Which turn function is more accurate and reliable?

[Samb19802000]

Hi Experts,

We can use the following two methods to turn the robot to a target angle.

1. DriveBase.drive(0, turn_rate: xx) with hub.imu.heading()
2. DriveBase.turn(xx)

my question is which method is more reliable and accurate?

I appreciate your feedback.

Thanks!!

[laurensvalk]

The accuracy is the same but they serve different purposes. If you just want to turn by a given angle, just use turn.

drive is more useful for things like line-following where you constantly change the turn rate based on the light reading, for example.

[Samb19802000]

Thanks for the reply.
I use the following code to turn left, and the turn is not smooth. As an example, if wanted to take a 90deg turn, I expected to turn ~88deg and then correct the delta. Instead, it takes 2,3 turns to complete the turn.

def left_turn_angle(angle):
    angle = (-angle) + hub.imu.heading()
    delta = angle - hub.imu.heading()
    while round(delta) not in range(-TOLERANCE, TOLERANCE) :
        drive_base.turn(delta)
        delta = angle - hub.imu.heading()

left_turn_angle(90)

Thanks,

[dlech]

Depending on how big TOLERANCE is, not in range(-TOLERANCE, TOLERANCE) could take a long time because it will check every single integer value between -TOLERANCE and TOLERANCE!

Perhaps better would be:

while not (-TOLERANCE <= delta <= TOLERANCE):

But looking at the bigger picture, it looks like you are trying to define a new function that does what drive_base.turn() already does if you just call it by itself. Pybricks Beta has a use_gyro option for the DriveBase constructor to tell it to use the gyro to assist with control.

[Samb19802000]

Thanks,
my tolerance is 1deg. Looks like I reinvented the wheel :-).
Did you refer to GyroDriveBase

[dlech]

Yes. Although we removed GyroDriveBase and replaced it with a use_gyro=True option for the DriveBase in v3.3.0b8.

[Samb19802000]

Thanks!!

[laurensvalk]

Reading between the lines, I think you're asking about a form of absolute angles.

To accomplish that, you can calculate the remaining angle and combine it with @dlech's answer:

drive_base.use_gyro(True)

# For example if you want to go to 180
remaining_angle = 180 - hub.imu.heading()
drive_base.turn(remaining_angle)

[Samb19802000]

Thanks!!