The Ball and Beam System: A Case Study of Virtual and ...

934 IEEE TRANSACTIONS ON INDUSTRIAL INFORMATICS, VOL. 11, NO. 4, AUGUST 2015

The Ball and Beam System: A Case Study of Virtualand Remote Lab Enhancement With Moodle

Luis de la Torre, Maria Guinaldo, Ruben Heradio, and Sebastian Dormido

Abstract—Web-based labs are key tools for distance educationthat help to illustrate scientific phenomena, which require costlyor difficult-to-assemble equipment. Easy Java Simulations (EJS) isan authoring tool that speeds up the creation of these kind of labs.An excellent proof of the EJS potential is the open source physics(OSP) repository, which hosts hundreds of free EJS labs. Learningmanagement systems, such as Moodle, provide social contextswhere students interact with each other. The work described inthis paper looks for the synergy of both tools, EJS and Moodle,by supporting the deployment of EJS labs into Moodle and thusenriching them with social features (e.g., chat, forums, and video-conference). To test this approach, the authors have created theball and beam lab, which helps students of automatic control engi-neering to train different advanced techniques (robust, fuzzy, andreset control), and compare their performance in relation to aconventional proportional-integral-derivative control.

Index Terms—Control engineering education, learningmanagement system, remote laboratory, virtual laboratory,web-based experimentation.

I. INTRODUCTION

I T IS COMMONLY accepted that digital media (such assimulations, videos, interactive screen experiments, or web

labs) can positively impact student knowledge, skills, and atti-tudes [1], [2]. Consequently, learning management systems(LMSs) and online experimentation have become widespreadin distance education.

LMSs support the administration, documentation, tracking,and reporting of training programs, classroom, and onlineevents.

Online experimentation is a broad concept that encompassesnot only virtual and remote experimentation, but also otheronline tools based in virtual reality, augmented reality, senso-rial devices, live videos, interactive videos, and serious games,which promote user immersion in virtual environments recre-ating the real experience [3], [4]. In particular, this paper isfocused on the so-called virtual and remote labs (following the

Manuscript received January 09, 2014; revised May 16, 2014, January 20,2015, and April 09, 2015; accepted June 03, 2015. Date of publication June 09,2015; date of current version July 31, 2015. This work was supported in part byproject DPI2012-31303, and in part by the Spanish Ministry of Economy andCompetitiveness. Paper no. TII-14-0847.

L. de la Torre, M. Guinaldo, and S. Dormido are with the Departamentode Informatica y Automatica, Universidad Nacional de Educacion a Distancia,Madrid 28040, Spain (e-mail: [email protected]; [email protected]; [email protected]).

R. Heradio is with the Departamento de Ingenieria de Software y SistemasInformaticos, Universidad Nacional de Educacion a Distancia, Madrid 28040,Spain (e-mail: [email protected]).

Color versions of one or more of the figures in this paper are available onlineat http://ieeexplore.ieee.org.

Digital Object Identifier 10.1109/TII.2015.2443721

terminology proposed in [5]), which make possible to illustratescientific phenomena that require costly or difficult-to-assembleequipment [6].

1) Virtual labs are computer-based simulations, which offersimilar views and ways of work to traditional hands-on laboratories [7]. Nowadays, virtual labs have evolvedinto interactive graphical user interfaces (GUIs), wherestudents can manipulate the experiment parameters andexplore its evolution.

2) Remote labs use real plants and physical devices, whichcan be used at distance [8]–[12], either by teleoperatingand receiving measurements from them or by modifyingsome input parameters and allowing simple visual obser-vation. Remote experimentation through the Internet hasbeen available from nearly two decades [13], [14] and itsinterest has not diminished over the years [15], [16].

Virtual and/or remote labs (VRLs) are complementary toolsthat can be brought together as hybrid labs [17]. An impor-tant concern about VRLs is that developing them from scratchrequires a huge effort. Easy Java Simulations1 (EJS) [18] helpsto overcome this problem. It is an authoring tool that speeds upand facilitates the creation of discrete computer simulations. Anexcellent proof of the EJS potential is the open source physics(OSP) repository,2 [19] which offers hundreds of EJS simu-lations that can be freely downloaded and modified to createnew simulations. During the last few years, EJS has grown forhelping to create web-accessible laboratories in control engi-neering education. With this objective in mind, recent releasesof EJS support connections with external applications, such asLabView3 and Matlab/Simulink.4 Hence, EJS not only is use-ful to create virtual labs, but also the GUIs of their remotecounterparts [20].

Although there is evidence of the positive effects that collab-orative student interaction has over VRL activities [21]–[23],most of the online labs developed to date suffer from a lackof providing social contexts, which support collaborative groupwork [24], [25]. A possible approach to enrich VRLs with col-laborative features is deploying them into LMSs. Thus, VRLstake advantage of the LMS capacity to support the virtualinteraction among participants.

Two different types of collaborative environments may beconsidered according to the moment when the student–student(or student–teacher) interaction takes place: asynchronous andsynchronous [26]. The first ones allow data exchange in flexible

1[Online]. Available: http://fem.um.es/Ejs/2[Online]. Available: http://www.compadre.org/osp/3[Online]. Available: http://www.ni.com/labview/esa/4[Online]. Available: http://www.mathworks.com/products/simulink/

1551-3203 © 2015 IEEE. Personal use is permitted, but republication/redistribution requires IEEE permission.See http://www.ieee.org/publications_standards/publications/rights/index.html for more information.

de la TORRE et al.: THE BALL AND BEAM SYSTEM: CASE STUDY 935

timetables and remote access to web-based course materi-als to carry out activities in an asynchronous way. They usecollaborative tools such as e-mail or forums for online commu-nication. This is the typical approach offered by most classicLMSs. However, students may likely feel less engaged withthe course if the instructor relies primarily on the use of asyn-chronous communication [27]. Furthermore, students do notreceive instant feedback from their questions and cannot talkin real time about results obtained in the learning activities.These limitations can be overcome by applying synchronoustechnologies where students interact with each other in realtime.

This paper presents several Moodle and EJS extensionscreated to support:

1) deploying EJS VRLs into Moodle;2) adding synchronous collaborative support to any VRL

developed with EJS;3) accessing directly the OSP repository from Moodle.As a case of study of the aforementioned extensions, this

paper describes a VRL that supports students of automatic con-trol engineering to train different advanced techniques, such asrobust, fuzzy, and reset control, and compare their performancein relation to a conventional proportional-integral-derivative(PID) control. The experimental plant considered for that pur-pose is the well-known ball and beam system, which facilitatesthe study of real control problems, such as the horizontal sta-bilization of an airplane [28]. In addition to the two workingmodes (simulated and real experimentation) provided by theVRL, the remote laboratory presented in this work offers anaugmented reality option that superimposes a graphical rep-resentation of the virtual system’s behavior over the imageprovided by the webcam. This allows a visual comparison ofthe theoretical response of the plant with the real response.

Finally, this paper reports an observational study where stu-dents were encouraged to carry out several voluntary lab assign-ments using the VRL (an example of assignment was analyzingthe differences between the experimental outcomes obtainedby teleoperating the remote lab and the theoretical resultscomputed with the virtual lab). The study provides empiricalevidence of positive correlations 1) between using virtual labsand the final exam grades students get; and 2) between thenumber of lab assignments that students finish and using VRLsdeployed into Moodle.

This paper is structured as follows. Section II summa-rizes related work. Section III describes the authors’ approach,i.e., the Moodle and EJS extensions, and the Ball and BeamVRL. Section IV sums up the experimental evaluation of thisapproach. Finally, Section V shows some conclusions regardingthis work.

II. RELATED WORK

VRLs have been recognized as key distance learning toolsfor teaching a wide range of topics, such as control engineer-ing [29], physics [30], and chemistry [31]. Although there isempirical evidence of the positive effects that collaborative stu-dent interaction has over lab activities [21], [22], [32], [33],most of the online labs developed to date suffer from a lack

of providing social contexts, which support collaborative groupwork [24], [34]. To overcome such limitation, the followingcomplementary approaches have been proposed.

1) Deploying VRLs into LMSs. Thus, VRLs take advantageof the LMS capacity to support the virtual interactionamong participants (students and teachers) by means ofboth synchronous (e.g., chat and videoconference) andasynchronous (e.g., whiteboards, forums, and mailinglist) collaboration tools. For instance, [35]–[39] integrateVRLs into Moodle, [40] into LADIRE, and [41] proposesa more general solution in which VRLs can be integratedinto many LMSs.

2) Embedding VRLs into virtual worlds. Some researcherssuggest that both entertainment and highly immersiveenvironments promote effective learning. To do so, VRLsare embedded into virtual worlds that provide multi-ple communication channels between users and improvepresence and awareness in the learning process. Forinstance, [42] and [43] integrate VRLs into second life,[44], [45] into the Sun project wonderland, and [46] intothe game half-life 2.

3) Supporting VRLs to be handled by multiple participantsat the same time. Under a simplistic approach, collabora-tion is limited to the use of communication tools such aschat or video-conference applications. Other approachesgo beyond by supporting the simultaneous interactionof several participants with the same lab [22], [36],[47]–[51]. This way the proper VRL acts as the maincommunication medium among participants.

The work presented in this paper encompasses many of theformer proposals. It deploys VRLs into LMSs and it makespossible VRLs to be handled simultaneously by multiple par-ticipants. The integration described in this paper of EJS VRLsinto Moodle has an enormous potential. For instance, the OSPoffers hundreds of EJS simulations that may be automati-cally integrated into Moodle by using the add-ons described inSection III-B.

A stable release of the authors’ open source code hasbeen checked, approved, and published by Moodle5; has beenincluded in the last official EJS release 4.3.7; and is being usedin the UNILabs web portal,6 which currently hosts 15 VRLs for10 university courses.

III. INTEGRATING VIRTUAL AND REMOTE LABS

INTO MOODLE

A. Preliminaries

The client–server architecture for remote laboratoriesdeployed using Moodle is shown in Fig. 1. Plants located at theuniversity labs are manipulated by the remote user through theInternet. A server computer acts as a middleware layer for eachof these remote labs. They are in charge of the translation ofincoming commands from the client and sending back measure-ments or other required information, as well as the acquisition

5The authors’ add-ons are freely available at: https://moodle.org/plugins/browse.php?list=set&id=27

6[Online]. Available: http://unilabs.dia.uned.es/


Fig. 1. Architecture of a remote lab deployed into Moodle.

and control loop tasks. A webcam pointing to the plant is oftenused to provide real-time image feedback at every moment.Another server computer is used to hold the webportal sup-ported by Moodle. This computer serves both the virtual labsapplications and the remote labs user interfaces to the clients.The booking system, needed for managing and arranging theconnections of students to the remote laboratories, is also estab-lished in the Moodle server. This booking system has beendeveloped by the authors and it is freely available on the URLgiven in Footnote 5.

1) EJS: It is a freeware, open-source tool developed in Java,specially designed for the creation of discrete computer simu-lations. The architecture of EJS derives from the model-view-control (MVC) paradigm, whose philosophy is that interactivesimulations must be composed of three parts.

1) The model describes the process under study in terms of:a) variables, which hold the different possible states ofthe process, and b) relationships between these variables,expressed by computer algorithms.

2) The view provides a graphical representation (either real-istic or schematic) of the process states; i.e., the GUI ofthe simulation.

3) The control defines certain actions that a user can performon the simulation.

EJS makes things even simpler eliminating the “control” ele-ment of the MVC paradigm and embedding one part in the viewand the other one in the model.

As an indicator of the widespread use of EJS, many VRLscreated or replicated with EJS, such as [52]–[55], can be foundin the literature.

2) OSP: The OSP project won the Science SPORE Prizein November 2011. Among many other resources for teachingand learning, this collection offers more than four hundred EJSsimulations, such as those described in [52]–[56].

3) Moodle: It is a widespread LMS that provides a socialcontext for students’ collaboration. Moodle enriches VRLs byfacilitating and promoting the tools for students discuss theexperiments between them and teachers, exchange their labreports, etc. In addition, Moodle helps to distribute all theconvenient resources for a complete online experiment. Forinstance, attached to the VRL, Moodle may include a descrip-tion of the phenomena under study, the task protocol that stu-dents must follow to achieve the goals of the VRL activities, etc.

B. Extending Moodle With VRLs

The “M” in Moodle stands for modular. The easiest and mostmaintainable way to add new functionalities to Moodle is bycreating an add-on. Since all the tools and resources in which

Fig. 2. Example of two users participating in a collaborative experimentalsession.

this work is based on are free (EJS, OSP, and Moodle), it wasimportant for the authors to offer the solution that joins all thesethings together also for free. Therefore, Moodle add-ons are theperfect way to achieve this objective.

1) EJSApp Add-On: To support the one-click deploymentof VRLs into Moodle, the EJSApp add-on has been developed.The EJSApp module supports are following.

1) Deploying VRLs written in EJS: EJSApp uses the newMoodle 2 feature File Picker, enabling EJS applications(either they are a simulation or virtual lab, or a remotelab user interface) to be uploaded not only from the usercomputer but also from a variety of repositories such asDropbox and Alfresco.

2) Controlling user access to the deployed labs: EJSAppincludes a booking system, which supports setting thestart and end dates when a VRL will be accessible to thestudents, the minimum grade students need to get in otheractivities as a previous condition before having access tothe lab, etc.

3) Backup and restore: EJSApp provides maintenance facil-ities, packaging VRLs into Moodle standard coursebackups.

4) Supervision and statistics: Access from Moodle users toVRLs is recorded and can be used for performing statis-tics and supervising the time students spend working ineach lab.

EJSApp is listed in the Moodle official site as one of the morethan 600 approved add-ons for Moodle. It received the MoodleHat Award on December 2012, just a few days after it was first


Fig. 3. OSP add-on for Moodle.

released. This award is given by the Moodle staff and only 18add-ons have received it by November 2013. Considering thenumber of existing add-ons up to this date, this means that onlya 3% of these add-ons get to receive this award. Another indi-cator of the high quality and/or utility of this tool is that it hasbeen downloaded more than 1300 times in less than one year.

2) EJSApp Collab Session Add-On: Moodle includes agood number of tools that provide asynchronous collaborativesupport (e.g., forums, and the messaging system). The authors’proposal takes advantage of such features by deploying VRLsinto Moodle. Moreover, the approach presented in this paperenriches Moodle collaborative support by providing a new fea-ture: the synchronous collaboration among the VRLs includedinto a Moodle course.

Fig. 2 shows an experimental session using the followingfeatures of the VRL described in Section III-C: 1) virtual exper-imentation, synchronous collaborative interaction, and skypecommunication between users. For each participant in a collab-orative session, there is a running instance of the shared VRL.The state of all the instances is synchronized, i.e., whenever aparticipant acts over its VRL instance, the changes produced onthe VRL state are propagated to the remainder of the partici-pants’ VRL instances. Thus, although there are running severalinstances of the VRL, the participants have the feeling of beingworking on the same VRL.

In addition, one of the participants plays the session directorrole, being responsible for starting, monitoring, and closing acollaborative session. The session director’s applet manages inrealtime the virtual class and synchronizes all the invited user’sapplets. She has a list of invited users connected to the virtualsession and can disconnect any invited user’s at any moment. Inorder to have a suitable floor control, connected invited user’sapplets are locked and they cannot interact with the shared VRL

in a first moment. They are only allowed to see in real timewhat the session director is doing in the shared application.This way the collaborative session avoids collisions of eventswhich can cause unwanted and incoherent results. This problemcould appear when the real equipment, controlled by the remotelab application, becomes uncontrollable due to unsuitable userinteractions. This could happen, e.g., if one of the users in thecollaborative session is commanding a motor to rotate clock-wise, whereas a second user is ordering the same motor to rotateanticlockwise at the same time.

To support the automated conversion of any existing EJSVRL into a collaborative lab, the authors also have extendedEJS. In particular, the official EJS release 4.3.7 already includesthe authors’ collaborative extension.

3) OSP Add-On: It allows Moodle users to connect theirFile Picker to the OSP digital library. Without this add-on, userscannot directly search for EJS simulations in the OSP digi-tal library from Moodle and adding them to the online course.Instead, they first have to go to the OSP webpage, downloadthe simulation or virtual lab to their own computer, then go totheir Moodle course and upload the simulation from their harddisk.

Thanks to the OSP add-on, users never need to leave theMoodle environment when adding/reorganizing the simulationactivities in their online courses, and they do not need to down-load the simulation file from OSP to their computer and thenupload it to their Moodle server. Instead, the file passes directlyfrom OSP to the Moodle server. Therefore, this tool providesteachers with a very fast and easy way to search, select, anddeploy virtual labs already created by the EJS community andavailable at the OSP repository. Fig. 3 shows a screen shot ofthe OSP add-on for Moodle when the keyword “sun” is used tomake a search for related simulations.


Fig. 4. Client–server architecture of the ball and beam remote lab.

C. A Case Study of VRL: The Ball and Beam System

To put into practice the authors’ approach and illustrate itsusefulness, a case study with a VRL is presented in this section.The ball and beam system is one of the most common setupsthat can be found in control laboratories. The reason for itspopularity is twofold.

1) It has applications to aerospace and automotive fields, aswell as to robotic industries.

2) Some challenging control problems can be studied withthis relative setup, e.g., open loop instability or the effectof strong nonlinearities.

Thus, the aim of this section is to describe briefly how theseissues can be tackled from the control engineering point ofview, and how they are illustrated in an interactive way by usingthe framework proposed in this work.

The virtual lab is completely implemented with EJS. As aresult, it is a stand-alone Java applet that may be run on aclient browser. Fig. 4 depicts the client–server architecture ofthe remote lab. In this case, the EJS applet acts as a sim-ple interface that interacts with a LabVIEW program on theserver side, which controls the real setup. The communicationEJS-LabVIEW is supported by the JiL Server7

Fig. 5 sketches the main variables in the virtual lab model,based on the real setup. The experimental plant presents twodegrees of freedom: 1) the movement of the ball over the beam;and 2) the movement of the motor that makes the beam angle αto change. In addition, two forces act on the ball: a translationalforce due to the gravity and a rotational force caused by therotational acceleration of the ball. The dynamical model of theball rolling over the beam can be easily derived. As a result, (1)is obtained

x(t) =5

7g sinα(t). (1)

For this equipment, the variations of α are related to the vari-ations in the servo-motor angle θ by (2), where r is the levelarm offset and L is the length of the beam

θr = Lα. (2)

Finally, the servo-motor dynamics is modeled as a first-ordersystem with an integrator represented by the following transferfunction:

θ(s)

V (s)=

−64.12s2 + 36.43s

. (3)

7JiL Server is freely available at https://github.com/UNEDLabs/jil-server[57], which connects EJS variables to LabVIEW variables via TCP/IP. Thanksto this approach, the student uses the same interface to perform both the virtualand the remote experiments.

Fig. 5. Sketch for the ball and beam system.

Fig. 6. Block diagram of the robust controller for the inner loop.

This VRL supports three control strategies: robust control,fuzzy control, and reset control. Students have to tune a num-ber of parameters for the different controllers and to drawconclusions about the advantages and issues of each one.

To tackle the two degrees of freedom (i.e., the angle of thebeam and the position of the ball), a cascade structure is used.It helps to reject disturbances and improves the dynamics of thecontrol loop. For the outer loop, the controlled variable is x.The output of this controller gives a set point for the variablecontrolled by the inner loop, the θ angle (see Fig. 5).

Taking a look back to the process dynamics [see (1) and (3)],the simplest control strategy is, for both the inner and the outerloop, the proportional-derivative (PD) controller described by(4). Thus, four gains have to be tuned, a couple for each controlloop. In general, the control law u(t) is given by

u(t) = Kp(ySP − y(t))−Kvdy(t)

dt(4)

where y is the output of the control loop, ySP is the set point,and Kp and Kv are the PD gains.

If conventional tuning methods want to be used for thissystem (e.g., pole placement [58]), (1) has to be linearized.Nevertheless, the approximation sinα ≈ α is only valid forsmall values of α. Hence, the control performance gets worseif the position of the ball moves away from the equilibrium orthe system is affected by disturbances. Thus, advanced controltechniques should be used.

Sections III-C1–III-C3 summarize the control strategies thisVRL supports. Later, Sections III-C4 and III-C5 sum up thekind of activities students may perform with the virtual andremote views of this lab.

1) Robust Control: The purpose of the robust control tech-niques is to take uncertainties into account systematically whenanalyzing a control system or when designing a controller [59].

One of the most popular robust controller design methods isthe McFarlane–Glover technique.


Fig. 7. GUI for the ball and beam system working on the simulation mode.

Fig. 8. System response for a sine wave reference of frequency 0.4 rad/s.

Fig. 9. System response for a sine wave reference of frequency 0.6 rad/s.

The design of a robust controller CR(s) is based on theweighted plant WP , where W (s) is denominated precompen-sator and P is the plant. The choice of W (s) depends onthe given specifications. Fig. 6 illustrates the previous idea forthe inner control loop, where the output is θ, i.e., the angle ofthe motor, and θSP and eθ represent the set point and the errorfor this variable, respectively.

The simplest choice of W (s) is a constant value. Thisgives a second-order controller for the system. If a higherorder precompensator is considered, the controller complexityincreases. W (s) determines the crossover frequency and theroll-off rate of Bode’s diagram. The parameter that measuresthe good or bad mismatch between the target and the achievedBode’s magnitude is called gamma (γ). The closer γ to the unit,the better.

Fig. 10. Membership functions of the fuzzy controller for the outer loop.

2) Fuzzy Control: It is an alternative for a great varietyof problems, as it provides a method to construct nonlinearcontrollers using heuristic information [60]. The fuzzy con-troller consists of the following elements: a rule base set,an interference mechanism, a fuzzyfication interface, and adefuzzification interface.

For the ball and beam system, fuzzy controllers have beendesigned for both the inner and the outer loop. They have twoinputs: the error and the derivative error.

Following the proposed approach in [61], membership func-tions have been defined as triangular, with seven linguistic


Fig. 11. GUI of the applet in remote mode.

TABLE ISAMPLE STATISTICS OF THE STUDENTS’ EXAM GRADES BY COURSE

terms (i.e., big negative, medium negative, small negative, zero,small positive, medium positive, and big positive).

3) Reset Control: A reset controller is described by impul-sive differential equations as follows:

⎧⎪⎨⎪⎩xr(t) = Arxr(t) +Bre(t), when e(t) �= 0

xr(t∗) = Arxr(t), when e(t) = 0

u(t) = Crxr(t)

(5)

where (Ar, Br, Cr) is the state space representation of the con-troller, xr is the state of the reset controller, e(t) and u(t) arethe input and output signals, and t∗ is the resetting time.

The motivation for reset control lies on the existence of someclasses of linear plants, such as those containing integrators,right half-plane poles or zeros, or time delays, that are verydifficult to control with linear controllers and are subject tolinearly unsolvable tradeoffs between competing design objec-tives. It has been shown that a nonlinear controller (like a resetcontroller) can overcome the limitation and outperforms anylinear solution [62].

The first results on reset control date back to the late fiftieswhen Clegg [63] showed that a reset integrator (known as Cleggintegrator) has a describing function similar to the frequencyresponse of a linear integrator but only with 38.1◦ phase laginstead of 90◦.

For the state of the PD controller, a reset control will providea better phase lag and improve the system response

u(t) =

{KP (ySP − y)−Kv

dydt , if ySP − y �= 0

0 if ySP − y = 0.(6)

4) Activities Supported by the Virtual Lab: The simulatedmode of the lab (see Fig. 7) serves students to get used to han-dling the experimental environment. Students can select on thetop menu which control law want to apply to the modeled sys-tem. More than one strategy can be selected at the same time,and so compare the efficiency of each one through the view andthe set of graphs at the right side.

Below the view of the simulation, three tabs contain aset of controls to change the different controllers parameters.Users can modify, e.g., the gains of the PD cascade controller,choose the precompensator for the robust controller, or alter theshape of the membership functions of the fuzzy controller. Anychange is performed online and the result can be immediatelyobserved in the view.

Disturbances can be induced by clicking on the ball orpressing a button. Therefore, the robustness of the differentcontrollers when rejecting disturbances can be compared.

The set point can be dragged manually, or students canchoose the frequency of its movement described as a sin func-tion. Figs. 8 and 9 show the response of the PD, robust, andfuzzy controllers for a particular set of parameters when the


Fig. 12. Box plot of the students’ exam grades by course.

reference is a sine wave of frequency 0.4 rad/s and 0.6 rad/s,respectively.

One of the most attractive parts of this web lab is the interfacedesigned for the fuzzy controller. The membership functionsare displayed in an additional window, where their propertiescan be modified globally (through sliders in the fuzzy tab) orindividually (clicking and dragging). Fig. 10 displays an exam-ple of the membership functions of the error and derivative errorof the outer controller.

Thus, the virtual lab activities include tuning the differentcontrollers, a comparative study of the disturbance rejection,and the set-point tracking. All this has to be reported beforeproceeding to the next step: the remote lab.

5) Activities Supported by the Remote Lab: Once studentsget familiar with the virtual lab and have reached the goals citedabove, they can test their control designs over the real system.Fig. 11 depicts the GUI of the EJS applet in this mode. Theview of the simulation mode is replaced by a real-time image ofthe real system. Users can select one of the three controllers tocheck its behavior with a particular set of parameters. Althoughthe simultaneous comparison of more than one controller is notavailable for the real plant, there is available a third workingmode of augmented reality that supports to compare the realsystem with the theoretical model.

The LabVIEW program running on the server, which imple-ments the three different controllers, includes some securitymechanisms, such as control signal saturation and an emer-gency stop routine triggered when the derivative of the controlsignal exceeds some bounds during a predefined period of time.

IV. EXPERIMENTAL EVALUATION

In terms of number of students, the Spanish Open University(UNED), with more than 260 000 students, is the biggest uni-versity of Spain and the second one in Europe, next to theEnglish Open University. To support their students, UNED iscomposed of a network of associated learning centers scat-tered around the world (more than 60 centers distributed across

Fig. 13. Histogram of the students’ exam grades according to the kindof lab used.

Fig. 14. Histogram of the students’ exam grades for both courses 2011–2012and 2012–2013.

Spain, Europe, America, and Africa). Unfortunately, the geo-graphical dispersion of the students makes impossible to pro-vide the scientific courses of UNED with traditional labs ata reasonable cost. To overcome this problem and help stu-dents to carry out lab experiments, the authors of this paperhave created the UNILABS web portal,8 which hosts VRLs fordifferent subjects taught at the UNED Schools of ComputerEngineering and Sciences. In course 2012–2013, the afore-mentioned schools had 4039 and 4605 students, respectively.In particular, the VRL described in Section III-C was devel-oped to provide support for the subject Automatic Control I,taught in the Faculty of Science, and the Instrumentation andControl Laboratory Practices and Intelligent Control subjectsof the Systems Engineering and Automatic Control Master ofthe School of Computer Engineering. This section reports theevaluation of the authors’ approach by analyzing the effect thatthe VRL and its deployment in Moodle had over the students’comprehension of advanced control techniques during courses2011–2012 and 2012–2013.

Statistical experiments may be classified into controlledexperiments and observational studies. In a controlled exper-iment, the investigators decide who will be in the treatment

8[Online]. Available: http://unilabs.dia.uned.es/


TABLE IIANOVA TEST

group and who in the control group (e.g., in a possible evalua-tion of the VRL usefulness, the treatment group would consistof those students that have used VRLs, whereas the con-trol group would be those that have not). In contrast, in anobservational study, the investigators do not assign the sub-jects to treatment or control groups: they just watch whathappens. Compared to observational studies, controlled exper-iments where subjects are randomly assigned to the treatmentand control groups have the advantage of supporting drawingcasual links between the independent and the dependent vari-ables [64]. Unfortunately, such kind of experiments cannot beperformed because they would violate ethical standards: it mustbe guaranteed that all students have access to any availablelab resource (i.e., the access should not be limited to somerandomly selected students just to support a statistical study).Thus, this section reports an observational study that draws cor-relational links between independent and dependent variables.In particular, Section IV-B reports positive correlation betweenperforming experiments on a virtual lab and the students’ finalexam grades, and Section IV-C shows a positive correlationbetween using VRLs deployed into Moodle and the number labassignments that students finish.

A. Participants

Students were encouraged to carry out two voluntary labassignments.

1) Undertaking the activities described in Section III-C4 byusing the virtual mode of the lab, thus tuning differentadvanced controllers (robust, fuzzy, and reset control) andcomparing their performance to conventional PID control.

2) Teleoperating the Quanser module BB01 through theremote mode of the lab to test the controllers designedin the simulation phase (i.e., when working with the vir-tual lab) and compare the experimental results with thetheoretical ones (obtained from the virtual lab).

In course 2011–2012, the VRL was available as a Java appletembedded in a simple static web page. In contrast, in course2012–2013, the VRL was deployed into Moodle by using theadd-ons described in Section III-B. This way the VRL wasenriched not only in the ways described in that section but alsowith the built-in social features provided by Moodle (forums,messages system, chats, etc.).

Table I and Fig. 12 summarize the grades students got for theAutomatic Control final exam in courses 2011–2012 and 2012–2013 (note that exam grades are rated on a 10-point scale).

B. Evaluating the VRL Usefulness

Histogram in Fig. 13 depicts students’ grades accordingto the kind of lab assignments performed. Note that, in this

TABLE IIIPOWER ANALYSIS

section, both courses 2011–2012 and 2012–2013 are consideredjointly. It suggests a possible correlation between the type of labactivity and the exam grades, whereas most of the best markedstudents completed some voluntary lab assignment, most of theworst marked ones did not perform any lab activity at all.

To check the statistical significance of the grade differencebetween the students who did not undertake any lab assign-ments, just the virtual one, and both the virtual and the remoteones, an ANOVA test was run. The following assumptions,required to run the test, were satisfied.

1) Normality of the Dependent Variable. In the present case,the dependent and independent variables are grades andkind of lab assignment, respectively. The shape of thedependent variable histogram (see Fig. 14), and its lowskew and kurtosis (see the last row in Table I) support theassumption that a normal distribution is approximatelyfollowed (as a common rule of thumb, skew > 3 andkurtosis > 10 indicates a non-normal distribution; in thiscase, skew = −0.15 and kurtosis = −0.69).

2) Homogeneity of the Variances. To check the similaritybetween the variances of the three groups of students(i.e., those who did not carry out any lab assignments,just the virtual one, and both the virtual and the remoteones), a Levene’s test was run, getting a F -value = 1.1and Pr(>F ) = 0.33. Due to 0.33 > 0.05, the test waspositively passed.

Table II summarizes the results of the ANOVA test. Sincethe p-value is less than 0.001 (in particular, p-value = 1.1 ·10−10), the experimental results are statistically highly signif-icant. Table III summarizes the power analysis of the ANOVAtest. Given the sample size and the effect size (i.e., the values ofη2 and Cohen’s f2), the ANOVA test has high statistical power.

According to the ANOVA test, there is an overall differencebetween the three groups of students. Nevertheless, ANOVAcannot identify where the differences are occurring between thegroups. Since some authors have reported that students perceivethat virtual labs are less effective than remote labs because sim-ulations do not feel as realistic [65], [66], the authors decided tocheck if there was a significant difference between the gradesof the students who just used the virtual mode of the lab andthose that used both the virtual and remote modes. To do so,ANOVA was complemented with a post hoc test. In particu-lar, Table IV summarizes the outcomes of the Tukey Honest


TABLE IVTUKEY HSD TEST

Fig. 15. Number of students who completed each type of lab experienceusing/and not using Moodle.

Significant Differences (HSD), which was run. According toHSD results, the following conclusions may be drawn.

1) The difference between the grades of: a) those studentsthat did not perform any lab assignment; and b) those thatjust used the virtual mode of the lab is statistically highlysignificant.

2) The difference between the grades of: a) those studentsthat did not perform any lab assignment; and b) thosethat used both the virtual and remote modes of the labis statistically highly significant.

3) The difference between the grades of: a) those studentswho just used the virtual mode of the lab; and b) thosethat used both the virtual and remote modes is not statis-tically significant. Remember that the remote assignmentwas repeating the experiment previously performed in vir-tual mode by teleoperating the Quanser module BB01.The goal of such repetition was mainly to help studentsto notice the differences between the real outcomes andthe theoretical ones. According to Table IV, this is notenough to influence the final course grades.

To sum up, the evaluation shows a positive correlationbetween exam grades and performing lab assignments with theball and beam online lab. However, the remote lab addition tothe virtual lab does not seem to pay off on the students’s grades.

C. Evaluating the Usefulness of Deploying VRLs into Moodle

Fig. 15 depicts the number of students who completed thelabs assignments in courses 2011–2012 (dark gray bars) and2012–2013 (light gray bars). The VRL was deployed intoMoodle just in course 2012–2013. So, Fig. 15 suggests a pos-itive correlation between the use of Moodle and the amount ofstudents who performed the lab assignments.

To check the aforementioned correlation, a Chi-square test ofindependence was run. The following assumptions, required torun the test, were checked.

TABLE VEXPECTED COUNTS FOR THE CHI-SQUARE TEST UNDER THE NULL

HYPOTHESIS

TABLE VICHI-SQUARE TEST

1) Observations independence. In the present case, observa-tions are independent of each other (i.e., not correlated).For instance, “students who performed the virtual labassignment were not influenced by students who did notcompleted any kind of lab activity.”

2) Adequate expected cell counts. Table V summarizesthe expected counts under the null hypothesis (i.e., thehypothesis that the number of students who performeda lab assignment do not depend on the Moodle usage).The dataset satisfies the following common rule of thumb:“expected counts must be ≥5 in 80% of the cells and therecannot be cells with zero counts.”

Table VI summarizes the results of the Chi-square test. Asthe p-value is less than 0.05 (in particular, p-value = 0.0037),the experimental results are statistically significant. Due to thesample size and the effect size (i.e., the Cramer’s V ), the testhas high statistical power.

V. CONCLUSION

Moodle and EJS are two free outstanding software tools fore-learning and VRL development, respectively. This work looksfor their synergy by supporting the deployment of EJS VRLsinto Moodle, the addition of synchronous collaborative featuresto VRLs, and providing direct access from Moodle to the OSPrepository.

To test the presented approach, a VRL has been createdto help students to train different advanced control tech-niques (robust, fuzzy, and reset control) and to comparetheir performance to conventional PID control. An obser-vational study has been performed revealing the positiveimpact of this VRL and its Moodle deployment over students’learning.


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Luis de la Torre received the M.Sc. degree in physicsfrom the Complutense University of Madrid, Madrid,Spain, in 2008, and the Ph.D. degree in computer sci-ence from the Universidad Nacional de Educacion aDistancia (UNED), Madrid, in 2013.

He is an Assistant Professor with the Departmentof Computer Sciences and Automatic Control,UNED. His research interests include virtual and/orremote labs, distance education, evolutionary algo-rithms, unmanned aerial vehicle (UAV), and pathplanning.

Maria Guinaldo received the M.S. degree in physicsand the B.S. degree in computer engineering fromthe University of Salamanca, Salamanca, Spain, in2008, and the Ph.D. degree in computer science fromthe Universidad Nacional de Educacion a Distancia(UNED), Madrid, Spain, in 2013.

Since 2008, she has been with the Department ofComputer Science and Automatic Control, UNED.Her research interests include networked control sys-tems, event-based control, control of multiagent sys-tems, and engineering education.

Ruben Heradio received the M.Sc. degree in com-puter science from the Polytechnic University ofMadrid, Madrid, Spain, in 2000, and the Ph.D. degreein computer science from the Universidad Nacionalde Educacion a Distancia (UNED), Madrid, in 2007.

Since 2001, he has been an Assistant Professorwith the Department of Software Engineering,UNED. His research interests include software engi-neering, computational logic, and e-learning.

Sebastian Dormido received the Ph.D. degree in sci-ence from the Complutense University of Madrid,Madrid, Spain, in 1971.

Currently, he is working as a Full Professor ofAutomatic Control with the Department of ComputerScience and Automatic Control, UniversidadNacional de Educacion a Distancia, Madridian. Hisresearch interests include automatic control andweb-based labs for distance education.

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