We describe the design and implementation of RSTATION, an object-oriented, modular robot simulator with hierarchical analysis capabilities. Modularity is achieved via the features of design encapsulation and enables grouping a set of interconnected components into a single component and dividing the robot system into several sets of subordinate modules recursively. By careful construction of the data types and classes, RSTATION allows for hierarchical simulation of the kinematics, and the dynamics at three levels: considering only main links (high-level), using simplified models including dynamic properties of transmission elements (intermediate level), and taking into account the detailed kinematics and dynamics of transmission elements (low-level). Submodules can be set to different resolution during a single simulation. The data types and classes also exploit a recent set of coordinate invariant robot analysis algorithms based on modern screw theory. Central to the low-level dynamic analysis capability is an algorithm for systematically extracting the constraint equations for general gearing systems. The various features of RSTATION are illustrated with a detailed case study of a commercial industrial robot.

Instantaneous kinematics and singularity analysis of a class of three-legged, 6-DOF parallel manipulators are addressed in this paper. A generic method of derivation of reciprocal screw and consequently, the instantaneous kinematics model is presented. The advantage of this formulation is that the instantaneous kinematics model possesses well-defined geometric meaning and algebraic structure. Singularity analysis is performed under three categories, namely forward, inverse and combined singularities. A new concept of Passive Joint Plane is introduced to correlate the physical structure of the manipulator and these geometric conditions. In the inverse kinematic analysis, a new approach is introduced. At each leg end point a characteristic parallel- epiped is defined whose sides are the linear velocity components from three main joints of the leg. An inverse singularity occurs when the volume of this parallelepiped becomes zero. Examples are demonstrated using RRRS and RPRS-type parallel manipulators.

The experimental evidence supports the validity of the principle of superposition for multi-finger prehension in humans. Forces and moments of individual digits are defined by two independent commands: “Grasp the object stronger/weaker to prevent slipping” and “Maintain the rotational equilibrium of the object”. The effects of the two commands are summed up.

This paper describes precision enhancement of an optical three-axis tactile sensor capable of detecting both normal force and tangential force. The sensor's single cell consists of a columnar feeler and 2-by-2 conical feelers. We have derived equations to precisely estimate the three-axis force from the area-sum and area-difference of the conical feelers' contact areas by taking into account wrench-length shrinkage caused by a vertical force. To evaluate the equations and determine constants included in the equations, we performed a series of calibration experiments using a manipulator-mounted tactile sensor and a combined load-testing machine. Subsequently. to evaluate the tactile sensor's practicality. it was mounted on the end of a robotic manipulator which rubbed flat specimens such as brass plates with step-heights of δ=0.05, 0.1, 0.2 mm and a brass plate with no step-height. We showed from the experimental data that the optical three-axis tactile sensor can detect not only the step-heights but also the distribution of the coefficient of friction, and that the sensor can detect fine plate inclination with accuracy to about ±0.4°.

This paper describes the development of a system that is capable of tiling mosaics using a robot according to requirements of the individual customer. The art of mosaic, in one form or another, has been practiced manually for thousands of years. Modern developments in materials and production techniques could be found as evidence that mosaic is very much alive in the new millennium. It is very costly and also difficult to find skilful people to tile mosaic. Therefore a computer-assisted robotic system has been constructed and applied. To activate the system a particular algorithm has been developed and successfully applied on an available SCARA robot.

Although numerous sophisticated nonlinear control algorithms exist in literature, it is still state of the art to use simple linear joint controllers in industrial robotic systems. Most nonlinear concepts are based on a more or less accurate inverse model of the robot. In this paper a forward-model-based control system, the so-called Model Following Control (MFC), for robot manipulators is presented. Its theoretical basics and its concept are explained. The quality and the applicability of the MFC control concept has been analyzed in many experiments. The MFC system is compared with classical linear controllers and nonlinear feedforward controllers with respect to robustness. Qualitative as well as quantitative results are presented and discussed.

An important concept proposed in the early stage of robot path planning field is the shrinking of the robot to a point and meanwhile expanding of the obstacles in the workspace as a set of new obstacles. The resulting grown obstacles are called the Configuration Space (Cspace) obstacles. The find-path problem is then transformed into that of finding a collision free path for a point robot among the Cspace obstacles. However, the research experiences obtained so far have shown that the calculation of the Cspace obstacles is very hard work when the following situations occur: 1. both the robot and obstacles are not polygons and 2. the robot is allowed to rotate. This situation is even worse when the robot and obstacles are three dimensional (3D) objects with various shapes. Obviously a direct path planning approach without the calculation of the Cspace obstacles is strongly needed. This paper presents such a new real-time robot path planning approach which, to the best of our knowledge, is the first one in the robotic community. The fundamental ideas are the utilization of inequality and optimization technique. Simulation results have been presented to show its merits.

This paper analyses the concept of velocity isotropy for Parallel Mechanisms with Actuation Redundancy (PMAR). The limits of classical indices based on the Jacobean matrix condition number are shown. It is proposed to use either the largest ellipsoid included in the operational polytop, or the operational polytop itself, as better representations of a PMAR capabilities. The polytop is studied because it is actually the accurate representation of a machine capability, while the largest ellipsoid remains similar to the classical tool roboticists are dealing with for decades. Velocity performance indices are proposed, and the ways to compute them efficiently are given.

We present an on-line learning system for the Italian and German languages especially created to help the people living in the Autonomous Province of Bolzano/Bozen prepare the so-called bilingual proficiency exam. In the first part of the paper we present the peculiar political, social and linguistic situation of the Province and describe the bilingual proficiency exam. After having clarified the background in which our learning system originates, we will concentrate on the system itself presenting the different parts it consists of. Section 4 will describe the system function, and section 5 will make some final comments and highlight future prospects.

This article discusses some theoretical and methodological problems and issues in the study of computer-supported learning activities with special reference to a discourse perspective in research. Special emphasis is laid on finding ways to reach the participant perspective in computer-supported collaborative learning projects, which are by nature polycontextual. By this term we refer to the diverse scenes and situations of learning activities that computer-supported learning involves. We will also address the issue of making claims on effective pedagogies, leaning on the theory of discourse as situated and constructive, which again sets special requirements on what kinds of assumptions and interpretations can and should be derived through empirical analysis of data. Instead of rushed normative guidelines for instruction we should now take time and examine critically what is really happening in computer-supported environments in real-life situations. A look at the particular is needed. An important question to examine, for example, is how students and teachers use these tools in their everyday lives and how these processes are talked about. We will discuss through a number of examples the multimodal and polycontextual nature of meaning making in participant activities during three different university language courses between 1998–2002. This article considers relevant research approaches with the aid of theoretical discussion and examples of analysis.

At the recent EUROCALL conference at the University of Limerick, my co-editor, Graham Chesters, remarked on two very heartening changes in the constituency of EUROCALL conference participants over the past ten years: one was the increasing number of younger teachers and researchers; the other was the multi-national representation, compared to the relatively small number of European countries who made up EUROCALL’s main body of members at the Hull conference in 1993.

This study examines the possible effects of a mailing list discussion on second/foreign language learning in the form of an explorative case study. Forty-six students in an elementary-level Japanese language class at a Canadian university participated. The study consists of three parts: interaction analysis, content analysis, and a student survey. The first two parts referenced the entire mailing list discussion archive. The number of the messages totaled 298. In order to analyze learner interaction, a map of interaction was designed and Levin, Kim and Riel’s (1990) Intermessage Reference Analysis (IRA) was applied. Content analysis was then carried out on the topics, context-type, and depth of learning process involved in each message. Lastly, a survey was distributed in order to discern participants’ perceptions towards the use of a mailing list for language learning. The results of the interaction and content analysis show how a mailing list discussion can provide a place to reflect on course content, enabling students to increase their linguistic knowledge through an exchange of ideas, thoughts, and opinions via student-centered interactions. The result of the participant survey shows that although the students’ participation in and perceptions towards the mailing discussion is not uniform, 35% of the students perceived the value of a mailing list discussion to be high. Through the examination of three different methods of analysis, the study concludes that there is a good potential for the use of mailing list discussions in second/foreign language learning. However, further research is necessary to determine which factors contribute to the successful use of this medium.

This paper presents a method for the assessment of oral fluency in Business English according to a two corpora-based lexical approach. The original query for our research is the possibility of estimating the level of oral skills among Business English (BE) learners by contrasting their word use in oral presentations with corpus data frequencies. Use of Information Technology (IT) resources and electronic BE corpora is thus measured in the evaluative approach to identify significant performance changes between learners who have used such electronic resources and learners who have not.

This article investigates commercial software design practices as they specifically relate to foreign language education. Commercial educational software companies currently produce the majority of language learning software available on the market. Commercial ventures producing CALL software share many design practices that call into question their educational validity. The design practices of commercial CALL software companies are incongruent with the goals of foreign language education. The problems associated with commercial CALL ventures can be seen in the cultural aspects of the programs, particularly when dealing with issues of cultural authenticity and representation. Practices that create these cultural problems are investigated and outlined in this article. The results of these problems are also highlighted to allow for better identification of problematic design practices. The identification of these problems is associated with educational software evaluation theory. A brief outline of educational software evaluation theory is given, as well as a proposal for a new framework for CALL software evaluation that incorporates issues of representation to better address the inaccuracies found in many commercial CALL software products.

The increasing emphasis on ‘e-learning’ in all sectors of education, including vocational and professional domains, offers great potential to provide interactive, up-dateable multimedia materials which allow greater flexibility of access and use. This paper reports on an EU-funded, e-learning project which aims to exploit on-line technology to develop intercultural business and language skills for European managers in the construction industy. It advocates an integrated approach to language and culture training, describing how a ‘cultural syllabus’ was designed to develop users’ understanding of key aspects of European work culture and practices alongside their professional language skills. The resulting matrix syllabus incorporates insights from theoretical frameworks together with factual information and authentic accounts of cross cultural work experiences. It argues that the growing demand for on-line learning materials needs to be matched by great attention to quality of course and materials design so that technology enhances, rather than detracts from, content and pedagogy.

Though we often speak of the development of CALL as an academic discipline and its growth as a field of inquiry, little evidence has to date been gathered to prove it. This descriptive study investigates the current state of and changes in CALL research output and its characteristics such as theoretical foundation, method of evidence gathering, and reporting standards. It is based on a numerical analysis of 91 research articles published in 1980–2000 in seven English language journals. CALL emerges from this study as a fast developing area of research, which draws on an increasingly diverse body of theory and methods from a number of cognate disciplines. CALL researchers are increasingly more confident about their research, as reflected in the high level of generalization present in the examined sample. This is not however matched by proper attention given in their reports to research credibility issues.

There has of late been a call among language practitioners for the sophisticated new markup language XML to be used in Web-based tools for language learning (Mills, 1999; Riley, 2001; Godwin-Jones, 2000). This paper describes just such an application: the development of an interactive electronic resource book of learning tasks for English Language Teaching (ELT). The electronic resource book incorporates an authenticity-centred approach to language learning materials design, viz language learning based on authentic texts complemented by authentic tasks. The paper covers a general introduction to XML, describes the pedagogical model (i.e. the authenticity-centred approach) that it was used to realise, and describes the development of the XML-based system operating the electronic resource book. Among the conclusions of this paper are that this trial application reveals XML to be ideally suited to the realisation of such pedagogical models and that its greatly enhanced information management and linking potential promises an exciting future in the field of language teaching by providing the possibility for pedagogy-led technology rather than technology-led pedagogy.

In this note, we consider a simple immigration birth–death process with total catastrophes and we obtain the transient probabilities. Our approach involves a renewal argument. It is comparatively simpler and leads to more elegant expressions than other approaches that appeared in the literature recently.