Computer Science and Engineering

The measurement of image disparity is a fundamental precursor to binocular depth estimation. Recently, Jenkin and Jepson (1988) and Sanger (1988) described promising methods based on the output phase behaviour of band-pass Gabor lters. Here we discuss further justi cation for such techniques based on the stability of band-pass phase behaviour as a function of typical distortions that exist between left and right views. In addition, despite this general stability, we show that phase signals are occasionally very sensitive to spatial position and variations in scale, in which cases incorrect measurements occur. We nd that the primary cause for this instability is the existence of singularities in phase signals. With the aid of the local frequency of the lter output (provided by the phase derivative) and the local amplitude information, the regions of phase instability near the singularities are detected so that potentially incorrect measurements can be identi ed. In addition, we show how the local frequency can be used away from the singularity neighbourhoods to improve the accuracy of the disparity estimates. Some experimental results are reported.

A k ey di culty in the design of multi-agent robotic systems is the size and complexity o f t h e space of possible designs. In order to make principled design decisions, an understanding of the many possible system con gurations is essential. To this end, we present a taxonomy that classi es multiagent systems according to communication, computational and other capabilities. We survey existing e orts involving multi-agent systems according to their positions in the taxonomy. We also present additional results concerning multi-agent systems, with the dual purposes of illustrating the usefulness of the taxonomy in simplifying discourse about robot collective properties, and also demonstrating that a collective can be demonstrably more powerful than a single unit of the collective.

We demonstrate that humans can use optic flow to estimate distance travelled when appropriate scaling information is provided. Eleven subjects were presented with visual targets in a virtual corridor. They were then provided with optic flow compatible with movement along the corridor and asked to indicate when they had reached the previously presented target position. Performance depended on the movement profile: for accelerations above 0.1 m/s 2 performance was accurate. Slower optic-flow acceleration resulted in an overestimation of motion which was most pronounced for constant velocity motion when the overestimation reached 170%. The results are discussed in terms of the usual synergy between multiple sensory cues to motion and the factors that might contribute to such a pronounced miscalibration between optic flow and the resulting perception of motion.

This paper describes an underwater walking robotic system being developed under the name AQUA, the goals of the AQUA project, the overall hardware and software design, the basic hardware and sensor packages that have been developed, and some initial experiments. The robot is based on the RHex hexapod robot and uses a suite of sensing technologies, primarily based on computer vision and INS, to allow it to navigate and map clear shallow-water environments.

To enhance presence, facilitate sensory motor performance, and avoid disorientation or nausea, virtual environments and related augmented-reality or telepresence applications require the percept of a stable environment. End-end tracking latency (display lag) degrades this illusion of stability and has been identified as a major fault of existing virtual environment systems. Oscillopsia refers to the perception that the visual world appears to swim about or oscillate in space and is a manifestation of this loss of perceptual stability of the environment. In this paper, we address the temporal characteristics of perceptual stability in virtual environments. The effects of end-end latency and head velocity were investigated psychophysically. Subjects became significantly more likely to report oscillopsia during head movements when end-end latency or head velocity were increased. It is concluded that perceptual instability of the world arises with increased head motion and increased display lag. Oscillopsia is expected to be more apparent in tasks requiring real locomotion, rapid head movement or augmented reality.

A method is presented for tracking the three dimensional motion of points from their changing two-dimensional perspective images as viewed by a nonconvergent binocular vision system. The algorithm relies on a general smoothness assumption to guide the tracking process, and application of the tracking algorithm to a three-dimensional moving light display based on Cutting's[1] Walker program as well as other domains are discussed.

A Stereo Active Vision Interface (SAVI) is introduced which detects frontal faces in real world environments and performs particular active control tasks dependent on hand gestures given by the person the system attends to. The SAVI system is thought of as a smart user interface for teleconferencing, telemedicine, and distance learning applications. To reduce the search space in the visual scene the processing is started with the detection of connected skin colour regions applying a new radial scanline algorithm.

1.1 Why a Taxonomy is Important A key difficulty in the design of multi-agent robotic systems is the size and complexity of the space of possible designs. In order to make principled design decisions, an understanding of the many possible system configurations is essential. In Dudek et al.[DJMW96] we presented a taxonomy that classifies multi-agent systems according to communication, computational and other capabilities.

Abstract The direction of 'up'has traditionally been measured by setting a line (luminous if necessary) to the apparent vertical, a direction known as the 'subjective visual vertical'(SVV); however for optimum performance in visual skills including reading and facial recognition, an object must to be seen the 'right way up'—a separate direction which we have called the 'perceptual upright'(PU). In order to measure the PU, we exploited the fact that some symbols rely upon their orientation for recognition.

Abstract AQUA, an amphibious robot that swims via the motion of its legs rather than using thrusters and control surfaces for propulsion, can walk along the shore, swim along the surface in open water, or walk on the bottom of the ocean. The vehicle uses a variety of sensors to estimate its position with respect to local visual features and provide a global frame of reference

Abstract Attending to multiple speakers in a video teleconferencing setting is a complex task. From a visual point of view, multiple speakers can occur at different locations and present radically different appearances. From an audio point of view, multiple speakers may be speaking at the same time, and background noise may make it difficult to localize sound sources without some a priori estimate of the sound source locations.

Abstract Visual motion can be a cue to travel distance when the motion signals are integrated. Distance estimates from visually simulated self-motion are imprecise, however. Previous work in our labs has given conflicting results on the imprecision: experiments by Frenz and Lappe had suggested a general underestimation of travel distance, while results from Redlick, Jenkin and Harris had shown an overestimation of travel distance.

The ARK mobile robot project has designed and implemented a series of mobile robots capable of navigating within industrial environments without relying on artificial landmarks or beacons. The ARK robots employ a novel sensor, Laser Eye, that combines vision and laser ranging to efficiently locate the robot in a map of its environment. Laser Eye allows self-location of the robot in both walled and open areas.