Teach the Robot to Decide
Until now you told the robot exactly what to do and when. In a match that is not enough. The robot must decide some things for itself.
A robot decides with a sensor and a rule.
The sensor
The intake has a sensor. It measures the distance to the game piece in centimetres.
| Reading | Meaning |
|---|---|
| 40 cm | The intake is empty |
| 18 cm | The game piece is inside the robot |
| 5 cm | The game piece is jammed against the back |
The reading gets smaller as the game piece comes in.
The bar under the robot is the whole problem. The red part on the left is where the piece jams. The green part is where the piece is safely inside. The orange line is where your rule will happen. Put the orange line in the green part. The blue dot is the reading right now.
The rule
A rule has three parts:
IF something is true, THEN do this.
Your task
Stop the intake when the game piece is inside the robot.
- For IF, tap the intake sensor.
- For IS, tap below.
- Move the slider to a value.
- For THEN, tap stop the intake.
- Tap Play.
Find the correct value
The value on the slider decides everything.
- Too large. The rule happens while the game piece is still outside. The intake stops too early and the piece does not come in.
- Too small. The rule never happens in time. The intake keeps pulling and the game piece jams.
There is a range of values that work, and the green part of the bar shows it. Find one end of the range, then the other, then use a value in the middle. This is how you tune anything on a robot.
Press Play at any time. It always starts again from the beginning.
Try the battery voltage instead of the intake sensor. The rule never happens, because the battery voltage does not change when a game piece arrives. A rule is only as good as the sensor you give it.
What you have learned
You have now done the three things that all robot code does:
- A button makes something happen. That is the driver.
- Steps happen in an order. That is autonomous.
- A sensor decides. That is everything else.
Next
Everything after this is the same three ideas with more detail. The next tutorial writes real Python, a few lines at a time.