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Sensor Failures (sensor + failure)

Distribution by Scientific Domains

Engineering	60%

Selected Abstracts

Robust Isolation Of Sensor Failures

ASIAN JOURNAL OF CONTROL, Issue 1 2003
R. Xu
ABSTRACT Sensor self-validity check is a critical step in system control and fault diagnostics. In this paper, a robust approach to isolate sensor failures is proposed. First, a residual model for a given system is built off-line and directly based on input-output measurement data. The residual model outputs are called "primary residuals" and are zero when there is no fault. Most conventional approaches to residual model generation are indirect, as they first require the determination of state-space or other models using standard system identification algorithms. Second, a new max-min design of structured residuals, which can maximize the sensitivity of structured residuals with respect to sensor failures, is proposed. Based on the structured residuals, one can then isolate the sensor failures. This design can also be done in an off-line manner. It is an optimization procedure that avoids local optimal solutions. Simulation and experimental results demonstrated the effectiveness of the proposed method. [source]

Assessment of different techniques for subcutaneous glucose monitoring in Type 1 diabetic patients during ,real-life' glucose excursions

DIABETIC MEDICINE, Issue 3 2010
J. K. Mader
Diabet. Med. 27, 332,338 (2010) Abstract Aims, To compare the accuracy of two marketed subcutaneous glucose monitoring devices (Guardian RT, GRT; GlucoDay S, GDS) and standard microdialysis (CMA60; MD) in Type 1 diabetic patients. Methods, Seven male Type diabetic patients were investigated over a period of 26 h simulating real-life meal glucose excursions. Catheters of the three systems were inserted into subcutaneous adipose tissue of the abdominal region. For MD, interstitial fluid was sampled at 30- to 60-min intervals for offline glucose determination. Reference samples were taken at 15- to 60-min intervals. All three systems were prospectively calibrated to reference. Median differences, median absolute relative differences (MARD), median absolute differences (MAD), Bland,Altman plot and Clark Error Grid were used to determine accuracy. Results, Bland,Altman analysis indicated a mean glucose difference (2 standard deviations) between reference and interstitial glucose of ,10.5 (41.8) % for GRT, 20.2 (55.9) % for GDS and 6.5 (35.2) % for MD, respectively. Overall MAD (interquartile range) was 1.07 (0.39; 2.04) mmol/l for GRT, 1.59 (0.54; 3.08) mmol/l for GDS and 0.76 (0.26; 1.58) mmol/l for MD. Overall MARD was 15.0 (5.6; 23.4) % (GRT), 19.7 (6.1; 37.6) % (GDS) and 8.7 (4.1; 18.3) % (MD), respectively. Total sensor failure occurred in two subjects using GRT and one subject using GDS. Conclusions, The three investigated technologies had comparable performance. Whereas GRT underestimated actual blood glucose, GDS and MD overestimated blood glucose. Considerable deviations during daily life meal glucose excursions from reference glucose were observed for all three investigated technologies. Present technologies may require further improvement until individual data can lead to direct and automated generation of therapeutic advice in diabetes management. [source]

Enhanced process monitoring for wastewater treatment systems

ENVIRONMETRICS, Issue 6 2008
Chang Kyoo Yoo
Abstract Wastewater treatment plants (WWTPs) remain notorious for poor data quality and sensor reliability problems due to the hostile environment, missing data problems and more. Many sensors in WWTP are prone to malfunctions in harsh environments. If a WWTP contains any redundancy between sensors, monitoring methods with sensor reconstruction such as the proposed one can yield a better monitoring efficiency than without a reconstruction scheme. An enhanced robust process monitoring method combined with a sensor reconstruction scheme to tackle the sensor failure problems is proposed for biological wastewater treatment systems. The proposed method is applied to a single reactor for high activity ammonia removal over nitrite (SHARON) process. It shows robust monitoring performance in the presence of sensor faults and produces few false alarms. Moreover, it enables us to keep the monitoring system running in the case of sensor failures. This guaranteed continuity of the monitoring scheme is a necessary development in view of real-time applications in full-scale WWTPs. Copyright © 2007 John Wiley & Sons, Ltd. [source]

Sensor network design for fault tolerant estimation

INTERNATIONAL JOURNAL OF ADAPTIVE CONTROL AND SIGNAL PROCESSING, Issue 1 2004
M. Staroswiecki
Abstract This paper addresses the problem of fault tolerant estimation and the design of fault tolerant sensor networks. Fault tolerance is defined with respect to a given estimation objective, namely a given functional of the system state should remain observable when sensor failures occur. Redundant and minimal sensor sets are defined and organized into an automaton which contains all the subsets of sensors such that the estimation objective can be achieved. Three criteria, which evaluate the system fault tolerance with respect to sensor failures when a reconfiguration strategy is used, are introduced: (strong and weak) redundancy degrees (RD), sensor network reliability (R), and mean time to non-observability (MTTNO). Sensor networks are designed by finding redundant sensor sets whose RD and/or R and/or MTTNO are larger than some specified values. A ship boiler example is developed for illustration. Copyright © 2004 John Wiley & Sons, Ltd. [source]