Hans-Rolf Tränkler

Sensor technology advances and future trends

Recent advances of sensor technologies have been powered by high-speed and low-cost electronic circuits, novel signal processing methods, and advanced manufacturing technologies. The synergetic interaction of new developments in these fields provides promising technical solutions increasing the quality, reliability, and economic efficiency of technical products. With selected examples, we will give an overview about the significant developments of methods, structures, manufacturing technologies, and signal processing characterizing todays sensors and sensor systems. Predominantly observed development trends in the future are discussed.

Recent advances in sensor technology

The recent advances of sensor technologies have been powered by high-speed and low-cost electronic circuits, novel signal processing methods and innovative advances in manufacturing technologies. The synergetic interaction of new developments in these fields allow completely novel approaches increasing the performance of technical products. Innovative sensor structures have been designed permitting self-monitoring or self-calibration. The rapid progress of sensor manufacturing technologies allows the production of systems and components with a low cost-to-performance ratio. Among microsystem manufacturing technologies, surface and bulk micromachining are increasingly winning recognition. The potential in the field of digital signal processing involves new approaches for the improvement of sensor properties. Multi-sensor systems can significantly contribute to the enhancement of the quality and availability of information. For this purpose, sophisticated signal processing methods based on data fusion techniques are more effective for an accurate computation of measurement values or a decision than usually used threshold based algorithms. In this state-of-the-art lecture we give an overview of the recent advances and future development trends in the field of sensor technology. We focus on novel sensor structures, manufacturing technologies and signal processing methods in individual and multi-sensor systems. The predominantly observed future development trends are: the miniaturization of sensors and components, the widespread use of multi-sensor systems and the increasing relevance of radio wireless and autonomous sensors.

Sensorless position control of electromagnetic linear actuator

Sensorless principles utilize the transducer characteristics of actuators during excitation. As the measured data are extracted directly from the actuator, an additional sensor is not required. The information on the armature position of a solenoid can be found in its impedance. With knowledge of the impedances dependency on the position, an online analysis method can determine the current position and feed a position control system. On basis of a simplified solenoid model a method for position estimation and control with a pulse width modulated power supply is proposed.

Energy-Management for Power Aware Portable Sensor Systems

The design of power aware wireless sensor systems has gained increasing importance in recent research. Challenges in designing such devices are a throughout energy scalable design of hardware, signal processing and communication and an energy-effective energy management. The power supply should be capable to `harvest ambient energy and to accumulate superfluous energy in an energy storage unit in order to be able to bridge low energy availability. After an overview of the state-of-the-art in key technologies for power-aware portable sensor systems, we focus in this paper on energy management. An effective energy management plays a key role for energy-aware adaptation of system operation. An accurate up-to-date measurement of stored energy and remaining usable storage capacity allows to optimize operation and to extend maintenance-free periods. As challenging example we present recent results for the diagnosis of electrochemical batteries by impedance spectroscopy (Troltzsch, 2005)

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.

Model performance improvement for a calibration-free temperature measurement based on p-n junctions

Abstract The p–n junction I – U characteristic offers the possibility to realize an easy applicable calibration-free measurement. In this paper, we present a new measurement method making use of an inverse problem consideration. A new p–n junction I – U characteristic model is specially developed for this method and taking into account semiconductor secondary effects is presented and compared to the reduced reduced Gummel–Poon Model (RGP). The experimental results show an improvement of one order relative to previous calibration-free methods like the method by Goloub (2.8xa0K). The temperature calculation procedure is more stable and converges much faster than with the RGP.

Improvement of Sensory Information using Multi-Sensor and Model-Based Sensor Systems

Many approaches can be pursued in order to improve information delivered by a sensor system. A signal processing based on the modeling of the sensor characteristic can be used in order to reduce undesired effects influencing the sensor signal. In this case we deal with an inverse reconstruction problem in which the measured quantity is calculated using a priori knowledge, e. g. collected during calibration processes. A further approach is to model the dependence on a steering quantity and to solve the corresponding inverse identification problem. In this case a set of sensor operating points are available at the same value of the measured quantity permitting new possibilities for improving sensory information. This kind of sensor systems can be called varied input sensor (VIS) and closes the gap between single sensors and multi sensor systems. Multi-sensor systems reach many advantages through integration of redundant and diverse sensor signals in order to achieve advantages, such as a better accuracy, a higher reliability or a better dynamic response

Sensoreigenschaften von Aktoren (Characteristics of Self-Sensing Actuator Systems)

Abstract Die in Aktorsystemen implizit enthaltenen Messeffekte können mit geeigneten Methoden der Signalverarbeitung ausgewertet werden und ermöglichen es, zusätzliche Sensoren für Position, Geschwindigkeit oder Kraft einzusparen. Nutzbare Messeffekte verschiedener elektro-mechanischer Aktortypen werden vorgestellt. Der Einfluss der statischen und dynamischen Kopplung zwischen Aktor- und Sensorsignal auf typische Sensoreigenschaften (Empfindlichkeit, Linearität, Temperaturverhalten) wird am Beispiel eines elektromagnetischen Antriebs diskutiert.

Diagnose von Gerätebatterien mit Impedanzspektrometrie (Diagnosis of Portable Secondary Batteries by Impedance Spectroscopy)

Abstract Zur Charakterisierung von Alterungseffekten von Gerätebatterien ist Impedanzspektroskopie eine der aussichtsreichsten Methoden, insbesondere bei der Trennung verschiedener Alterungseffekte. Bei einem breiten Einsatz der Impedanzspektroskopie im Online-Betrieb ergeben sich spezielle Anforderungen. Messzeiten müssen trotz niedriger Frequenzen kurz sein, was durch die Verwendung mehrfrequenter Signale erreicht wird. Modelle müssen mit verschiedenen Batterietypen verwendbar sein, weshalb Modelle von Mischelektroden Anwendung finden. Die Modellparameter müssen ohne Nutzerinteraktion bestimmt werden, daher wird eine Kombination von Evolutionären Verfahren und dem Levenberg-Marquardt-Algorithmus verwendet. Experimentelle Untersuchungen an einer Lithium-Ion-Zelle zeigen die Eignung der Impedanzspektroskopie zur Charakterisierung von Alterungseffekten. Eine Verringerung der Kapazität um 14% nach 230 Entlade-/Ladezyklen sowie eine Veränderung des Elektrolytwiderstandes, des Durchtrittswiderstandes und des Warburgkoeffizienten um jeweils etwa 60% wurden beobachtet.

Bodenfeuchtemessung mittels Impedanzspektroskopie (Soil Moisture Measurement with Impedance Spectroscopy)

Abstract Verfahren zur Bestimmung der Bodenfeuchte haben diverse Nachteile aufgrund hoher Kosten und der Abhängigkeit der gemessenen Signale von den Materialeigenschaften des Bodens. Durch die Nutzung der Methode der Impedanzspektroskopie kann ein höherer Informationsgehalt im frequenzabhängigen Real- und Imaginärteil der Dielektrizitätskonstante bei der gesuchten Bodenfeuchte generiert werden. Untersuchungen zeigen, dass mathematische und physikalische Methoden für die Signalverarbeitung bei der bodenartunabhängigen Bodenfeuchtemessung genutzt werden können.