Exploration Rover

Python code and building instructions for the LEGO MINDSTORMS Robot Inventor Official Fan Inventions (51515).

Exploration Rover

Six-wheeled rover with instruments to explore new worlds.




from pybricks.hubs import InventorHub
from pybricks.pupdevices import Motor, ColorSensor, UltrasonicSensor
from pybricks.parameters import Port, Direction, Icon, Color
from pybricks.tools import wait, StopWatch

class ExplorationRover():
    """Control the Mars Exploration Rover."""
    # In this robot, we want to detect red and cyan/teal "mars rocks".
    ROCK_COLORS = (Color.RED, Color.CYAN)

    # These are the gears between the motor and the rear wheels.
    REAR_GEARS = (8, 24, 12, 20)
    # An animation of heart icons of varying brightness, giving a heart beat.
    HEART_BEAT = [Icon.HEART * i/100 for i in list(range(0, 100, 4)) + list(range(100, 0, -4))]
    def __init__(self):
        # Initialize each motor with the correct direction and gearing.
        self.left_rear_wheels = Motor(Port.E, Direction.CLOCKWISE, self.REAR_GEARS)
        self.right_rear_wheels = Motor(Port.F, Direction.COUNTERCLOCKWISE, self.REAR_GEARS)
        self.left_front_wheel = Motor(Port.C, Direction.COUNTERCLOCKWISE, None)
        self.right_front_wheel = Motor(Port.D, Direction.CLOCKWISE, None)

        # Initialize sensors, named after the Perseverance Mars Rover instruments.
        self.mast_cam = UltrasonicSensor(Port.B)
        self.sherloc = ColorSensor(Port.A)
        # Initialize the hub and start the animation
        self.hub = InventorHub()
        self.hub.display.animate(self.HEART_BEAT, 30)
    def calibrate(self):
        # First, measure the color of the floor. This makes it easy to explicitly
        # ignore the floor later. This is useful if your floor has a wood color,
        # which can appear red or yellow to the sensor.
        self.floor_color = self.sherloc.hsv()
        # Set up all the colors we want to distinguish, including no color at all.
        self.sherloc.detectable_colors(self.ROCK_COLORS + (self.floor_color, None))

    def drive(self, speed, steering, time=None):
        # Drive the robot at a given speed and steering for a given amount of time.
        # Speed and steering is expressed as degrees per second of the wheels.
        self.left_rear_wheels.run(speed + steering)
        self.left_front_wheel.run(speed + steering)
        self.right_rear_wheels.run(speed - steering)
        self.right_front_wheel.run(speed - steering)

        # If the user specified a time, wait for this duration and then stop.
        if time is not None:
    def stop(self):
        # Stops all the wheels.

    def scan_rock(self, time):
        # Stops the robot and moves the scan arm.
        # During the given duration, scan for rocks.
        watch = StopWatch()
        while watch.time() < time:
            # If a rock color is detected, display it and make a sound.
            if self.sherloc.color() in self.ROCK_COLORS:
        # Turn the arm motor and restore the heartbeat animation again.
        self.hub.display.animate(self.HEART_BEAT, 30)

# The main program starts here. First, initialize the robot.
rover = ExplorationRover()

# Make sure the sensor is at the lowest point and pointing at the floor for
# correct calibration. Then this will calibrate for the floor color.

# Drive around while watching out for colored rocks and obstacles.
while True:
    # Start driving.
    rover.drive(speed=100, steering=0)

    # Wait until we see a rock or another obstacle.
    while rover.sherloc.color() not in rover.ROCK_COLORS and rover.mast_cam.distance() > 500:

    # If it's a rock, scan it.
    if rover.sherloc.color() in rover.ROCK_COLORS:
    # Back up.
    rover.drive(speed=-100, steering=0, time=2000)

    # Turn around.
    rover.drive(speed=0, steering=100, time=2000)

This project was submitted by Laurens Valk.