Analog implementation of a robust control strategy for mechanical systems

An analog implementation of a control structure with disturbance identification for mechanical systems is presented. This control structure is based on a discontinuous observer that estimates the state and the disturbances in the plant, improving the robustness of the closed loop system which also displays a control input free from chattering. The control structure, built with operational amplifiers, is simple, showing good performance for stabilization, regulation, and tracking objectives. The performance of the circuit is compared with a digital implementation based on a real-time data acquisition card to control a simple pendulum. In addition, the circuit performance is illustrated on an industrial 2-DOF robot

In-phase and anti-phase synchronization of oscillators with Huygens' coupling

In this experimental study, the synchronized motion observed in pairs of nonlinear oscillators coupled through a suspended rigid bar, is analyzed. In particular, the dynamics of two mass-spring-damper oscillators and the dynamics of two van der Pol oscillators are considered. It is shown that in both cases, the oscillators may exhibit in-phase and anti-phase synchronization. The experiments are executed in an experimental setup, consisting of two mass-spring-damperoscillators coupled through a suspended rigid bar. A relation between the obtained results and Huygens’ experiment of pendulum clocks is emphasized

Synchronization of weakly nonlinear oscillators with Huygens' coupling

In this paper, the occurrence of synchronization in pairs of weakly nonlinear selfsustained oscillators that interact via Huygens’ coupling, i.e. a suspended rigid bar, is treated. In the analysis, a generalized version of the classical Huygens’ experiment of synchronization of two coupled pendulum clocks is considered, in which the clocks are replaced by arbitrary self-sustained oscillators. Sufficient conditions for the existence and stability of synchronous solutions in the coupled system are derived by using the Poincar´e method. The obtained results are supported by computer simulations and experiments conducted on a dedicated experimental platform. It is demonstrated that the mass of the coupling bar is an important parameter with respect to the limit synchronous behaviour in the oscillators

Filtering Approaches for Dealing with Noise in Anomaly Detection

The leading workhorse of anomaly (and attack) detection in the literature has been residual-based detectors, where the residual is the discrepancy between the observed output provided by the sensors (inclusive of any tampering along the way) and the estimated output provided by an observer. These techniques calculate some statistic of the residual and apply a threshold to determine whether or not to raise an alarm. To date, these methods have not leveraged the frequency content of the residual signal in making the detection problem easier, specifically dealing with the case of (e.g., measurement) noise. Here we demonstrate some opportunities to combine filtering to enhance the performance of residual-based detectors. We also demonstrate how filtering can provide a compelling alternative to residual-based methods when paired with a robust observer. In this process, we consider the class of attacks that are stealthy, or undetectable, by such filtered detection methods and the impact they can have on the system

VVV High Proper Motion Survey

Here we present survey of proper motion stars towards the Galactic Bulge and an adjacent plane region base on VISTA-VVV data. The searching method based on cross-matching photometric Ks-band CASU catalogs. The most interesting discoveries are shown.Peer reviewe

Measurement driven quantum evolution

We study the problem of mapping an unknown mixed quantum state onto a known pure state without the use of unitary transformations. This is achieved with the help of sequential measurements of two non-commuting observables only. We show that the overall success probability is maximized in the case of measuring two observables whose eigenstates define mutually unbiased bases. We find that for this optimal case the success probability quickly converges to unity as the number of measurement processes increases and that it is almost independent of the initial state. In particular, we show that to guarantee a success probability close to one the number of consecutive measurements must be larger than the dimension of the Hilbert space. We connect these results to quantum copying, quantum deleting and entanglement generation.Comment: 7 pages, 1 figur

Memory Engram Cells Have Come of Age

The idea that memory is stored in the brain as physical alterations goes back at least as far as Plato, but further conceptualization of this idea had to wait until the 20th century when two guiding theories were presented: the “engram theory” of Richard Semon and Donald Hebb’s “synaptic plasticity theory.” While a large number of studies have been conducted since, each supporting some aspect of each of these theories, until recently integrative evidence for the existence of engram cells and circuits as defined by the theories was lacking. In the past few years, the combination of transgenics, optogenetics, and other technologies has allowed neuroscientists to begin identifying memory engram cells by detecting specific populations of cells activated during specific learning epochs and by engineering them not only to evoke recall of the original memory, but also to alter the content of the memory.RIKEN Brain Science InstituteHoward Hughes Medical InstituteJPB Foundatio

Parametric and machine learning-based analysis of the seismic vulnerability of adobe historical buildings damaged after the September 2017 Mexico earthquakes

In September 2017, two strong earthquakes hit the central region of Mexico, producing substantial damage to the historical buildings. A retroactive analysis for assessing the pre-event seismic vulnerability of these constructions allowed for testing the suitability of an existing parameter-based approach based on material and geometrical features. More than 160 adobe buildings in four municipalities of the State of Morelos were surveyed and included in a vulnerability-oriented GIS database. Data were collected on-site and managed by resorting to open-source GIS software combined with a Python-based database management tool and a cloud-based platform for onsite data collection using mobile devices. The parameter-based approach was used for assessing the analytical seismic vulnerability of the buildings and implementing a secondary, more conservative assessment that considers uncertainties associated with the data acquisition process. The capabilities of the database were further used to train a Machine Learning algorithm aimed at overcoming some representativeness limitations of the parameter-based analytical method. This third approach was found to be suitable for assessing the vulnerability of the building typologies addressed in this investigation. Although the implementation discussed in this paper is limited to a specific vernacular typology, it can be used to conduct customized local calibrations.- This work was partly financed by FCT/MCTES through national funds (PIDDAC) under the R & D Unit Institute for Sustainability and Innovation in Structural Engineering (ISISE), under reference UIDB/04029/2020. This research was funded by the Portuguese Foundation for Science and Technology (FCT) through grant number PD/BD/150385/2019. The field campaigns in the State of Morelos were financed by the Instituto de Ingenieria - Universidad Nacional Autonoma de Mexico (Institute of Engineering - National Autonomous University of Mexico) through the project R562