Fault Tolerant Air Bubble Sensor using Triple Modular Redundancy Method

Detection of air bubbles in the blood is important for various medical treatments that use Extracorporeal Blood Circuits (ECBC), such as hemodialysis, hemofiltration and cardio-pulmonary bypass. Therefore a reliable air bubble detector is needed. In this study designed a fault tolerant air bubble detector. Triple Modular Redundancy (TMR) method is used on the sensor section. A voter circuit of the TMR will choose one of three sensor output to be processed further. Application of TMR will prevent errors in the detection of air bubbles, especially if the sensor fails to work

Reliability analysis of an ultra-reliable fault tolerant control system

This report analyzes the reliability of NASA's Ultra-reliable Fault Tolerant Control System (UFTCS) architecture as it is currently envisioned for helicopter control. The analysis is extended to air transport and spacecraft control using the same computational and voter modules applied within the UFTCS architecture. The system reliability is calculated for several points in the helicopter, air transport, and space flight missions when there are initially 4, 5, and 6 operating channels. Sensitivity analyses are used to explore the effects of sensor failure rates and different system configurations at the 10 hour point of the helicopter mission. These analyses show that the primary limitation to system reliability is the number of flux windings on each flux summer (4 are assumed for the baseline case). Tables of system reliability at the 10 hour point are provided to allow designers to choose a configuration to meet specified reliability goals

Study and application of direct RF power injection methodology and mitigation of electromagnetic interference in ADCs

There are many publications available in literature regarding the DPI (Direct Power Injection) technique for electronic systems, but few works specifically addressed for mixed-signal converters, which are components existent in almost all electronic devices. IEC 62132-4(International Electrotechnical Commission, 2006) and 62132-1(International Electrotechnical Commission, 2006) standards describe a method for measuring immunity of integrated circuits (IC) in the presence of conducted RF disturbances. This method ensures a high degree of repeatability and correlation of immunity measurements. Knowledge of the electromagnetic immunity of an IC allows the designer to decide if the system will need external protection, and how much effort should be directed to this solution. In this context, the purpose of this work is the study and application of the DPI methodology for injection of EMI in a mixed-signal programmable device, evaluating mitigation possibilities, with special focus on the analog-to-digital converters (ADCs). The main objective is to evaluate the impact of electromagnetic interference (EMI) on different converters (two Successive Approximation Register ADCs, operating with distinct sampling rate and a Sigma-Delta ADC) of the Cypress Semiconductor Programmable SoC (System-on-Chip), PSoC 5LP. Additionally a previously proposed fault tolerance methodology, based on triplication with hardware and time diversity is tested. Results show distinct behaviors of each converter to conducted EMI. Finally, the tested tolerance technique showed to be suitable to reduce error rate of such data acquisition system operating under EMI disturbance.Existem muitas publicações disponíveis na literatura sobre a técnica de DPI (Direct Power Injection ou injeção direta de energia) para sistemas eletrônicos, mas poucos trabalhos direcionados para conversores de sinais mistos, que são componentes existentes em quase todos os dispositivos eletrônicos. As normas IEC 62132-4 (IEC, 2006) e 62132-1 (IEC, 2006) descrevem um método para medir a imunidade de circuitos integrados (CI) na presença de distúrbios de RF conduzidos. Este método garante um alto grau de repetibilidade e correlação das medições da imunidade. O conhecimento da imunidade eletromagnética de um CI permite que o projetista decida se o sistema precisará de proteção externa e quanto esforço deve ser direcionado para esta solução. Nesse contexto, o objetivo deste trabalho é o estudo e aplicação da metodologia DPI para injeção de interferência eletromagnética em um dispositivo programável de sinal misto, avaliando as possibilidades de mitigação, com foco especial em conversores analógico-digitais (ADCs). O principal objetivo é avaliar o impacto da interferência eletromagnética em diferentes conversores (dois ADCs baseados em aproximação sucessiva, operando com taxa de amostragem distintas e um ADC do tipo Sigma-Delta) do SoC(System-on-Chip) programável da Cypress Semiconductor, PSoC 5LP. Além disso, é testada uma metodologia de tolerância a falhas proposta anteriormente, baseada em triplicação com diversidade de hardware e temporal. Os resultados mostram comportamentos distintos de cada conversor para a interferência eletromagnética conduzida. Finalmente, a técnica de tolerância testada mostrou-se adequada para reduzir a taxa de erros desse sistema de aquisição de dados operando sob perturbação eletromagnética

Failure detection and isolation investigation for strapdown skew redundant tetrad laser gyro inertial sensor arrays

The degree to which flight-critical failures in a strapdown laser gyro tetrad sensor assembly can be isolated in short-haul aircraft after a failure occurrence has been detected by the skewed sensor failure-detection voting logic is investigated along with the degree to which a failure in the tetrad computer can be detected and isolated at the computer level, assuming a dual-redundant computer configuration. The tetrad system was mechanized with two two-axis inertial navigation channels (INCs), each containing two gyro/accelerometer axes, computer, control circuitry, and input/output circuitry. Gyro/accelerometer data is crossfed between the two INCs to enable each computer to independently perform the navigation task. Computer calculations are synchronized between the computers so that calculated quantities are identical and may be compared. Fail-safe performance (identification of the first failure) is accomplished with a probability approaching 100 percent of the time, while fail-operational performance (identification and isolation of the first failure) is achieved 93 to 96 percent of the time

Avionics architecture studies for the entry research vehicle

This report is the culmination of a year-long investigation of the avionics architecture for NASA's Entry Research Vehicle (ERV). The Entry Research Vehicle is conceived to be an unmanned, autonomous spacecraft to be deployed from the Shuttle. It will perform various aerodynamic and propulsive maneuvers in orbit and land at Edwards AFB after a 5 to 10 hour mission. The design and analysis of the vehicle's avionics architecture are detailed here. The architecture consists of a central triply redundant ultra-reliable fault tolerant processor attached to three replicated and distributed MIL-STD-1553 buses for input and output. The reliability analysis is detailed here. The architecture was found to be sufficiently reliable for the ERV mission plan

Design Solutions For Modular Satellite Architectures

The cost-effective access to space envisaged by ESA would open a wide range of new opportunities and markets, but is still many years ahead. There is still a lack of devices, circuits, systems which make possible to develop satellites, ground stations and related services at costs compatible with the budget of academic institutions and small and medium enterprises (SMEs). As soon as the development time and cost of small satellites will fall below a certain threshold (e.g. 100,000 to 500,000 €), appropriate business models will likely develop to ensure a cost-effective and pervasive access to space, and related infrastructures and services. These considerations spurred the activity described in this paper, which is aimed at: - proving the feasibility of low-cost satellites using COTS (Commercial Off The Shelf) devices. This is a new trend in the space industry, which is not yet fully exploited due to the belief that COTS devices are not reliable enough for this kind of applications; - developing a flight model of a flexible and reliable nano-satellite with less than 25,000€; - training students in the field of avionics space systems: the design here described is developed by a team including undergraduate students working towards their graduation work. The educational aspects include the development of specific new university courses; - developing expertise in the field of low-cost avionic systems, both internally (university staff) and externally (graduated students will bring their expertise in their future work activity); - gather and cluster expertise and resources available inside the university around a common high-tech project; - creating a working group composed of both University and SMEs devoted to the application of commercially available technology to space environment. The first step in this direction was the development of a small low cost nano-satellite, started in the year 2004: the name of this project was PiCPoT (Piccolo Cubo del Politecnico di Torino, Small Cube of Politecnico di Torino). The project was carried out by some departments of the Politecnico, in particular Electronics and Aerospace. The main goal of the project was to evaluate the feasibility of using COTS components in a space project in order to greatly reduce costs; the design exploited internal subsystems modularity to allow reuse and further cost reduction for future missions. Starting from the PiCPoT experience, in 2006 we began a new project called ARaMiS (Speretta et al., 2007) which is the Italian acronym for Modular Architecture for Satellites. This work describes how the architecture of the ARaMiS satellite has been obtained from the lesson learned from our former experience. Moreover we describe satellite operations, giving some details of the major subsystems. This work is composed of two parts. The first one describes the design methodology, solutions and techniques that we used to develop the PiCPoT satellite; it gives an overview of its operations, with some details of the major subsystems. Details on the specifications can also be found in (Del Corso et al., 2007; Passerone et al, 2008). The second part, indeed exploits the experience achieved during the PiCPoT development and describes a proposal for a low-cost modular architecture for satellite

Fault Tolerant Air Bubble Sensor using Triple Modular Redundancy Method

Detection of air bubbles in the blood is important for various medical treatments that use Extracorporeal Blood Circuits (ECBC), such as hemodialysis, hemofiltration and cardio-pulmonary bypass. Therefore a reliable air bubble detector is needed. This study presents the design of a new fault tolerant air bubble detector. Triple Modular Redundancy (TMR) method is used on the sensor section. A voter circuit of the Triple Modular Redundancy will choose one of three sensor outputs to be processed further. Application of Triple Modular Redundancy will prevent errors in the detection of air bubbles, especially if the sensor fails to work

Multiband Spectrum Access: Great Promises for Future Cognitive Radio Networks

Cognitive radio has been widely considered as one of the prominent solutions to tackle the spectrum scarcity. While the majority of existing research has focused on single-band cognitive radio, multiband cognitive radio represents great promises towards implementing efficient cognitive networks compared to single-based networks. Multiband cognitive radio networks (MB-CRNs) are expected to significantly enhance the network's throughput and provide better channel maintenance by reducing handoff frequency. Nevertheless, the wideband front-end and the multiband spectrum access impose a number of challenges yet to overcome. This paper provides an in-depth analysis on the recent advancements in multiband spectrum sensing techniques, their limitations, and possible future directions to improve them. We study cooperative communications for MB-CRNs to tackle a fundamental limit on diversity and sampling. We also investigate several limits and tradeoffs of various design parameters for MB-CRNs. In addition, we explore the key MB-CRNs performance metrics that differ from the conventional metrics used for single-band based networks.Comment: 22 pages, 13 figures; published in the Proceedings of the IEEE Journal, Special Issue on Future Radio Spectrum Access, March 201