song, J., Rietmann, M., Geiger, A., Black, M. J., Hilliges, O. IEEE Transactions on Pattern Analysis and Machine Intelligence (PAMI), 1-15, April 2023 (Published)
Neural fields have revolutionized the area of 3D reconstruction and novel view synthesis of rigid scenes. A key challenge in making such methods applicable to articulated objects, such as the human body, is to model the deformation of 3D locations between the rest pose (a canonical space) and the deformed space. We propose a new articulation module for neural fields, Fast-SNARF, which finds accurate correspondences between canonical space and posed space via iterative root finding. Fast-SNARF is a drop-in replacement in functionality to our previous work, SNARF, while significantly improving its computational efficiency. We contribute several algorithmic and implementation improvements over SNARF, yielding a speed-up of 150× . These improvements include voxel-based correspondence search, pre-computing the linear blend skinning function, and an efficient software implementation with CUDA kernels. Fast-SNARF enables efficient and simultaneous optimization of shape and skinning weights given deformed observations without correspondences (e.g. 3D meshes). Because learning of deformation maps is a crucial component in many 3D human avatar methods and since Fast-SNARF provides a computationally efficient solution, we believe that this work represents a significant step towards the practical creation of 3D virtual humans.
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Robotic Materials Patent High Strain Peano Hydraulically Amplified Self-healing Electrostatic (HASEL) Transducers Keplinger, C. M., Wang, X., Mitchell, S. K. (US Patent 11635094), April 2023
High strain hydraulically amplified self-healing electrostatic transducers having increased maximum theoretical and practical strains are disclosed. In particular, the actuators include electrode configurations having a zipping front created by the attraction of the electrodes that is configured orthogonally to a strain axis along which the actuators. This configuration produces increased strains. In turn, various form factors for the actuator configuration are presented including an artificial circular muscle and a strain amplifying pulley system. Other actuator configurations are contemplated that include independent and opposed electrode pairs to create cyclic activation, hybrid electrode configurations, and use of strain limiting layers for controlled deflection of the actuator.
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Empirical Inference Article Uncovering the Organization of Neural Circuits with Generalized Phase Locking Analysis Safavi, S., Panagiotaropoulos, T. I., Kapoor, V., Ramirez-Villegas, J. F., Logothetis, N., Besserve, M. PLOS Computational Biology, 19(4):45, Public Library of Science, April 2023 (Published) bioRxiv DOI BibTeX

Robotic Materials Physical Intelligence Bioinspired Autonomous Miniature Robots Article A Versatile Jellyfish-Like Robotic Platform for Effective Underwater Propulsion and Manipulation Wang, T., Joo, H., Song, S., Hu, W., Keplinger, C., Sitti, M. Science Advances, 9(15), American Association for the Advancement of Science, April 2023, Tianlu Wang and Hyeong-Joon Joo contributed equally to this work. (Published)
Underwater devices are critical for environmental applications. However, existing prototypes typically use bulky, noisy actuators and limited configurations. Consequently, they struggle to ensure noise-free and gentle interactions with underwater species when realizing practical functions. Therefore, we developed a jellyfish-like robotic platform enabled by a synergy of electrohydraulic actuators and a hybrid structure of rigid and soft components. Our 16-cm-diameter noise-free prototype could control the fluid flow to propel while manipulating objects to be kept beneath its body without physical contact, thereby enabling safer interactions. Its against-gravity speed was up to 6.1 cm/s, substantially quicker than other examples in literature, while only requiring a low input power of around 100 mW. Moreover, using the platform, we demonstrated contact-based object manipulation, fluidic mixing, shape adaptation, steering, wireless swimming, and cooperation of two to three robots. This study introduces a versatile jellyfish-like robotic platform with a wide range of functions for diverse applications.
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Empirical Inference Article Adapting to noise distribution shifts in flow-based gravitational-wave inference Wildberger, J., Dax, M., Green, S. R., Gair, J., Pürrer, M., Macke, J. H., Buonanno, A., Schölkopf, B. Physical Review D, 107(8), April 2023 (Published) DOI BibTeX

Empirical Inference Conference Paper BaCaDI: Bayesian Causal Discovery with Unknown Interventions Hägele, A., Rothfuss, J., Lorch, L., Somnath, V. R., Schölkopf, B., Krause, A. Proceedings of the 26th International Conference on Artificial Intelligence and Statistics (AISTATS) , 206:1411-1436, Proceedings of Machine Learning Research, (Editors: Ruiz, Francisco and Dy, Jennifer and van de Meent, Jan-Willem), PMLR, April 2023 (Published) URL BibTeX

Empirical Inference Conference Paper Backtracking Counterfactuals von Kügelgen, J., Mohamed, A., Beckers, S. Proceedings of the Second Conference on Causal Learning and Reasoning (CLeaR), 213:177-196, Proceedings of Machine Learning Research, (Editors: van der Schaar, Mihaela and Zhang, Cheng and Janzing, Dominik), PMLR, April 2023 (Published) URL BibTeX

Empirical Inference Conference Paper Causal Triplet: An Open Challenge for Intervention-centric Causal Representation Learning Liu, Y., Alahi, A., Russell, C., Horn, M., Zietlow, D., Schölkopf, B., Locatello, F. Proceedings of the Second Conference on Causal Learning and Reasoning (CLeaR), 213:553-573, Proceedings of Machine Learning Research, (Editors: van der Schaar, Mihaela and Zhang, Cheng and Janzing, Dominik), PMLR, April 2023 (Published) URL BibTeX

Empirical Inference Conference Paper Dataflow graphs as complete causal graphs Paleyes, A., Guo, S., Schölkopf, B., Lawrence, N. D. 2nd International Conference on AI Engineering - Software Engineering for AI (CAIN), 7-12, IEEE, April 2023 (Published) arXiv DOI BibTeX

Haptic Intelligence Article Effects of Automated Skill Assessment on Robotic Surgery Training Brown, J. D., Kuchenbecker, K. J. The International Journal of Medical Robotics and Computer Assisted Surgery, 19(2):e2492, April 2023 (Published)
Background: Several automated skill-assessment approaches have been proposed for robotic surgery, but their utility is not well understood. This article investigates the effects of one machine-learning-based skill-assessment approach on psychomotor skill development in robotic surgery training. Methods: N=29 trainees (medical students and residents) with no robotic surgery experience performed five trials of inanimate peg transfer with an Intuitive Surgical da Vinci Standard robot. Half of the participants received no post-trial feedback. The other half received automatically calculated scores from five Global Evaluative Assessment of Robotic Skill (GEARS) domains post-trial. Results: There were no significant differences between the groups regarding overall improvement or skill improvement rate. However, participants who received post-trial feedback rated their overall performance improvement significantly lower than participants who did not receive feedback. Conclusions: These findings indicate that automated skill evaluation systems might improve trainee selfawareness but not accelerate early-stage psychomotor skill development in robotic surgery training.
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Haptic Intelligence Article Haptify: A Measurement-Based Benchmarking System for Grounded Force-Feedback Devices Fazlollahi, F., Kuchenbecker, K. J. IEEE Transactions on Robotics, 39(2):1622-1636, April 2023 (Published)
Grounded force-feedback (GFF) devices are an established and diverse class of haptic technology based on robotic arms. However, the number of designs and how they are specified make comparing devices difficult. We thus present Haptify, a benchmarking system that can thoroughly, fairly, and noninvasively evaluate GFF haptic devices. The user holds the instrumented device end-effector and moves it through a series of passive and active experiments. Haptify records the interaction between the hand, device, and ground with a seven-camera optical motion-capture system, a 60-cm-square custom force plate, and a customized sensing end-effector. We demonstrate six key ways to assess GFF device performance: workspace shape, global free-space forces, global free-space vibrations, local dynamic forces and torques, frictionless surface rendering, and stiffness rendering. We then use Haptify to benchmark two commercial haptic devices. With a smaller workspace than the 3D Systems Touch, the more expensive Touch X outputs smaller free-space forces and vibrations, smaller and more predictable dynamic forces and torques, and higher-quality renderings of a frictionless surface and high stiffness.
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Empirical Inference Article Instrumental variable regression via kernel maximum moment loss Zhang, R., Imaizumi, M., Schölkopf, B., Muandet, K. Journal of Causal Inference, 11(1), April 2023 (Published) DOI BibTeX

Empirical Inference Conference Paper Iterative Teaching by Data Hallucination Qiu, Z., Liu, W., Xiao, T., Liu, Z., Bhatt, U., Luo, Y., Weller, A., Schölkopf, B. Proceedings of the 26th International Conference on Artificial Intelligence and Statistics (AISTATS) , 206:9892-9913, Proceedings of Machine Learning Research, (Editors: Ruiz, Francisco and Dy, Jennifer and van de Meent, Jan-Willem), PMLR, April 2023 (Published) URL BibTeX

Empirical Inference Robust Machine Learning Article Jacobian-based Causal Discovery with Nonlinear ICA Reizinger, P., Sharma, Y., Bethge, M., Schölkopf, B., Huszár, F., Brendel, W. Transactions on Machine Learning Research, April 2023 (Published) URL BibTeX

Perceiving Systems Patent Method and systems for labelling motion-captured points J., B. M., Ghorbani, N. (US Patent App.~17/949,087), April 2023 (Published)
Computer-implemented methods are provided for labelling motion-captured points that correspond to markers on an object. The methods include obtaining the motion-captured points, processing a representation of the motion-captured points in a trained self-attention unit to obtain label scores for the motion-captured points, and assigning labels based on the label scores.
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Empirical Inference Article Neural Importance Sampling for Rapid and Reliable Gravitational-Wave Inference Dax, M., Green, S. R., Gair, J., Pürrer, M., Wildberger, J., Macke, J. H., Buonanno, A., Schölkopf, B. Physical Review Letters, 130(17), April 2023 (Published) DOI BibTeX

Empirical Inference Conference Paper Nonparametric Indirect Active Learning Singh, S. Proceedings of the 26th International Conference on Artificial Intelligence and Statistics (AISTATS) , 206:2515-2541, Proceedings of Machine Learning Research, (Editors: Ruiz, Francisco and Dy, Jennifer and van de Meent, Jan-Willem), PMLR, April 2023 (Published) URL BibTeX

Empirical Inference Conference Paper On the Interventional Kullback-Leibler Divergence Wildberger, J. B., Guo, S., Bhattacharyya, A., Schölkopf, B. Proceedings of the Second Conference on Causal Learning and Reasoning (CLeaR), 213:328-349, Proceedings of Machine Learning Research, (Editors: van der Schaar, Mihaela and Zhang, Cheng and Janzing, Dominik), PMLR, April 2023 (Published) URL BibTeX

Empirical Inference Article The ENCODE Imputation Challenge: a critical assessment of methods for cross-cell type imputation of epigenomic profiles Schreiber*, J., Boix*, C., Lee, J. W., Li, H., Guan, Y., Chang, C., Chang, J., Hawkins-Hooker, A., Schölkopf, B., Schweikert, G., Carulla, M. R., Canakoglu, A., Guzzo, F., Nanni, L., Masseroli, M., Carman, M. J., Pinoli, P., Hong, C., Yip, K. Y., Spence, J. P., et al. Genome Biology, 24, April 2023, *co‑first authors (Published) DOI BibTeX

Empirical Inference Conference Paper Unsupervised Object Learning via Common Fate Tangemann, M., Schneider, S., von Kügelgen, J., Locatello, F., Gehler, P., Brox, T., Kümmerer, M., Bethge, M., Schölkopf, B. Proceedings of the Second Conference on Causal Learning and Reasoning (CLeaR), 213:281-327, Proceedings of Machine Learning Research, (Editors: van der Schaar, Mihaela and Zhang, Cheng and Janzing, Dominik), PMLR, April 2023 (Published) arXiv URL BibTeX

Haptic Intelligence Miscellaneous Wearable Biofeedback for Knee Joint Health Rokhmanova, N. Extended abstract (5 pages) presented at the ACM SIGCHI Conference on Human Factors in Computing Systems (CHI) Doctoral Consortium, Hamburg, Germany, April 2023 (Published)
The human body has the tremendous capacity to learn a new way of walking that reduces its risk of musculoskeletal disease progression. Wearable haptic biofeedback has been used to guide gait retraining in patients with knee osteoarthritis, enabling reductions in pain and improvement in function. However, this promising therapy is not yet a part of standard clinical practice. Here, I propose a two-pronged approach to improving the design and deployment of biofeedback for gait retraining. The first section concerns prescription, with the aim of providing clinicians with an interpretable model of gait retraining outcome in order to best guide their treatment decisions. The second section concerns learning, by examining how internal physiological state and external environmental factors influence the process of learning a therapeutic gait. This work aims to address the challenges keeping a highly promising intervention from being widely used to maintain pain-free mobility throughout the lifespan.
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Physical Intelligence Article Hygroscopic Materials Guo, S., De Wolf, S., Sitti, M., Serre, C., Tan, S. C. Advanced Materials, 36(12), Wiley, Weinheim, March 2023 (Published) DOI BibTeX

Dynamic Locomotion Article Muscle prestimulation tunes velocity preflex in simulated perturbed hopping Izzi, F., Mo, A., Schmitt, S., Badri-Spröwitz, A., Häufle, D. Scientific Reports, 13:4559, Nature Publishing Group, March 2023 (Published)
Muscle fibres possess unique visco-elastic properties, which generate a stabilising zero-delay response to unexpected perturbations. This instantaneous response—termed “preflex”—mitigates neuro-transmission delays, which are hazardous during fast locomotion due to the short stance duration. While the elastic contribution to preflexes has been studied extensively, the function of fibre viscosity due to the force–velocity relation remains unknown. In this study, we present a novel approach to isolate and quantify the preflex force produced by the force–velocity relation in musculo-skeletal computer simulations. We used our approach to analyse the muscle response to ground-level perturbations in simulated vertical hopping. Our analysis focused on the preflex-phase—the first 30 ms after impact—where neuronal delays render a controlled response impossible. We found that muscle force at impact and dissipated energy increase with perturbation height, helping reject the perturbations. However, the muscle fibres reject only 15\% of step-down perturbation energy with constant stimulation. An open-loop rising stimulation, observed in locomotion experiments, amplified the regulatory effects of the muscle fibre’s force–velocity relation, resulting in 68\% perturbation energy rejection. We conclude that open-loop neuronal tuning of muscle activity around impact allows for adequate feed-forward tuning of muscle fibre viscous capacity, facilitating energy adjustment to unexpected ground-level perturbations.
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Organizational Leadership and Diversity Article The Organizational Psychology of Gig Work: An Integrative Conceptual Review Cropanzano, R., Keplinger, K., Lambert, B. K., Caza, B., Ashford, S. J. Journal of Applied Psychology, 108(3):492-519, March 2023 (Published) Psychology of Gig Work Psychology of Gig Work DOI BibTeX

Autonomous Vision Article KITTI-360: A Novel Dataset and Benchmarks for Urban Scene Understanding in 2D and 3D Liao, Y., Xie, J., Geiger, A. IEEE Transactions on Pattern Analysis and Machine Intelligence, 45(3):3292-3310, IEEE, March 2023 (Published) DOI BibTeX

Haptic Intelligence Miscellaneous A Lasting Impact: Using Second-Order Dynamics to Customize the Continuous Emotional Expression of a Social Robot Burns, R. B., Kuchenbecker, K. J. Workshop paper (5 pages) presented at the HRI Workshop on Lifelong Learning and Personalization in Long-Term Human-Robot Interaction (LEAP-HRI), Stockholm, Sweden, March 2023 (Published)
Robots are increasingly being developed as assistants for household, education, therapy, and care settings. Such robots need social skills to interact warmly and effectively with their users, as well as adaptive behavior to maintain user interest. While complex emotion models exist for chat bots and virtual agents, autonomous physical robots often lack a dynamic internal affective state, instead displaying brief, fixed emotion routines to promote or discourage specific user actions. We address this need by creating a mathematical emotion model that can easily be implemented in a social robot to enable it to react intelligently to external stimuli. The robot's affective state is modeled as a second-order dynamic system analogous to a mass connected to ground by a parallel spring and damper. The present position of this imaginary mass shows the robot's valence, which we visualize as the height of its displayed smile (positive) or frown (negative). Associating positive and negative stimuli with appropriately oriented and sized force pulses applied to the mass enables the robot to respond to social touch and other inputs with a valence that evolves over a longer timescale, capturing essential features of approach-avoidance theory. By adjusting the parameters of this emotion model, one can modify three main aspects of the robot's personality, which we term disposition, stoicism, and calmness.
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