Heinrich Ruser

Informationsfusion – Eine Übersicht (Information Fusion – An Overview)

Mit Informationsfusion wird der Prozess bezeichnet, Daten aus unterschiedlichen Sensoren oder Informationsquellen mit dem Ziel zu verknüpfen, neues oder präziseres Wissen über physikalische Größen, Ereignisse und Situationen zu gewinnen. Im Beitrag werden eine Systematisierung der verschiedenen Ansätze und Modelle der Informationsfusion vorgenommen und allgemeine Kriterien bei der Herangehensweise an die Fusionsaufgabe vorgestellt. Ausgehend von den Anforderungen an die Messaufgabe bestimmen die Art und das bekannte oder erlernbare Wissen über die Informationsquellen und die Messobjekte sowie der vertretbare mathematische Aufwand die Wahl der Fusionsalgorithmen. Hierzu wird ein Überblick über verschiedene methodische Ansätze gegeben, welche in vielen Anwendungen eine wichtige Rolle spielen. Information fusion denotes the process of combining data from different sensors or information sources to obtain new or more precise knowledge on physical quantities, events, or situations. This paper undertakes a systematization of the existing models and approaches to information fusion and presents general criteria to accomplish the fusion task. Starting with the requirements of the measurement task, both the type and the knowledge of the information sources and the measurands as well as the mathematical complexity constrain the choice of the fusion algorithms. We give an overview of different approaches which play an important role in many applications.

Feature extraction from an infrared sensor array for localization and surface recognition of moving cylindrical objects

The paper presents a low-cost solution for the determination of characteristic properties of roughly cylindrical objects like size, location, trajectory and velocity of motion, and surface reflectivity. In particular, the problems of identifying different items on a conveyer belt and reliably determining the number of persons getting into or out of a room is addressed. Two arrays of several infrared (IR) emitter-receiver pairs, working on a reflection light scanner principle, are mounted on opposite sides of the area of observation. The emitters are driven successively in time, hence no signal overlapping and cross-talk occur. Two configurations of the IR array were compared. From simple light Intensity measurements, a variety of properties of (cylindrical) objects can be deduced. A surface modeling with elementary reflectors is proposed and results are shown proving its potential. The model parameters are obtained by an optimization procedure, Variants of the processing for object characterization are discussed.

Smart robust wind sensor using a simple optimization procedure

An effective wind sensor consisting of merely three temperature-dependent resistors is described. The sensing elements are placed under a known angle to each other around a cylindrical flow body in its asymmetrical flow field. Based on sensor models obtained by pre-operation measurements, the wind velocity as well as the wind direction are calculated from output voltages by an optimization procedure. Besides the measurement result itself, also its quality follows directly from the optimization output giving a tool to monitor on-line the sensors state. As a further improvement, by periodic excitation of the sensor, measuring the thermal impedance of the device the various sources of influence like the ambient temperature and rain drops can be separated. A prototype sensor has been developed and evaluated with satisfactory results: The accuracies of wind velocity and direction estimation are below 5% and 2deg, resp

Correlated microwave-ultrasonic multi-sensor for reliable measurements of velocity and range

The potential of the combination of ultrasound and microwaves to improve existing sensors in terms of sensitivity and reliability is demonstrated. While noise and disturbances affect both waves differently, signal returns form target reflectors will be coherent. With data fusion performed on the signal level, the applicability is significantly improved compared with multisensors based on complementary sensor outputs. A compact low-cost sensor for the robust measurement of presence, velocity and distance of objects, using 24 GHz microwaves and 40 kHz ultrasound, has been designed. Key issues for a smart sensor design, inherently exploited by the multisensor approach, are the adaptation to the environment, self calibration and function monitoring. The design and operating parameters of the multisensor system are discussed and evidence for the satisfactory performance is given.

Self-controlled PTC sensor for reliable overfill protection of liquids

The paper deals with the design of sensors with automatic self-control. A PTC thermistor was selected, which is used as a level sensor to prevent overfill of liquids in tanks. In self-heated mode, the I-U characteristic is basically dependent on the unloading resistance value R/sub T/ of the PTC sensor itself, the thermal resistance R/sub W/ and the temperature T/sub M/ of the medium that is surrounding it. This I-U characteristic of the sensor in thermally steady state in still air is modelled. Problems in detecting the liquid level occur for a soiled sensor surface or liquids with high temperature and/or high viscosity (e.g. crude oil). A solution to this worst-case scenario is to determine R/sub W/ continuously from the I-U characteristic of the PTC thermistor in function. The constant monitoring of the sensor parameters enables an automatic sensor self control, e.g. to identify slow changes of the sensor parameters due to corrosion and dust layers on the sensor surface or ageing.

Low-cost weather sensor based on thermal impedance measurements

Two examples of self-controlled wind and weather sensors for everyday usage based on temperature-dependent resistors are described and the potential for further enhancing sensor properties like long-term stability, self-calibration and selectivity is discussed. To measure the velocity and direction of wind, three PTC elements are placed under a known angle to each other around a cylindrical flow body. Based on sensor models obtained by pre-operation measurements, the interesting properties are calculated from output voltages by an optimization procedure. Besides the measurement result itself, also its quality follows directly from the optimization output giving a tool to monitor on-line the sensors state. By periodically changing the power supply of the sensing element and measuring parameters of the resulting thermal impedance, various sources of influence like ambient temperature, rain drops or snow on the devices surface can be separated. Prototype sensors have been developed and evaluated with satisfactory results.

„Multisignal“-Sensorik am Beispiel von Witterungssensoren auf der Basis temperaturabhängiger Widerstände (Weather Sensor Based on Temperature-Dependent Resistors Using “Multi-signal”-Analysis)

Im Beitrag werden einfache Witterungssensoren, z. B. an automatisch geöffneten Fenstern, auf der Basis von Kaltleitern und einfachen Pt-100-Widerstandsthermometern vorgestellt, welche ihre Informationen aus einer „Multisignal”-Auswertung beziehen. Ein Aufbau, bestehend aus drei Kaltleiter-Elementen, dient zur Bestimmung der Windrichtung und der Windgeschwindigkeit, wobei das Ergebnis der in die Signalauswertung einbezogenen Optimierungsprozedur eine Aussage über die Qualität der Messungen liefert und damit eine Monitoring-Funktion für den Sensorzustand darstellt. Bei periodischer Anregung des Pt-100-basierten Witterungssensors werden aus der Auswertung der thermischen Impedanz mittels einer Gütefunktion die Windstärke und die Umgebungstemperatur sowie die Zustände Regen, Schnee bzw. Eis mit ausreichender Genauigkeit bestimmt. Während des Betriebs werden dabei auch die Modellparameter und damit die Messunsicherheit des Sensors überwacht. Dadurch können Driften, z. B. durch zunehmende Verschmutzung oder Alterung, erkannt und korrigiert werden. Uncomplex weather sensors based on PTC thermistors and Pt100 thermal resistors are described to be used e. g. for automated opening of windows. The performance needed is achieved through so-called “multi-signal” processing. A set-up consisting of three thermistors is used to obtain the wind direction and velocity using the result of an optimization procedure which constitutes a quality measure of the sensor measurements, giving a tool to on-line monitor the sensor’s state. With periodic excitation of a Pt100 thermal resistor the wind velocity as well as rain, snow, ice, and temperature are derived from the thermal impedance with sufficient accuracy and reliability. During operation, the parameters of the sensor model are observed, allowing drifts due to soiling or ageing to be detected and compensated.

Smart two-element PTC wind sensor

A smart, low-cost wind sensor consisting of just two self-heated PTC (positive temperature coefficient) elements is described. Placing the elements asymmetrically in a cylindrical shell, the wind vector can be reliably measured in two dimensions. Inherent measurement errors due to incipient soiling of the sensor surface, ohmic bridges, shortcuts and ageing of the electrical parameters, are detected with an automatic self-calibration procedure and effectively compensated for. The instants for automatic recalibration are determined without any additional assistance, when identical signals from both sensor elements are observed. The parameters of the PTC sensor model are then determined from the elements I-U-characteristics and used to correct all measured data during operation.

Automatische Lüftung zur Sicherung von Behaglichkeit, Luftqualität und Energieeinsparung im privaten Lebensbereich (Regulated Ventilation to Ensure Thermal Comfort, Air Quality and Energy Conservation in Residential Homes)

Die bedarfsgerechte Lüftung von Räumen hat großen Einfluss auf das Wohlbefinden und die thermische Behaglichkeit von anwesenden Personen sowie auf den Energieverbrauch. Um eine gezielte Frischluftzufuhr in Wohnräumen zu ermöglichen, benötigt eine automatische Lüftungssteuerung Messsysteme zur Luftqualitätsbeurteilung, insbesondere zur Erfassung der Konzentration des Leitgases Kohlendioxid (CO2) sowie der Feuchte. Messtechnische Untersuchungen ergaben, dass die Messung der CO2-Konzentrationen im Raum an allen nicht direkt von Außenluft berührten Positionen erfolgen kann. Die Auswertung des Heizenergieverbrauchs zeigte, dass — entgegen der bisher vorherrschenden Meinung — eine geregelte kontinuierliche Spaltlüftung keine energetischen Nachteile gegenüber der Stoßlüftung hat. Zusammen mit der verbesserten thermischen Behaglichkeit aufgrund viel geringerer Temperaturschwankungen und deutlich reduziertem Zugluftrisiko erweist sich die geregelte Spaltlüftung als überlegen zur Sicherung von Behaglichkeit, Luftqualität und Energieeinsparung im privaten Lebensbereich. The ventilation of rooms by demand can have great influence on the well-being and the thermal comfort as well as on the energy consumption. For a demand-oriented supply with fresh air, an automatic ventilation system needs sensors to monitor the indoor air quality, especially to determine the carbon dioxide (CO2) gas concentration and the humidity in the room. Investigations showed that the CO2 concentration can be measured at all positions in the room, which are not directly affected by fresh air. In contrast to the predominant opinion a regulated continuous split ventilation has energetically no disadvantage over shock ventilation. Along with improved thermal comfort due to the much smaller temperature variations and a significantly reduced draught risk, the split ventilation appears to be superior to shock ventilation in terms of thermal comfort, air quality, and energy conservation in residential homes.

Sensitivity monitoring of amperometric gas sensors based on impedance spectroscopy

For a large variety of gases, amperometric gas sensors work with high reliability. While the zero point of these sensors is relatively stable in time, the sensitivity and cross-sensitivity can change considerably over time, resulting in incorrect measurements. This can be critical for many applications. Hence, a permanent monitoring of the sensitivity is desired. This paper describes a simple method for automatic monitoring of the sensitivity of amperometric gas sensors, based on impedance spectroscopy measurements. The results show a strong correlation of the sensor sensitivity with the sensors double-layer capacity, providing a comfortable tool to monitor the sensors behaviour. An on-line approximation of the characteristic sensor parameters is carried out.