Actuator fault reconstruction using FDI system based on sliding mode observers

Interplanetary space missions require spacecraft autonomy in order to fulfill the mission objective. The fault detection and isolation (FDI) system increases the level of autonomy and can ensure the safety of the spacecraft by detecting and isolating potential faults before they become critical. The proposed FDI system is based on an innovative bank of SMOs (sliding mode observers), designed for different fault scenarios cases. The FDI system design aims to detect and isolate actuators and measurement units’ faults used by the satellite control system and considers the nonlinear model of the satellite dynamics. This approach gives the possibility of fault reconstruction based on the information provided by an equivalent injection signal, allowing to reconstruct external perturbances and faults. The SMO chattering phenomenon is avoided by using the pseudo-sliding function, being a linear approximation of the signum function, which gives the possibility of using the equivalent injection signal for fault reconstruction purposes. The proposed fault reconstruction methodology is illustrated by a case study for a 6U Cubesat

Mixed H

The purpose of the present paper is to provide a performance analysis approach of networked systems with fading communication channels. For a Ricean model of the fading communication channel, it is shown that the resulting system has a hybrid structure including the continuous-time dynamics of the networked systems and a discrete-time dynamics of the communication channels. Moreover, this resulting hybrid system has both multiplicative and additive noise terms. The performance analysis naturally leads to an H2/H∞-type norm evaluation for systems with finite jumps and multiplicative noise. It is proved that this norm depends on the stabilizing solution of a specific system of coupled Riccati's equations with jumps. A state-feedback design problem to accomplish a mixed H2/H∞ performance is also considered. A numerical iterative procedure allowing to compute the stabilizing solution of the Riccati-type system with jumps is presented. The theoretical results are illustrated by numerical results concerning the tracking performances of a flight formation with fading communication channel. The paper ends with some concluding remarks

El libre acceso a la justicia a principios del siglo XXI

Free access to justice represents the procedural principle with universal value and at this moment we can say that it is the foundation of the organization of any democratic judicial system. Consecrated for the first time in the content of art. 8 of the Universal Declaration of Human Rights, this principle was later included in the content of all international or union acts, or in national constitutions that promote democratic principles and promote people”s fundamental rights and freedoms. Moreover, the principle of the access to justice paved the way for the consolidation of judicial guarantees, being one of the most important guarantees that the state must offer to any parson who addresses the justice system. Therefore, free access to justice has an intersting developement in almost all judicial system of states that respect democratic values. In this sense, the present study aims to highlight, on the one hand, the ECtHR”s perceprion of this principle and, on the other hand, the impact of the digititalization of judicial procedures on free access to justice.El libre acceso a la justicia representa el principio procesal con valor universal y en este momento podemos decir que es el fundamento de la organización de todo sistema judicial democrático. Consagrada por primera vez en el contenido del art. 8 de la Declaración Universal de los Derechos Humanos, este principio fue posteriormente incluido en el contenido de todos los actos internacionales o comunitarios, o en las constituciones nacionales que promueven los principios democráticos y promueven los derechos y libertades fundamentales de las personas. Por otra parte, el principio de libre acceso a la justicia abrió el camino para la consolidación de las garantías judiciales, siendo una de las garantías más importantes que el Estado debe ofrecer a cualquier persona que se dirija al sistema de justicia. Por tanto, el libre acceso a la justicia tiene un desarrollo interesante en casi todos los sistemas judiciales de los estados que respetan los valores democráticos. En este sentido, el presente estudio pretende evidenciar, por un lado, la percepción del TEDH sobre este principio y, por otro, el impacto de la digitalización de los procedimientos judiciales en el libre acceso a la justicia

Satellites FDI system design using sliding mode observers

This paper presents a fault detection and isolation system for the satellites attitude control. The fault detection and isolation system is based on an innovative bank of sliding mode observers, designed taking into account the satellite nonlinear dynamics. The observers are based on the sliding mode control theory, thus being robust to parametric uncertainties and bounded disturbances. A pseudo-sliding law is used to avoid the chattering effect and to reconstruct disturbances and faults based on equivalent injection signal. The bank of observers contains a total of seven sliding mode observers designed for different working scenarios. The first sliding mode observer is called the global observer and it is used to detect the fault appearance in the system, based on the equivalent injection signal. The other sliding mode observers are used to isolate and report any malfunction that may occur in the satellite's guidance and control unit. In order to reduce false alarms a mean window is used over the equivalent injection signal.</jats:p

Safety Management for Unmanned Aviation

In Air Traffic Management (ATM), Safety Management Systems (SMS) provide the principal vehicle for implementing safety policies, practices and procedures in accordance with internationally agreed Standards. In a constantly changing operating environment, it is essential to maintain SMS effectiveness to maintain and enhance levels of ATM safety. Research at the University Politehnica of Bucharest (UPB) has analysed the major, fast-rising threats to ATM safety emerging in the field of unmanned aviation. After considering the operating environment in terms of control arrangements and unmanned vehicle types, the relationship between ATM and Unmanned Traffic Management (UTM) is examined. It is concluded that the SMS supporting ATM requires enhancement to address the risks arising from the emergence of unmanned aviation and relevant enhancement measures are therefore proposed. Further, research shows that detailed safety management arrangements to support UTM are not yet defined. Indicative SMS requirements for UTM are therefore derived and presented.</jats:p