The following design requirements must be met by your robot:

Odometer:

• Must determine the robots X , Y and
• Must display the X , Y and on the LCD display.
• X and Y must be in cm.

• X and Y can be negative.
• must be in degrees.
• must range from [0 , 359.9]:

When the value increases past 360, it should return to 0.

When the value decreases past 0, it should wrap to 359.9

• The zero values for (X , Y ), i.e. (0,0), must respect the convention shown in Figure 3.

Demonstration

The design must satisfy the requirements by completing the demonstration outlined below.

Design presentation

Before demoing the design, your group will be asked some questions for less than 5 minutes. You will present your design and answer questions designed to test your individual understanding of the lab concepts. Each person will be graded individually.

You must present your workflow, an overview of the hardware design, and an overview of the software functionality. Visualizing software with graphics such as flow charts is valuable.

Float Motors

The TA will check whether the X , Y and values are updated correctly on the robots LCD screen by floating the robots motors/wheels.

All three axes (X , Y, ) are checked:

• X & Y values work 5 points
• values work 5 points

E.g. if the (X, Y, ) convention is set as in Figure 1, then:

• Moving both wheels forward should increase Y .
• Moving both wheels backward should decrease Y .
• Moving the right wheel backward and the left wheel forward simultaneously should increase .
• Moving the right wheel forward and the left wheel backward simultaneously should decrease .

Figure 1: Robot faces north at 0^o.

E.g. if the (X, Y, ) convention is set as in Figure 2, then:

• Moving both wheels forward should increase X .
• Moving both wheels backward should decrease X .
• Moving the right wheel backward and the left wheel forward simultaneously should increase .
• Moving the right wheel forward and the left wheel backward simultaneously should decrease .

Figure 2: Robot faces east at 90^o.

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Odometry Check

The TA will ask you to run your robot off the center of a tile, as shown by S in Figure 3. The robot should then follow the 3-by-3 tile square trajectory using SquareDriver . The robot should work using odometry. Throughout the demo, the TA will observe the reported (X , Y , ) values on the robots LCD screen. When the robot stops at the final position (X F , Y F ) near S , the final readings on the LCD screen (X , Y , ) are used to evaluate the odometers accuracy and calculate the error distance as:

= (X X_F)² + (Y Y_F)²

Note that the error is calculated as the Euclidean distance between:

• The odometers readings (X ,Y ) , which signifies where the robot thinks it is with respect to

the origin (0,0), and

• The final actual position (X F , Y F ) , which ideally should be the point S where the robot started the 3-by-3 tile square trajectory.

This means that it is not an issue if your robot does not return to the exact starting point S , as long as the odometer reports a position that matches its real-world location.

Point grid based on error :

[0, 3] cm 5 points

(3, 6] cm 2.5 points

(6, ) cm 0 points

Point grid based on the difference between the displayed and actual :

[0, 15] 5 points

(15, 30] 2.5 points

(30, ) 0 points

(0, 0)

Figure 3. 3-by-3 tile trajectory using SquareDriver.

Implementation instructions

1. In java , implement your odometer design in the run() method of the Odometer class. This class is threaded and will run continuously when your robot is working.
2. In java , tweak the values of WHEEL_RAD and BASE_WIDTH so that your robot drives in a square pattern when calling SquareDriver.drive().

Report Requirements

The following sections must be included in your report. Answer all questions in the lab report and copy them into your report. For more information, refer to the Lab Submission Instructions. 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) must be shown. The design evaluation section is expected to be within half a page (excluding graphics).

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.

Odometer test ( 10 independent trials)

1. Note the starting position S of the robots center and consider it to be (0 ,0) for this trial.
2. Run the robot in a 3-by-3 square using java.
3. Measure its resulting signed X F and Y F position with respect to its starting position S . Note the reported values of X and Y shown for the odometer.

Section 3: Test Analysis

Present the following analysis in a table in your report

1. Compute the Euclidean error distance of the position for each test.
2. Compute the mean and standard deviation for X , Y , and . That means, you need to perform 3 mean and 3 standard deviation calculations in total. Use the sample standard deviation formula. Show one sample calculation for both mean and standard deviation formulas.

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Answer the following questions in your report

1. What does the standard deviation of X, Y and tell you about the accuracy of the odometer? What causes changes in standard deviation?

2. What is the sampling frequency of your odometer (i.e. the frequency at which the tacho count is measured)? What is the tradeoff of having a high sampling frequency versus a low sampling frequency?

Section 4: Observations and Conclusions

• Is the error you observed in the odometer tolerable for larger distances? What happens if the robot travels 5 times the 3-by-3 grids distance?

• Do you expect the odometers error to grow linearly with respect to travel distance? Why?

Section 5: Further Improvements

• Propose a means of reducing the slip of the robots wheels using software.
• Propose a means of improving the accuracy of the odometer using one or more light

sensors.