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Pybricks support and general discussion
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Improve pitch measurements by incorporating the gyro #1198

Open Devilly opened 1 year ago

Devilly commented 1 year ago

Discussed in https://github.com/orgs/pybricks/discussions/1194

Originally posted by **Devilly** August 3, 2023 I've got a piece of code that does nothing more than continuously reading the pitch value of a Technic Hub. ```python from pybricks.hubs import TechnicHub from pybricks.pupdevices import Motor, UltrasonicSensor from pybricks.parameters import Button, Color, Direction, Port, Side, Stop from pybricks.geometry import Axis from pybricks.robotics import DriveBase from pybricks.tools import wait, StopWatch from usys import stdin, stdout hub = TechnicHub(Axis.X, Axis.Z) hub.light.on(Color.GREEN) motor_left = Motor(Port.A, Direction.COUNTERCLOCKWISE) motor_right = Motor(Port.B) motors = [ motor_right, motor_left ] while(True): wait(500) tilt = hub.imu.tilt()[0] print(str(tilt)) # for motor in motors: # motor.run(1000) ``` An example output of this when putting the hub against a static object is this: `-47 -47 -47 -47 -47 -47 -47 -47 -47 -47 -47 -47 -47 -47` This is exactly what I would expect. A constant value. When I then enable the motor lines of code and run again: `-47 -30 -39 -39 -44 -45 -45 -31 -50 -52 -46 -46 -39` The values go all over the place. The motors have nothing attached to them so the hub stays in the exact same position as before. Any idea what's going on or what I can test more to find out the cause?

In short: shakiness of moving motors influences the pitch a lot, which can be improved by taking gyro measurements also into account when calculating the pitch.

laurensvalk commented 1 year ago

Thanks for opening this issue! We should be able to do this when we include full 3D attitude estimation.

Then we can use its estimated vertical vector instead of the gravity measurement to compute the tilt values.