Cooperative federated filtering approach for enhanced position estimation and sensor fault tolerance in ad-hoc vehicle networks

The present study addresses a solution to the position and orientation estimation problem of vehicles in ad-hoc vehicle networks using decentralised filtering. Specifically, a distributed filter operating in a cooperative federated structure for enhancing the estimation accuracy of vehicles state over unreliable wireless communication networks subject to uncertain and limited measurements is proposed. The filter relies on a variety of position measurements obtained from the on-board vehicle positioning system, from other cooperating vehicles in the vicinity, as well as from the immediate roadside environment via communication. Direct distance measurements between vehicles, furthermore, between vehicles and the stationary elements of the infrastructure can be used, if available, as highly accurate reference measurements. The study demonstrates how successfully the novel idea of cooperative federated filtering in addressing the demands of both fault tolerance and enhanced estimation accuracy in ad-hoc vehicle networks can be used.     

Reliability analysis of cluster-based ad-hoc networks

The mobile ad-hoc wireless network (MAWN) is a new and emerging network scheme that is being employed in a variety of applications. The MAWN varies from traditional networks because it is a self-forming and dynamic network. The MAWN is free of infrastructure and, as such, only the mobile nodes comprise the network. Pairs of nodes communicate either directly or through other nodes. To do so, each node acts, in turn, as a source, destination, and relay of messages. The virtue of a MAWN is the flexibility this provides; however, the challenge for reliability analyses is also brought about by this unique feature. The variability and volatility of the MAWN configuration makes typical reliability methods (e.g. reliability block diagram) inappropriate because no single structure or configuration represents all manifestations of a MAWN. For this reason, new methods are being developed to analyze the reliability of this new networking technology. New published methods adapt to this feature by treating the configuration probabilistically or by inclusion of embedded mobility models. This paper joins both methods together and expands upon these works by modifying the problem formulation to address the reliability analysis of a cluster-based MAWN. The cluster-based MAWN is deployed in applications with constraints on networking resources such as bandwidth and energy. This paper presents the problem's formulation, a discussion of applicable reliability metrics for the MAWN, and illustration of a Monte Carlo simulation method through the analysis of several example networks.     

Phase-diversity wave-front sensor for imaging systems

A phase-diversity wave-front sensor has been developed and tested at the Lockheed Palo Alto Research Labs (LPARL). The sensor consists of two CCD-array focal planes that record the best-focus image of an adaptive imaging system and an image that is defocused. This information is used to generate an object-independent function that is the input to a LPARL-developed neural network algorithm known as the General Regression Neural Network (GRNN). The GRNN algorithm calculates the wave-front errors that are present in the adaptive optics system. A control algorithm uses the calculated values to correct the errors in the optical system. Simulation studies and closed-loop experimental results are presented.     

Fault-tolerant sensor systems using evolvable hardware

This paper describes a system that is robust with respect to a sensor failure. The system utilizes multiple sensor inputs (three in this case) connected to a programmable device that averages the outputs from the sensors. The programmable device is programmed using evolvable hardware techniques. If one or more of the input sensors fail, then the controller detects the failure and initiates a reprogramming of the circuit. The system then continues to operate with a reduced number of sensors. The failure detection is accomplished by comparing the actual system output with a Kalman-filter estimate of the output. If the actual output and the filter estimate differ by an amount greater than the system uncertainty, then a failure is noted. The system is robust to several different failure modes: sensor fails as open circuit, sensor fails as short circuit, partial failures, multiple sensors fail, field programmable analog array input amplifier failure. This paper describes the experimental setup as well as results using actual temperature sensors. For all failure types, the system was able to recover to within 2% of the target value.     

Process of self-organization in metal

Conclusions 1. As a result of special features of the physical and chemical structure the dissipative structure in the solid forms only in a thin subsurface layer of the metal during friction and represents dynamic nonequilibrium interaction of the diffusion flow of climbing dislocation with counterflows of vacancies. This results in inhalation of the dislocations which formed during deformation of the layer (selective transfer).2. In addition to special conditions (selective dissolution), formation of the dissipative structure in the surface layer is supported by the proximity of the surface creating suitable conditions for saturating the layer with the vacancies and for formation of a dislocation sink. The fact that these conditions do not exist in the volume indicates that the dissipation systems are insufficient for organizing the dissipative structure in the volume of the solid.3. If the phase transition in dislocation movement is not completed by the evolution of the structures as in, for example, the system of boundary friction (close system), the development of dissipative subsystems nevertheless may continue (synergetics of the zero order) together with an increase of the degree of chaos.4. Structural adaptability in the closed system of the solid (synergetics of the zero order), generated from the outside or formed naturally during evolution of the structures, may be used to reduce the entropy rate.A. A. Blagonravov Engineering Institute, Russian Academy of Sciences, Moscow. Translated from Fiziko-Khimicheskaya Mekhanika Materialov, Vol. 29, No. 2, pp. 19–27, March–April, 1993.     

Instrumentation architecture and sensor fusion for systems control

This paper presents a systematic approach for the design of an instrumentation architecture and a sensor data fusion concept which together enable the robust control of complex electromechanical systems. The development is based on the theory of hyperstability. Earlier results are generalized and previous restrictions on sensors are relaxed to broaden the applicability of the proposed method. Experimental results validate the methodology and confirm its efficacy in practical applications     

Measurement converter for sensor signals in modular systems

We consider a factility for measurement of signals from different types of sensors; the system complies with the CAMAC and VME standards, and it is designed to increase measurement accuracy. We present the basic characteristics of the system. Translated from Izmeritel'naya Tekhnika, No. 11, pp. 15–17, November, 1997.     

Nanoparticle metal-oxide films for micro-hotplate-based gas sensor systems

We report on the use of either reactive magnetron sputtering or screen printing to deposit tin and tungsten-oxide gas-sensitive layers onto integrated micromachined arrays. The procedures allow the deposition of the sensing layers before membranes have been etched, which leads to gas microsensors with an excellent fabrication yield. The microstructure of the sensitive films is analyzed by means of SEM and EDX. The response of the different microarrays to ethanol, acetone, and ammonia vapors and their binary mixtures, and toxic gases such as NO/sub 2/ and CO, is studied at different operating temperatures. The response of the different sensors to ambient humidity is also investigated. Finally, it is shown that by using PCA and fuzzy ARTMAP neural networks, it is possible to simultaneously identify and quantify the toxic gases with a 100% success rate. A 95% success rate is obtained in the semi-quantitative analysis of vapors and vapor mixtures. These results prove the viability and usefulness of the techniques introduced to obtain integrated sensor microarrays that are suitable for battery-powered gas/vapor monitors.     

The self-organization of space and time

Self-organization is clearly relevant to biology, chemistry, Earth science, economics and other sciences that have to deal with big and complicated issues. This paper shows that self-organization also has a great deal to do with fundamental physics, including quantum mechanics, relativity, quantum gravity and cosmology. This paper also aims to give some insight into what self-organization means and discusses questions such as the kinds of methods that can be used to understand self-organization and how self-organization relates to other modes of explanation such as reductionism.     

A gradient thermodynamic theory of self-organization

Summary In this paper we present a gradient theory of internal variables in a thermodynamic context of the Gibbs free energy density ø. A fundamental point of the theory is that ø is a function of three different classes of internal variables: (a) tensorial dissipative and local; (b) vectorial dissipative and non-local and (c) vectorialinviscid and non-local. These classes obey different types of evolution equations. The ones pertaining to the non-local variables are partial differential equations of the diffusion-reaction type. We associate the inviscid non-local variables with energy release mechanisms and show that they lead to patterned deformation, otherwise known as self-organization. We conclude by giving a solution to the problem of a flat plate in nominal axial tension and derive various types of deformation patterns that result from small but unavoidable experimental deviations from this loading.     

Site-controlled self-organization of InAs quantum dots

In situ site-control techniques for self-organized InAs quantum dots (QDs) have been developed using an electron beam (EB) and a scanning tunneling microscope (STM) probe combined with molecular beam epitaxy. In the in situ EB-assisted process, InAs dots are preferentially formed in shallow, sub-μm-size GaAs holes with the InAs supply. We find that the specific slope of a hole acts as a favorable site for dot formation. In the in situ STM probe-assisted process, the size and pitch of the holes are considerably reduced into nanoscale. InAs QDs are then self-organized only at the hole sites due to strain-induced selective nucleation. Using this process, two- and three-dimensional QD arrays are fabricated with nanometer precision.     

Operating systems and network protocols for wireless sensor networks

Sensor network protocols exist to satisfy the communication needs of diverse applications, including data collection, event detection, target tracking and control. Network protocols to enable these services are constrained by the extreme resource scarcity of sensor nodes-including energy, computing, communications and storage-which must be carefully managed and multiplexed by the operating system. These challenges have led to new protocols and operating systems that are efficient in their energy consumption, careful in their computational needs and miserly in their memory footprints, all while discovering neighbours, forming networks, delivering data and correcting failures.     

A feasible noise estimation algorithm for resource-limited sensor systems

Fault tolerance and self-checking capabilities are key features of modern smart sensors, which often require the integration of additional signal processing facilities. In high-volume production areas such as automotive applications, however, optimized controllers are employed that typically have only limited computing resources. This paper examines several algorithms to assess the noise in a quasi-closed loop measurement channel under the assumption that the stimulus can be held constant during noise measurement. Starting from the definition of standard deviation, we propose several modifications and obtain an easy-to-implement algorithm relying entirely on addition and shift operations. Numerical experiments based on simulated and measured noise verify the practicability of the approach. The proposed algorithm has already been successfully implemented in a capacitive angular speed sensor system for automotive applications.     

Location and sequencing of imperfect inspection operations in serial multi-stage production systems

An integrated approach to the problem of allocation of inspection effort in multistage production systems is presented. The problem addresses multiple inspection operations, different disposition policies and inspection, production and repair errors. Quality and cost transfer functions are developed to model production operations and different types of inspection operations in a unified manner and to facilitate the recursive computations required to evaluate alternative system configurations. We formulate the combined inspection location and sequencing problem as a nonlinear mathematical programming problem and solve it with a branch and bound technique, using a heuristic to generate a feasible solution and upper bound. These developments are illustrated with a numerical example.     

Development of a portable fiber-optic current sensor for power systems monitoring

The paper presents a portable fiber-optic current sensor (FOCS), based on the Faraday effect, with a magnetic concentrator. Both the optical sensing head and electronic processing block are illustrated. A detailed experimental study to confirm the performance of the device is also reported. According to the measured values of ac rms current up to 1 kA, a calibration procedure was performed. The paper provides an analysis of the results obtained for various conductor displacements within the concentrator. The well-known temperature dependence of the Faraday current sensor and its influence on the measurement accuracy are tested by means of a special double-layer thermal insulated chamber. The calibrated and characterized FOCS is applied for harmonic analysis of the current. The results clearly illustrate the nature of the sensing process and demonstrate odd-order harmonics presence, as predicted by the mathematical model. The paper indicates that the developed device is suitable for the power systems monitoring.     

Evaluation of sensor materials for ultrasonic thermometry In coal gasification systems

The success of ultrasonic thermometry, in coal gasification systems depends on the selection of approprzate sensor materzal(s) that can withstand the hostile environment exhibit good. acoustic sen~itivity to temperature and show long-term stability or reproducibility of acoustic properties in the environment. Six candidate materials SS 310, Incoloy 800, sapphire, alumina, spinel and chrome oxide - were selected based on pilot-plant. experience and laboratory studies of materials performance in coal galasification environments. They were exposed in two simulated coal gasification environment, Westinghouse low-Btu (British thermal unit) at 871°C for 15 hand Texaco medium-Btu at 982°C for 15 h. The physical and acoustic properties of the materzals before and after exposure to the gasification environments are presented, together With a discussion on the long-term performance predictions of the materials for ultrasonic thermometry.     

Comparison between two detection systems for fiber-optic chemical sensor applications

Two optical detection system designs are compared for fiber-optic chemical sensor applications. A single grating spectrograph with fiber-optic input and photodiodes at three different wavelengths is compared to 1x3 fiber-optic splitters and photodiode detectors with integrated interference filters. The splitters are used to direct the optical power to the filter photodiodes. Three types of 1x3 commercially available splitters were tested: a 400 microm fused glass fiber-optic coupler, a 1000 microm fused plastic fiber-optic coupler, and a 1000 microm glass fiber-optic bundle. This study finds that the fiber-splitter-based detection systems have similar stray light, signal-to-noise ratio, and long-term absorbance stability compared to the spectrograph detection system with a modest improvement in spectral resolution (from approximately 12 nm to approximately 6 nm). It is also much smaller in size and lower in cost. Applications of the two systems in a colorimetric CO2 partial pressure sensor are compared and similar accuracy and precision are achieved.