Obstacle Avoidance

This example project shows how you can make a robotic vehicle respond to its environment using sensors. The robot drives at a given speed until it detects an obstacle with the UltrasonicSensor. Then the robot backs up, turns around, and continues driving until it detects a new obstacle.

Building instructions

Click here to find all building instructions for the Educator Bot, or use this link to go to the ultrasonic sensor attachment directly.

Figure 24 Robot Educator with the Ultrasonic Sensor

Example program

#!/usr/bin/env pybricks-micropython

"""
Example LEGO® MINDSTORMS® EV3 Robot Educator Ultrasonic Sensor Driving Base Program
-----------------------------------------------------------------------------------

This program requires LEGO® EV3 MicroPython v2.0.
Download: https://education.lego.com/en-us/support/mindstorms-ev3/python-for-ev3

Building instructions can be found at:
https://education.lego.com/en-us/support/mindstorms-ev3/building-instructions#robot
"""

from pybricks.hubs import EV3Brick
from pybricks.ev3devices import Motor, UltrasonicSensor
from pybricks.parameters import Port
from pybricks.tools import wait
from pybricks.robotics import DriveBase

# Initialize the EV3 Brick.
ev3 = EV3Brick()

# Initialize the Ultrasonic Sensor. It is used to detect
# obstacles as the robot drives around.
obstacle_sensor = UltrasonicSensor(Port.S4)

# Initialize two motors with default settings on Port B and Port C.
# These will be the left and right motors of the drive base.
left_motor = Motor(Port.B)
right_motor = Motor(Port.C)

# The DriveBase is composed of two motors, with a wheel on each motor.
# The wheel_diameter and axle_track values are used to make the motors
# move at the correct speed when you give a motor command.
# The axle track is the distance between the points where the wheels
# touch the ground.
robot = DriveBase(left_motor, right_motor, wheel_diameter=55.5, axle_track=104)

# Play a sound to tell us when we are ready to start moving
ev3.speaker.beep()

# The following loop makes the robot drive forward until it detects an
# obstacle. Then it backs up and turns around. It keeps on doing this
# until you stop the program.
while True:
    # Begin driving forward at 200 millimeters per second.
    robot.drive(200, 0)

    # Wait until an obstacle is detected. This is done by repeatedly
    # doing nothing (waiting for 10 milliseconds) while the measured
    # distance is still greater than 300 mm.
    while obstacle_sensor.distance() > 300:
        wait(10)

    # Drive backward for 300 millimeters.
    robot.straight(-300)

    # Turn around by 120 degrees
    robot.turn(120)