In this paper we present our results on using electromyographic (EMG) sensor arrays for finger gesture recognition. Sensing muscle activity allows to capture finger motion without placing sensors directly at the hand or fingers and thus may be used to build unobtrusive body-worn interfaces. We use an electrode array with 192 electrodes to record a high-density EMG of the upper forearm muscles. We present in detail a baseline system for gesture recognition on our dataset, using a naive Bayes classifier to discriminate the 27 gestures. We recorded 25 sessions from 5 subjects. We report an average accuracy of 90% for the within-session scenario, showing the feasibility of the EMG approach to discriminate a large number of subtle gestures. We analyze the effect of the number of used electrodes on the recognition performance and show the benefit of using high numbers of electrodes. Cross-session recognition typically suffers from electrode position changes from session to session. We present two methods to estimate the electrode shift between sessions based on a small amount of calibration data and compare it to a baseline system with no shift compensation. The presented methods raise the accuracy from 59% baseline accuracy to 75% accuracy after shift compensation. The dataset is publicly available.

Any user interface which automatically interprets the user's input using natural modalities like gestures makes mistakes. System behavior depending on such mistakes will confuse the user and lead to an erroneous interaction flow. The automatic detection of error potentials in electroencephalographic data recorded from a user allows the system to detect such states of confusion and automatically bring the interaction back on track. In this work, we describe the design of such a self-correcting gesture interface, implement different strategies to deal with detected errors, use a simulation approach to analyze performance and costs of those strategies and execute a user study to evaluate user satisfaction. We show that self-correction significantly improves gesture recognition accuracy at lower costs and with higher acceptance than manual correction.

We introduce BioKIT, a new Hidden Markov Model based toolkit to preprocess, model and interpret biosignals such as speech, motion, muscle and brain activities. The focus of this toolkit is to enable researchers from various communities to pursue their experiments and integrate real-time biosignal interpretation into their applications. BioKIT boosts a flexible two-layer structure with a modular C++ core that interfaces with a Python scripting layer, to facilitate development of new applications. BioKIT employs sequence-level parallelization and memory sharing across threads. Additionally, a fully integrated error blaming component facilitates in-depth analysis. A generic terminology keeps the barrier to entry for researchers from multiple fields to a minimum. We describe our onlinecapable dynamic decoder and report on initial experiments on three different tasks. The presented speech recognition experiments employ Kaldi [1] trained deep neural networks with the results set in relation to the real time factor needed to obtain them.

We propose a vision-based system that recognizes handwriting in mid-air. The system does not depend on sensors or markers attached to the users and allows unrestricted character and word input from any position. It is the result of combining handwriting recognition based on Hidden Markov Models with multi-camera 3D hand tracking. We evaluated the system for both quantitative and qualitative aspects. The system achieves recognition rates of 86.15% for character and 97.54% for small-vocabulary isolated word recognition. Limitations are due to slow and low-resolution cameras or physical strain. Overall, the proposed handwriting recognition system provides an easy-to-use and accurate text input modality without placing restrictions on the users.

We demonstrate our airwriting interface for mobile hands-free text entry. The interface enables a user to input text into a computer by writing in the air like on an imaginary blackboard. Hand motion is measured by an accelerometer and a gyroscope attached to the back of the hand and data is sent wirelessly to the processing computer. The system can continuously recognize arbitrary sentences based on a predefined vocabulary in real-time. The recognizer uses Hidden Markov Models (HMM) together with a statistical language model. We achieve a user-independent word error rate of 11% for a 8K vocabulary based on an experiment with nine users.

Endsuleit and Mie (2003) have proposed a model for the robust and private evaluation of a function within a group of cooperating mobile agents, called an agent alliance. The model has been given abstractly and is based on a cryptographic protocol for secure multi-party computation. This paper aims on the investigation of the complexity of a threshold signature performed within the alliance model. The goal is to achieve a practical security model in which agents can be allowed to act fully autonomously in their users name without relying on a trusted authority