Sangyoon Lee

Haptic control of a mobile robot: a user study

We address the problem of teleoperating a mobile robot using shared autonomy: an on-board controller performs obstacle avoidance while the operator uses the manipulandum of a haptic probe to designate the desired speed and rate of turn. Sensors on the robot are used to measure obstacle range information. We describe a strategy to convert such range information into forces, which are reflected to the operators hand, via the haptic probe. This haptic information provides feedback to the operator in addition to imagery from a front-facing camera mounted on the mobile robot. Extensive experiments with a user population show that the added haptic feedback significantly improves operator performance in several ways (reduced collisions, increased minimum distance between the robot and obstacles) without a significant increase in navigation time.

Haptic teleoperation of a mobile robot: a user study

The problem of teleoperating a mobile robot using shared autonomy is addressed: An onboard controller performs close-range obstacle avoidance while the operator uses the manipulandum of a haptic probe to designate the desired speed and rate of turn. Sensors on the robot are used to measure obstacle-range information. A strategy to convert such range information into forces is described, which are reflected to the operators hand via the haptic probe. This haptic information provides feedback to the operator in addition to imagery from a front-facing camera mounted on the mobile robot. Extensive experiments with a user population both in virtual and in real environments show that this added haptic feedback significantly improves operator performance, as well as presence, in several ways (reduced collisions, increased minimum distance between the robot and obstacles, etc.) without a significant increase in navigation time.

Numerical algorithms for spatial registration of line fiducials from cross-sectional images.

We present several numerical algorithms for six-degree-of-freedom rigid-body registration of line fiducial objects to their marks in cross-sectional planar images, such as those obtained in CT and MRI, given the correspondence between the marks and line fiducials. The area of immediate application is frame-based stereotactic procedures, such as radiosurgery and functional neurosurgery. The algorithms are also suitable to problems where the fiducial pattern moves inside the imager, as is the case in robot-assisted image-guided surgical applications. We demonstrate the numerical methods on clinical CT images and computer-generated data and compare their performance in terms of robustness to missing data, robustness to noise, and speed. The methods show two unique strengths: (1) They provide reliable registration of incomplete fiducial patterns when up to two-thirds of the total fiducials are missing from the image; and (2) they are applicable to an arbitrary combination of line fiducials without algorithmic modification. The average speed of the fastest algorithm is 0.3236 s for six fiducial lines in real CT data in a Matlab implementation.

A robotic library system for an off-site shelving facility

This paper describes a unique robotics project, Comprehensive Access to Printed Materials (CAPM), within the context of libraries. As libraries provide a growing array of digital library services and resources, they continue to acquire large quantities of printed material. This combined pressure of providing electronic and print-based resources and services has led to severe space constraints for many libraries, especially academic research libraries. Consequently, many libraries have built or plan to build off-site shelving facilities to accommodate printed materials. An autonomous mobile robotic library system has been developed to retrieve items from bookshelves and carry them to scanning stations located in the off-site shelving facility. In subsequent stages, remote users will be able to trigger this process through a web interface in order to achieve real-time browsing of printed materials. Enhanced commercial robot systems are used in this project. The developments of the robot design, control systems, simulations, experiments and results are presented.

Effects of haptic feedback, stereoscopy, and image resolution on performance and presence in remote navigation

Traditionally, the main goal of teleoperation has been to successfully achieve a given task as if performing the task in local space. An emerging and related requirement is to also match the subjective sensation or the user experience of the remote environment, while maintaining reasonable task performance. This concept is often called presence or (experiential) telepresence, which is informally defined as the sense of being in a mediated environment. In this paper, haptic feedback is considered as an important element for providing improved presence and reasonable task performance in remote navigation. An approach for using haptic information to experientially teleoperate a mobile robot is described. Haptic feedback is computed from the range information obtained by a sonar array attached to the robot, and delivered to a users hand via a haptic probe. This haptic feedback is provided to the user, in addition to stereoscopic images from a forward-facing stereo camera mounted on the mobile robot. The experiment with a user population in a real-world environment showed that haptic feedback significantly improved both task performance and user-felt presence. When considering user-felt presence, no interaction among haptic feedback, image resolution, and stereoscopy was observed, that is, haptic feedback was effective, regardless of the fidelity of visual elements. Stereoscopic images also significantly improved both task performance and user-felt presence, but high-resolution images only significantly improved user-felt presence. When considering task performance, however, it was found that there was an interaction between haptic feedback and stereoscopy, that is, stereoscopic images were only effective when no force feedback was applied. According to the multiple regression analysis, haptic feedback was a higher contributing factor to the improvement in performance and presence than image resolution and stereoscopy.

Affective property evaluation of virtual product designs

In addition to the intended functionality of the product, its affective properties (or Kansei) have emerged as important evaluation criteria for the successful marketing of the product. Recently, immersive virtual reality systems have been suggested as an ideal platform for affective analysis of an evolving design because of among other things, the natural style of interaction they offer when examining the product. In this paper, we compare the effectiveness of three types of virtual environments for evaluating the affective properties of mobile phones to that of the real. Each virtual environment offers different degrees of realism in terms of visual, aural, and tactile aspects. Our experiment has shown that the virtual affective evaluation results correlated very highly with that of the real, and but no statistically significant difference could be found between the three systems. This finding was contrary to our initial thought and the conventional notion that the characteristics of immersive virtual reality systems would contribute to making it a better platform for virtual evaluation of product designs. Thus, it goes to say that employing immersive systems is not necessarily cost effective solution for affective analysis of product designs (desktop VR system suffices).

Interhelical Angle and Distance Preferences in Globular Proteins

Orientational preferences between interacting helices within globular proteins have been studied extensively over the years. A number of classical structural models such as knobs into holes and ridges into grooves were developed decades ago to explain perceived preferences in interhelical angle distributions. In contrast, relatively recent works have examined statistical biases in angular distributions which result from spherical geometric effects. Those works have concluded that the predictions of classical models are due in large part to these biases. In this article we perform an analysis on the largest set of helix-helix interactions within high-resolution structures of nonhomologous proteins studied to date. We examine the interhelical angle distribution as a function of spatial distance between helix pairs. We show that previous efforts to normalize angle distribution data did not include two important effects: 1), helices can interact with each other in three distinct ways which we refer to as line-on-line, endpoint-to-line, and endpoint-to-endpoint, and each of these interactions has its own geometric effects which must be included in the proper normalization of data; and 2), all normalizations that depend on geometric parameters such as interhelical angle must occur before the data is binned to avoid artifacts of bin size from biasing the conclusions. Taking these two points into account, we find that there are very pronounced preferences for helices to interact at angles of approximately +/-160 and +/-20 degrees in the line-on-line case. This pattern persists when the closest alpha-carbons in the helices vary from 4 to 12 A. The endpoint-to-line and endpoint-to-endpoint cases also exhibit distinct preferences when the data is normalized properly. Analysis of the local structural interactions which give rise to these preferences has not been studied here and is left for future work.

Evaluation of pointing techniques for ray casting selection in virtual environments

Various techniques for object selection in virtual environments have been proposed over the years. Among them, the virtual pointer or ray-casting is one of the most popular method for object selection because it is easy and intuitive to use and allows the user to select objects that are far away. Variants of the virtual pointer metaphor include the Aperture, Flashlight, and Image plane method as categorized as such. In a monoscopic environment, these methods are essentially 2D interaction techniques, as the selection is made effectively on the image plane. Such a 2D based selection (or more generally, interaction) method has an added advantage in that it can find many good uses in 3D environments ranging from a simple 2D oriented subtask (object selection on a constrained surface, menu selection) to a situation where a whole 2D application (e.g. sketching tool, desktop manager) is embedded in the 3D environment. In this paper, we experimentally compare the performance of four different virtual pointer implementations, namely, the direct image plane selection, head-directed pointer, hand directed pointer and head-hand directed pointer. The experimental results revealed that the direct image plane selection produced the best performance among the four in terms of both task completion time and the pixel-level pointing error.

Novel Algorithms for Robust Registration of Fiducials in CT and MRI

In this paper we present several numerical algorithms for registering fiducials in planar CT or MRI images to their corresponding three-dimensional locations. The unique strength of these methods is their ability to robustly handle incomplete fiducials patterns, even in extreme cases when as much as one third of the fiducial data is missing from the images. We compare the effectiveness of these algorithms in terms of flops and robustness on actual CT data sets.

Incorporating co-presence in distributed virtual music environment

In this paper, we present PODIUM (POstech Distributed virtual Music environment), a distributed virtual environment that allows users to participate in a shared space and play music with other participants in a collaborative manner. In addition to playing virtual instruments, users can communicate and interact in various ways to enhance the collaboration and, thus, the quality of the music played together. Musical messages are generated note by note through interaction with the keyboard, mouse, and other devices, and transmitted through an IP-multicasting network among participants. In addition to such note-level information, additional messages for visualization, and interaction are supported. Real world based visualization has been chosen, against, for instance, abstract music world based visualization, to promote co-presence (e.g. recognize and interact with other players), which is deemed important for collaborative music production. In addition to the entertainment purpose, we hope that DVME will find great use in casual practice sessions for even professional performers/orchestras/bands.Since even a slight interruption in the flow of the music or out - of-synch graphics and sound would dramatically decrease utility of the system, we employ various techniques to minimize the network delay. An adapted server-client architecture and UDP s are used to ensure fast packet deliveries and reduce the data bottleneck problem. Time-critical messages such as MIDI messages are multicasted among clients, and the less time-critical and infrequently updated messages are sent through the server. Predefined animations of avatars are invoked by interpreting the musical messages. Using the latest graphics and sound processing hardware, and by maintaining an appropriate scene complexity, and a frame rate sufficiently higher than the fastest note duration, the time constraint for graphics and sound synchronization can be met. However, we expect the network delay could cause considerable problems when the system is scaled up for many users and processing simultaneous notes (for harmony). To assess the scalability, we carried out a performance analysis of our system model to derive the maximum number of simultaneous participants. For example, according to our data, about 50 participants should be able to play together without significant disruption, each using one track with five simultaneous notes and for playing a musical piece at a speed of 16 ticks per second in a typical PC/LAN environment.In hopes of enhancing the feeling of co-presence among participants, a simple sound localization technique is used to compute panning and relative volumes from positions and orientations of participants. This reduced sound localization model is used also in order to minimize the computational cost and the network traffic. Participants can send predefined messages by interacting with the keyboard, mouse, and other input devices. All of the predefined messages are mapped into simple avatar motions, such as playing various types of instruments (players), making applause (audience), and conducting gestures (conductors). We believe that for coordinated music performance, indirect interaction will be the main interaction method, for example, exchanging particular gestures, signals, and voice commands to synchronize music, confirming and reminding expression of the upcoming portion of the music, and just exchanging glances to enjoy each others emotion. In this view, there would be mainly three groups of participants: conductor, players, and the audience, playing different roles, but creating co-presence together through mutual recognition. We ran a simple experiment comparing the music performance of two groups of participants, one provided with co-presence cues and the other without, and found no performance edge by the group with the co-presence cues. Such a result can serve as one guideline for building music-related VR applications.