4D: Gyroscope

Make sure that your CoDrone Mini is paired before starting the lesson! If you forgot how to do this, make sure to review how to pair to Blockly here.

Gyro sensors are a lot like compasses — they sense rotational motion and detect orientation to figure out what direction something is facing. They’re used in everything from space shuttles to cell phones, and your CoDrone! Gyroscopes are necessary to stabilize your drone while you are flying, since many factors could cause your drone to drift off course. A gyroscope can measure how far and in which direction your drone is tilting or rotating. Using some math and algorithms, a drone can try and correct any unwanted displacements to remain stable. Displacement is a movement from one position to another position.

There are three orientations that we are concerned with when we are flying a drone for stability: roll, pitch, and yaw. The gyro sensor in your CoDrone will return values from 0 to 180 degrees that correspond to the degrees the drone turned to the right, and 0 to -180 when turned to the left. 

Did you notice that throttle is not included? When a drone flies straight up or down, the change in position is not an angular (turning) displacement but a vertical displacement, which is measured by the height sensor.

Like a lot of things, this can be better explained through observation. You will learn how to get the degrees that the drone moved in each of the following directions since the moment your drone pairs: 

• tilted left or right (roll)
• tilted forward or backward (pitch), 
• tilted left or right (yaw) 

Test each axis (roll, pitch, and yaw) individually. Print each value 50 times using a repeat loop. Change the angle by selecting the axis on the dropdown menu.

Previously, when you wanted to turn 90 degrees you needed to guess how many seconds you needed to turn. Now that you have access to the gyroscope data, you don’t have to guess. This time, you will use a while loop to keep turning until the angle becomes greater than 90 or less than -90, depending on the direction you want to go. First, you will write a code that will turn CoDrone Mini to the left 90 degrees.

After you takeoff, it would be a good idea to print the current reading to make sure that you are starting at 0 degrees. Then, set your yaw value and move() in a loop while the yaw angle is less than 90 degrees. Once the angle reading goes above 90 degrees, the while loop will break and CoDrone Mini should land.

Write a program that will turn CDM to the right 90 degrees. Remember, turning right means negative yaw!

You have written code to turn 90 degrees, but it would be useful to turn it into a function. That way you can call the function over and over without rewriting all of the code. Create a function block that contains your code for turning left 90 degrees. 

You will notice that we added a set_yaw(0) block at the end of the function. This is to make sure your drone won’t want to keep spinning for the rest of the program!

Challenge: Write a function called “turn right 90 degrees” that you can use in your program.

Now that you have a function that can turn left 90 degrees, use it in a for loop to fly in the shape of a square. Remember, a square has four equal sides, so use a repeat block to pitch forward and turn four times.

What if you wanted to turn 45 degrees instead? Or maybe 30? Our function would be much more useful if it could handle any number of degrees from 0 to 180 in either direction.

This time, create a function with a parameter. Instead of hard-coding the 90 degrees value, you will use a variable as a placeholder for the number of degrees you want to turn left.

Using your custom function from above, write a program that flies in an equilateral triangle. Each turn should be 120 degrees.