Fractional order modelling of contact with the environment in flexible robot applications

[Abstract] The control of flexible robots that interact with the environment presents some difficulties because the mechanical environment is unknown. In this kind of applications, force robust control rather than position control is required. The purpose of this paper is to model the mechanical impedance of the environment contacted by a flexible link based on the well-known spring-damper system typically used in the literature, considering models of both integer and fractional order. In particular, four models are identified: 1) linear regression model, 2) spring-damper model, 3) spring-damper model that also includes a spring for the robotic arm, and 4) fractional order extension of spring-damper model. Experimental results (impacts with ten different objects) are given to identify the parameters of the considered models. The goodness of the adjustment is analyzed by a set of performance indices. The results show that fractional models may have better performance in comparison with classical alternatives proposed in the literature for the objects used in this study.[Resumen] El control de robots flexibles que interactúan con el entorno presenta algunas dificultades porque se desconoce el entorno mecánico. En este tipo de aplicaciones, se requiere un control robusto en lugar de un control de posición. El propósito de este trabajo es modelar la impedancia mecánica del entorno contactado por un enlace flexible basado en el conocido sistema de amortiguador de resortes que se usa típicamente en la literatura, considerando modelos de orden entero y fraccional. En particular, se identifican cuatro modelos: 1) modelo de regresión lineal, 2) modelo de amortiguador de resorte, 3) modelo de amortiguador de resorte que también incluye un resorte para el brazo robótico, y 4) extensión de orden fraccional del modelo de amortiguador de resorte. Se dan resultados experimentales (impactos con diez objetos diferentes) para identificar los parámetros de los modelos considerados. La bondad del ajuste se analiza mediante un conjunto de índices de rendimiento. Los resultados muestran que los modelos fraccionarios pueden tener un mejor rendimiento en comparación con las alternativas clásicas propuestas en la literatura para los objetos utilizados en este estudio.Ministerio de Economía y Competitividad; DPI2016-80547-

Study in COMSOL of the generation of traveling waves in an AEF robot by piezoelectric actuation

[Abstract] This paper presents a study of motion of an artificial eukaryotic flagellum (AEF) microrobot in COMSOL Multiphysics®. The microrobot is essentially a body, consisting of an aluminum beam structure with two piezoelectric patches bonded on its surface. It requires the same voltage with different frequencies or phases be applied to each piezoelectric or use one of the piezoelectrics as absorber in order to generate a traveling wave on the body. Different types of actuation are simulated to demonstrate that a non-reciprocal motion can be obtained with this kind of configuration.[Abstract] Este artículo presenta un estudio del movimiento de un microrobot de eukaryotic flagellum (AEF) en COMSOL Multiphysics®. El microrobot es esencialmente un cuerpo, que consiste en una estructura de vigas de aluminio con dos parches piezoeléctricos adheridos en su superficie. Requiere que se aplique la misma tensión con diferentes frecuencias o fases a cada piezoeléctrico o use uno de los piezoeléctricos como absorbente para generar una onda viajera en el cuerpo. Se simulan diferentes tipos de actuación para demostrar que se puede obtener un movimiento no recíproco con este tipo de configuración.Ministerio de Economía y Competitividad; DPI2016-80547-

Robots nadadores tipo flagelo bacteriano de pequeñas dimensiones: desarrollo de prototipos y plataformas de prueba

[Resumen] Este artículo presenta las primeras experiencias de nuestro equipo de investigación en el desarrollo de robots nadadores tipo flagelo helicoidal de pequeñas dimensiones (de unos pocos centímetros) capaces de navegar en un fluido en condiciones de bajo número de Reynolds. Se presentan dos prototipos de robots que difieren entre sí principalmente en la forma de actuación: robot nadador con actuación magnética externa, cuyo desplazamiento es posible gracias a un imán permanente en rotación, y robot nadador autopropulsado, mediante un motor de pequeñas dimensiones. Se describen tanto los prototipos desarrollados como las plataformas de prueba asociadas, así como los primeros experimentos realizados. El principal objetivo es demostrar que la actuación de los robots funciona, mientras que la propulsión de los mismos es una cuestión más delicada que requiere de una profundización e investigación mayor.Junta de Extremadura; GR15178https://doi.org/10.17979/spudc.978849749808

Frequency response of IPMC actuators: physical characterization and identification for control

[Abstract] Ionic polymer metal composite (IPMC) actuators have promising applications in robotics and medicine in a not distance future, which will require a big knowledge in different fields, such as, manufacturing, material characterization and control theory. In this paper, frequency response of several IPMC actuators, cut from the same bulk IPMC sheet with a micro laser etching machine, is analyzed. Specifically, the objective is to 1) characterize each actuator, i.e., determine how cutting affects to the parameters of the physical model of this kind of actuators, and 2) identify a model for each actuator for control purposes. The frequency responses have been obtained experimentally in LabVIEW by attaching a couple of gold electrodes to each IPMC unit and measuring the tip deection by means of a laser distance meter.[Resumen] Los actuadores de compuesto de polímero metálico iónico (IPMC) tienen aplicaciones prometedoras en robótica y medicina en un futuro no lejano, lo que requerirá un gran conocimiento en diferentes campos, como la fabricación, la caracterización de materiales y la teoría de control. En este documento, se analiza la respuesta de frecuencia de varios actuadores IPMC, cortados de la misma hoja de IPMC a granel con una máquina de grabado por láser micro. Específicamente, el objetivo es 1) caracterizar cada actuador, es decir, determinar cómo afecta el corte a los parámetros del modelo físico de este tipo de actuadores, y 2) identificar un modelo para cada actuador con fines de control. Las respuestas de frecuencia se han obtenido experimentalmente en LabVIEW al conectar un par de electrodos de oro a cada unidad IPMC y medir la división de la punta por medio de un medidor de distancia láser.Ministerio de Economía y Competitividad; DPI2016-80547-

The transiting multi-planet system HD3167: a 5.7 MEarth Super-Earth and a 8.3 MEarth mini-Neptune

HD3167 is a bright (V=8.9 mag) K0V star observed by the NASA's K2 space mission during its Campaign 8. It has been recently found to host two small transiting planets, namely, HD3167b, an ultra short period (0.96 d) super-Earth, and HD3167c, a mini-Neptune on a relatively long-period orbit (29.85 d). Here we present an intensive radial velocity follow-up of HD3167 performed with the FIES@NOT, [email protected], and HARPS-N@TNG spectrographs. We revise the system parameters and determine radii, masses, and densities of the two transiting planets by combining the K2 photometry with our spectroscopic data. With a mass of 5.69+/-0.44 MEarth, radius of 1.574+/-0.054 REarth, and mean density of 8.00(+1.0)(-0.98) g/cm^3, HD3167b joins the small group of ultra-short period planets known to have a rocky terrestrial composition. HD3167c has a mass of 8.33 (+1.79)(-1.85) MEarth and a radius of 2.740(+0.106)(-0.100) REarth, yielding a mean density of 2.21(+0.56)(-0.53) g/cm^3, indicative of a planet with a composition comprising a solid core surrounded by a thick atmospheric envelope. The rather large pressure scale height (about 350 km) and the brightness of the host star make HD3167c an ideal target for atmospheric characterization via transmission spectroscopy across a broad range of wavelengths. We found evidence of additional signals in the radial velocity measurements but the currently available data set does not allow us to draw any firm conclusion on the origin of the observed variation.Comment: 18 pages, 11 figures, 5 table

A new group of Palaeolithic painted hands from the southern Iberian Peninsula. Las Estrellas cave (Castellar de la Frontera, Cádiz)

This work presents a review of the rock art conserved at a site located in the autonomous community of Andalusia, known in the preceding literature as the Las Estrellas cave (Castellar de la Frontera, Cádiz). This is a large open-air rocky shelter, in which various schematic style pictographs were found, in the early years of this century. During a recent visit to the site, the existence of an important Palaeolithic figurative set was also noted, which includes representations of fauna and a small series of outlines of hands. This article deals with the generic analysis of the art catalogued in the cave up to the present moment, paying special attention to the set of the aforementioned Palaeolithic handprints, which have been documented using digital 3d technology. Similarly, its contextualization in Andalusian Palaeolithic art will be taken into account and a first chronological approximation of this interesting and varied figurative system will be made.Presentamos en este trabajo la revisión de las manifestaciones de arte rupestre conservadas en una estación localizada en la comunidad autónoma de Andalucía, conocida en la literatura precedente como cueva de Las Estrellas (Castellar de la Frontera, Cádiz). Se trata de un abrigo rocoso de grandes dimensiones, abierto al aire libre, en el que ya se había constatado, en los primeros años del presente siglo, la presencia de diversas pictografías de estilo esquemático. Durante una visita reciente al enclave se ha advertido, además, la existencia de un importante conjunto figurativo de cronología paleolítica que incluye representaciones de fauna y una pequeña serie de improntas de manos en negativo. Este artículo aborda el análisis genérico de las grafías catalogadas hasta el momento en la cavidad, atendiendo con especial detalle al conjunto de las citadas huellas de manos paleolíticas, que han sido documentadas usando tecnología digital 3d. De igual modo, se tendrán en cuenta su contextualización en el arte paleolítico andaluz y una primera aproximación cronológica a este interesante y variado complejo figurativo

The Multiplanet System TOI-421: A Warm Neptune and a Super Puffy Mini-Neptune Transiting a G9 V Star in a Visual Binary

We report the discovery of a warm Neptune and a hot sub-Neptune transiting TOI-421 (BD-14 1137, TIC 94986319), a bright (V = 9.9) G9 dwarf star in a visual binary system observed by the Transiting Exoplanet Survey Satellite (TESS) space mission in Sectors 5 and 6. We performed ground-based follow-up observations—comprised of Las Cumbres Observatory Global Telescope transit photometry, NIRC2 adaptive optics imaging, and FIbre-fed Echellé Spectrograph, CORALIE, High Accuracy Radial velocity Planet Searcher, High Resolution Échelle Spectrometer, and Planet Finder Spectrograph high-precision Doppler measurements—and confirmed the planetary nature of the 16 day transiting candidate announced by the TESS team. We discovered an additional radial velocity signal with a period of five days induced by the presence of a second planet in the system, which we also found to transit its host star. We found that the inner mini-Neptune, TOI-421 b, has an orbital period of P_b = 5.19672 ± 0.00049 days, a mass of M_b = 7.17 ± 0.66 M⊕, and a radius of R_b = 2.68^(+0.19)_(-0.18) R⊕, whereas the outer warm Neptune, TOI-421 c, has a period of Pc = 16.06819 ± 0.00035 days, a mass of M_c = 16.42^(+1.06)_(-1.04) M⊕, a radius of R_c = 5.09^(+0.16)_(-0.15) R⊕ and a density of ρ_c = 0.685^(+0.080)_(-0.072) g cm⁻³. With its characteristics, the outer planet (ρ_c = 0.685^(+0.080)_(-0.072) g cm⁻³) is placed in the intriguing class of the super-puffy mini-Neptunes. TOI-421 b and TOI-421 c are found to be well-suited for atmospheric characterization. Our atmospheric simulations predict significant Lyα transit absorption, due to strong hydrogen escape in both planets, as well as the presence of detectable CH4 in the atmosphere of TOI-421 c if equilibrium chemistry is assumed

SuperCam Calibration Targets: Design and Development

SuperCam is a highly integrated remote-sensing instrumental suite for NASA’s Mars 2020 mission. It consists of a co-aligned combination of Laser-Induced Breakdown Spectroscopy (LIBS), Time-Resolved Raman and Luminescence (TRR/L), Visible and Infrared Spectroscopy (VISIR), together with sound recording (MIC) and high-magnification imaging techniques (RMI). They provide information on the mineralogy, geochemistry and mineral context around the Perseverance Rover. The calibration of this complex suite is a major challenge. Not only does each technique require its own standards or references, their combination also introduces new requirements to obtain optimal scientific output. Elemental composition, molecular vibrational features, fluorescence, morphology and texture provide a full picture of the sample with spectral information that needs to be co-aligned, correlated, and individually calibrated. The resulting hardware includes different kinds of targets, each one covering different needs of the instrument. Standards for imaging calibration, geological samples for mineral identification and chemometric calculations or spectral references to calibrate and evaluate the health of the instrument, are all included in the SuperCam Calibration Target (SCCT). The system also includes a specifically designed assembly in which the samples are mounted. This hardware allows the targets to survive the harsh environmental conditions of the launch, cruise, landing and operation on Mars during the whole mission. Here we summarize the design, development, integration, verification and functional testing of the SCCT. This work includes some key results obtained to verify the scientific outcome of the SuperCam system