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Added notes on percent calibration and balance

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Fabio Manganiello 2021-08-29 23:30:47 +02:00
parent 44dff804d0
commit 16f6ea8ed3
1 changed files with 13 additions and 0 deletions
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static/pages/Build-an-open-source-drone-with-a-Raspberry-Pi-and-Platypush.md
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@ -1429,6 +1429,10 @@ logger = getLogger(__name__)
step = 25
# Duration of each step pulse during the transients
step_duration = 0.03
# Maximum percentage of change. You can calibrate this
# value to achieve less abrupt rotations of the drone
# around its axes
max_percent = 0.5
def normalize_thrust(channel: int, percent: float) -> int:
"""
@ -1438,6 +1442,7 @@ def normalize_thrust(channel: int, percent: float) -> int:
static thrust value for a given channel.
"""
pwm = get_plugin('pwm.pca9685')
percent *= max_percent
static_thrust = static_thrusts[channel]
percent = max(-1., min(1., percent))
thrust = static_thrust * (1 + percent)
@ -1495,6 +1500,14 @@ def move(movement: Movement, percent: float):
pwm.write(channels=channel_values, step=step, step_duration=step_duration)
```
You'll notice that in this snippet we have managed the percentage of change in a balanced way between the motors.
For instance, a +100% pitch change (meaning drone that moves forward at the maximum inclination) is achieved by
increasing the power that goes to the two motors on the back by 50% compared to their static thrust values, and the
power supplied to the motors on the front is decreased by 50% instead. This makes sure that even when the drone is
moving the power supplied to the motors remains more or less constant, because while the speed of a pair of motors
increases, the speed of the other pair always decreases. Calibrating the `max_percent` value can also help you achieve
less abrupt movements - if the drones rotates too much around a certain axis it may lose balance and start falling.
Now that we have a function that can easily translate the desired percentage of change along a certain direction into
the appropriate PWM values for the motor channels, let's connect them to our joystick controls. With Platypush running
and the controller connected, move the analog controls on your joystick and check the lines logged by the application.