Felix Bach

An augmented reality home-training system based on the mirror training and imagery approach

Mirror training and movement imagery have been demonstrated to be effective in treating several clinical conditions, such as phantom limb pain, stroke-induced hemiparesis, and complex regional pain syndrome. This article presents an augmented reality home-training system based on the mirror and imagery treatment approaches for hand training. A head-mounted display equipped with cameras captures one hand held in front of the body, mirrors this hand, and displays it in real time in a set of four different training tasks: (1) flexing fingers in a predefined sequence, (2) moving the hand into a posture fitting into a silhouette template, (3) driving a “Snake” video game with the index finger, and (4) grasping and moving a virtual ball. The system records task performance and transfers these data to a central server via the Internet, allowing monitoring of training progress. We evaluated the system by having 7 healthy participants train with it over the course of ten sessions of 15-min duration. No technical problems emerged during this time. Performance indicators showed that the system achieves a good balance between relatively easy and more challenging tasks and that participants improved significantly over the training sessions. This suggests that the system is well suited to maintain motivation in patients, especially when it is used for a prolonged period of time.

The Importance of Synchrony and Temporal Order of Visual and Tactile Input for Illusory Limb Ownership Experiences – An fMRI Study Applying Virtual Reality

In the so-called rubber hand illusion, synchronous visuotactile stimulation of a visible rubber hand together with ones own hidden hand elicits ownership experiences for the artificial limb. Recently, advanced virtual reality setups were developed to induce a virtual hand illusion (VHI). Here, we present functional imaging data from a sample of 25 healthy participants using a new device to induce the VHI in the environment of a magnetic resonance imaging (MRI) system. In order to evaluate the neuronal robustness of the illusion, we varied the degree of synchrony between visual and tactile events in five steps: in two conditions, the tactile stimulation was applied prior to visual stimulation (asynchrony of −300 ms or −600 ms), whereas in another two conditions, the tactile stimulation was applied after visual stimulation (asynchrony of +300 ms or +600 ms). In the fifth condition, tactile and visual stimulation was applied synchronously. On a subjective level, the VHI was successfully induced by synchronous visuotactile stimulation. Asynchronies between visual and tactile input of ±300 ms did not significantly diminish the vividness of illusion, whereas asynchronies of ±600 ms did. The temporal order of visual and tactile stimulation had no effect on VHI vividness. Conjunction analyses of functional MRI data across all conditions revealed significant activation in bilateral ventral premotor cortex (PMv). Further characteristic activation patterns included bilateral activity in the motion-sensitive medial superior temporal area as well as in the bilateral Rolandic operculum, suggesting their involvement in the processing of bodily awareness through the integration of visual and tactile events. A comparison of the VHI-inducing conditions with asynchronous control conditions of ±600 ms yielded significant PMv activity only contralateral to the stimulation site. These results underline the temporal limits of the induction of limb ownership related to multisensory body-related input.

Data processing of high-rate low-voltage distribution grid recordings for smart grid monitoring and analysis

Power networks will change from a rigid hierarchic architecture to dynamic interconnected smart grids. In traditional power grids, the frequency is the controlled quantity to maintain supply and load power balance. Thereby, high rotating mass inertia ensures for stability. In the future, system stability will have to rely more on real-time measurements and sophisticated control, especially when integrating fluctuating renewable power sources or high-load consumers like electrical vehicles to the low-voltage distribution grid.In the present contribution, we describe a data processing network for the in-house developed low-voltage, high-rate measurement devices called electrical data recorder (EDR). These capture units are capable of sending the full high-rate acquisition data for permanent storage in a large-scale database. The EDR network is specifically designed to serve for reliable and secured transport of large data, live performance monitoring, and deep data mining. We integrate dedicated different interfaces for statistical evaluation, big data queries, comparative analysis, and data integrity tests in order to provide a wide range of useful post-processing methods for smart grid analysis.We implemented the developed EDR network architecture for high-rate measurement data processing and management at different locations in the power grid of our Institute. The system runs stable and successfully collects data since several years. The results of the implemented evaluation functionalities show the feasibility of the implemented methods for signal processing, in view of enhanced smart grid operation.

Power Grid Time Series Data Analysis with Pig on a Hadoop Cluster Compared to Multi Core Systems

In order to understand the dependencies in the power system we try to derive state information by combining high-rate voltage time series captures at different locations together with data analysis at different scales. This may enable large-scale simulation and modeling of the grid. Data captured by our recently introduced Electrical Data Recorders (EDR) and power grid simulation data are stored in the large scale data facility (LSDF) at Karlsruhe Institute of Technology (KIT) and growing rapidly in size. In this article we compare classic sequential multithreaded time series data processing to a distributed processing using Pig on a Hadoop cluster. Further we present our ideas for a better organization for our raw- and metadata that is indexable, searchable and suitable for big data.

Ein Ansatz zur automatisierten Erstellung umfangreicher und komplexer Simulationsmodelle für elektrische Übertragungsnetze aus OpenStreetMap-Daten

Zusammenfassung Lastfluss-Simulationen in Stromnetzen stellen die Grundlage für regelungstechnische Analysen dar, auch und gerade für Smart Grids der Zukunft. Die Generierung und die Verwaltung von komplexen und umfangreichen Stromnetzmodellen mit Berücksichtigung variabler regionaler Modellgranularität ist eine große Herausforderung, zumal die manuelle Erstellung aufgrund der enormen Datenmenge sehr schwer durchzuführen ist. Im vorliegenden Beitrag wird ein Ansatz zur automatisierten Generierung von Stromnetzmodellen ausschließlich aus OpenStreetMap-Daten, frei verfügbaren öffentlichen und amtlichen Datenbanken sowie Geo-Webdiensten vorgestellt. Eine neue Methode zur Generierung von dynamischen Lasten basierend auf Voronoi-Geopartitionierung unter Berücksichtigung der Netztopologie wird zudem ausgearbeitet. Ein erstes, voll automatisiert erstelltes Stromnetzmodell für das Übertragungsnetz in Baden-Württemberg wird mit dynamischer Lastflusssimulation evaluiert.

One year high rate low voltage recording - Devices, methods and results

Power system management currently advances from rigid to flexible and requires highly sophisticated monitoring and control in the future. In order to contribute to a more detailed analysis and to provide a fundamental database for simulation and investigation we developed the recording device EDR (Electrical Data Recorder). Synchronized continuous high rate captures of low voltage time series are stored in a central database without any data reduction. Since more than one year we already record voltage transient information from the KIT campus power supply. We checked the device for accuracy, for reliability and developed methods for large scale data storage and for use with simulation. In this paper we present these devices and methods, as well the improvements, derived from the experiences we gathered in our studies. We conclude that the EDR provides high accuracy and precision; our data storage and retrieval methods are fast and appropriate; but available simulation tools need improvements. The system is now ready for productive use in the low voltage supply grid.

Vision-based Hand Representation and Intuitive Virtual Object Manipulation in Mixed Reality

In this paper we introduce a method for representation of the human hand in virtual or mixed environments and interaction with virtual objects. We use a head-mounted display with two cameras installed on top to record the user s hand, which is then cut out and shown in the virtual environment. Extracted features like silhouette and fingertip positions enable direct visual interaction with objects in virtual worlds. Applications of the approach are presented and feature extraction methods, the overlay technique and the hardwareand software setup of the system are described. Finally the benefits and limitations of the approach are discussed.

Illusory Hand Ownership Induced by an MRI Compatible Immersive Virtual Reality Device

In this paper, we introduce a virtual reality based setup for triggering and studying illusory sensations of limb ownership as known from the popular rubber hand illusion. Unlike a similar setup introduced recently, this experiment is triggered by software automatically, which provides for a good synchrony and for high accuracy of visuotactile stimulation. The system is usable inside a magnetic resonance scanner which allows observing cortical activations at the same time. We tested two participants, one highly and the other lowly susceptible to the induction of illusory limb ownership, assessing their subjective experiences as well as their brain activity using functional magnetic resonance imaging. We present preliminary results suggesting that our setup induces illusory ownership experiences for a virtual limb successfully, accompanied by neuronal activation in integrative brain areas.

Preparing the electrical data recorder for comparative power network measurements

As the power system management currently advances from rigid to flexible, highly sophisticated monitoring and control is required in the future. By developing the Electrical Data Recorder (EDR) and preparing the device for comparative tests in low voltage power network at multiple locations we intend to contribute to a more detailed analysis and to provide a fundamental database for simulation and investigation. Using EDR devices, high rate captures of low voltage time series are acquired synchronously and are stored in a central large database without any information reduction. We performed extensive tests according to the IEC 61000-4-30 standard in order to assure the comparability of the measured values. Special attention was paid to the synchronization for achieving temporal coincidence of values measured at different locations. We developed methods for large scale data storage and interfaces for 3rd party simulation packages. In this paper we present the preparation of the device and the test procedures as well as the results. We report on the methods we already provide for data management and analysis. We conclude that the EDR provides sufficient accuracy and precision for comparative tests; our data storage and retrieval methods are fast and reliable; and we did not find 3rd party simulation tools appropriate for our needs, yet. However, the measurement system is ready for productive use in the low voltage supply grid.