Need help with non repeatable go straight

[naruto1980]

Dear,
I am a coach of FLL team. We start using both Prime Spike and Pybricks this year. The latest problem we have is to make the robot go straight. I asked this question on Reddit and got answer but then sometime this solution work but sometime not. Please help me with the issue. Below is the code section we see it happens many time and we still not figure out how to solve this

drive_base.straight(150) # go backward to straight robot
drive_base.use_gyro(False) # turn off use gyro
drive_base.straight(200) # run straight to square with wall
drive_base.reset() # reset angle 
drive_base.use_gyro(True) # turn on use gyro 
drive_base.straight(-540) # drive straight to mission model

The last line is when sometime robot go straight and sometime it goes curve. I don't think dust is an issue because the run after that it goes straight.

Thank you!

[laurensvalk]

Thanks for taking the time to move your question here. That really helps us keep track.

Did you change the speed of your robot? Is it possible that this last step is quite fast? Does it work with the default speed?

[naruto1980]

Thanks for point out, the comment is wrong.

[naruto1980]

I have my kids print out the angle of the drive base after every turn and below is the result. Beside that is it a good idea if we have a function to read in the angle and try to compensation back to have correct value? I think about that but many time the angle print out is not correct compare with I try to turn the robot slowly after resetting.

angle 0: 0
angle 1: -113
angle 2: -23
angle 3: 4
angle 4: -23
angle 5: 8
angle 6: -113
End Collect Krill
Start Boat Mission
Angle before straight -202
angle 7: 0
angle 8: 20
angle 9: 66
The program was stopped (SystemExit).

from pybricks.hubs import PrimeHub
from pybricks.pupdevices import Motor, ColorSensor, UltrasonicSensor, ForceSensor
from pybricks.parameters import Button, Color, Direction, Port, Side, Stop, Axis
from pybricks.robotics import DriveBase
from pybricks.tools import wait, StopWatch

# Initialize configuration robot
# ==============================
hub = PrimeHub(top_side=-Axis.X, front_side=Axis.Y)

left_motor = Motor(Port.E, Direction.COUNTERCLOCKWISE)
right_motor = Motor(Port.A)
front_motor = Motor(Port.D)
back_motor = Motor(Port.C)

drive_base = DriveBase(left_motor, right_motor, wheel_diameter=62.4, axle_track=112)

# Initialize attachments
#=======================
front_motor.run_until_stalled(300,duty_limit=40)
#back_motor.run_until_stalled(-300,duty_limit=40)

# Flip the crabs
#===============
drive_base.settings(straight_speed=200,turn_rate=50)
drive_base.straight(50)
drive_base.reset() # (0 deg)
print('angle 0:',drive_base.angle())
drive_base.use_gyro(True)
drive_base.settings(straight_speed=150)
drive_base.straight(-150) 
drive_base.turn(-90) # turn left (-90 deg)
print('angle 1:',drive_base.angle())
drive_base.straight(-190) # go to the crab
drive_base.settings(turn_rate=200)
drive_base.turn(85) # turn right (-5 deg)
print('angle 2:',drive_base.angle())
# Catch octopus
#=============
drive_base.settings(straight_speed=150,turn_rate=50)
drive_base.straight(-240)

# Get krill
#==========
drive_base.settings(straight_speed=200,turn_rate=50)
drive_base.straight(140) # go backward
drive_base.turn(30) # turn to get krill (25 deg)
print('angle 3:',drive_base.angle())
drive_base.straight(-240) # go to krill area
drive_base.turn(-25) # turn straight (0 deg)
print('angle 4:',drive_base.angle())
drive_base.straight(-200) # collect krill
drive_base.settings(straight_speed=100,turn_rate=50)
# get last krill
drive_base.turn(30) # turn to get krill (30 deg)
print('angle 5:',drive_base.angle())
drive_base.straight(-100)
drive_base.turn(-120) # (-80 deg)
print('angle 6:',drive_base.angle())
# push the krills at the location X
drive_base.settings(straight_speed= 200)
drive_base.straight(-160)
drive_base.straight(150)
print("End Collect Krill")

# Flip banana boats
#==================
print("Start Boat Mission")
drive_base.settings(straight_speed=150,turn_rate=50)
drive_base.turn(-90) 
print('Angle before straight ', drive_base.angle())
drive_base.straight(150) # go backward to straight robot
drive_base.use_gyro(False)
drive_base.straight(200)
drive_base.reset()
print('angle 7:',drive_base.angle())
drive_base.use_gyro(True)
drive_base.straight(-540) # drive to the boat
drive_base.turn(45) # turn to the boat
print('angle 8:',drive_base.angle())
front_motor.run_angle(300,-300) # lower the attachment
drive_base.straight(60) # go to the boat
front_motor.run_angle(150,180) # raise the boat
drive_base.settings(turn_rate=200)
drive_base.turn(45) # flip the boat
print('angle 9:',drive_base.angle())
front_motor.run_until_stalled(-300,duty_limit=40)
front_motor.run_until_stalled(300,duty_limit=40)

# Go pickup Plankton artifact
#============================
drive_base.straight(-50)
drive_base.turn(-90)
print('angle 10:',drive_base.angle())
drive_base.straight(400)
drive_base.use_gyro(False)
drive_base.straight(100)
drive_base.reset()
print('angle 11:',drive_base.angle())
drive_base.use_gyro(True)
drive_base.straight(-250)
drive_base.turn(90)
front_motor.run_angle(-300,250) # lower attachment
drive_base.straight(80)
front_motor.run_angle(300,120)
drive_base.straight(-100)
front_motor.run_until_stalled(50, duty_limit=40) # pickup artifact
drive_base.straight(-250)

# Pickup Seabed Sample artifact
#=====================
drive_base.settings(straight_speed= 150,turn_rate=50)
drive_base.turn(45)
drive_base.straight(-50)
drive_base.turn(-45)
drive_base.straight(-500)
drive_base.straight(155) # go backward
drive_base.turn(-90)
front_motor.run_angle(300,-150)
drive_base.straight(50)
front_motor.run_until_stalled(50, duty_limit=40) # pickup artifact
#drive_base.straight(-100)

# Go collect krill
#=======================
drive_base.turn(90)
drive_base.straight(-200)
drive_base.turn(-45)
drive_base.straight(-400)

[laurensvalk]

You could also try our beta version to see if this makes a difference. There have been a few improvements to the gyro since the previous stable release.

Going back to your original question:

The last line is when sometime robot go straight and sometime it goes curve

Do you have a video of this happening? With a program that is as short as possible. It doesn't seem to occur on my robot.

I have my kids print out the angle of the drive base after every turn

When the gyro is in use, drivebase.angle() will print the gyro angle. Otherwise, it will print the robot angle based on the wheels, which are generally not the same so that might explain the difference

You might like to print hub.imu.heading() to see a consistent result there.

[naruto1980]

Thanks, I will give beta version a try. As I understand, I need to upgrade the platform first, correct?
I will also try to collect video and share with you.

[laurensvalk]

Yes, you will automatically get a notification in the app about updating the firmware if you'd forget to do so.

When you go back, you can install the corresponding firmware again.