A semidefinite relaxation procedure for fault-tolerant observer design

A fault-tolerant observer design methodology is proposed. The aim is to guarantee a minimum level of closed-loop performance under all possible sensor fault combinations while optimizing performance under the nominal, fault-free condition. A novel approach is proposed to tackle the combinatorial nature of the problem, which is computationally intractable even for a moderate number of sensors, by recasting the problem as a robust performance problem, where the uncertainty set is composed of all combinations of a set of binary variables. A procedure based on an elimination lemma and an extension of a semidefinite relaxation procedure for binary variables is then used to derive sufficient conditions (necessary and sufficient in the case of one binary variable) for the solution of the problem which significantly reduces the number of matrix inequalities needed to solve the problem. The procedure is illustrated by considering a fault-tolerant observer switching scheme in which the observer outputs track the actual sensor fault condition. A numerical example from an electric power application is presented to illustrate the effectiveness of the design

Relay synchronization in multiplex networks

Relay (or remote) synchronization between two not directly connected oscillators in a network is an important feature allowing distant coordination. In this work, we report a systematic study of this phenomenon in multiplex networks, where inter-layer synchronization occurs between distant layers mediated by a relay layer that acts as a transmitter. We show that this transmission can be extended to higher order relay configurations, provided symmetry conditions are preserved. By first order perturbative analysis, we identify the dynamical and topological dependencies of relay synchronization in a multiplex. We find that the relay synchronization threshold is considerably reduced in a multiplex configuration, and that such synchronous state is mostly supported by the lower degree nodes of the outer layers, while hubs can be de-multiplexed without affecting overall coherence. Finally, we experimentally validated the analytical and numerical findings by means of a multiplex of three layers of electronic circuits.the analytical and numerical findings by means of a multiplex of three layers of electronic circuits

Unión de péptidos a superficies de titanio para la mejora de la osteointegración

El presente estudio pretende mejorar el proceso de osteointegración del implante de titanio mediante la biofuncionalización de su superficie. Para ello se ha realizado una previa silanización de la superficie y una posterior unión covalente entre el silano y un péptido el cual posee la secuencia RGD. Se han estudiado diferentes aspectos como es la estabilidad tanto de conjunto titanio-silano como silano-péptido. Finalmente se ha realizado un ensayo de adhesión celular utilizando células osteoblásticas MG63 cuyas muestras de titanio han sido previamente biofuncionalizadas con el proceso estudiado.This study aims to improve the osseointegration process of the titanium implant through surface biofunctionalization. Samples were silanised on the surface and afterwards a peptide with the RGD sequence was covalently attached to the silane. Specific characteristics of the stability of the union titanium-silane as well as silane-peptide were studied. Finally cell adhesion studies to samples biofunctionalized with the technique studied in this work were made with MG63 osteoblastic cells.Peer Reviewe

Fault-tolerant Wide-area Control for Power Oscillation Damping

The effectiveness of using both local and remote (wide-area) feedback signals for power oscillation damping (POD) controllers is first demonstrated. The challenge is then to guarantee a minimum level of dynamic performance with only the local signals following a sudden loss of remote signals. A case study on the Nordic equivalent system is presented to show that the closed-loop response could deteriorate if the remote signals are lost. A fault-tolerant control (FTC) design methodology is presented to solve this problem and ensure an acceptable performance level even in case of loss of remote signals. The FTC design methodology is based on simultaneous regional pole-placement for normal and loss of (remote) signals conditions. First the problem is solved non-iteratively using a Linear Matrix Inequality (LMI) approximation and then it is shown that, although this procedure is linear and easy to implement, it has a drawback: the value of one of the control matrices is fixed before calculating the others. An iterative procedure is presented instead to ameliorate this problem and potentially improve the damping of the system. Case studies on the Nordic equivalent system confirm that the proposed iterative fault tolerant controller (FTCit) is able to improve performance against the non-iterative fault tolerant controller (FTC) and produce acceptable performance in case of loss of the remote signals while the response with a CC is unacceptable if a fault occurs

Anodización del titanio para la mejora ante la degradación química de material quirúrgico

The titanium alloys used in orthopaedic and dental implants are corrosion-resistant and compatible with the human body due to the titanium oxid film which forms spontaneously on the implant surface. However, the utilization of more than one type of alloy or metal on the same patient and the fragility and the thin thickness of the oxid layer, can give rise to the appearance of the corossion phenomena and/or ion release. It is well known that enough concentration of metallic particles are toxic, and are able to produce lnflammation, allergy genetic mutations or carcinogenic processes. With the purpose of minimize the corrossion in the implants and the metallic ion release to the physiological environment it is possible to grow up the titanium oxid layer in a controlled way to have a tough, homogeneous and stable layer with the anodization technique. In this work it is evaluated the improvements in corrosion resistance and the decrease of the metallic ion release due to the anodized layer

Anodización del titanio para la mejora ante la degración química de material quirúrgico.

The titanium alloys used in orthopaedic and dental implants are corrosion-resistant and compatible with the human body due to the titanium oxid film which forms spontaneously on the implant surface. However, the utilization of more than one type of alloy or metal on the same patient and the fragility and the thin thickness of the oxid layer, can give rise to the appearance of the corossion phenomena and/or ion release. It is well known that enough concentration of metallic particles are toxic, and are able to produce lnflammation, allergy genetic mutations or carcinogenic processes. With the purpose of minimize the corrossion in the implants and the metallic ion release to the physiological environment it is possible to grow up the titanium oxid layer in a controlled way to have a tough, homogeneous and stable layer with the anodization technique. In this work it is evaluated the improvements in corrosion resistance and the decrease of the metallic ion release due to the anodized layer