mirror of
https://github.com/pybricks/pybricks-api.git
synced 2026-09-12 09:37:25 +00:00
160 lines
4.7 KiB
ReStructuredText
160 lines
4.7 KiB
ReStructuredText
More about Motors
|
|
===========================================
|
|
|
|
The Motor Class
|
|
^^^^^^^^^^^^^^^
|
|
|
|
.. autoclass:: pybricks.builtins.Motor
|
|
:no-members:
|
|
|
|
.. rubric:: Measuring
|
|
|
|
.. automethod:: pybricks.builtins.Motor.speed
|
|
|
|
.. automethod:: pybricks.builtins.Motor.angle
|
|
|
|
.. automethod:: pybricks.builtins.Motor.reset_angle
|
|
|
|
.. automethod:: pybricks.builtins.Motor.stalled
|
|
|
|
.. rubric:: Motion
|
|
|
|
.. automethod:: pybricks.builtins.Motor.stop
|
|
|
|
.. automethod:: pybricks.builtins.Motor.run
|
|
|
|
.. automethod:: pybricks.builtins.Motor.run_time
|
|
|
|
.. automethod:: pybricks.builtins.Motor.run_angle
|
|
|
|
.. automethod:: pybricks.builtins.Motor.run_target
|
|
|
|
.. automethod:: pybricks.builtins.Motor.run_until_stalled
|
|
|
|
.. rubric:: Manual motion control
|
|
|
|
The following methods are useful if you want full manual control of
|
|
the motor.
|
|
|
|
.. automethod:: pybricks.builtins.Motor.dc
|
|
|
|
.. automethod:: pybricks.builtins.Motor.track_target
|
|
|
|
.. attribute:: control
|
|
|
|
The motors use PID control to accurately track the speed and
|
|
angle targets that you specify. You can change its behavior through the
|
|
``control`` attribute of the motor. See :ref:`control` for an overview
|
|
of available methods.
|
|
|
|
Motor Tips & Tricks
|
|
^^^^^^^^^^^^^^^^^^^
|
|
|
|
The difference between ``run_angle`` and ``run_target``
|
|
-------------------------------------------------------
|
|
|
|
*TODO*
|
|
|
|
.. _stalled:
|
|
|
|
Using stall detection
|
|
---------------------
|
|
|
|
When a motor cannot move any further despite using the maximally allowed torque
|
|
we say that the motor is stalled. Something could be blocking the motor, or the
|
|
load is just too heavy. For example, if you manually hold the motor shaft still
|
|
while the motor is busy executing a command, the motor will stall.
|
|
|
|
What can I do with stall detection?
|
|
+++++++++++++++++++++++++++++++++++
|
|
|
|
Stall detection is useful to detect that a motor can't move any further. This
|
|
can be used to detect an endpoint of a mechanism. For example, you can detect
|
|
whether a robotic hand is fully closed, because the gripper motor simply can't
|
|
go further. This way, you don't need a touch or light sensor to detect this.
|
|
|
|
*TODO: How, what, why. Also explain run_until_stalled. Rack & pinion example.*
|
|
|
|
When is a motor stalled?
|
|
++++++++++++++++++++++++
|
|
|
|
TODO
|
|
|
|
.. _gears:
|
|
|
|
Using gears
|
|
-----------------
|
|
Many LEGO robots use mechanisms with gears to change the speed and torque
|
|
output of a motor. Let's consider the following dial mechanism.
|
|
|
|
*TODO: INSERT PICTURE OF MOTOR WITH 12z gear AND 36z gear.*
|
|
|
|
This gear train slows down the dial on the output axle by a factor of 3.
|
|
Therefore, if you want to rotate the dial by 90 degrees, the motor has to
|
|
rotate by 270 degrees. To turn at 200 degrees per second, the motor has to
|
|
turn at 600 degrees per second, and so on.
|
|
|
|
To avoid using this factor 3 everywhere in your program, you can use the
|
|
`gears` setting of the :class:`.Motor` object, as shown in this example::
|
|
|
|
# This example uses the EV3 brick, but the same
|
|
# technique applies to other programmable hubs.
|
|
ev3 = EV3Brick()
|
|
|
|
# Initialize the motor. See picture above.
|
|
dial = Motor(Port.C, Direction.COUNTERCLOCKWISE, gears=[12, 36])
|
|
|
|
# Turn the dial by 90-degrees
|
|
dial.run_angle(500, 90)
|
|
|
|
# Print the dial angle
|
|
print(dial.angle())
|
|
|
|
# Turn the dial back to the original position
|
|
dial.run_target(500, 0)
|
|
|
|
When you use any of the other methods, the same scaling is applied. For
|
|
example, you can print the angle of the dial as shown above. This will print
|
|
90 (approximately), even though the motor has turned 270 degrees.
|
|
|
|
Notice that there is no magic going on. It is just a convenient scaling
|
|
function. This helps you organize your code. For example, if you change
|
|
your mechanism to use different gears, you only have to change the first line
|
|
of this example.
|
|
|
|
.. _control:
|
|
|
|
The Control Class
|
|
^^^^^^^^^^^^^^^^^
|
|
|
|
The ``Motor`` class uses PID control to accurately track your commanded target
|
|
angles. Similarly, the ``DriveBase`` class uses two of such controllers:
|
|
one to control the heading and one to control the traveled distance.
|
|
|
|
You can change the control settings through the following attributes:
|
|
|
|
- ``Motor.control``
|
|
- ``DriveBase.heading_control``
|
|
- ``DriveBase.distance_control``
|
|
|
|
These are all instances of the ``Control`` class given below.
|
|
|
|
.. autoclass:: pybricks.builtins.Control
|
|
:no-members:
|
|
|
|
.. rubric:: Control status
|
|
|
|
.. automethod:: pybricks.builtins.Control.stalled
|
|
|
|
.. automethod:: pybricks.builtins.Control.active
|
|
|
|
.. rubric:: Control settings
|
|
|
|
.. automethod:: pybricks.builtins.Control.limits
|
|
|
|
.. automethod:: pybricks.builtins.Control.pid
|
|
|
|
.. automethod:: pybricks.builtins.Control.target_tolerances
|
|
|
|
.. automethod:: pybricks.builtins.Control.stall_tolerances
|