Combining series elastic actuation and magneto-rheological damping for the control of agile locomotion

All-terrain robot locomotion is an active topic of research. Search and rescue maneuvers and exploratory missions could benefit from robots with the abilities of real animals. However, technological barriers exist to ultimately achieving the actuation system, which is able to meet the exigent requirements of these robots. This paper describes the locomotioncontrol of a leg prototype, designed and developed to make a quadruped walk dynamically while exhibiting compliant interaction with the environment. The actuation system of the leg is based on the hybrid use of series elasticity and magneto-rheological dampers, which provide variable compliance for natural-looking motion and improved interaction with the ground. The locomotioncontrol architecture has been proposed to exploit natural leg dynamics in order to improve energy efficiency. Results show that the controller achieves a significant reduction in energy consumption during the leg swing phase thanks to the exploitation of inherent leg dynamics. Added to this, experiments with the real leg prototype show that the combined use of series elasticity and magneto-rheologicaldamping at the knee provide a 20 % reduction in the energy wasted in braking the knee during its extension in the leg stance phase

Exploiting the Internet Resources for Autonomous Robots in Agriculture

Autonomous robots in the agri-food sector are increasing yearly, promoting the application of precision agriculture techniques. The same applies to online services and techniques implemented over the Internet, such as the Internet of Things (IoT) and cloud computing, which make big data, edge computing, and digital twins technologies possible. Developers of autonomous vehicles understand that autonomous robots for agriculture must take advantage of these techniques on the Internet to strengthen their usability. This integration can be achieved using different strategies, but existing tools can facilitate integration by providing benefits for developers and users. This study presents an architecture to integrate the different components of an autonomous robot that provides access to the cloud, taking advantage of the services provided regarding data storage, scalability, accessibility, data sharing, and data analytics. In addition, the study reveals the advantages of integrating new technologies into autonomous robots that can bring significant benefits to farmers. The architecture is based on the Robot Operating System (ROS), a collection of software applications for communication among subsystems, and FIWARE (Future Internet WARE), a framework of open-source components that accelerates the development of intelligent solutions. To validate and assess the proposed architecture, this study focuses on a specific example of an innovative weeding application with laser technology in agriculture. The robot controller is distributed into the robot hardware, which provides real-time functions, and the cloud, which provides access to online resources. Analyzing the resulting characteristics, such as transfer speed, latency, response and processing time, and response status based on requests, enabled positive assessment of the use of ROS and FIWARE for integrating autonomous robots and the Internet

The SOPHIE search for northern extrasolar planets. V. Follow-up of ELODIE candidates: Jupiter-analogs around Sun-like stars

We present radial-velocity measurements obtained in a programs underway to search for extrasolar planets with the spectrograph SOPHIE at the 1.93-m telescope of the Haute-Provence Observatory. Targets were selected from catalogs observed with ELODIE, mounted previously at the telescope, in order to detect long-period planets with an extended database close to 15 years. Two new Jupiter-analog candidates are reported to orbit the bright stars HD150706 and HD222155 in 16.1 and 10.9 yr at 6.7 (+4.0,-1.4) and 5.1(+0.6,-0.7) AU and to have minimum masses of 2.71 (+1.44,-0.66) and 1.90 (+0.67,-0.53) M_Jup, respectively. Using the measurements from ELODIE and SOPHIE, we refine the parameters of the long-period planets HD154345b and HD89307b, and publish the first reliable orbit for HD24040b. This last companion has a minimum mass of 4.01 +/- 0.49 M_Jup orbiting its star in 10.0 yr at 4.92 +/- 0.38 AU. Moreover, the data provide evidence of a third bound object in the HD24040 system. With a surrounding dust debris disk, HD150706 is an active G0 dwarf for which we partially corrected the effect of the stellar spot on the SOPHIE radial-velocities. HD222155 is an inactive G2V star. On the basis of the previous findings of Lovis and collaborators and since no significant correlation between the radial-velocity variations and the activity index are found in the SOPHIE data, these variations are not expected to be only due to stellar magnetic cycles. Finally, we discuss the main properties of this new population of long-period Jupiter-mass planets, which for the moment, consists of fewer than 20 candidates. These stars are preferential targets either for direct-imaging or astrometry follow-up to constrain the system parameters and for higher precision radial-velocity to search for lower mass planets, aiming to find a Solar System twin.Comment: accepted for publication in Astronomy & Astrophysic

Little change in the sizes of the most massive galaxies since z = 1

Recent reports suggest that elliptical galaxies have increased their size dramatically over the last ~8 Gyr. This result points to a major re-think of the processes dominating the latetime evolution of galaxies. In this paper we present the first estimates for the scale sizes of brightest cluster galaxies (BCGs) in the redshift range 0.8 < z < 1.3 from an analysis of deep Hubble Space Telescope imaging, comparing to a well matched local sample taken from the Local Cluster Substructure Survey at z ~ 0.2. For a small sample of 5 high redshift BCGs we measure half-light radii ranging from 14 - 53 kpc using de Vaucuoleurs profile fits, with an average determined from stacking of 32.1 \pm 2.5 kpc compared to a value 43.2 \pm 1.0 kpc for the low redshift comparison sample. This implies that the scale sizes of BCGs at z = 1 are ~ 30% smaller than at z = 0.25. Analyses comparing either Sersic or Petrosian radii also indicate little or no evolution between the two samples. The detection of only modest evolution at most out to z = 1 argues against BCGs having undergone the large increase in size reported for massive galaxies since z = 2 and in fact the scale-size evolution of BCGs appears closer to that reported for radio galaxies over a similar epoch. We conclude that this lack of size evolution, particularly when coupled with recent results on the lack of BCG stellar mass evolution, demonstrates that major merging is not an important process in the late time evolution of these systems. The homogeneity and maturity of BCGs at z = 1 continues to challenge galaxy evolution models.Comment: Accepted for publication in MNRA

Survey for Transiting Extrasolar Planets in Stellar Systems. II. Spectrophotometry and Metallicities of Open Clusters

We present metallicity estimates for seven open clusters based on spectrophotometric indices from moderate-resolution spectroscopy. Observations of field giants of known metallicity provide a correlation between the spectroscopic indices and the metallicity of open cluster giants. We use \chi^2 analysis to fit the relation of spectrophotometric indices to metallicity in field giants. The resulting function allows an estimate of the target-cluster giants' metallicities with an error in the method of \pm0.08 dex. We derive the following metallicities for the seven open clusters: NGC 1245, [m/H]=-0.14\pm0.04; NGC 2099, [m/H]=+0.05\pm0.05; NGC 2324, [m/H]=-0.06\pm0.04; NGC 2539, [m/H]=-0.04\pm0.03; NGC 2682 (M67), [m/H]=-0.05\pm0.02; NGC 6705, [m/H]=+0.14\pm0.08; NGC 6819, [m/H]=-0.07\pm0.12. These metallicity estimates will be useful in planning future extra-solar planet transit searches since planets may form more readily in metal-rich environments.Comment: 38 pages, including 12 figures. Accepted for publication in A