Development of an XML-based lab for remote control experiments on a servo motor

International Journal of Electrical Engineering Education, Apr 2005 by Pastor, R, Mart�n, C, S�nchez, J, Dormido, S

Abstract

In this paper, an XML-based framework, known as RELATED, is used to build a remote lab for providing experience of control engineering on a servo motor using components distributed across the Internet. This new approach allows different groups to share their hardware and software resources and to facilitate the creation of networks of virtual/remote laboratories.

Keywords distance learning; PID control; remote operations; virtual laboratories

Laboratory experiments play and will certainly continue to play an important role in control engineering education.1 One significant tendency in the field of control practice is the increasing use of virtual instrumentation. In fact in major production facilities, operators are often trained in plant operation using a simulation environment (instead of the real process) to drive virtual instruments. What is obvious is that experimentation in situ with a plant or real object cannot be replaced by a simulation or training simulators, especially the sensations perceived by the student in the experiment.2'3 Practical education needs to be based on errors and irregularities, as occurs in mechanical, electrical or chemical systems, as opposed to the ideal icons and environments represented on a computer display.

One vital aspect of control engineering education is therefore that laboratory and practical work need to provide engineering students with a taste of real situations, measurement and instrumentation, with all their attendant problems.4 One idea is to allow the students to perform real experiments, in real time, on real equipment, but over the Internet.

The use of remote labs for supporting and integrating the activity of a control engineering course is in fact a widely discussed issue. An analysis of the recent solutions developed for remote labs, where different laboratory experiments are run remotely via a Web interface, is reported in Ref. [5]. Different solutions of remote control engineering laboratories are presented and discussed in Refs [6] and [7] where remote control was applied to a robot arm. A remote measurement lab is also described in Ref. [8]. In all the proposed solutions the remote user (the client) is connected via Internet to a dedicated Web server that interacts with the computers of the laboratory used for controlling (monitoring) the real processes.

The rapid progress of Internet technology and its increasing popularity has prompted several educational institutions to develop Internet laboratories.9"14 With the help of an on-line Internet laboratory for control experiments, educators can be encouraged to design control engineering courses that combine theoretical issues and practical activities. Via the Internet, on-line laboratories could offer more flexibility to prepare assignments for students that require experimentation with real phenomena. In addition, an Internet laboratory allows a better use of equipment either by local or by remote users since they can access to the labs from anywhere and anytime with just an Internet connection. This sharing of resources not only brings down the experiment cost per student, but equipment will also be made available to more students since the time and space constraints normally associated with a traditional laboratory can be removed.

This concept of remote labs provides both vertical and horizontal integration of control education and addresses several problems faced by engineering educators such as the high cost of didactical setups, the duplication of resources when several departments attempt to offer their own control laboratories, the rapid obsolescence of equipment, and the difficulty of providing technical support.

In this general context, there are many works focused on the development of virtual and remote laboratories conducted through the Internet but all these remote and virtual laboratories are timely efforts by different research groups working independently.10,13,15,19 Use of the software and hardware of other universities is not contemplated, and neither is taking advantage of work previously carried out by others. That is to say, until now, a methodology or a standard for the construction of networks of virtual/remote laboratories based on previous developments has not existed.

Therefore, formal specification of these laboratories becomes necessary, in such a way that the most expensive tasks can be automated; for instance, resource management or user administration. A separation is also obtained between the development of the laboratory (mainly when it is necessary to implement real-time control mechanisms), and the additional effort of 'publishing on the Web'.

Laboratory specification

A formal specification for a virtual or remote laboratory must define transparent access to it, and this access must be independent of the type of system. To do this, it becomes necessary to use some linguistic mechanism that allows instructors to define these systems in an abstract way; that is, a meta-language is necessary. In this case, access to these systems (virtual or remote) will be made by means of an Internet navigator, therefore the idea of using the XML standard (Extended Markup Language) for the formal specification of these systems is obtained in a natural way. This XML-based specification declares a group of labels (components of the system) to describe the expected behaviour that will be implemented by means of the remote or virtual system (components include concepts like experiments and interactive visualisation).