Geehyuk Lee

Accelerometer Signal Processing for User Activity Detection

Estimation of human motion states is important enabling technologies for realizing a pervasive computing environment. In this paper, an improved method for estimating human states from accelerometer data is introduced. Our method for estimating human motion state utilizes various statistics of accelerometer data, such as mean, standard variation, skewness, kurtosis, eccentricity, as features for classification, and is expected to be more robust than other existing methods that rely on only a few simple statistics. A series of experiments for testing the effectiveness of the proposed method has been performed, and its result is presented.

Force gestures: augmenting touch screen gestures with normal and tangential forces

Force gestures are touch screen gestures augmented by the normal and tangential forces on the screen. In order to study the feasibility of the force gestures on a mobile touch screen, we implemented a prototype touch screen device that can sense the normal and tangential forces of a touch gesture on the screen. We also designed two example applications, a web browser and an e-book reader, that utilize the force gestures for their primary actions. We conducted a user study with the prototype and the applications to study the characteristics of the force gestures and the effectiveness of their mapping to the primary actions. In the user study we could also discover interesting usability issues and collect useful user feedback about the force gestures and their mapping to GUI actions.

SplitBoard: A Simple Split Soft Keyboard for Wristwatch-sized Touch Screens

Text entry on a smartwatch is a challenging problem due to the devices limited screen area. In this paper, we introduce the SplitBoard, which is a soft keyboard designed for a smartwatch. As the user flicks left or right on the keyboard, it switches between the left and right halves of a QWERTY keyboard. We report the results of two user experiments where the SplitBoard was compared to an ordinary QWERTY keyboard, the ZoomBoard, SlideBoard, and Qwerty-like keypad. We measured the initial performance with new users for each method. The SplitBoard outperformed all other techniques in the experiments. The SplitBoard is expected to be a viable option for smartwatch text entry because of its light processing requirements, good performance, and immediate learnability.

The bifurcating neuron network 2: an analog associative memory

The Bifurcating Neuron (BN), a chaotic integrate-and-fire neuron, is a model of a neuron augmented by coherent modulation from its environment. The BN is mathematically equivalent to the sine-circle map, and this equivalence relationship allowed us to apply the mathematics of one-dimensional maps to the design of a BN network. The study of the bifurcating diagram of the BN revealed that the BN, under a suitable condition, can function as an amplitude-to-phase converter. Also, being an integrate-and-fire neuron, it has an inherent capability to function as a coincidence detector. These two observations led us to the design of the BN Network 2 (BNN-2), a pulse-coupled neural network that exhibits associative memory of multiple analog patterns. In addition to the usual dynamical properties as an associative memory, the BNN-2 was shown to exhibit volume-holographic memory: it switches to different pages of its memory space as the frequency of the coherent modulation changes, meaning context-sensitive memory.

Analog realization of arbitrary one-dimensional maps

An increasing number of applications of a one-dimensional (1-D) map as an information processing element are found in the literature on artificial neural networks, image processing systems, and secure communication systems. In search of an efficient hardware implementation of a 1-D map, we discovered that the bifurcating neuron (BN), which was introduced elsewhere as a mathematical model of a biological neuron under the influence of an external sinusoidal signal, could provide a compact solution. The original work on the BN indicated that its firing time sequence, when it was subject to a sinusoidal driving signal, was related to the sine-circle map, suggesting that the BN can compute the sine-circle map. Despite its rich array of dynamical properties, the mathematical description of the BN is simple enough to lend itself to a compact circuit implementation. In this paper, we generalize the original work and show that the computational power of the BN can be extended to compute an arbitrary 1-D map. Also, we describe two possible circuit models of the BN: the programmable unijunction transistor oscillator neuron, which was introduced in the original work as a circuit model of the BN, and the integrated-circuit relaxation oscillator neuron (IRON), which was developed for more precise modeling of the BN. To demonstrate the computational power of the BN, we use the IRON to generate the bifurcation diagrams of the sine-circle map, the logistic map, as well as the tent map, and then compare them with exact numerical versions. The programming of the BN to compute an arbitrary map can be done simply by changing the waveform of the driving signal, which is given to the BN externally; this feature makes the circuit models of the BN especially useful in the circuit implementation of a network of 1-D maps.

RemoteTouch: touch-screen-like interaction in the tv viewing environment

We explored the possibility of touch-screen-like interaction with a remote control in the TV-viewing environment. A shadow representing the users thumb touches the screen, presses a button, flicks a cover-flow list, and draws a simple stroke, while the thumb stays and moves on and above the touchpad. In order to implement the concept we developed an optical touchpad for tracking the thumb hovering over its surface, and designed a TV application to demonstrate possible new interaction styles. Throughout two iterations of prototyping, we corrected some of our false expectations, and also verified its potential as a viable option for a TV remote control. This paper presents technical issues and requirements for the hover-tracking touchpad and a complete report of our user studies to explore touch-screen-like interaction for the TV.

Interaction techniques for unreachable objects on the touchscreen

Large-screen mobile devices have recently been introduced. While they can display more information on the screen, they have raised the issue of thumb reachability during one-handed use. To solve this problem, we designed four factorial combinations of two triggering techniques (Edge and Large touch) and two selection techniques (Sliding screen and Extendible cursor). A prototype realizing the four interaction techniques was implemented, and a user study was conducted to examine the benefits and problems faced while using these techniques in both portrait and landscape orientations. User study exhibited a significant advantage of Edge triggering with Extendible cursor technique. Also, we collected meaningful comments from the user interview.

Investigating the Information Transfer Efficiency of a 3x3 Watch-back Tactile Display

A watch-back tactile display (WBTD) is expected to be a viable supplement to the user interface limitations of a smartwatch. However, its design requires that many design parameters such as tactor types and stimulus patterns be determined. We conducted a series of experiments to explore the design space of a WBTD consisting of 3×3 tactors. We demonstrated that tactor types and the temporal patterns and locus of a stimulus produce statistically significant effects on the efficiency of a WBTD. The experimental results can act as a practical guideline for the design of an efficient WBTD.

TapBoard: making a touch screen keyboard more touchable

We propose the TapBoard, a touch screen software keyboard that regards tapping actions as keystrokes, and other touches as touched states. In a series of user studies, we could validate the effectiveness of the TapBoard concept. First, we could show that tapping to type is in fact compatible with the existing typing skill of most touch screen keyboard users. Second, users could soon adapt to the TapBoard and learn to rest their fingers in a touched state. Finally, we confirm by a controlled experiment that there is no difference in the text entry performance between the TapBoard and a traditional touch screen software keyboard. In addition to these experimental results, we demonstrate a few new interaction techniques that will be made possible by the TapBoard.

ForceDrag : using pressure as a touch input modifier

It is common to use modifier keys in a PC environment in order to change drag modes, but mobile devices with a touch screen do not provide this option. Thus, we present ForceDrag to address this issue, which is a touch drag operation where pressure is used as a modifier key to change touch drag modes. We also introduce the concept of force lock and we compare three selection techniques for performing a force lock in a user study. We also describe a prototype implementation and discuss early user feedback on ForceDrag.