mirror of
https://github.com/pybricks/pybricks-api.git
synced 2026-09-12 01:24:17 +00:00
Laurens Valk
cb9393020d
Move Port from hub classes back to common parameters module. This would have had too much impact on existing users, so undo it. Notes if we are ever bringing it back again: - The idea behind this was to ultimately allow for unique ports in a multi-hub scenario: ev3 = EV3Brick() ev3.Port.A # This is port A on this particular instance This may still be added while leaving the existing Port enum in place, which would then always be the ports of the hub on which the code runs.
135 lines
4.2 KiB
ReStructuredText
135 lines
4.2 KiB
ReStructuredText
More about Motors
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===========================================
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The Motor Class
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^^^^^^^^^^^^^^^
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.. autoclass:: pybricks.builtins.Motor
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:no-members:
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.. rubric:: Measuring
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.. automethod:: pybricks.builtins.Motor.speed
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.. automethod:: pybricks.builtins.Motor.angle
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.. automethod:: pybricks.builtins.Motor.reset_angle
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.. automethod:: pybricks.builtins.Motor.stalled
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.. rubric:: Motion
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.. automethod:: pybricks.builtins.Motor.stop
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.. automethod:: pybricks.builtins.Motor.run
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.. automethod:: pybricks.builtins.Motor.run_time
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.. automethod:: pybricks.builtins.Motor.run_angle
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.. automethod:: pybricks.builtins.Motor.run_target
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.. automethod:: pybricks.builtins.Motor.run_until_stalled
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.. rubric:: Manual motion control
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The following methods are useful if you want full manual control of
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the motor.
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.. automethod:: pybricks.builtins.Motor.dc
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.. automethod:: pybricks.builtins.Motor.track_target
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.. rubric:: Changing motor settings
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.. automethod:: pybricks.builtins.Motor.set_run_settings
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.. automethod:: pybricks.builtins.Motor.set_dc_settings
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.. automethod:: pybricks.builtins.Motor.set_pid_settings
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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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When the motor is stalled, the :meth:`.stalled` will return ``True``.
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Specifically, the motor is stalled when the duty cycle computed by the
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PID controllers has reached the maximum (so ``duty`` = ``duty_limit``)
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and still the motor cannot reach a minimal speed
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(so ``speed`` < ``stall_speed``) for a period of at
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least ``stall_time``.
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You can change the ``duty_limit``, ``stall_speed``, and ``stall_time``
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settings using and :meth:`.set_pid_settings`
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in order to change the sensitivity to being stalled.
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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 :class:`.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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