FredBot: FRee EDucational RoBOTics Platform
-
Upload
celestialexpression -
Category
Documents
-
view
221 -
download
0
Transcript of FredBot: FRee EDucational RoBOTics Platform
-
7/30/2019 FredBot: FRee EDucational RoBOTics Platform
1/12
FredBot; the Free Education Robot
Tabor Henderson
Lab Assistant
Department of Physics Metropolitan State University of Denver
July 23, 2013
Abstract
This paper describes an open-source hardware platform (FredBot) in-
tended as a candidate replacement for the blackbox-style lab platforms
provided by Pasco and other educational lab equipment manufacturers.
We discuss the educational opportunities provided by open-source hard-
ware, as well as the expected difficulties. We begin with our motivations,
then replicate a Pasco data set with FredBot, and compare the two sets.
From this comparison, we develop our ideas for next steps. We con-
clude that open source hardware provides remarkably complete data and
a holistic learning experience, but requires thorough development before
deployment.
1 Motivation
The undergraduate physics lab currently uses Pasco products for almost all of
our equipment needs, including physical items like kinetics tracks and carts,
and electronic components, like the 750-series interface box and sensors. While
generally well-made, the Pasco equipment is very expensive. The 750-series
1
-
7/30/2019 FredBot: FRee EDucational RoBOTics Platform
2/12
boxes cost over $700, and have already been replaced by the 950-series, which
costs $900. These devices mediate between the lab computers and sensors,
and this is where I first realized how easily they could be replaced. This is
also the biggest flaw in Pascos products; they all rely on the interface box,
forcing experiments to rely on real-time communication between the desktop and
sensors. Our biggest problem with the Pasco equipment has been the interface
boxes, almost always with their USB firmware. FredBot avoids this issue entirely
by design, but it comes with a loss in educational experience. FredBot trades the
ability to view real time data for a transparent, open platform. Pascos approach
is a blackbox style design, in which the students dont need information on
the nature of their data-collection apparatus. With this design, students dont
need to understand that their motion sensor is actually a position sensor, only
that it provides data up to a certain accuracy. 1
With FredBot, we pursue three design elements: reliability, clarity, and cost.
FredBot is essentially bulletproof by way of modularity. If any component
fails, it is replaceable for less than $30. FredBot also functions completely
transparently; it relies on less than 40 lines of code, and all functions are explicit.
There is no motion sensor with FredBot; only a position sensor, a datalog,
and the students ability to manipulate that data. Finally, the current version of
FredBot costs less than $100 plus assembly time, and could provide serviceable
data in most of our kinetics labs.
2 Description of Materials
The Arduino open source prototyping platform is the core of FredBot. It in-
cludes a development environment with many libraries. In fact, we did not
1As a student, the author personally benefited from this. Watching the real-time graph
of kinetic vs. potential energy was fascinating, and a powerful learning experience. This
advantages are lost with FredBot, but may be recoverable with additional development.
2
-
7/30/2019 FredBot: FRee EDucational RoBOTics Platform
3/12
write more than 10 lines of code for the main program; it simply consists of
two pieces of integrated library code. A major feature of the Arduino platform
is its shield system. This allows major components to be dropped in and
expanded further by the user. Available shields include our memory module
listed above, various types of wireless communication, touchscreens, high volt-
age controllers, sensor relays, and more. Additionally, shields always leave at
least some of the mainboards pins open for other sensors. We utilize both fea-
tures in FredBot.
FredBot itself is simply the components above assembled in the enclosure. It
is sufficiently compact to be mounted securely to the Pasco kinetics carts with
velcro straps. The Ping))) sensor needs a fairly large target. We mounted Fred-
Bot to the cart, allowing the target (10.012.5cm cardboard sheet) to remain
stationary. This provided initial data, but it was not easily comparable to Pasco
data. So, we collected data using both systems in a consistent way, described
below.
Description Cost
Arduino Uno Rev 3 open source prototyping board $25
Seeed Studio SD/mSD shield $10
Parallax Inc. Ping))) Ultrasonic distance sensor $30
Radioshack Enclosure Project Skeleton Kit $25
battery pack & miscellaneous connectors $5
total $95
3 Data Collection Procedure
To compare the two data collection systems, we collected position data from the
end of a kinetics cart, with the ultrasonic senors pointing at the cart in both
3
-
7/30/2019 FredBot: FRee EDucational RoBOTics Platform
4/12
cases. We collected data on a kinetics cart standing still, as it fell down an
inclined track, and after an impulse away from the sensor. Due to differences
between the systems, we collected all of the Pasco data, then all of the FredBot
data. FredBot required reprogramming between each run, which significantly
slowed progress.
With the Pasco equipment, we collected data on three runs of each type
listed above at 10Hz, 20Hz, and 50Hz resolutions, for a total of nine data sets.
This frequencies result in a delay between data points of 0.1s, 0.05s, and 0.02s,
respectively. With FredBot, the Ping))) sensor triggers after a five microsecond
signal high, releasing a sound pulse, then returns the signal high when the
pulse echo hits the sensor. Then, the program converts the time difference into a
position and delays. We ran with the delay at 100ms, 50ms, 25ms, and 10ms to
approximate 10Hz, 20Hz, 50Hz and 100Hz cycle times. This resulted in twelve
data sets.
4 Analysis
Presented are the charts generated from the data runs. The raw position data
has a few anomalies in the FredBot runs, in particular in the impulse runs, and
in one fall run. These are probably due to the experimenters clumsiness, as
they all occur as the cart is released. Also note that the data on the stationary
cart is somewhat deceiving; all three of the Pasco runs occured with the cart
at the same spot, the four FredBot runs occured with the cart in four distinct
positions.
Despite the anomalies, FredBot succeeded in providing data at a higher reso-
lution than the Pasco sensor. We believe this ability is worth developing further,
4
-
7/30/2019 FredBot: FRee EDucational RoBOTics Platform
5/12
and integrating into pedagogical design. 2
5 Next steps
There are many possibilities for integrating open source designs in the class-
room. FredBot, as it stands, provides one such possibility, but it could be much
improved. We could try to develop FredBot into a drop-in replacement for prod-
ucts like Pascos interface boxes. However, this requires development of a signal
generator, additional sensors, and a more robust software package. Also, trying
for a Pasco workalike probably misses the purpose of open source. Pascos
products are effective in the classroom because they facilitate a particular learn-
ing style, that which tolerates suspension of disbelief and abstractions. When
one can delve completely into the context of physics, its hard to beat their plat-
form. But some students, inevitably, find the equipment itself more interesting
than the content its supposed to teach. Arduino, being an open platform, in-
vites a different, more experiential learning style. Those students distracted
from physics by gadgets will hopefully find their perspectives enhanced by see-
ing exactly how their experiment works.
Besides Arduino, other open source platforms are available. Arduino has
a thriving user community which shows no sign of slowing down in the near
future. The Arduino platform is used by hackers worldwide in everything from
quadcopters to automatic gardens. I believe it to be as permanent as Pasco.
However, any open platform provides the same basic benefits, and most can
make use of the same sensor systems.
We believe the most useful immediate next step would be exploring alterna-
2The analysis given here is rudimentary, and comes with the note that we would gladly
work more with the data, given some advice on how to make it useful.
5
-
7/30/2019 FredBot: FRee EDucational RoBOTics Platform
6/12
tive sensors in the same or similar lab experiments. For example, accelerometers,
commonly deployed in mobile devices have grown highly accurate and robust.
These sensors could provide cleaner data, less susceptible to environmentally
introduced errors. Alternately, we could focus on developing the ultrasonic sys-
tem to the standard required currently. As a third possibility, we could pursue
alternate open source platforms. Finally, rather than continue developing spe-
cific lab components, we could begin equipping the Society of Physics Students
chapter with the necessary equipment for developing lab experiments. Experi-
ment development could earn the student money, class credit, or fulfill an honors
requirement. In summary, our next steps could include:
1. Development using alternate sensors
2. Further development using ultrasonic sensor
3. Development using alternate platforms
4. Organizational development
We seek recommendations and advice. Please email any and all thoughts to
tabor.hendersongmail.com.
6
-
7/30/2019 FredBot: FRee EDucational RoBOTics Platform
7/12
6 Graphics
7
-
7/30/2019 FredBot: FRee EDucational RoBOTics Platform
8/12
8
-
7/30/2019 FredBot: FRee EDucational RoBOTics Platform
9/12
9
-
7/30/2019 FredBot: FRee EDucational RoBOTics Platform
10/12
10
-
7/30/2019 FredBot: FRee EDucational RoBOTics Platform
11/12
11
-
7/30/2019 FredBot: FRee EDucational RoBOTics Platform
12/12
12