Hardware Analysis and Synthesis Lab 3 Introduction to Engineering and Design
3.1 Objective
Upon completion of this lab, the student will be able to: define the concept of product evaluation, explain the importance of accurate measurements and how they relate to both precision and accuracy, and describe a self-developed method of troubleshooting.
The student must also be able to present a final evaluation of the product, based on the tests specified in the lab.
3.2 Introduction
3.3.1
Background Information
Engineers are often given the task of evaluating a product or a procedure.
Evaluating prototypes based on repeatable tests and accurate measurements is essential to ensure reliable results. This is the reason that some products spend years in testing and development before they are finally made available to the consumer.
3.3.2
Theory
When taking measurements, an average measurement must be attained. An average can be calculated by repeating a test several times adding the results and dividing by the number of tests ( Average ( A p
)

P
1

P
2

P
3

...

P n
N
). This average must then be compared to an accepted value or standard (P s
).
The result of the comparison of average and standard is called the error or accuracy (e = P s
- A p
). Precision is the repeatability of a result, or how close the results
41

Hardware Analysis and Synthesis Lab 3 Introduction to Engineering and Design are to each other ( Pr ecision

P high

P low
). The following pictures can help clarify accuracy and precision .
Accurate &
Precise
Accurate but
Imprecise
Inaccurate but
Precise
Inaccurate &
Imprecise
3.2.3
Ideal Results
The ideal results for this experiment are to have a robot that is accurate and precise in all tests.
3.3
Materials

RoboLab Robotics kit

Protractor/ruler

Computer with RoboLab software
3.4
Rules of the Competition
Not applicable

Timer
3.5 Procedure
Problem Statement
You have been hired by an engineering firm to build and evaluate a robotics kit by building a specified robot design. The robotics kit will be sold to the public for approximately $200. You have been asked to test the robot design and the overall kit, and to make suggestions for future improvements of the design.
3.5.1
Design

Build a robot according to the lab handout given to you by your TA.
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Hardware Analysis and Synthesis Lab 3 Introduction to Engineering and Design
3.5.2
Test

Program each robot for each of the specified tests. See page 48 for guidance.

For each of the tests specified, record the standard, average, accuracy, and precision.

If your robot does not operate correctly, troubleshoot the problem.

Get your TA to initial your original data.
Distance Test
In this test the robot will go forward a certain distance in the time specified in the program. Test the robot’s accuracy and precision of distance when set to travel for a period of time. Before testing begins the standard must be found. To find the standard, program the robot to go forward for 5 seconds. (Note: The specific times may need to be adjusted based on the model of robot that you are testing.) Measure the distance traveled, and divide by 5, then multiple by 4. This is number is the standard, and testing can begin.
Now, set the robot to travel for 4 seconds and measure the distance traveled. Repeat the test ten times. Read the section on the angle test before performing this test.
Angle (Deviation) Test
In this test the robot will move forward a set amount of time and the angle of deviation will be recorded. The angle of deviation is the angle between the place where the robot is expected to move (straight ahead) and the place where the robot actually moves. This test can be performed at the same time as the Distance test. (Note: Since the robot is expected to travel in a straight line, the standard is 0

.)

Use the protractor to draw a 0

line from the start point.

Place the robot at the start point. Make sure to identify a reference point on the robot.

Run the same program as in the distance test.

Make a mark at the reference point and draw a line from the start point to this mark.

Measure the angle of deviation.

Repeat this procedure for 10 trials.
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Hardware Analysis and Synthesis Lab 3 Introduction to Engineering and Design
Rotation Test
In this test the robot will rotate around an axis. By running the rotation test with a time of 5 seconds and dividing this time by 5, you will determine how many degrees your robot rotates for 1 sec. This is the standard. With the standard in mind, determine how many degrees, theoretically, your robot should rotate for 4 seconds. (These times may need to be adjusted in order to get reasonable results).

Write the program in RoboLab that will be needed to perform this test. (Refer to the
Addendum at the end of this lab for help with RoboLab.)

Download the rotation program from the computer to the RCX.

Mark a center point on the sheet of paper.

Center the robot on the center point as best as you can. Identify a reference point on the robot and mark it on the sheet of paper.

Run the program

Mark the reference point after rotation and measure the angle rotated.

Divide this value by 5 to determine the angle of rotation for 1 sec.

Go back to the RoboLab program and change the time for 5 seconds to 4 seconds.

Download the program to the RCX.

Run the program for 10 trials.

After each trial make sure to measure the angle rotated by the robot.
3.5.3
Data

You should have measurements for each test you have conducted.
3.5.4
Analysis

Calculate the average, accuracy, and precision value for each test (See page
46). Determine whether the robot is accurate and precise for each test you have conducted.
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Hardware Analysis and Synthesis Lab 3 Introduction to Engineering and Design
3.6
Discussion Topics
Independent Report (One report per student)

Discuss the concept of product evaluation.

Discuss the importance of testing products in the engineering field.

Explain the terms standard, average, accuracy, and precision.

Assess the techniques used in the testing process.

Discuss better testing methods for the robot design.

Make a final evaluation of the product. (Be sure to refer to accuracy and precision in your evaluation).
3.7
Closing
Make sure that the robot is returned to the kit and that no parts are missing.
Return the kit to your TA and clean up your workstation. Get all original data signed by your TA. If you wish to use the robot in your presentation, notify your recitation TA.
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Hardware Analysis and Synthesis Lab 3 Introduction to Engineering and Design
Note: this information must be included in the discussion topics for the report and presentation.
In order for engineers to make a qualitative conclusion based on experimental test data, it is important to determine how well does a device measure against a standard. Without such benchmarks, engineers cannot determine the quality of the product (if it is good or not). For this lab, the students will be using an 80% passing criteria. If a test was found to be greater than 80%, than it can be concluded that the test passed. Else, if the test performed at a level lower than 80%, it can be concluded that the test failed.
The two criteria that will be used to determine whether a test passed or failed, is the percent accuracy and percent precision.
By determining the percentage of accuracy of an experiment, and comparing the percentage against a standard, an engineer can make a determination, based on experimental evidence, whether it passed or failed. The equation governing the percent accuracy is the following:
% Acc



1

P
S

A
P
P
S


100 %
Where:
%Acc is the percent accuracy
P
S
is the standard value
A
P
is the value measured in the lab
Examples:
1.
If P
S
was determined to be 5 cm and A
P
was found to be 7 cm. Then the percent accuracy (% Acc ) is 60%. This test does not pass the 80% criteria.
2.
If A
P
was found to be 25 ft, then the result of the equation is –300%. Since a negative percentage has no meaning in engineering, it can be said that the product has percent accuracy of zero. Any percent accuracy less than zero are considered to be equal to zero.
This concept helps an engineer determine how precise a device is based on how close it tests to its standard. The equation governing percent precision is:
% Prec

100 e

BP
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Hardware Analysis and Synthesis Lab 3 Introduction to Engineering and Design
Where:
%Prec is the percent precision
B is the exponential decay factor
P is the actual precision measured in the lab
Each individual test requires the use of a different exponential decay factor ( B ).

Distance Test: B = 0.0972

Angle of Deviation Test: B = 0.0323

Rotational Test: B = 0.0093

Time Unit Test: B = 0.4375
Example:
1.
For the Distance Test, if the precision ( P ) was measured to be 0.5 cm, the percent precision ( %Prec ) is equal to 95.3%. This test passes the 80% criteria.
2.
For the Angle of Deviation Test, if the precision was measured to be 10.25

, the percent precision is equal to 71.8%. This test does not pass the 80% criteria.
Tabulation of Results
To conclude if the overall product is worthy of manufacturing or selling, then 80% of the tests should pass their respective criteria. To determine this, tabulate the data in the following manner:
Accuracy %Acc Pass/Fail Precision %Prec Pass/Fail
Distance Test
Angle of Deviation Test
Rotational Test
Time Unit Test
Based on the above example, if it was found that 6 out of 8 tests passed their respective criterion, then it can be determined that this product is not worthy of manufacturing or selling, since it has only passed 75% of its tests.
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Hardware Analysis and Synthesis Lab 3 Introduction to Engineering and Design
Before Attempting to do ANY programming in RoboLab, make sure that the extras have been installed. To do this, first follow the Steps to Creating a Program in
RoboLab , and then in either window that opens, pull down the “Project” menu and click on “Install {Remove} Extras”. Click on “Install Extras” and then Click on the check mark. Completely exit the program. The extras will be installed the next time you open the program.

Steps to Creating a Program in RoboLab
1.
Start the RoboLab Program.
2.
Select “Programmer”
3.
In the “Inventor” section double click on “Inventor 4”.

You will need to understand how to use the tools pallet. By pulling down the
Windows menu, and selecting “tools pallet” you can access the tools pallet. The tools pallet contains 4 main tools that you will need all the time.
The Arrow is used to move icons and wires around, and to select icons and/or wires.
The Hand is used to select text within a textbox or numbers within a numeric constant for editing.
The Spool is used to “wire” icons together.
The text tool is used to insert new text boxes or to edit existing text boxes. It can also be used to edit numeric constants.
 There are seven “parts” or icons that you will need to understand how to use in order to write the programs for this lab. The Functions pallet (accessed in the same manner as the tools pallet) contains all the “icons”. Each of the icons has several connections, or places where wires can be attached (not all connections must be filled, as some have default settings). In order to determine the default values of any connections, double click on the icon and a window will pop up with a description.
To find out what each of these connections does, or to get a general description of the icon, pull down the help menu and select “Show Help”. Then place the mouse over the icon.
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Hardware Analysis and Synthesis Lab 3 Introduction to Engineering and Design
The green light is found directly on the functions pallet. Every program must start with a green light. The green light has only one connection, which goes to the first command of the program.
The red light is found directly on the functions pallet. Every program must end with a red light. The red light has only one connection, which comes from the last command of the program.
The motor forward and motor reverse icons are found directly on the functions pallet. These icons control the outputs. Each of these icons has four connections. There is one “begin”, and one “end” that indicate the program flow. The other two connections are modifier connections (ports connection and power level connection).
The port icon is found in the “Modifier” menu on the functions pallet. This icon is used as a modifier to other icons. It indicates which output ports will be affected by the parent icon. The port icon has two connections, one connects to the parent icon, and the other can be connected to a second port modifier.
The timer icon is found in the “wait for” menu of the functions pallet. This icon delays the program for a set amount of time. The icon has three connections. Two of them indicate the program flow. The third connection is made to a numeric constant to set the number of seconds of the delay.
The numeric constant icon is found in the “Modifier” menu on the functions pallet.
This icon is used as a modifier to other icons. In the instance of a motor control, this icon is attached to the power lever connection and can be set to any integer between 0 and 7.
In the instance of a timer, this icon can be set to any value (including decimal values).
The stop output icon is found directly on the functions pallet. This icon shuts off motors or lights attached to the outputs. The icon has three connections. Two connections indicate the program flow. The third connection is made to a port icon to select which ports to turn off.
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Hardware Analysis and Synthesis Lab 3 Introduction to Engineering and Design
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