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Morphological Neural Computation Restores Discrimination of Naturalistic Textures in Trans-radial Amputees

Authors: Alberto Mazzoni, Calogero M. Oddo, Giacomo Valle, Domenico Camboni, Ivo Strauss, Massimo Barbaro, Gianluca Barabino, Roberto Puddu, Caterina Carboni, Lorenzo Bisoni, Jacopo Carpaneto, Fabrizio Vecchio, Francesco M. Petrini, Simone Romeni, Tamas Czimmermann, Luca Massari, Riccardo di Iorio, Francesca Miraglia, Giuseppe Granata, Danilo Pani, Thomas Stieglitz, Luigi Raffo, Paolo M. Rossini & Silvestro Micera

 

Abstract

Humans rely on their sense of touch to interact with the environment. Thus, restoring lost tactile sensory capabilities in amputees would advance their quality of life. In particular, texture discrimination is an important component for the interaction with the environment, but its restoration in amputees has been so far limited to simplified gratings. Here we show that naturalistic textures can be discriminated by trans-radial amputees using intraneural peripheral stimulation and tactile sensors located close to the outer layer of the artificial skin. These sensors exploit the morphological neural computation (MNC) approach, i.e., the embodiment of neural computational functions into the physical structure of the device, encoding normal and shear stress to guarantee a faithful neural temporal representation of stimulus spatial structure. Two trans-radial amputees successfully discriminated naturalistic textures via the MNC-based tactile feedback. The results also allowed to shed light on the relevance of spike temporal encoding in the mechanisms used to discriminate naturalistic textures. Our findings pave the way to the development of more natural bionic limbs.

Reference

  • Published in:Scientific Reports (Volume 10, Article number: 527, 2020)
  • DOI: 10.1038/s41598-020-57454-4 yy
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  • Date: 2020
Posted on: January 21, 2020

On the Redundancy Detection in Keyframe-based SLAM

Authors: Schmuck, Patrik; Chli, Margarita

 

Abstract

Egomotion and scene estimation is a key component in automating robot navigation, as well as in virtual reality applications for mobile phones or head-mounted displays. It is well known, however, that with long exploratory trajectories and multi-session mapping for long-term autonomy or collaborative applications, the maintenance of the ever-increasing size of these maps quickly becomes a bottleneck. With the explosion of data resulting in increasing runtime of the optimization algorithms ensuring the accuracy of the Simultaneous Localization And Mapping (SLAM) estimates, the large quantity of collected experiences is imposing hard limits on the scalability of such techniques. Considering the keyframe-based paradigm of SLAM techniques, this paper investigates the redundancy inherent in SLAM maps, by quantifying the information of different experiences of the scene as encoded in keyframes. Here we propose and evaluate different information-theoretic and heuristic metrics to remove dispensable scene measurements with minimal impact on the accuracy of the SLAM estimates. Evaluating the proposed metrics in two state-of-the-art centralized collaborative SLAM systems, we provide our key insights into how to identify redundancy in keyframe-based SLAM.

Reference

  • Published in: 2019 International Conference on 3D Vision (3DV)
  • DOI: 10.1109/3DV.2019.00071
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  • Date: 2019
Posted on: January 16, 2020

Events-to-Video: Bringing Modern Computer Vision to Event Cameras

  • Authors: Rebecq, Henri; Ranftl, René; Koltun, Vladlen; Scaramuzza, Davide

Event cameras are novel sensors that report brightness changes in the form of asynchronous “events” instead of intensity frames. They have significant advantages over conventional cameras: high temporal resolution, high dynamic range, and no motion blur. Since the output of event cameras is fundamentally different from conventional cam-eras, it is commonly accepted that they require …

Posted on: November 12, 2019

Sensory feedback restoration in leg amputees improves walking speed, metabolic cost and phantom pain

Authors: Petrini, Francesco Maria; Bumbasirevic, Marko; Valle, Giacomo; Ilic, Vladimir; Mijović, Pavle; Čvančara, Paul, Barberi, Federica; Katic, Natalija; Bortolotti, Dario; Andreu, David; Lechler, Knut; Lesic, Aleksandar; Mazic, Sanja; Mijović, Bogdan, Guiraud, David; Stieglitz, Thomas; Alexandersson, Asgeir; Micera, Silvestro; Raspopovic, Stanisa

 

Conventional leg prostheses do not convey sensory information about motion or interaction with the ground to above-knee amputees, thereby reducing confidence and walking speed in the users that is associated with high mental and physical fatigue. The lack of physiological feedback from the remaining extremity to the brain also contributes to the generation of phantom limb pain from the missing leg. To determine whether neural sensory feedback restoration addresses these issues, we conducted a study with two transfemoral amputees, implanted with four intraneural stimulation electrodes in the remaining tibial nerve (ClinicalTrials.gov identifier NCT03350061). Participants were evaluated while using a neuroprosthetic device consisting of a prosthetic leg equipped with foot and knee sensors. These sensors drive neural stimulation, which elicits sensations of knee motion and the sole of the foot touching the ground. We found that walking speed and self-reported confidence increased while mental and physical fatigue decreased for both participants during neural sensory feedback compared to the no stimulation trials. Furthermore, participants exhibited reduced phantom limb pain with neural sensory feedback. The results from these proof-of-concept cases provide the rationale for larger population studies investigating the clinical utility of neuroprostheses that restore sensory feedback.

Reference

Posted on: November 7, 2019

Biomechanical effects of passive hip springs during walking

Authors: Haufe, Florian L; Wolf, Peter; Riener, Robert; Grimmer, Martin

 

Passive spring-like structures can store and return energy during cyclic movements and thereby reduce the energetic cost of locomotion. That makes them important components of the human body and wearable assistive devices alike. This study investigates how springs placed anteriorly across the hip joint affect leg joint angles and powers, and leg muscle activities during level walking at 0.5 to 2.1 m/s.

We hypothesized that the anterior hip springs (I) load hip extension, (II) support hip flexion and (III) affect ankle muscle activity and dynamics during walking. Effects at the ankle were expected because hip and ankle redistribute segmental power in concert to achieve forward progression.

We observed that the participants’ contribution to hip power did not increase during hip extension as the spring stored energy. Simultaneously, the activities of plantarflexor muscles that modulate energy storage in the Achilles tendon were reduced by 28% (gastrocnemius medialis) and 9% (soleus). As the spring returned energy with the onset of hip flexion, the participants’ contribution to hip power was reduced by as much as 23%. Soleus activity before push-off increased by up to 9%.

Instead of loading hip extension, anterior hip springs seem to store and return parts of the energy normally exchanged with the Achilles tendon. Thereby, the springs support hip flexion but may reduce elastic energy storage in and hence recoil from the Achilles tendon. This interaction should be considered during the design and simulation of wearable assistive devices as it might – depending on user characteristics – enhance or diminish their overall functionality.

Reference

Posted on: November 7, 2019

An Omnidirectional Aerial Manipulation Platform for Contact-Based Inspection

Authors: Bodie, Karen; Brunner, Maximilian; Pantic, Michael; Walser, Stefan; Pfändler, Patrick; Angst, Ueli; Siegwart, Roland; Nieto, Juan

This paper presents an omnidirectional aerial manipulation platform for robust and responsive interaction with unstructured environments, toward the goal of contact-based inspection. The fully actuated tilt-rotor aerial system is equipped with a rigidly mounted end-effector, and is able to exert a 6 degree of freedom force and torque, decoupling the system’s translational and rotational dynamics, and enabling precise interaction with the environment while maintaining stability. An impedance controller with selective apparent inertia is formulated to permit compliance in certain degrees of freedom while achieving precise trajectory tracking and disturbance rejection in others. Experiments demonstrate disturbance rejection, push-and-slide interaction, and on- board state estimation with depth servoing to interact with local surfaces. The system is also validated as a tool for contact-based non-destructive testing of concrete infrastructure.

Reference

  • Detailed record: arXiv
  • DOI:
  • Date: 2019
Posted on: October 22, 2019

Multiple Hypothesis Semantic Mapping for Robust Data Association

Authors: Bernreiter, Lukas; Gawel, Abel; Sommer, Hannes; Nieto, Juan; Siegwart, Roland; Cadena Lerma, Cesar

In this letter, we present a semantic mapping approach with multiple hypothesis tracking for data association. As semantic information has the potential to overcome ambiguity in measurements and place recognition, it forms an eminent modality for autonomous systems. This is particularly evident in urban scenarios with several similar-looking surroundings. Nevertheless, it requires the handling of a non-Gaussian and discrete random variable coming from object detectors. Previous methods facilitate semantic information for global localization and data association to reduce the instance ambiguity between the landmarks. However, many of these approaches do not deal with the creation of completely globally consistent representations of the environment and typically do not scale well. We utilize multiple hypothesis trees to derive a probabilistic data association for semantic measurements by means of position, instance, and class to create a semantic representation. We propose an optimized mapping method and make use of a pose graph to derive a novel semantic SLAM solution. Furthermore, we show that semantic covisibility graphs allow for a precise place recognition in urban environments. We verify our approach using real-world outdoor dataset and demonstrate an average drift reduction of 33% w.r.t. the raw odometry source. Moreover, our approach produces 55% less hypotheses on average than a regular multiple hypothesis approach.

Reference

Posted on: October 22, 2019

CVI-SLAM—Collaborative Visual-Inertial SLAM

Authors: Karrer, Marco; Schmuck, Patrik; Chli, Margarita

With robotic perception constituting the biggest impediment before robots are ready for employment in real missions, the promise of more efficient and robust robotic perception in multiagent, collaborative missions can have a great impact on many robotic applications. Employing an ubiquitous and well-established visual-inertial setup onboard each agent, in this letter, we propose CVI-SLAM, a novel visual-inertial framework for centralized collaborative simultaneous localization and mapping (SLAM). Sharing all information with a central server, each agent outsources computationally expensive tasks, such as global map optimization to relieve onboard resources and passes on measurements to other participating agents, while running visual-inertial odometry onboard to ensure autonomy throughout the mission. Thoroughly analyzing CVI-SLAM, we attest to its accuracy and the improvements arising from the collaboration, and evaluate its scalability in the number of participating agents and applicability in terms of network requirements.

Reference

Posted on: October 22, 2019

Cortico–reticulo–spinal circuit reorganization enables functional recovery after severe spinal cord contusion

Authors: Asboth, Leonie; Friedli, Lucia; Beauparlant, Janine; Martinez-Gonzalez, Cristina; Anil, Selin; Rey, Elodie; Baud, Laetitia; Pidpruzhnykova, Galyna; Anderson, Mark A.; Shkorbatova, Polina; Batti, Laura; Pagès, Stephane; Kreider, Julie; Schneider, Bernard L.; Barraud, Quentin; Courtine, Grégoire

Severe spinal cord contusions interrupt nearly all brain projections to lumbar circuits producing leg movement. Failure of these projections to reorganize leads to permanent paralysis. Here we modeled these injuries in rodents. A severe contusion abolished all motor cortex projections below injury. However, the motor cortex immediately regained adaptive control over the paralyzed legs during electrochemical neuromodulation of lumbar circuits. Glutamatergic reticulospinal neurons with residual projections below the injury relayed the cortical command downstream. Gravity-assisted rehabilitation enabled by the neuromodulation therapy reinforced these reticulospinal projections, rerouting cortical information through this pathway. This circuit reorganization mediated a motor cortex–dependent recovery of natural walking and swimming without requiring neuromodulation. Cortico–reticulo–spinal circuit reorganization may also improve recovery in humans.

Reference

Posted on: October 22, 2019

Vision-based Control of a Quadrotor in User Proximity: Mediated vs End-to-End Learning Approaches

Authors:  Mantegazza, Dario; Guzzi, Jérôme, Gambardella, Luca M.; Giusti, Alessandro

We consider the task of controlling a quadrotor to hover in front of a freely moving user, using input data from an onboard camera. On this specific task we compare two widespread learning paradigms: a mediated approach, which learns an high-level state from the input and then uses it for deriving control signals; and an end-to-end approach, which skips high-level state estimation altogether. We show that despite their fundamental difference, both approaches yield equivalent performance on this task. We finally qualitatively analyze the behavior of a quadrotor implementing such approaches.

Reference

  • Detailed record: arXiv
  • DOI: 
  • Date: 2019
Posted on: October 21, 2019