sorting bird

[MichaelVerschaeve]

I coded the BrickPecker from The Lego Boost Activity Book by Daniele Benedettelli with PyBricks:

brickpecker.mp4

from pybricks.hubs import MoveHub
from pybricks.pupdevices import Motor, ColorDistanceSensor
from pybricks.parameters import Button, Color, Direction, Port, Side, Stop
from pybricks.robotics import DriveBase
from pybricks.tools import wait, StopWatch

hub = MoveHub()
birdHeight = 200
# reset
# part A: spin away, close beak, tilt up
motorA = Motor(Port.A,Direction.COUNTERCLOCKWISE)
motorB = Motor(Port.B,Direction.CLOCKWISE,[[24,12],[8,28]])
# motorA.run_angle(200,-300)
motorA.run_time(200,300,Stop.HOLD,False)
motorB.run_time(200,300)
motorA.run_time(-150,300)
# part B: down and close until stall, then up to default angle
motorA.run_until_stalled(100,duty_limit=40)
motorA.run_angle(200,-birdHeight)
# part C,
motorA.reset_angle(0) 
motorA.run(-50)
angleBStart = motorB.angle()
motorB.run_until_stalled(-50,duty_limit=40)
motorA.hold()
angleBStop = motorB.angle()
correction = -motorA.angle()+angleBStop-angleBStart
print(correction)
motorA.run_angle(200,5+correction)
motorB.run_angle(200,5)
motorA.reset_angle(0);
motorB.reset_angle(0);
wait(1000)

sensor = ColorDistanceSensor(Port.C)

def Spin(degree):
    rel = degree-motorB.angle()
    motorA.run_angle(400,rel,Stop.HOLD,False)
    motorB.run_target(400,degree)

def PickAndPlace(degree):
    motorA.run_angle(100,birdHeight)
    Spin(0)
    motorA.run_angle(100, -birdHeight)
    Spin(degree)
    motorA.run_angle(100,birdHeight)
    motorA.run_angle(100, -birdHeight)

Spin(60)
while True:
    hub.light.on(Color.VIOLET)
    wait(100)
    color = sensor.color()
    if (color == Color.RED):
        hub.light.on(color)
        PickAndPlace(74)
    elif (color == Color.YELLOW):
        hub.light.on(color)
        PickAndPlace(114)
    elif (color == Color.GREEN):
        hub.light.on(color)
        PickAndPlace(154)
    elif (color == Color.WHITE):
        hub.light.on(color)
        PickAndPlace(185)

I'm new to this, so any suggestions for improvements are appreciated.
Issue I'm having:

• The color scanner detects blue a lot, probably because most of the creation is blue, so I removed it from the possible colors and replaced it with white, perhaps I should combine with a distance reading ?

[dlech]

This looks like a very nice program.

You can play around with sensor.detectable_colors(...) to try to get better color matching if the default is giving you trouble.

Some Python style tips to make this easier to read (at least for people who are used to reading Python):

• Names of "constants" are written as UPPER_SNAKE_CASE.
• Class names are written as PascalCase
• All other names are written as lower_snake_case.
• Grouping all of the hub/motor/sensors declarations together makes it easy to see what hardware is being used all in one place
• Semicolons are not needed
• Parentheses are not needed in if statements.
• "Sparse is better than dense." Space after commas and around operators make it easier to read.
• Named parameters can make it more obvious what a function call does, e.g. wait=False.

from pybricks.hubs import MoveHub
from pybricks.pupdevices import Motor, ColorDistanceSensor
from pybricks.parameters import Button, Color, Direction, Port, Side, Stop
from pybricks.robotics import DriveBase
from pybricks.tools import wait, StopWatch

hub = MoveHub()
motor_a = Motor(Port.A,Direction.COUNTERCLOCKWISE)
motor_b = Motor(Port.B,Direction.CLOCKWISE, [[24, 12], [8, 28]])
sensor = ColorDistanceSensor(Port.C)

BIRD_HEIGHT = 200


def reset():
    # part A: spin away, close beak, tilt up
    # motor_a.run_angle(200,-300)
    motor_a.run_time(200, 300, Stop.HOLD, False)
    motor_b.run_time(200, 300)
    motor_a.run_time(-150, 300)

    # part B: down and close until stall, then up to default angle
    motor_a.run_until_stalled(100, duty_limit=40)
    motor_a.run_angle(200, -BIRD_HEIGHT)

    # part C
    motor_a.reset_angle(0) 
    motor_a.run(-50)
    angle_b_start = motor_b.angle()
    motor_b.run_until_stalled(-50, duty_limit=40)
    motor_a.hold()
    angle_b_stop = motor_b.angle()
    correction = -motor_a.angle() + angle_b_stop - angle_b_start

    print("correction:", correction)

    motor_a.run_angle(200, 5 + correction)
    motor_b.run_angle(200, 5)
    motor_a.reset_angle(0)
    motor_b.reset_angle(0)

    wait(1000)


def spin(degree):
    rel = degree - motor_b.angle()
    motor_a.run_angle(400, rel, Stop.HOLD, wait=False)
    motor_b.run_target(400, degree)

def pick_and_place(degree):
    motor_a.run_angle(100, BIRD_HEIGHT)
    spin(0)
    motor_a.run_angle(100, -BIRD_HEIGHT)
    spin(degree)
    motor_a.run_angle(100, BIRD_HEIGHT)
    motor_a.run_angle(100, -BIRD_HEIGHT)


# Main program

reset()
spin(60)

while True:
    hub.light.on(Color.VIOLET)

    wait(100)

    color = sensor.color()

    if color == Color.RED:
        hub.light.on(color)
        pick_and_place(74)
    elif color == Color.YELLOW:
        hub.light.on(color)
        pick_and_place(114)
    elif color == Color.GREEN:
        hub.light.on(color)
        pick_and_place(154)
    elif color == Color.WHITE:
        hub.light.on(color)
        pick_and_place(185)

[MichaelVerschaeve]

Yes, much more readable, thanks. I have a C++/C# background where naming conventions are somewhat different, I was following neither ;)
I had read the documentation about the detectable colors method, but for this application it turns out the standard colors are perfectly fine. It's just that it seems the sensor can detect colors at quite a long distance, it was seeing the blue from the bird or chute and occasionally also the red from the birds legs. Doing a distance scan and requiring that the distance is 0 (I use < 10 as condition, reported distance for the blue was 20) addresses the issue.

[laurensvalk]

Nice work! Some additional ideas: Instead of calling the motors motorA, you could call them something like beak_motor.

[MichaelVerschaeve]

Thx. I was more or less transcribing the creative canvas code from Danny's book, there the motors are documented as just motor A and motor B. Motor A controls a "grab and lift" mechanism, so something like "beak_and_lift_motor" could do, but becomes a bit lengthy. Also, when spin_motor (motor B) runs, "grab_and_lift_motor" needs to run in sync so the relative movement to the grab and lift mechanism stays zero... I think I'll stick with motor_a and motor_b, but will document what they do where they are defined...

I'd like to point out that I very much like the gearing parameter in the motor constructor, Danny's code contained quite a bit of scaling operations (divide or multiply by 1.75) which are now not necessary...

[laurensvalk]

Glad to hear the gears feature is getting some good use! 😄

[mabba18]

Thank you so much for putting togther this program. This is exactly why I really like PyBricks. I had gotten the book awhile ago, and made the bird. It worked fine, but demo-ing it was a pain having to keep it connected to a device.

Decided to re-build it. Didn't feel the need to stick with only using Boost parts, so I choose to theme it after the classic parrot.

Using PyBricks, it worked great all day at a public event!

Here is the code I used, incorporating the above ideas of limiting the scanning distance, it works now with the original colours:

Details

from pybricks.hubs import MoveHub
from pybricks.pupdevices import Motor, ColorDistanceSensor
from pybricks.parameters import Button, Color, Direction, Port, Side, Stop
from pybricks.robotics import DriveBase
from pybricks.tools import wait, StopWatch

hub = MoveHub()
motor_a = Motor(Port.A,Direction.COUNTERCLOCKWISE)
motor_b = Motor(Port.B,Direction.CLOCKWISE, [[24, 12], [8, 28]])
sensor = ColorDistanceSensor(Port.C)

BIRD_HEIGHT = 200


def reset():
    # part A: spin away, close beak, tilt up
    # motor_a.run_angle(200,-300)
    motor_a.run_time(200, 300, Stop.HOLD, False)
    motor_b.run_time(200, 300)
    motor_a.run_time(-150, 300)

    # part B: down and close until stall, then up to default angle
    motor_a.run_until_stalled(100, duty_limit=40)
    motor_a.run_angle(200, -BIRD_HEIGHT)

    # part C
    motor_a.reset_angle(0) 
    motor_a.run(-50)
    angle_b_start = motor_b.angle()
    motor_b.run_until_stalled(-50, duty_limit=40)
    motor_a.hold()
    angle_b_stop = motor_b.angle()
    correction = -motor_a.angle() + angle_b_stop - angle_b_start

    print("correction:", correction)

    motor_a.run_angle(200, 5 + correction)
    motor_b.run_angle(200, 5)
    motor_a.reset_angle(0)
    motor_b.reset_angle(0)

    wait(1000)


def spin(degree):
    rel = degree - motor_b.angle()
    motor_a.run_angle(400, rel, Stop.HOLD, wait=False)
    motor_b.run_target(400, degree)

def pick_and_place(degree):
    motor_a.run_angle(100, BIRD_HEIGHT)
    spin(0)
    motor_a.run_angle(100, -BIRD_HEIGHT)
    spin(degree)
    motor_a.run_angle(100, BIRD_HEIGHT)
    motor_a.run_angle(100, -BIRD_HEIGHT)


# Main program

reset()
spin(60)

while True:
    hub.light.on(Color.VIOLET)

    wait(100)

    color = sensor.color()
    distance = sensor.distance()

    print("colour:", color)
    print("distance:", distance)

    if color == Color.RED and distance <= 10:
        hub.light.on(color)
        pick_and_place(74)
    elif color == Color.YELLOW and distance <= 10:
        hub.light.on(color)
        pick_and_place(114)
    elif color == Color.GREEN and distance <= 10:
        hub.light.on(color)
        pick_and_place(153)
    elif color == Color.BLUE and distance <= 10:
        hub.light.on(color)
        pick_and_place(185)

Here is another program I used. This connects the remote, and allows any button press to trigger the bird:

Details

from pybricks.hubs import MoveHub
from pybricks.pupdevices import Motor, ColorDistanceSensor, Remote
from pybricks.parameters import Button, Color, Direction, Port, Side, Stop
from pybricks.robotics import DriveBase
from pybricks.tools import wait, StopWatch

hub = MoveHub()
motor_a = Motor(Port.A,Direction.COUNTERCLOCKWISE)
motor_b = Motor(Port.B,Direction.CLOCKWISE, [[24, 12], [8, 28]])
sensor = ColorDistanceSensor(Port.C)

BIRD_HEIGHT = 200


def reset():
    # part A: spin away, close beak, tilt up
    # motor_a.run_angle(200,-300)
    motor_a.run_time(200, 300, Stop.HOLD, False)
    motor_b.run_time(200, 300)
    motor_a.run_time(-150, 300)

    # part B: down and close until stall, then up to default angle
    motor_a.run_until_stalled(100, duty_limit=40)
    motor_a.run_angle(200, -BIRD_HEIGHT)

    # part C
    motor_a.reset_angle(0) 
    motor_a.run(-50)
    angle_b_start = motor_b.angle()
    motor_b.run_until_stalled(-50, duty_limit=40)
    motor_a.hold()
    angle_b_stop = motor_b.angle()
    correction = -motor_a.angle() + angle_b_stop - angle_b_start

    print("correction:", correction)

    motor_a.run_angle(200, 5 + correction)
    motor_b.run_angle(200, 5)
    motor_a.reset_angle(0)
    motor_b.reset_angle(0)

    wait(1000)


def spin(degree):
    rel = degree - motor_b.angle()
    motor_a.run_angle(400, rel, Stop.HOLD, wait=False)
    motor_b.run_target(400, degree)

def pick_and_place(degree):
    motor_a.run_angle(100, BIRD_HEIGHT)
    spin(0)
    motor_a.run_angle(100, -BIRD_HEIGHT)
    spin(degree)
    motor_a.run_angle(100, BIRD_HEIGHT)
    motor_a.run_angle(100, -BIRD_HEIGHT)

# Connect Remote
remote = Remote(timeout=5000)

# Main program

reset()
spin(60)

while True:
    hub.light.on(Color.VIOLET)
    remote.light.on(Color.VIOLET)
    wait(50)

    color = sensor.color()
    distance = sensor.distance()
    pressed = remote.buttons.pressed()

    if color == Color.RED and distance <= 10 and pressed != ():
        hub.light.on(color)
        remote.light.on(color)
        pick_and_place(74)
    elif color == Color.YELLOW and distance <= 10 and pressed != ():
        hub.light.on(color)
        remote.light.on(color)
        pick_and_place(114)
    elif color == Color.GREEN and distance <= 10 and pressed != ():
        hub.light.on(color)
        remote.light.on(color)
        pick_and_place(153)
    elif color == Color.BLUE and distance <= 10 and pressed != ():
        hub.light.on(color)
        remote.light.on(color)
        pick_and_place(185)

Here is a video of it in operation with the remote.

[MichaelVerschaeve]

Awesome! Being able to demo the bird at events was also the main reason I chose pybricks. The remote control is also cool, in automatic mode the bird finishes quite fast and you can keep filling the slide all day... Also have in the meanwhile added the distance < 10 options, otherwise blue and white get detected erroneously... Like the classic parrot look, you should get the lego house pirate to go along with it ;)