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Session T4A
978-1-4244-1970-8/08/$25.00 ©2008 IEEE
October 22 – 25, 2008, Saratoga Springs, NY
38
th
ASEE/IEEE Frontiers in Education Conference
T4A
-
18
NEESit MacBook Accelerometer and Video Sensor
Platform (iSeismograph) for Education and
Research
Lelli Van Den Einde, Wei Deng, Patrick Wilson, Ahmed Elgamal, and Paul Hubbard
University of California, San Diego, lellivde@sdsc.edu, weideng@sdsc.edu, prwilson@ucsd.edu, elgamal@ucsd.edu,
hubbard@sdsc.edu
Abstract
- Current Macintosh laptop computers are
equipped with a 3-axis accelerometer that detects sudden
shock and impact and enables the hard drive to “freeze”
and save its contents. In addition, the newer Intel-based
MacBook and MacBookPro laptops have built-in iSight
video
cameras
for
use
in
video
conferencing
communications.
The
Network
for
Earthquake
Engineering Simulation (NEES) Cyberinfrastructure
Center (NEESit) has exploited these capabilities and has
developed an educational and research platform for
measurement and recording of vibrations and dynamic
response. The system employs the NEESit Real-time data
Viewer (RDV) that enables the real-time streaming of
acceleration
data
synchronized
with
video,
and
automatically saves data into a database repository
(NEEScentral).
Through
NEEScentral,
earthquake
engineering
students
and
research
collaborators
worldwide can access the recorded data online and
engage in joint projects, potentially at a worldwide scale.
The following paper provides an overview of the
information technology framework for the NEESit
MacBook Accelerometer and Video Sensor Platform
(iSeismograph) and its capabilities, and provides an
example of its potential for collaboration through a
classroom application for undergraduate education in
earthquake engineering.
Index Terms
– Data streaming, earthquake engineering,
MacBook, real-time.
I
NTRODUCTION
Earthquake
engineering
education
initiatives
are
continuously
being
developed
to
provide
learning
opportunities for students and educators at all levels, as well
as continuing education for practitioners. With information
technology increasingly being incorporated into the field of
earthquake engineering, the development of education and
research tools to stimulate interest in engineering and
science at the earliest levels and promote the development of
future leaders in earthquake engineering mitigation at the
undergraduate and graduate levels has been facilitated. The
Network for Earthquake Engineering Simulation (NEES)
Cyberinfrastructure Center (NEESit) has developed an
innovative platform for earthquake engineering education
and research making use of commercial off-the-shelf
technology and open source software tools. The NEESit
MacBook Accelerometer and Video Sensor Platform
(iSeismograph) makes use of newer Intel-based MacBook
and MacBook Pro laptops that are equipped with a 3-axis
accelerometer to detect motion and a built-in iSight video
camera for use in video conferencing communications. It
provides a system that enables students and researchers to
measure and record vibrations and dynamic response in a
laboratory or real-life setting, and archives the data in the
NEES central data repository (NEEScentral [1]). The system
employs open source software (the NEESit Real-time data
Viewer (RDV) [2] and Data Turbine [3] and [4]), which
provide an interface and the middleware for viewing real-
time, streaming acceleration data synchronized with video.
The data is automatically stored into a project in the
NEEScentral database, which provides an environment that
promotes worldwide collaboration.
Highlights of the NEESit MacBook Sensor Platform
include:
•
Real-time acceleration data acquisition and video
capture
•
Real-time data and video archiving and replay of
historical data
•
Synchronization between sensor data and video images
•
Automatic upload of synchronized data into the
NEEScentral Data Repository for worldwide access
•
Collaboration platform for sharing data sets.
The following paper describes elements of the NEESit
MacBook
application.
Details
about
the
underlying
information
technology
(IT)
framework
are
initially
presented followed by an overview of a pilot classroom
project applied to an undergraduate earthquake engineering
course that utilized the technology. All software and
documentation is available for use and can be accessed from
the NEESit iSeismograph software page [5].
I
NFORMATION
T
ECHNOLOGY
F
RAMEWORK
I. The MacBook Hardware
Most of the recent Macintosh laptop computers today are
equipped with a 3-axis accelerometer (Sudden Motion
Session T4A
978-1-4244-1970-8/08/$25.00 ©2008 IEEE
October 22 – 25, 2008, Saratoga Springs, NY
38
th
ASEE/IEEE Frontiers in Education Conference
T4A
-
19
Sensor or SMS [6]). The original MacBook Pro uses the
Kionix KXM52-1050 three-axis accelerometer chip, with a
dynamic range of +/- 2g and a bandwidth up to 1.5 KHz.
The built-in accelerometer helps to freeze the hard drive and
save its contents when a sudden motion is detected. The
newer Intel-based MacBook and MacBookPro also have
built-in iSight cameras. Combined with open source
software
packaged
by
NEESit
(iSeismograph),
these
MacBooks can serve as a flexible, cost-effective and
portable education-and-outreach tool. All of these features
come in a small package (12.78" x 8.92" x 1.08") based on
Apple’s specification for a MacBook 13". With proper
calibration, they can also be used for real-time gravity or
acceleration measurements.
II. Using the iSeismograph Software to Configure your
MacBook System
The iSeismograph software can be downloaded from
NEESit's iSeismograph software page [5] and installed on a
local MacBook laptop. Once downloaded (Safari by default
saves a tar file in the Desktop directory), a Terminal window
can be opened (Finder->Go->Utilities->Terminal), and the
commands shown in Figure 1 can be executed to extract the
files contained in the tar file to the local home directory.
Following these commands, three icons will be created on
the local desktop, allowing the user to easily launch the
required programs to record and upload data.
FIGURE 1
T
ERMINAL
W
INDOW TO
E
XTRACT
F
ILES
.
As shown in Figure 2, the first icon is used to clean up
any historical data that was previously captured by the
iSeismograph program, the second icon is used to launch
iSeismograph to capture the real-time accelerometer data
and video, and the third icon is used to upload the recorded
data to the NEEScentral data repository (described in further
detail in Section IV).
After double-clicking on the run_experiment.sh icon,
the user should wait for 10-15 seconds until the green light
of the iSight camera comes on, and both data and video
channels show up in the application, as illustrated in the left
pane in Figure 3.
FIGURE 2
I
CONS
C
REATED ON
D
ESKTOP
.
FIGURE 3
I
NITIAL
RDV I
NTERFACE WITH
D
ATA AND
V
IDEO CHANNELS
.
III. Displaying Synchronized Data Using the Real-time Data
Viewer (RDV) and Data Turbine
The window shown in Figure 3 is the main user interface for
the Real-time Data Viewer (RDV) [2], which was launched
by the run_experiment.sh script. RDV provides a graphical
display for the user to view and analyze live or archived
time-synchronized data from a Data Turbine server ([3] and
[4]), which is running in the background to collect and
synchronize the data. In iSeismograph, the Data Turbine
server is setup to archive several hours of data. The data can
be streamed in real-time or replayed over the full timeline of
recorded data. The run_experiment.sh script also launches
two data acquisition programs (sms-rbnb and ISightToRbnb)
in the background to stream the accelerometer data and
Session T4A
978-1-4244-1970-8/08/$25.00 ©2008 IEEE
October 22 – 25, 2008, Saratoga Springs, NY
38
th
ASEE/IEEE Frontiers in Education Conference
T4A
-
20
video files from the iSight camera into the Data Turbine
server.
As highlighted as numbered boxes in Figure 4, the RDV
user interface is composed of five main panels: 1) Control
panel; 2) Channels panel; 3) Properties panel; 4) Data
Viewing panel; and 5) Event Marker panel. All available
channels from the Data Turbine server are listed inside the
Channels panel (box 2 in Figure 4), and are organized by
source names (for example, Apple Accelerometer, iSight).
To show the channels available for viewing from a particular
source, the user must double-click on the source name. Once
the channels are expanded, a new data panel is opened in the
Data Viewing panel (box 4 in Figure 4). When channels are
selected and data panels are opened, a user can click on the
Real-time button on the Control panel (box 1 in Figure 4) to
start viewing the real-time streaming of data and video.
FIGURE 4
RDV D
ISPLAYING
S
YNCHRONIZED
D
ATA AND
V
IDEO IN
R
EAL
-
TIME
.
The Data Viewing panel (box 4 in Figure 4) plots the
time-series data for the acceleration in the z-direction
directly adjacent to the video panel for the iSight camera.
During an experiment, these panels can be used to observe
the real-time sensor readings and synchronized video. At any
time during or after an experiment, clicking on any location
on the timeline inside the Control panel (box 1 in Figure 4)
will allow the user to replay archived data synchronized with
video. When reviewing archived data, the user can click on
the Play button inside the Control panel to replay the data at
the original data rate. The playback rate can also be adjusted
so data is presented slower or faster than real-time to aid in
analysis.
At the bottom of the RDV window an Event Marker
panel (box 5 in Figure 4) allows the user to make notes
about important events during an experiment. Once an event
marker is added from this panel, it is displayed on the global
timeline in the Control panel, which makes it possible to
quickly point out "interesting" data points for later review.
Additionally, an automated data upload script was created
that looks for specific “start” and “stop” markers to
automatically identify the time range for uploading data to
the NEEScentral data repository (automated script is
described in more detail in Section V). More information
about the RDV user interface can be found in the RDV User
Guide [7]. A video demonstrating the iSeismograph
application can be found on YouTube [8].
IV. Sharing Data via the NEEScentral Data Repository
NEEScentral [1] is the data repository for the NEES
initiative and provides a collaborative portal environment
that allows students and researchers from disparate locations
to share data and resources through an easy to use web
interface. NEEScentral provides a centralized location for
researchers to securely organize, store, and share data and
metadata in a non-proprietary format. After obtaining a
NEEScentral user account [9], users are able to create
private workspaces and invite other registered NEEScentral
users to participate. Data residing in NEEScentral can be
searched and exported, and customizable reports can be
generated. Refer to the NEEScentral User Guide for more
detailed information about the features and how to use the
data repository [10].
NEEScentral is organized in a conceptual hierarchy as
shown in Figure 5. The hierarchy provides a single, high-
level, standardized model for storing data that is universal to
all disciplines in the earthquake engineering community.
The organizational hierarchy is based on four directory
levels: project, experiment or simulation, trial or run, and
data. At the coarsest level of the hierarchy is the project
directory, which provides a general container for secure data
sharing within a collaborative team. The second level
provides extensive mechanisms for inputting metadata about
the setup of an experiment or simulation, including
information about input motions, coordinate spaces, sensor
location
plans,
and
scale
factors.
Experiments
and
simulations contain one or more trials or runs that define
further changes to configuration parameters. At the lowest
level of the hierarchy are directories for archiving the data
associated with each experiment. NEEScentral also provides
the capability to create unstructured projects where users can
create their own directory structure rather than using the
NEES hierarchy as described in Figure 5.
FIGURE 5
NEES
CENTRAL
P
ROJECT
H
IERARCHY
S
TRUCTURE
.
Session T4A
978-1-4244-1970-8/08/$25.00 ©2008 IEEE
October 22 – 25, 2008, Saratoga Springs, NY
38
th
ASEE/IEEE Frontiers in Education Conference
T4A
-
21
The NEESit iSeismograph has been integrated directly
with NEEScentral allowing the synchronized data and video
captured with the system to be uploaded automatically to the
NEEScentral data repository. The tool used for automatic
upload is described in more detail in the following section.
V. Automatic Transmission of Data Wirelessly into
NEEScentral
Once the data is successfully captured in the Data Turbine
server’s archive, the upload_data.sh script can be executed
to transmit data via MacBook’s wireless network interface
into the NEEScentral data repository. To use this script, the
MacBook needs to be verified to have Internet access via its
wireless network interface. The best way to verify this is to
use a browser to access http://central.nees.org and check if
the
webpage
can
be
shown.
After
launching
the
upload_data.sh script, it will ask a number of questions that
describe where the data is to be uploaded in the NEEScentral
data repository (such as NEEScentral login information, the
project and experiment where the data will reside, etc) (refer
to Figure 6). Once this information is inputted, the data is
automatically
transmitted
into
the
NEEScentral
data
repository.
FIGURE 6
I
NTERACTIVE
D
ATA
U
PLOAD
S
CRIPT
.
A pilot earthquake engineering classroom project,
which was conducted utilizing the NEESit iSeismograph
platform, is described in the following section and includes
high level instructions for how to use the technology to
understand the dynamic response of a cantilever beam. To
support this educational example, a special project was
created in NEEScentral and each student in the class was
given login access to the shared workspace. In addition to
promoting
the
basic
understanding
of
earthquake
engineering
concepts,
the
NEEScentral
collaborative
environment also provides the opportunity to increase the
technological capabilities of the students.
P
ILOT
E
ARTHQUAKE
E
NGINEERING
C
LASSROOM
P
ROJECT
Assessment of the functionality and potential for educational
application of the iSeismograph system was made through a
pilot classroom project conducted at the University of
California, San Diego (UCSD). Approximately 90 students
participated in this exercise as a project for an undergraduate
earthquake engineering course.
Benefits to the students
included visual and quantitative demonstration of basic
dynamic principles and early exposure to methods of data
acquisition
and
processing
of
experimental
data.
A
document
providing
general
recommendations
for
instructors wishing to effectively use the iSeismograph
system in a classroom exercise similar to this earthquake
engineering pilot program can be found in [11].
I. Project Objective
Developing an understanding of fundamental principles of
structural dynamics is critical at the most basic level in
earthquake engineering.
The objective of this classroom
exercise was to create an experimental configuration that
students with limited or no exposure to these fundamental
principles could use to measure dynamic properties of an
actual physical structure.
The UCSD pilot project
demonstrated measurement of the first natural frequency and
damping ratio of an adjustable length cantilever beam in free
vibration. By imposing a displacement on the beam and
measuring the acceleration response after the beam is
released, these dynamic properties were determined. Length
of the cantilever beam was varied to demonstrate the effects
of changing the length in the free vibration response.
II. Experiment Setup
A simple structure was constructed for this experiment,
which consisted of a 9' long timber beam of known elastic
modulus that was attached to the top of a heavy concrete
block by an adjustable clamp (Figure 7). A rigid fixity was
assumed at the clamp.
To minimize the impact of the
MacBook mass on the free vibration response, it was
secured to the beam near the clamped end. The length of the
cantilever beam was considered to be the length from the
clamp to the end of the beam. Students were able to easily
change the beam length by loosening the clamp and pulling
or pushing the beam.
FIGURE 7
F
REE
V
IBRATION
T
ESTING
A
PPARATUS
.
III. Class Logistics
Several simple steps were required in preparation for
conducting the class experiment utilizing the NEESit
software and services. Initially, the instructor and each
student were required to register for a free account at
Session T4A
978-1-4244-1970-8/08/$25.00 ©2008 IEEE
October 22 – 25, 2008, Saratoga Springs, NY
38
th
ASEE/IEEE Frontiers in Education Conference
T4A
-
22
NEEScentral [9].
A class project was created at
NEEScentral and an Experiment was created under the
project. Each student was added as a member of the project
and experiment, and was given privileges to view, create and
edit the project. This allowed them the proper permissions to
upload and download data to and from the site.
For the pilot project, students were divided into teams of
six students. For each team, a trial was created under the
project experiment in NEEScentral. This allowed each team
to send their data to their respective trial. With the project,
experiment and trials created in NEEScentral, and the
appropriate privileges given to the students, each team was
able to conduct the experiment and automatically archive
their data in NEEScentral by following the instructions
found in the experimental procedure handout [12]. The use
of NEEScentral as a collaboration environment to share data
and course documents can be applied to many kinds of
educational applications regardless of the use of the
iSeismograph platform.
IV. Representative classroom data sets
Each team of students was required to submit a report
describing
the
classroom
project
which
included
a
comparison of theoretical predictions and experimental
results for the pilot cantilever beam experiment.
Theoretical analysis included predicting the natural
frequency of vibration, (
ω
) of the cantilever beam based on
(1), where
E
is the modulus of elasticity (assumed as 1350
ksi for the wood used in this experimented),
I
is the mass
moment of inertia as calculated by (2), and
b
,
h
,
L
, and
m
are
the beam width, beam thickness, beam length, and mass of
the beam per unit length (assumed as 0.2 lb/in), respectively.
(1)
(2)
For simplicity, the mass of the MacBook was ignored
(recall that the MacBook should be secured near the clamped
end of the beam to minimize its impact on the natural
frequency of the beam).
Students
analyzed
the
data
by
reviewing
the
acceleration response graph from the experiment. An
example is shown in Figure 8 for the case where the
cantilever beam length was 77.7".
During the experiment, students recorded the beam
width (b = 15.4") and thickness (h = 0.5625"). Using these
measured dimensions as well as given properties and
equations, the theoretically predicted natural frequency
could be determined. For the described example case, the
theoretical natural frequency was calculated as 14.2 rad/sec
or 2.3 Hz.
The students were able to evaluate the
experimental natural frequency by counting the peaks in the
acceleration response graph (Figure 8) over a given period of
time. For this case, the observed natural frequency was 2.4
Hz. Students also used the logarithmic decrement method to
approximate the observed damping in the beam [13].
Following the analysis of their own data, each team was
able to download data from other teams, approximate the
natural frequency from the experimental acceleration
response graph and back-calculate the length of the beam
that was used during other experiments.
FIGURE 8
E
XPERIMENTAL
A
CCELERATION
R
ESPONSE OF
C
ANTILEVER
B
EAM
.
S
UMMARY
: P
OTENTIAL FOR
E
DUCATION AND
R
ESEARCH
The
pilot
earthquake
engineering
classroom
project
described herein provides an example use case for the
NEESit
MacBook
Accelerometer
and
Video
Sensor
Platform (iSeismograph) for educational purposes that
allows simple earthquake engineering concepts to be
introduced in a novel manner.
The unique collaborative
framework shows great potential for other education and
research efforts. Because the MacBook laptop hardware
provides an inexpensive sensor and data acquisition system,
it can be placed in the field (such as mounted on a bridge)
and used for real-time health monitoring applications. The
framework provides the essential elements to allow for
automated on-line continuous monitoring of structural
systems. Data streamed in real-time from the accelerometer
and the iSight video camera enables researchers and students
to remotely observe the performance and vibration response
of the structural systems. Because of the regular automated
archival of the data into the NEEScentral Data Repository,
researchers can access archived data for further analyses.
Furthermore, if left in a data acquiring mode, the NEESit
iSeismograph system can serve as a live seismograph that
measures acceleration and captures video during a real
earthquake event. Other similar software development
efforts have leveraged the MacBook technology [15], or
have used similar SMS sensor technology for IBM Thinkpad
laptops with a Linux operating system [16].
Session T4A
978-1-4244-1970-8/08/$25.00 ©2008 IEEE
October 22 – 25, 2008, Saratoga Springs, NY
38
th
ASEE/IEEE Frontiers in Education Conference
T4A
-
23
A
CKNOWLEDGMENT
The authors would like to acknowledge Jason Hanley, Moji
Soltani and Terry Weymouth for their software development
contributions to this platform, and the National Science
Foundation for funding this effort through the Network for
Earthquake Engineering Simulation (NEES) effort (Award
CMS-0402490). Furthermore, the authors would like to
acknowledge CREARE [3] and the Open Source Data
Turbine Initiative [4] for their contributions to developing
the middleware that supports this iSeismograph platform.
One of the data acquisition programs (sms-rbnb) used in this
platform was built on the SMS Java Library [17].
R
EFERENCES
[1]
NEEScentral Data Repository: https://central.nees.org
[2]
NEESit RDV Software Page: http://it.nees.org/software/rdv/index.php
[3]
CREARE Commercial Data Turbine Software:
http://rbnb.creare.com/rbnb/index.html
[4]
Open Source Data Turbine Initiative: http://dataturbine.org/
[5]
NEESit iSeismograph software page:
http://it.nees.org/software/iSeismograph
[6]
MacBook Sudden Motion Sensor
http://docs.info.apple.com/article.html?artnum=300781
[7]
RDV User Guide: http://it.nees.org/library/telepresence/rdv-users-
guide.php.
[8]
YouTube Video of iSeismograph:
http://www.youtube.com/watch?v=tdumHmrX8ss
[9]
NEEScentral User Account Page:
https://central.nees.org/acct/index.php
[10] NEEScentral User Guide: http://it.nees.org/library/data/NEEScentral-
users-guide.php#11
[11] Deng, W., and Wilson, P., “Using iSeismograph and the NEEScentral
Data Repository for Earthquake Engineering Experiments”, NEESit,
TN-2008-01, http://it.nees.org/documentation/pdf/TN-2008-01_Deng-
Cantilever-Beam-Experiment-Instructions.pdf.
[12] Wilson, P., and Deng, W., “Cantilever Beam Experiment using the
NEEScentral Data Sharing Archive”, NEESit, TN-2008-02,
http://it.nees.org/documentation/pdf/TN-2008-02_Wilson-Cantilever-
Beam-Experiment.pdf.
[13] Chopra, A. K., (2001). “Dynamics of Structures,” Second Edition,
Prentice Hall, Upper Saddle River, New Jersey: p. 52.
[14] http://it.nees.org/support/workshops/2007/2wfcree/TN-2007-
01_Hubbard.pdf
[15] Apple Software application (SeisMac):
http://www.suitable.com/tools/seismac.html
[16] SMS on Thinkpad/Linux
http://www.almaden.ibm.com/cs/people/marksmith/tpaps.html
[17] SMS Java Library: http://www.shiffman.net/p5/sms
A
UTHOR
I
NFORMATION
Lelli
Van
Den
Einde
Assistant
Director,
NEES
Cyberinfrastructure Center, San Diego Supercomputer
Center,
University
of
California,
San
Diego,
lellivde@sdsc.edu
Wei Deng
, Production Infrastructure Support Manager,
NEES
Cyberinfrastructure
Center,
San
Diego
Supercomputer Center, University of California, San Diego,
Patrick Wilson
, Graduate Student, Department of Structural
Engineering,
University
of
California,
San
Diego,
prwilson@ucsd.edu
Ahmed Elgamal
, Professor, Department of Structural
Engineering,
University
of
California,
San
Diego,
elgamal@ucsd.edu
Paul Hubbard
, Software Developer and co-PI, CLEOS, San
Diego Supercomputer Center, University of California, San
Diego, hubbard@sdsc.edu
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