Keihachiro Tachibana

Virtual object manipulation on a table-top AR environment

We address the problems of virtual object interaction and user tracking in a table-top augmented reality (AR) interface. In this setting there is a need for very accurate tracking and registration techniques and an intuitive and useful interface. This is especially true in AR interfaces for supporting face to face collaboration where users need to be able to easily cooperate with each other. We describe an accurate vision-based tracking method for table-top AR environments and tangible user interface (TUI) techniques based on this method that allow users to manipulate virtual objects in a natural and intuitive manner. Our approach is robust, allowing users to cover some of the tracking markers while still returning camera viewpoint information, overcoming one of the limitations of traditional computer vision based systems. After describing this technique we describe its use in prototype AR applications.

The effects of shadow representation of virtual objects in augmented reality

In this paper, we describe the effects of shadow representation of virtual objects in augmented reality. Optical consistency is important in order to create realistic augmented reality environments. We focus on providing accurate shadows and made two assumptions about the effects of shadow representation of virtual objects. First, that the shadow of virtual objects provides a stronger connection between the real world and virtual objects and so increases virtual object presence. Second, that the shadow of virtual objects provides depth cues and so makes three-dimensional perceptions easier for the users of the interface. We report on two experiments that show that these assumptions are correct. We also find that users report that a characteristic shadow shape provides more virtual object presence in spite of incorrect virtual light direction.

A registration method based on texture tracking using ARToolKit

In this paper, we propose a computer-vision based registration method for augmented reality based on template matching. Computer-vision tracking methods for augmented reality applications typically use a special fiducial markers such as squares or circles. Our new method uses a black square fiducial of ARToolKit to obtain the initial tracking condition, but does not use it in subsequent iterative tracking phases. Several natural feature points are extracted from the tracked object by offline image analysis. While tracking the object, some of these feature points are selected for template matching and the object pose and position are calculated. Even when the initial tracking square is no longer in view, our method produces robust tracking at real time frame rates.

A city-planning system based on augmented reality with a tangible interface

This demonstration shows a city-planning system based on augmented reality with tangible user interface. Miniature models, illustrations and graphical computer displays have been used for the comparison and consideration in city-planning process. Augmented reality technology enables users to consider city plans more effectively and easily. One important issue of the augmented reality environment is how user can manipulate 3D structures that are displayed as virtual objects. It has to be intuitive and easy so that it may not disturb users thought. We propose a new direct manipulation method based on the concept called tangible user interface. User holds a transparent cup upside down and can pick up, move or delete a virtual object by using it.

MagicCup: a tangible interface for virtual objects manipulation in table-top augmented reality

We propose a tangible interface for virtual object manipulation in table-top augmented reality based on ARToolKit. It is designed for city planning. Augmented reality technology enables users to consider city plans more effectively and easily. One important issue of the augmented reality environment is how a user can manipulate 3D structures that are displayed as virtual objects. It has to be intuitive and easy so that it may not disturb a users thoughts. We propose a new direct manipulation method based on a tangible user interface. The user holds a transport cup upside down and can pick up, move or delete a virtual object.

Polyhedral Surface Modeling with a Diffusion System

This paper presents a method of generating polyhedral surfaces by using a diffusion system that calculates the positional and normal vectors on their vertices. The system generates smooth shapes that satisfy the minimum norm property, and can be extended to imitate the shape controls of curvature continuous surfaces with bias and tension parameters. The shape of a surface is determined by the stable state of nonlinear and local calculations between vertices, and is easily controlled by adding constraints on arbitrary vertices. Such bottom‐up calculation of surfaces enhances flexibility in the interactive design of complicated free‐form shapes.

A Space-Division Optical Wireless Communication System for Fully Distributed Multiple Autonomous Mobile Robots

Abstract This paper describes the realization of a space-division optical communication system specifically designed to perform local inter-robot communication in fully distributed multiple autonomous mobile robot systems. Requirements for autonomy and robustness of communication functions among moving robots are discussed. The communication system uses a set of modules, or transceivers, which is arranged in the circumference of the robot body. Each module comprises an IR detector/receiver and an IR transmitter. Each IR module detects the angle of incidence of infrared rays. Space-division communication networks can be created, because a robot can commumcate with more than one robot through different modules at the same time. Hardware realization and performance measurements are illustrated to reveal the effectiveness of the developed system.

A Space-Division Optical Wireless Inter-Robot Communication System with Mutual Localization Ability for Multiple Autonomous Mobile Robots

Abstract This paper presents a space-division optical wireless inter-robot communication system for multiple mobile robots. Infrared optical wireless communication is suitable for the mobile robots, because of its low level of interference in multiple directions. However, optical wireless communication is lost when either of the robots runs and/or rotates due to the nature of infrared rays. The proposed communication system has many infrared transceivers, which face all directions. The system can maintain circuit connections by exchanging transceivers. Furthermore it can communicate at the same time with more than one robot in different positions by using different transceivers. As an example of local sensing capabilities of the system, mutual localization using transceivers on three communicating robots is also described. Hardware realization and performance measurements are illustrated to reveal the effectiveness of the proposed system.

Implementation of Communicating Sequential Processes for Distributed Robot System Architectures

Abstract This paper describes an implementation procedure of distributed control software for robot-based manufacturing systems. Robots and other devices such as conveyors and manufacturing machines are defined as object-oriented communicating sequential processes. A modular and hierarchical approach is adopted to define a set of Petri net type diagrams, which represent concurrent control processes for such devices, and asynchronous and synchronous interactions in global process interaction nets. Operational specifications are directly transformed to executable codes in a parallel programming language, such as occam. Implementations of control software on a multiprocessing environment and transputer networks are comparatively evaluated.

A computer network based control architecture for autonomous distributed multirobot systems

This paper presents the specification and implementation procedure using a microcomputer network based autonomous distributed control architecture for industrial multirobot systems. The procedure is based on the concept of data flow network controlled by communicating sequential processes to perform coordinated tasks. Robots and other computerized industrial devices such as conveyors and manufacturing machines are defined as object-oriented Petri nets. A modular and hierarchical approach is adopted to define a set of Petri net type diagrams which represent concurrent activities of control processes for such devices. Asynchronous and synchronous interactions are modelled by places and transitions, respectively, in global process interaction nets. The control software is implemented on a computer network using Inmos transputers with true parallel processing and message passing primitives efficiently handled in hardware. Petri net based models are directly and efficiently transformed to corresponding codes in occam, the high level parallel programming language defined for the transputer.