Sensor fault-tolerant state estimation by networks of distributed observers

We propose a state estimation methodology using a network of distributed observers. We consider a scenario in which the local measurement at each node may not guarantee the system’s observability. In contrast, the ensemble of all the measurements does ensure that the observability property holds. As a result, we design a network of observers such that the estimated state vector computed by each observer converges to the system’s state vector by using the local measurement and the communicated estimates of a subset of observers in its neighborhood. The proposed estimation scheme exploits sensor redundancy to provide robustness against faults in the sensors. Under suitable conditions on the redundant sensors, we show that it is possible to mitigate the effects of a class of sensor faults on the state estimation. Simulation trials demonstrate the effectiveness of the proposed distributed estimation scheme

Switching-based Sinusoidal Disturbance Rejection for Uncertain Stable Linear Systems

The problem of rejection of sinusoidal disturbances with known frequencies acting on an unknown singleinput single-output linear system is addressed in this note. We present a new approach that does not require knowledge of the frequency response of the transfer function over the frequency of interest. The proposed methodology reposes upon the combination of the classic feedforward control algorithm and logic-based switching. The use of three different switching logics is proposed in this paper, namely: pre-routed, dwell-time and hysteresis switching. A comparative evaluation of the three switching strategies is performed via a simulation study

Providing incentives to encourage a control program of hooded crows (Corvus corone cornix L., 1758): a case study in Rieti province (Italy), 2005-10

Amici, A., Adriani, S., Bonanni, M., Serrani, F

Influence of stochastic estimation on the control of subsonic cavity flow – A preliminary study

This work aims at understanding how the different elements involved in the feedback loop influence the overall control performance of a subsonic cavity flow based on reducedorder modeling. To this aim we compare preliminary and limited sets of experimental results obtained by modifying some relevant characteristics of the loop. Our results support the findings in the literature that use of quadratic stochastic estimation is preferable to the linear one for real-time update of the model parameters. They also seem to indicate the merit of using more than one time sample of the pressure for performing the real-time update of the model through stochastic estimation. The effect of using two different sets of pressure signals for the stochastic estimation also corroborates previous findings indicating the need for optimizing the number and the placement of the sensors used in the feedback control loop. Finally we observed that the characteristics of the actuator can alter significantly the overall control effect by introducing in the feedback loop additional, undesirable frequency components that are not modeled and hence controlled. A compensator for the actuator is currently being designed that will alleviate this problem thus enabling a clearer understanding of the overall control technique

Efectos estructurales de la política energética en la economía argentina, 1989-2014.

El objetivo de este artículo es describir las políticas energéticas desarrolladas desde las reformas neoliberales hasta 2014, para determinar los impactos estructurales que dichas políticas tuvieron sobre la economía argentina. La metodología utilizada consistió en utilizar fuentes secundarias, tales como legislación oficial y estadísticas públicas, y en la reconstrucción de la voz de los principales actores involucrados, con declaraciones en medios gráficos. Asimismo, se desplegaron técnicas cuantitativas para confirmar la relación entre las principales variables. El trabajo muestra cómo desde las reformas neoliberales de la década de 1990 se impulsó una dinámica del sector que fue desacoplando la oferta y la demanda energética. Como respuesta, el gobierno nacional promovió las importaciones para zanjar tal brecha, situación que finalmente impactó en la macroeconomía, acelerando el déficit fiscal, profundizando el quiebre del balance de pagos y agudizando la restricción externa, situación que más que una crisis energética terminaría ocasionando una crisis del modelo energético

Assessing the feasibility of augmenting fall detection systems by relying on UWB-based position tracking and a home robot

Falls in the home environment are a primary cause of injury in older adults. According to the U.S. Centers for Disease Control and Prevention, every year, one in four adults 65 years of age and older reports experiencing a fall. A variety of different technologies have been proposed to detect fall events. However, the need to detect all fall instances (i.e., to avoid false negatives) has led to the development of systems marked by high sensitivity and hence a significant number of false alarms. The occurrence of false alarms causes frequent and unnecessary calls to emergency response centers, which are critical resources that should be utilized only when necessary. Besides, false alarms decrease the level of confidence of end-users in the fall detection system with a negative impact on their compliance with using the system (e.g., wearing the sensor enabling the detection of fall events). Herein, we present a novel approach aimed to augment traditional fall detection systems that rely on wearable sensors and fall detection algorithms. The proposed approach utilizes a UWB-based tracking system and a home robot. When the fall detection system generates an alarm, the alarm is relayed to a base station that utilizes a UWB-based tracking system to identify where the older adult and the robot are so as to enable navigating the environment using the robot and reaching the older adult to check if he/she experienced a fall. This approach prevents unnecessary calls to emergency response centers while enabling a tele-presence using the robot when appropriate. In this paper, we report the results of a novel fall detection algorithm, the characteristics of the alarm notification system, and the accuracy of the UWB-based tracking system that we implemented. The fall detection algorithm displayed a sensitivity of 99.0% and a specificity of 97.8%. The alarm notification system relayed all simulated alarm notification instances with a maximum delay of 106 ms. The UWB-based tracking system was found to be suitable to locate radio tags both in line-of-sight and in no-line-of-sight conditions. This result was obtained by using a machine learning-based algorithm that we developed to detect and compensate for the multipath effect in no-line-of-sight conditions. When using this algorithm, the error affecting the estimated position of the radio tags was smaller than 0.2 m, which is satisfactory for the application at hand

Role of land set-up systems on soil (Physicochemical) conditions

Land reclamation and drainage networks represent one of the most ancient human modifications of the Italian soilscape, where tailored land set-up systems were developed in agro-and forest-ecosystems in three millennia of man’s activity. Most of once manually maintained land settings are currently scarcely working or even disappeared because of the cost needed for their mainte-nance and the advent of mechanization that have simplified the field organization. The scarce attention to the soil experienced in the last decades, has accelerated soil erosion and flooding events, which entailed high costs in terms of money and human lives, but also caused reduction of soil thickness, water holding capacity, and fertility. In view of a sustainable agriculture, it is mandatory to assess the role of land set-up systems, which for centuries have been key in protecting soil from erosion, but also in increasing soil fertility. Such an effort cannot be made without considering the different pedo-climatic conditions and land uses of the Italian ter-ritory, which is different with respect to the past because of the multiple transformations made to favour the mechanization of agriculture. In this review we discuss the main effect of Italian land settings on the soilscape and on soil physicochemical condi-tions. Since land settings were developed centuries ago, detailed information about their effect on specific soil parameters is scarce in the scientific literature; thus, in some case, we provide information gathered in places where land set-up systems are still present. mm

Feedback control design for subsonic cavity flows

A benchmark problem in active aerodynamic flow control, suppression of strong pressure oscillations induced by flow over a shallow cavity, is addressed in this paper. Proper orthogonal decomposition and Galerkin projection techniques are used to obtain a reduced-order model of the flow dynamics from experimental data. The model is made amenable to control design by means of a control separation technique, which makes the control input appear explicitly in the equations. A prediction model based on quadratic stochastic estimation correlates flow field data with surface pressure measurements, so that the latter can be used to reconstruct the state of the model in real time. The focus of this paper is on the controller design and implementation. A linear-quadratic optimal controller is designed on the basis of the reduced-order model to suppress the cavity flow resonance. To account for the limitation on the magnitude of the control signal imposed by the actuator, the control action is modified by a scaling factor, which plays the role of a bifurcation parameter for the closed-loop system. Experimental results, in qualitative agreement with the theoretical analysis, show that the controller achieves a significant attenuation of the resonant tone with a redistribution of the energy into other frequencies, and exhibits a certain degree of robustness when operating in off-design conditions

Experimental results and bifurcation analysis on scaled feedback control for subsonic cavity flows

In this paper, we present the latest results of our ongoing research activities in the development of reduced-order models based feedback control of subsonic cavity flows. The model was developed using the Proper Orthogonal Decomposition of Particle Image Velocimetry images in conjunction with the Galerkin projection of the Navier-Stokes equations onto the resulting spatial eigenfunctions. Stochastic Estimation method was used to obtain the state estimation of the Galerkin system from real time surface pressure measurements. A linear-quadratic optimal controller was designed to reduce cavity flow resonance and tested in the experiments. Real-time implementation shows a significant reduction of the sound pressure level within the cavity, with a remarkable attenuation of the resonant tone and a redistribution of the energy into various modes with lower energy levels. A mathematical analysis of the performance of the LQ control, in agreement with the experimental results, is presented and discussed