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https://github.com/pybricks/pybricks-api.git
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Laurens Valk
6278aeb1b6
Now that we have reduced the complexity of the docstrings and after moving the control settings to a separate page, it is no longer necessary to have simplified motor docs.
115 lines
3.5 KiB
ReStructuredText
115 lines
3.5 KiB
ReStructuredText
More about Motors
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===========================================
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Motor Tips & Tricks
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^^^^^^^^^^^^^^^^^^^
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The difference between ``run_angle`` and ``run_target``
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-------------------------------------------------------
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*TODO*
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.. _stalled:
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Using stall detection
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---------------------
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When a motor cannot move any further despite using the maximally allowed torque
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we say that the motor is stalled. Something could be blocking the motor, or the
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load is just too heavy. For example, if you manually hold the motor shaft still
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while the motor is busy executing a command, the motor will stall.
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What can I do with stall detection?
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+++++++++++++++++++++++++++++++++++
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Stall detection is useful to detect that a motor can't move any further. This
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can be used to detect an endpoint of a mechanism. For example, you can detect
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whether a robotic hand is fully closed, because the gripper motor simply can't
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go further. This way, you don't need a touch or light sensor to detect this.
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*TODO: How, what, why. Also explain run_until_stalled. Rack & pinion example.*
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When is a motor stalled?
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++++++++++++++++++++++++
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TODO
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.. _gears:
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Using gears
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-----------------
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Many LEGO robots use mechanisms with gears to change the speed and torque
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output of a motor. Let's consider the following dial mechanism.
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*TODO: INSERT PICTURE OF MOTOR WITH 12z gear AND 36z gear.*
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This gear train slows down the dial on the output axle by a factor of 3.
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Therefore, if you want to rotate the dial by 90 degrees, the motor has to
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rotate by 270 degrees. To turn at 200 degrees per second, the motor has to
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turn at 600 degrees per second, and so on.
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To avoid using this factor 3 everywhere in your program, you can use the
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`gears` setting of the ``Motor`` object, as shown in this example::
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# This example uses the EV3 brick, but the same
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# technique applies to other programmable hubs.
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ev3 = EV3Brick()
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# Initialize the motor. See picture above.
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dial = Motor(Port.C, Direction.COUNTERCLOCKWISE, gears=[12, 36])
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# Turn the dial by 90-degrees
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dial.run_angle(500, 90)
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# Print the dial angle
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print(dial.angle())
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# Turn the dial back to the original position
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dial.run_target(500, 0)
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When you use any of the other methods, the same scaling is applied. For
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example, you can print the angle of the dial as shown above. This will print
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90 (approximately), even though the motor has turned 270 degrees.
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Notice that there is no magic going on. It is just a convenient scaling
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function. This helps you organize your code. For example, if you change
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your mechanism to use different gears, you only have to change the first line
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of this example.
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.. _control:
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The Control Class
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^^^^^^^^^^^^^^^^^
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The ``Motor`` class uses PID control to accurately track your commanded target
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angles. Similarly, the ``DriveBase`` class uses two of such controllers:
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one to control the heading and one to control the traveled distance.
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You can change the control settings through the following attributes:
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- ``Motor.control``
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- ``DriveBase.heading_control``
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- ``DriveBase.distance_control``
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These are all instances of the ``Control`` class given below.
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.. autoclass:: pybricks.builtins.Control
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:no-members:
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.. rubric:: Control status
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.. automethod:: pybricks.builtins.Control.stalled
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.. automethod:: pybricks.builtins.Control.active
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.. rubric:: Control settings
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.. automethod:: pybricks.builtins.Control.limits
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.. automethod:: pybricks.builtins.Control.pid
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.. automethod:: pybricks.builtins.Control.target_tolerances
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.. automethod:: pybricks.builtins.Control.stall_tolerances
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