Description
Design objectives
1. To design a ping-pong ball launching device capable of launching a ball into a 30 cm by 30
cm area at least 120 cm from the release point of the device 95% of the time (see Figure 1).
2. Provide mobility for this device by mounting on a suitably modified two-wheeled robot.
Figure 1. Example map
ECSE 211 Design Principles & Methods
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Design requirements
The following design requirements must be met:
• The system must satisfy the design requirements
from Lab 4 with respect to localization, with the
following exceptions:
o You must follow the (X,Y,θ) convention
specific to this lab (refer to Figure 2).
o You are free to use either rising or falling edge
localization.
o You are not required to provide a way of
selecting rising or falling edge.
o You do not have to wait for user input after
completing ultrasonic or light localization.
• You must allow for the following data to be entered
using either the buttons and LCD display OR an
easily modifiable section in your code:
1. The coordinates of the Target point (Tx,Ty).
• Your robot will start in Corner 0 (0,0), localize, and then proceed to a suitable launch point
for getting the ball to the specified target point. Note: the launch point chosen must be no
closer than 120cm (4 tiles).
• Your robot must complete its demonstration procedure in a maximum of 5 minutes.
Method
• Using the kit parts available, build a ping-pong ball launching mechanism. You may also
use string and elastic bands, but may not modify any kit parts.
• Test your device by launching ping-pong balls onto the field or floor tiles with it and
measuring their (x, y) landing position relative to some target point (i.e. a nearby grid line
intersection):
o Determine the center of the landing positions, , by taking the mean of
the landing positions:
Figure 2. Robot faces east at
90°.
ECSE 211 Design Principles & Methods
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o Then, compute the standard deviation of the landing positions:
o If and , then the required 95% success rate is
achieved. If not, modify your design and repeat testing.
Demonstration (30 points)
The design must satisfy the requirements by completing the demonstration outlined below.
Design presentation (5 points)
Before demoing the design, your group will be asked some questions for approximately 5 minutes.
You will present your design (hardware and software) and answer questions to test your
understanding of the lab concepts. Grades will apply to the entire group, although TAs reserve
the right to grade individually if they deem it necessary.
You must present your workflow, an overview of the hardware design, and an overview of the
software functionality. Visualizing software with graphics such as flowcharts is valuable.
Stationary Launch (10 points)
Manually place your robot at the optimal launch position relative to the target point specified by
the TA. Demonstrate your design by launching five (5) ping-pong balls from a distance at least
120 cm from the target tile and hitting the same 30 cm by 30 cm tile each time. Your demo
grade will be equal to your success rate (2 points for each ball landing within the target tile). Be
sure to record launch position and the point at which the ping-pong ball first hits the ground.
One of the challenges here is determining the landing position of the ball to a reasonable
degree of accuracy. Prior to demonstrating in the lab, you should perform experiments to
gather enough sample data to yield reliable statistics. You may be asked to present this data as
part of your demonstration.
Mobile Launch (15 points)
In this demonstration you will place your robot in Corner 0 and key in (or hard code) the target
position specified by the TA. Set up your program to wait for the press of the Center button
before localizing and navigating to the computed launch position. Your display should clearly
ECSE 211 Design Principles & Methods
© Instructor and Teaching Assistant generated course materials (e.g., handouts, notes,
summaries, assignments, exam questions, etc.) are protected by law and may not be copied
or distributed in any form or in any medium without explicit permission of the instructor. Note
that infringements of copyright can be subject to follow up by the University under the Code of
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show the coordinates of both the launch and target positions before the button is pressed.
Once the button is pressed, your robot should proceed to the launch point, stop, issue a long
BEEP, and then proceed to launch the ball.
Design your code so that once a ball is launched, the machine stops to allow manual reloading.
Pushing the Center button should initiate a pause for 5 seconds (to allow the vehicle to stabilize
from the button press) followed by a launch. This process repeats until the program is halted.
As with the stationary launch, your score is determined by your success rate (3 points for each
ball landing within the target tile).
ECSE 211 Design Principles & Methods
© Instructor and Teaching Assistant generated course materials (e.g., handouts, notes,
summaries, assignments, exam questions, etc.) are protected by law and may not be copied
or distributed in any form or in any medium without explicit permission of the instructor. Note
that infringements of copyright can be subject to follow up by the University under the Code of
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Provided materials
Sample code
No sample code is provided for this lab.
Physical material
You will be issued with a set of ping-pong balls. Other material (e.g. plastic bands) to be provided
by the team.
Implementation instructions
The implementation of this lab is at your discretion. Since this lab will be done in conjunction with
the entire design team, you have the opportunity to explore different solution approaches.
ECSE 211 Design Principles & Methods
© Instructor and Teaching Assistant generated course materials (e.g., handouts, notes,
summaries, assignments, exam questions, etc.) are protected by law and may not be copied
or distributed in any form or in any medium without explicit permission of the instructor. Note
that infringements of copyright can be subject to follow up by the University under the Code of
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Report Requirements
The following sections must be included in your report. Answer all questions in the report and
copy them into your report. For more information, refer to ECSE211SubmissionInstructions.pdf.
Always provide justifications and explanations for all your answers.
Section 1: Design Evaluation
You should concisely explain the overall design of your software and hardware. You must present
your workflow, an overview of the hardware design, and an overview of the software functionality.
You must briefly talk about your design choices before arriving at your final design. Visualizing
hardware and software with graphics (i.e. flowcharts, class diagrams) is valuable.
Section 2: Test Data
This section describes what data must be collected to evaluate your design requirements. Collect
the data using the methodology described below and present it in your report.
Stationary Launch (20 independent trials)
• Collect a minimum of 20 ball positions recorded as (x, y) coordinates.
• The launch position must be a minimum of 4 tiles distant from the target.
• You might consider using cellphone video to record the landing position of the balls.
Mobile Launch (10 independent trials)
• Collect a minimum of 10 ball positions starting from localization.
• For each trial, record the actual launch position in addition to the ball position at landing
Section 3: Test Analysis
Stationary Launch
• Calculate the mean and standard deviation of the target error from your observations of
landing position.
• Assuming that the error is drawn from a normal distribution, determine the 95% confidence
interval for your launcher in the stationary case.
• Show the above as a plot.
Mobile Launch
• Repeat the above analysis.
ECSE 211 Design Principles & Methods
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summaries, assignments, exam questions, etc.) are protected by law and may not be copied
or distributed in any form or in any medium without explicit permission of the instructor. Note
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Section 4: Observations and Conclusions
• Which statistic is most closely related to the repeatability of your mechanism? Explain.
• Would you expect this statistic to be sensitive to error in launch position? If so why; if not,
why not?
• Using the statistical model (above) you computed for your stationary launcher, determine
the probability of a successful hit, for a confidence interval of +/- 15cm. How does this
compare to your actual success rate.
• Repeat for the case of the mobile launcher.
Section 5: Further Improvements
• Given your observations, what changes to your design would likely improve the repeatability
of your results?
• The alternative to modifying the design is to consider a strategy that increases the likelihood
of success. Given the statistics determined for your launcher in both the stationary and
mobile cases, calculate the minimum number of launches required to guarantee at least one
successful hit for each case. (Hint: Binomial Distribution).
ECSE 211 Design Principles & Methods 8th October,
© Instructor and Teaching Assistant generated course materials (e.g., handouts, notes,
summaries, assignments, exam questions, etc.) are protected by law and may not be copied
or distributed in any form or in any medium without explicit permission of the instructor. Note
that infringements of copyright can be subject to follow up by the University under the Code of
Student Conduct and Disciplinary Procedures.
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Frequently asked questions (FAQ)
1. What happens if the field test run takes longer than 5 minutes?
The TA will conclude your demo at the 5-minute mark and will award 0 points for all the
remaining, incomplete parts.
