2.2: Advanced Routing (Using Coordinates)

When you think of a coordinate system, what do you think of? You might think of the Cartesian plane taught in math class.

The “origin” is your starting point, located at x=0 and y=0, or where the two lines intersect. X-Values to the right of the origin (greater than 0) are positive, and x-values to the left of the origin (less than 0) are negative. Similarly, y-values above the origin are positive and y-values below the origin are negative. We can define any point on the plane with an ordered pair. In the picture above, (-1,-2) means that from the origin, we are one unit to the left and 2 units down.

Let’s practice! What are the coordinates of these points?

Now, imagine Zumi is on this plane starting at the origin facing the positive x-axis. If you told Zumi to go to point C -> B -> Origin, what would the path look like?

Answers:

a) (-2,2)

b) (4,-2)

c) (4,4)

d) (-2,4)

First, you need to calibrate your Zumi to drive at accurate distances. The speed calibration works by measuring the black and white line markers on the speed calibration road piece which you can download and print here.

With this piece you can run the speed calibration function which will drive Zumi over 5 road markers. The speed calibration sheet must be printed to scale in order for it to work successfully. Each of the road marker pieces are spaced 2 centimeters apart. Zumi uses this information to predict the speed it travels at. From the Senior driving commands menu, place the speed_calibration() block in your workspace.

Place your Zumi on the indicated marker on the speed calibration sheet. When you run the speed calibration code some values will be displayed in the console. They correspond to the line of best fit that represent the relationship between your Zumi driving and distance. Don’t worry yet about what that means! The following are examples for a specific Zumi that has been tested, your values will be different.

Once you have your values, your Zumi will automatically be calibrated to try and accurately drive those distances.

Remember the coordinate example from earlier? Now you are going to have Zumi drive in that pattern! From the origin, Zumi will drive to (4,4), then to (4,-2), and finally back to the origin (0,0). Here’s a refresher for what that looks like.

Let’s start with the first coordinate. Grab the move_to_coordinate() block from the Senior driving commands menu and place it in the workspace.

This function has three parameters: the desired x-coordinate, the desired y-coordinate, and the units. In this case, we will use inches since the speed_calibration() function saves everything in inches. If you want to use centimeters, make sure to change the third parameter to “centimeters” using the dropdown menu.

Change the x and y coordinates to the first point (4,4).

Then, add the coordinate (4,-2) then go back to (0,0)! Run the code and see if it matches what you predicted.

Using the move_to_coordinate() command, try to make the Zumi drive in a square formation!

Hint: Get some graph paper and map out some possible coordinates first!

Here is just one possible solution. You can make yours bigger, smaller, or in any direction!

Want to try a more challenging activity? Try making the outline of the T-shaped block from the game Tetris! You can use this picture as a reference or pick any of the Tetris blocks. Scroll down for a solution!

Example Code:

In this lesson, you learned how to calibrate your Zumi to drive distances accurately using the speed calibration sheet. To use it, line up Zumi’s wheels with the arrows and run the speed_calibration() block. This block saves Zumi’s speed predictions in inches. After you have calibrated, you can use move_to_coordinate() to move to any coordinate on the coordinate plane! Remember that at the beginning of each program, Zumi always starts at (0,0) facing the positive X-axis.