A Direct Circuit ExperimentSystem in Non-ImmersiveVirtual Environments forEducation and Entertainment

QUANG-CHERNG HSU

Department of Mechanical Engineering, National Kaohsiung University of Applied Sciences, 415 Chien-Kung Road,

Kaohsiung 807, Taiwan

Received 13 February 2004; accepted 27 December 2004

ABSTRACT: This article proposes to contribute to the goal of ‘‘The Popular Science

Teaching Research Project’’ as well as to enhance the programming abilities of mechanical

engineering students. Topics being included as example are in physical science, which include

battery, lamp, and electric circuit. These materials are designed, based on virtual-reality

technology that is suitable for students as early as fourth-grade students of primary school. It

will help the students become familiar with new computer technology and provide an

opportunity to study while playing virtual reality computer games. The benefits of the

developed application software system of virtual reality are virtualization of teaching

equipment, cost reduction of teaching materials, unlimited teaching style, and optimization

of learning procedures. � 2005 Wiley Periodicals, Inc. Comput Appl Eng Educ 13: 146�152, 2005;

Published online in Wiley InterScience (www.interscience.wiley.com); DOI 10.1002/cae.20044

Keywords: virtual reality; circuit experiment; physical modeling; software design; virtual

experiment

INTRODUCTION

Virtual reality (VR) is a high-end user interface that

involves real-time simulation and interactions through

multiple sensorial channels. Three important char-

acteristics are: immersion, interaction, and imagina-

tion [1]. Virtual environment (VE) is an alternative

word for VR when especially focusing on graphical

exhibition. McNeill and his colleagues [2] developed

a spoken-dialogue system for navigation in non-

immersive virtual environments by using natural

language-processing technology. The scientific com-

munity has been working in this field for some years,

having recognized VR as a powerful human-computer

interface. VR in surgery and medicine are promising

application areas [3]. The use of VR in surgery

impacts a number of distinct areas, such as teaching

Correspondence to Q.-C. Hsu (hsuqc@cc.kuas.edu.tw).Contract grant sponsor: National Science Council, Taiwan;

contract grant number: NSC 90-2515-S-151-003-.

� 2005 Wiley Periodicals Inc.

146

human anatomy and pathology, surgical-procedure

training for new surgeons, surgical planning of

complex procedures, navigational and informational

aid during surgery, and predicting operational out-

comes [4].

Education and entertainment are also other

important VR application areas. Kumar and his

colleagues [5] created a web-based interactive virtual

experiment on microelectronics for early engineering

students. The web material is presented in an intuitive

and highly visual 3D form that is accessible to a

diverse group of students. Through the use of highly

engaging VR, the ‘‘Virtual Lab’’ addresses edu-

cational opportunities at high school, community

college, and university levels. Ou and his colleagues

[6] developed an interactive web-based training tool

for CAD in a virtual environment along with an

integrated graphics real-time system. Duarte and Butz

[7] have developed an intelligent universal virtual

laboratory to provide a more realistic and enhanced

learning experience. Entertainment was the driving

force of early VR technology and is presently its large

market. Therefore, in this article, the author develops

a direct circuit experiment system in non-immersive

virtual environments for education and entertainment.

The basic concept is to provide a virtual environ-

ment for students, by which they can manipulate

virtual objects like lamp, battery, motor, wire, etc. and

try to find what happens when a virtual circuit layout

has been finished or changed, just as in a real

experiment.

THEORETICAL BACKGROUNDS

The theoretical backgrounds of VR are a combination

of psychology, computer graphics, database, real and

distributed system, electronics, robotics, and multi-

media, etc. For computer graphics, the theories of

solid modeling, surface modeling, transformation,

3D clipping, color graphic, collision, shading, and

projection are well developed [8]. All of these are

elements in the basic technologies for VR; however,

the deficiency will be limitations of computation

speed and close to human eye visualization.

According to the different communication devices

between computer and human, VR offers four types:

desktop (non-immersion), immersion, CAVES, and

web. When desktop VR is used, the operator will see

virtual and real environments at the same time. If

immersion VR is used, one is abstracted from the real

world and put into the computer-generated environ-

ments. CAVES VR allows several observers’ look at

the same virtual scene at high resolution and 3D

images with stereo sounds. Web-based VR is an

extension of desktop VR which allows many manip-

ulators, operate at the same time in Internet.

The proposed system belongs to desktop VR.

However, in addition to normal devices like keyboard

and mouse, the joystick is also applied in the proposed

system to enhance the entertainment effect. The vir-

tual objects are constructed by using AutoCAD and

the textures are pasted in by using True Space. Finally,

by using EON Studio [9] and Visual BASIC (VB)

script programming, the proposed virtual experiment

system is finished as is described in details in the

following sections.

CREATION OF A NON-IMMERSIVEVIRTUAL ENVIRONMENT

Background Knowledge

The background knowledge of direct-circuit experi-

ment is as follows: (1) according to the layout of

elements, such as lamps, electric wires, motors,

batteries, the system should respond how many short

and closed circuits occur in that layout. (2) Identifying

how many shared elements between two nearest

closed circuits. (3) Accumulating the total voltages

and electric resistances exist in each closed circuit.

(4) Deriving the equation, based on mesh-current

method in each closed circuit. (5) Using the Gaussian-

elimination method [10] to solve for current value in

each closed circuit. (6) Setting the brightness of each

lamp or the rotation speed of each motor according to

the electric current. In order to mimic real-time

simulation of the direct-circuit experiment, if an

element is added or removed in electric layout, the

proposed system should repeat the previous six steps

automatically.

The creation of such a non-immersive virtual

system consists in constructing CAD models, arran-

ging virtual environments and interface between

virtual and real worlds, building hierarchy of virtual

objects in simulation trees, planning activation and

sequence between each objects in route trees, and

programming.

CAD Models for Virtual Objects

The virtual objects used in the direct-circuit experi-

ment are circuit board, binding posts, electric wires,

lamps, motors, batteries, etc. By using CAD software,

the solid modeling of virtual objects are constructed as

shown in Figure 1.

DIRECT CIRCUIT EXPERIMENT SYSTEM 147

Virtual Environments and Interface

Other than virtual-experimental objects, the virtual

environments also need a table and cabinet to store

and position all of them. Figure 2 shows the planned

virtual environments used in the proposed virtual

experiment. The table is in front of the cabinet (called

cabinet frame). The circuit board and binding posts

(called basement frame) are placed on the table. The

other virtual experimental objects are stored inside of

the cabinet. For reducing the complexity of checking

whether the wire is contact with other component or

not, the proposed system assumes, when components

connect into binding posts, the electric current can

flow through between them. It is also hard to generate

an electric wire that can be flexible as in a real world.

Therefore, in the proposed system the electric wires

are always straight.

In order to construct a handling interface by

which all the virtual experimental objects can be

manipulated easily as well as to navigate in the virtual

environments, the 2-axis and 14-button joystick is

used. This joystick should be installed under the

Figure 3 The simulation tree represents the frame-

work of the current study.

Figure 2 Virtual environments of direct circuit

experiment.

Figure 1 Virtual objects in solid modeling.

148 HSU

Windows operation system. There are three major

manipulations: (1) the walking of operator in first-

person viewpoint; (2) the choice, pick, and placement

of current object; (3) the movement or positioning of

an object. The operation of manipulator in the virtual

laboratory includes translation and rotation that can be

activated at anytime by a joystick. Mouse keys can

also activate the choice, pick, and placement of cur-

rent object, such as lamp or wire, anytime. This mani-

pulation is the first and necessary step when beginning

a virtual experiment. The movement or positioning of

current object is also activated by joystick, by which

each virtual object can be moved to anyplace of circuit

board and locked in definite positions. If an object is

moved or repositioned, the virtual environment should

perform according to the previous mentioned back-

ground knowledge.

Simulation Tree

The simulation provided by EON Studio involves

three main actions—adding and enhancing 3D

graphic objects, defining behavioral properties for

these objects, and specifying how users will interact

with them in the simulation. The files containing 3D

objects, textures, and sounds can be imported into

EON Studio. In simulation tree, the framework of this

simulation should be provided that includes the

viewpoint, the lighting, the hierarchy of virtual

objects, etc. The interaction between any two virtual

objects can be added in the route tree. However, the

more complex functions such as solving linear

algebraic equations can be finished by VB script

programming.

Figure 3 depicts the simulation tree of the current

study that consists of: Camera node, Ambient light

node, Lovely animation—motor node, My tree node,

and Joystick node. The first two nodes are default

nodes that represent the status of view and light.

Lovely animation—motor node responds the pre-

defined animation of virtual objects including wire,

lamp, battery, and motor. My tree node is the major

node that comprises several main frames of virtual

objects, such as Cabinet frame and Basement frame.

There are a lot of virtual objects in the Cabinet frame

such as cabinet sub-frame, lamps with different color,

motors with different color, batteries with different

color, electric wires with different color, and several

glasses in front of the cabinet. There are two main

sub-frames in the Basement frame: ir-table (represent-

ing a circuit board) and connecting pole (representing

binding posts). All these nodes comprise the frame of

the current simulation.

Routes Window

Routes window is used to connect the nodes and

define how they will behave when data are sent

between them. Node behavior is also affected by

where the node is placed in a simulation tree, as well

Figure 4 Rotation node ‘‘mg’’ is used to control ‘‘motor G’’ rotation both in simulation tree and routes window.

DIRECT CIRCUIT EXPERIMENT SYSTEM 149

as the settings in its properties window. The Routes

window provides a graphic representation of all defined

routes. Connections between nodes are shown as lines,

running from the triggering node’s out-field to the

corresponding in-field of the target node. Out-fields

are represented by an arrow and in-fields by a dot.

Figure 4 depicts how to control a motor fan

rotation. In the simulation tree, motor G is divided

into two sub-frames: body (without blade) and blade.

A rotation node ‘‘mg’’ is defined and placed under the

blade frame. A script node called ‘‘Basement receive’’

governs with how much current will flow through this

motor and transferring the rotation speed to rotation

node ‘‘mg.’’ This algorithm can also be used to control

motor R by ‘‘mr’’ or to control other virtual objects,

like lamps, by passing information to texture nodes

‘‘br,’’ ‘‘bg,’’ and ‘‘bb.’’

VB Script Programming

Scripting in EON is a method to solve a large

calculation works or special purposes. The data from

Script node fields storing single values is accessible as

ordinary variables in VBScript subroutines. For each

in-event field in the Script node a subroutine named

On_name() can be written. The subroutine is executed

when the Script node receives the name in-event.

Figure 5 lists a part of VB script language for

Figure 6 Demonstration of picking virtual object and layout in the basement.

Figure 5 Listing a part of VB script language for debugging, when key ‘‘D’’ is pressed the subroutine On_debg()

is operated.

150 HSU

debugging. When key ‘‘D’’ is pressed, the keyboard

sensor node ‘‘Debug’’ is activated and sends a

message called ‘‘debg’’ as an in-event field to

‘‘Basement receive’’ script node. In the same time,

the subroutine On_debg() is operated to print some

data on screen for debug. A lot of tasks should be

conducted by VB script programming, such as:

responding how many short and closed circuits in

that layout, identifying how many shared elements

between two adjacent-closed circuits, accumulating

the total voltages and electric resistances in each

closed circuit, solving current value in each closed

circuit by numerical method, and adjusting the bright-

ness of each lamp or the rotation speed of each motor

according to electric current.

RESULTS AND DISCUSSION

Based on the above descriptions and constructions, a

non-immersion virtual environment for direct-circuit

experiment has been created. Figure 6 depicts picking

virtual-experimental objects from a cabinet and

layouting into a circuit board in such a virtual environ-

ment. In order to test the accuracy and performance of

the virtual experiment system, several tests have been

conducted. The first one was a simple circuit layout

for one battery, one lamp, and two electric wires, as

shown in Figure 7. The lamp was bright. The second

test was to add two wires and one motor-fan to

compose another closed circuit using the same battery

in both, as shown in Figure 8. The motor-fan rotated

(however, it can not be seen on paper) and brightness

of the lamp was the same as in Figure 7. The third test

was to add two more wires, another lamp, and to

compose a multiple circuit, as shown in Figure 9. The

two lamps had the same brightness. The last test was

to exchange one battery and one wire such that the

batteries were in opposition, as shown in Figure 10.

The lamps turned off and the motor stopped rotating.

All above tests demonstrate the validity of the pro-

posed virtual environments.

Figure 10 An inoperative circuit layout.

Figure 9 A multiple composed circuit layout for two

batteries, two lamps, one motor fan, and six electric

wires.

Figure 8 A composed circuit layout for one common

battery, one lamp, one motor fan, and four electric

wires.

Figure 7 A simple circuit layout for one battery, one

lamp, and two electric wires.

DIRECT CIRCUIT EXPERIMENT SYSTEM 151

CONCLUSIONS

The purpose of the proposed virtual experiment

system for direct circuit is based on the basic training

of department of mechanical engineering: computer-

aided design, computer-aided drawing, and computer

programming; to extend their software design abil-

ities. The developed virtual environments can be

provided to primary school students to explore or

layout the simple and basic direct circuit experiments.

Based on the demonstrating examples: the simple

circuit, the complex circuit, the multiple complex

circuits, and the invalid circuit, the proposed system

behaved smooth, true and natural. It can be used as a

computer-aided tool to assist real experiments as well

as used as an entertainment toy.

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BIOGRAPHY

Quang-Cherng Hsu is an associate profes-

sor at the National Kaohsiung University of

Applied Sciences, Taiwan. He received his

PhD in mechanical engineering at the

National Chen Kung University, Taiwan. In

2003�2004, he was a visiting scholar at the

Center for Advanced Polymer and Compo-

site Engineering at The Ohio State Uni-

versity. His research interests focus in

precision manufacturing (such as sheet

metal forming and forging), molecular dynamics simulation of

nano imprint processes, and virtual experiment system develop-

ments for education and entertainment.

152 HSU