In previous navigation programs, our scripts only made the cyber:bot execute a list of movements predefined by you, the programmer. Now that you can write a script to make the cyber:bot monitor whisker switches and trigger action in response, you can also write a script that lets the cyber:bot drive and select its own maneuver if it bumps into something. This is an example of autonomous robot navigation.
Whisker Navigation Overview
The roaming_with_whiskers.py script makes the cyber:bot go forward while monitoring its whisker inputs, until it encounters an obstacle with one or both of them. As soon as the cyber:bot senses whisker electrical contact, it uses an if…elif…else statement to decide what to do. The decision code checks for various whisker pressed/not pressed combinations, and calls navigation functions to execute back-up-and-turn maneuvers. Then, the cyber:bot resumes forward motion until it bumps into another obstacle.
Example Script: roaming_with_whiskers.py
Let’s try the script first, and then take a closer look at how it works.
- Set the cyber:bot board's 3-position power switch to position 1.
- Enter, save, and flash roaming_with_whiskers.py.
- Disconnect the cyber:bot from its programming cable, and set the power switch to 2.
- Put the cyber:bot on the floor, and try letting it roam. When it contacts obstacles in its path with its whisker switches, it should back up, turn, and then roam in a new direction.
# roaming_with_whiskers.py from cyberbot import * def forward(): bot(18).servo_speed(75) bot(19).servo_speed(-75) def backwards(): bot(18).servo_speed(-75) bot(19).servo_speed(75) sleep(250) def right(): bot(18).servo_speed(75) bot(19).servo_speed(75) sleep(250) def left(): bot(18).servo_speed(-75) bot(19).servo_speed(-75) sleep(250) while True: whisker_left = bot(7).read_digital() whisker_right = bot(9).read_digital() if whisker_left == 0 and whisker_right == 0: backwards() right() elif whisker_left == 1 and whisker_right == 0: backwards() left() elif whisker_left == 0 and whisker_right == 1: backwards() right() else: forward()