Dimensionality reduction for probabilistic movement primitives

Humans as well as humanoid robots can use a large number of degrees of freedom to solve very complex motor tasks. The high-dimensionality of these motor tasks adds difficulties to the control problem and machine learning algorithms. However, it is well known that the intrinsic dimensionality of many human movements is small in comparison to the number of employed DoFs, and hence, the movements can be represented by a small number of synergies encoding the couplings between DoFs. In this paper, we want to apply Dimensionality Reduction (DR) to a recent movement representation used in robotics, called Probabilistic Movement Primitives (ProMP). While ProMP have been shown to have many benefits, they suffer with the high-dimensionality of a robotic system as the number of parameters of a ProMP scales quadratically with the dimensionality. We use probablistic dimensionality reduction techniques based on expectation maximization to extract the unknown synergies from a given set of demonstrations. The ProMP representation is now estimated in the low-dimensional space of the synergies. We show that our dimensionality reduction is more efficient both for encoding a trajectory from data and for applying Reinforcement Learning with Relative Entropy Policy Search (REPS)

Uncertainty in near-surface wind speed trends at seasonal time scales

Observational studies have identified wind speed trends in the last decades [1,2] attributed to several factors such as changes in the land use, aerosol emissions or atmospheric circulation. However, in spite of the potential impact of this long-term variability in wind energy activities, this type of variability has not been fully characterized yet. As a consequence such information is not currently incorporated in wind power decision-making processes related to planning and management. long-term wind speed variability. For some of these users it is still difficult to identify the most suitable dataset for their specific needs, because a comparison of the quality of the wind speed data from different reanalyses at global scale is not readily available. For this reason, the present study investigates the wind speed long-term trends at global scale in the last decades (1981-2015) using three state-of-the-art reanalyses: ERA-Interim (ERA-I), the Japanese 55-year Reanalysis (JRA-55) and Modern Era Retrospective-Analysis for Research and Applications (MERRA-2)

User evaluation of an interactive learning framework for single-arm and dual-arm robots

The final publication is available at link.springer.comSocial robots are expected to adapt to their users and, like their human counterparts, learn from the interaction. In our previous work, we proposed an interactive learning framework that enables a user to intervene and modify a segment of the robot arm trajectory. The framework uses gesture teleoperation and reinforcement learning to learn new motions. In the current work, we compared the user experience with the proposed framework implemented on the single-arm and dual-arm Barrett’s 7-DOF WAM robots equipped with a Microsoft Kinect camera for user tracking and gesture recognition. User performance and workload were measured in a series of trials with two groups of 6 participants using two robot settings in different order for counterbalancing. The experimental results showed that, for the same task, users required less time and produced shorter robot trajectories with the single-arm robot than with the dual-arm robot. The results also showed that the users who performed the task with the single-arm robot first experienced considerably less workload in performing the task with the dual-arm robot while achieving a higher task success rate in a shorter time.Peer ReviewedPostprint (author's final draft

Comparison of ultrasound-guided versus blind interventions for supraspinatus tendinopathy : A cadaveric study

Background. The treatment of supraspinatus tendinopathy remains a challenge for the health professional. This study aims to analyze the precision of needle interventions in lesions of the supraspinatus tendon when conducting them in an ultrasound-guided or non-ultrasound guided (blind) manner. Methods. Study on cadaver with infiltrations performed under ultrasound control or blind after randomization of the parts and participants. Twenty fresh cadaveric shoulders and 30 practitioners with experience using musculoskeletal ultrasound and doing needle interventions. Each practitioner performed 4 ultrasound-guided and 4 unguided punctures. This provided 240 punctures that were analyzed in 3 different anatomical cuts, thus providing a database of 720 measurements for statistical analysis. Results. Statistically significant differences were observed (p<0.0001) in the distance to the bullet point between the ultrasound-guided and the non-guided infiltrations. It was estimated that the unguided punctures were performed on average 10mm farther from the bullet point than the 'ultrasound-guided' punctures. The ultrasound-guided punctures demonstrated 95% precision while the unguided punctures had a precision rate of 12.5% (p <0.0001). Conclusion. Interventions of the supraspinatus tendon should be performed in an ultrasound-guided manner to facilitate administration of the treatment in the proper area

Estructura cristalina y molecular de la dihidrazida malonica anhidra

[ES] En este trabajo se presenta la estructura cristalina y molecular de la hidracida malónica anhidra. La estructura cristalina ha sido resuelta por difracción de Rayos X. Las dimensiones de la celda elemental son: a = 6.986Å, b0 = 4.828Å, c0 = 17.619Å, β = 93.490, V = 593.19Å y su grupo espacial es el P21/c, Z = 4.[EN] In this paper, the crystal and molecular structure of the nalonic dihydrazide has been solved by means of the X-Ray difraction and the direct methods. The unit cell dimensions are: a = 6.986Å, b0 = 4.828Å, c0 = 17.619Å, β = 93.490, V = 593.19Å y su grupo espacial es el P21/c, Z = 4.Peer reviewe

Cepas del género Penicillium aisladas en Cataluña

En el presente trabajo intentamos la clasificación de 133 cepas pertenecientes a 37 especies del género Penicillium Link, aisladas en Cataluña, así como la descripción macro y microscópica de todas ellas para su posible inclusión en un índice de la flora micológica de nuestro país

Characterization of acoustic diffusion using refracto-vibrometry

Refracto-vibrometry is a relatively new measurement technique that is sensitive to variations in the optical refractive index of a medium caused by changes in acoustic pressure within that medium (the acousto-optic effect). It has so far been employed primarily as a qualitative visualization tool for airborne sound propagation because determining sound pressure level at a point using the technique is difficult and inefficient. Instead, the authors propose that this optical technique is well suited for determining dimensionless quantities, such as coefficients describing scattering uniformity from a surface. A new measurement and analysis process relying on refracto-vibrometry has been developed and used to determine acoustic diffusion coefficients through purely optical means for the first time. A quadratic residue diffuser is used as an arbitrary test surface, and refracto-vibrometry measurements of its polar response have been performed and results compared to a boundary element model. The benefits and limitations of the optical method over the traditional microphone-based approach are discussed