Passive Electric Field Sensing for Ubiquitous and Environmental Perception

Electric Field Sensing plays an important role in the research branches of Environmental Perception as well as in Ubiquitous Computing. Environmental Perception aims to collect data of the surroundings, while Ubiquitous Computing has the objective of making computing available at any time. This includes the integration of sensors to perceive environmental influences in an unobtrusive way. Electric Field Sensing, also referenced as Capacitive Sensing, is an often used sensing modality in these research fields, for example, to detect the presence of persons or to locate touches and interactions on user interfaces. Electric Field Sensing has a number of advantages over other technologies, such as the fact that Capacitive Sensing does not require direct line-of-sight contact with the object being sensed and that the sensing system can be compact in design. These advantages facilitate high integrability and allow the collection of data as required in Environmental Perception, as well as the invisible incorporation into a user's environment, needed in Ubiquitous Computing. However, disadvantages are often attributed to Capacitive Sensing principles, such as a low sensing range of only a few centimeters and the generation of electric fields, which wastes energy and has several more problems concerning the implementation. As shown in this thesis, this only affects a subset of this sensing technology, namely the subcategory of active capacitive measurements. Therefore, this thesis focuses on the mainly open area of Passive Electric Field Sensing in the context of Ubiquitous Computing and Environmental Perception, as active Capacitive Sensing is an open research field which already gains a lot of attention. The thesis is divided into three main research questions. First, I address the question of whether and how Passive Electric Field Sensing can be made available in a cost-effective and simple manner. To this end, I present various techniques for reducing installation costs and simplifying the handling of these sensor systems. After the question of low-cost applicability, I examine for which applications passive electric field sensor technology is suitable at all. Therefore I present several fields of application where Passive Electric Field Sensing data can be collected. Taking into account the possible fields of application, this work is finally dedicated to the optimization of Passive Electric Field Sensing in these cases of application. For this purpose, different, already known signal processing methods are investigated for their application for Passive Electric Field sensor data. Furthermore, besides these software optimizations, hardware optimizations for the improved use of the technology are presented

Optimizations for Passive Electric Field Sensing

Passive electric field sensing can be utilized in a wide variety of application areas, although it has certain limitations. In order to better understand what these limitations are and how countervailing measures to these limitations could be implemented, this paper contributes an in-depth discussion of problems with passive electric field sensing and how to bypass or solve them. The focus lies on the explanation of how commonly known signal processing techniques and hardware build-up schemes can be used to improve passive electric field sensors and the corresponding data processing

Kontextbasiertes Dokumentenmanagement in intelligenten Wohnumgebungen

Heutzutage werden vermehrt verschiedenste Multimediageräte miteinander in immer weiter wachsenden intelligenten Umgebungen vernetzt. Obwohl diese Netze heutzutage Dank mobiler Technik und WLAN fast omnipräsent sind, arbeiten die darin enthaltenen Abspielgeräte immer noch weitgehend distinkt voneinander. Das einfache Abspielen einer Datei auf dem Wiedergabegerät A, die ursprünglich auf Gerät B beherbergt wird, ist daher, trotz der theoretisch vorhandenen Möglichkeit durch die Vernetzung, eine komplizierte Aufgabe geworden. Besonders das Abspielen und Anzeigen von Dateien auf Multimediageräten mit verschiedenen, unter Umständen begrenzten Wiedergabefähigkeiten ist ein nicht triviales Problem. Aktuelle Lösungen aus der Industrie setzen hier momentan noch auf wenig interoperable Ansätze in proprietären Systemen. Einzelne Multimediageräte gleicher Hersteller lassen sich so zwar intelligent verbinden, gerade mit Hinsicht auf die Benutzbarkeit skaliert das System jedoch schlecht, die (auch physikalische) Verteilung erhöht die Schwierigkeit des Zugangs zu den Funktionen und die Steuerung ist weitgehend unabhängig vom Kontext des Benutzers. In dieser Arbeit wird daher eine Lösung entwickelt, deren Fokus insbesondere auf dem kontextbasierten Abspielen von Dateien liegt. Genauer auf dem Wiedergeben von Video-, Musik-, Bild- sowie Textdateien auf Ausgabegeräten mit unterschiedlichen Darstellungsmöglichkeiten, sowie der Verteilung dieser Multimediadateien zwischen den Geräten. Im Zentrum steht hierbei ein mobiles Gerät zur Visualisierung der räumlichen Verteilung aller Geräte unter Einbeziehung der Position des Benutzers und der intuitiven Verschiebung von Dateien verschiedener Typen zwischen diesen

Activity recognition based on electric potential sensing

Electric fields are influenced by the human body and other conducting materials. This property can be used to detect presence of human bodies. For the detection of presence and activity recognition, mostly capacitive measurement techniques are used. Despite the fact that capacitive sensing is an fairly old technology, since it has been around since the 1920's, it is still a hot topic of ongoing research works. Today, capacitive measurement techniques are used in touch-screens, in the automobile industry and many other fields of Ubiquitous Computing. But a drawback of the capacitive technology is the energy consumption, which is an important aspect of mobile devices. That is why, in this thesis, i investigate the potential of electric potential sensing (EPS), a purely passive capacitive measurement technique, which can be implemented with an extremely low power consumption. First, the most commonly used capacitive measurement techniques will be analyzed and how they work. This is done to understand the pros and cons of electric potential sensing compared to other technologies. After analyzing electric potential sensing and related capacitive measurement techniques, we will have a closer look at some possible areas of application of electric potential sensing in an explorative studie. Hence, multiple experiments, involving electric potential sensing in various environmental settings for different use-case scenarios, will be conducted. This is done to evaluate the best use-case for this technology. Then, after selecting the most suitable use-case for activity recognition with EPS, two sensor systems are developed, discussed and evaluated. At the end, the benefits and limitations of EPS will be concluded with regards to capacitive sensing

Context-Based Document Management in Smart Living Environments

Nowadays an increasingly wide variety of multimedia devices can be networked together in ever-growing smart environments. Although these networks, thanks to mobile technology and Wi-Fi, are almost ubiquitous by now, the players therein are still working largely distinct from one another. To simply play a file on the playback device A, which is originally housed on device B, is therefore a complicated task, despite the theoretical possibility provided by existing networking. Especially playing and viewing files on multimedia devices under various circumstances and limited reproduction capabilities is a non-trivial problem. Current solutions from industry still put little interoperable approaches in proprietary systems. Individual multimedia devices of the same manufacturer can be combined intelligently, but with respect to the usability the system scales poorly, the (also physical) distribution increases the difficulty of access to the functions and control is largely independent of the user's context. In this work, a solution is developed, which focuses in particular on the context-based playback of files: sending video, music, image and text files to output devices with different display options, as well as the distribution of these multimedia files between devices. Activities are centered on a mobile device for visualizing the spatial distribution of all devices, including the user's position and the intuitive movement of files of various types between them

Context-Based Document Management in Smart Living Environments

Nowadays an increasingly wide variety of multimedia devices can be networked together in ever-growing smart environments. Although these networks, thanks to mobile technology and Wi-Fi, are almost ubiquitous by now, the players therein are still working largely distinct from one another. To simply play a file on the playback device A, which is originally housed on device B, is therefore a complicated task, despite the theoretical possibility provided by existing networking. Especially playing and viewing files on multimedia devices under various circumstances and limited reproduction capabilities is a non-trivial problem. Current solutions from industry still put little interoperable approaches in proprietary systems. Individual multimedia devices of the same manufacturer can be combined intelligently, but with respect to the usability the system scales poorly, the (also physical) distribution increases the difficulty of access to the functions and control is largely independent of the user's context. In this work, a solution is developed, which focuses in particular on the context-based playback of files: sending video, music, image and text files to output devices with different display options, as well as the distribution of these multimedia files between devices. Activities are centered on a mobile device for visualizing the spatial distribution of all devices, including the user's position and the intuitive movement of files of various types between them

Linoc: A Prototyping Platform for Capacitive and Passive Electrical Field Sensing

In this paper the Linoc prototyping toolkit is presented. It is a sensor toolkit that focuses on fast prototypingof sensor systems, especially on capacitive ones. The toolkit is built around two capacitive and two ElectricPotential Sensing (EPS) groups providing unobtrusive proximity detection in the field of Human ComputerInterface (HCI). The toolkits focus lies on its usability and connectivity in order to be adapted in future researchand novel use cases. A common obstacle in the beginning of a project is the time required to familiarize withpresent tools and systems, before the actual project can be attended to. Another obstacle while tackling newtasks is the actual physical connection of sensors to the processing unit. This situation can be even worsedue to dependencies on previous work, most of the times not fully documented and missing knowledge evenif the the original designer is involved. Good toolkits can help to overcome this problem by providing alayer of abstraction and allowing to work on a higher level. If the toolkit however requires too much time tofamiliarize or behaves too restrictive, its goal has been missed and no benefits are generated. To assess thequality of the Linoc prototyping toolkit, it was evaluated in terms of three different aspects: demonstration,usage and technical performance. The usage study found good reception, a fast learning curve and an interestto use the toolkit in the future. Technical benchmarks for the capacitive sensors show a detectable range equalto its predecessors and several operational prototypes prove that the toolkit can actually be used in projects

New approaches for localization and activity sensing in smart environments

Smart environments need to be able to fulfill the wishes of its occupants unobtrusively. To achieve this goal, it has to be guaranteed that the current state environment is perceived at all times. One of the most important aspects is to find the current position of the in- habitants and to perceive how they move in this environment. Numerous technologies enable such supervision. Particularly challenging are marker-free systems that are also privacy-preserving. In this paper, we present two such systems for localizing inhabitants in a Smart Environment using - electrical potential sensing and ultrasonic Doppler sensing. We present methods that infer location and track the user, based on the acquired sensor data. Finally, we discuss the advantages and challenges of these sensing technologies and provide an overview of future research directions

VeinXam: A Low-Cost Deep Veins Function Assessment

A venous insufficiency, to which the deep veins of the lower human extremities are particularly susceptible, can lead to serious diseases, such as a deep vein thrombosis (DVT) with subsequent risks of severe implications, e.g. pulmonary embolism or a post-thrombotic syndrome (PTS) [6]. The current standard procedure to diagnose venous insufficiency is performed exclusively in medical offices and hospitals in the form of in-patient treatments with special medical equipment. This hurdle for the patient, combined with the often diffuse symptoms of venous insufficiency [7], may lead to a late discovery of diseases such as DVTs and increases the risk of secondary diseases as well as treatment costs [3]. To address these issues, we propose a novel method for continuous monitoring of the current venous function by adapting the Light Reflection Rheography (LLR) and using low-cost wearable sensor technology and a smartphone app, aiming to deliver critical early stage information about pathological changes of the blood flow in the lower limbs