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lessons learned, attempt 3 #697

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52 changes: 32 additions & 20 deletions docs/commands.rst
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Expand Up @@ -108,38 +108,50 @@ Diagnostics
Setting up Sensorless
-------------------------------------------------------------------------------

The ODrive can run without encoder/hall feedback, but there is a minimum speed, usually around a few hundred RPM.
The ODrive can run without encoder/hall feedback, but there is a minimum speed, usually around a few hundred RPM.
In other words, sensorless mode does not support stopping or changing direction!

Sensorless mode starts by ramping up the motor speed in open loop control and then switches to closed loop control automatically.
The sensorless speed ramping parameters are in :code:`axis.config.sensorless_ramp`.
The :code:`vel` and :code:`accel` (in [radians/s] and [radians/s^2]) parameters control the speed that the ramp tries to reach and how quickly it gets there.
When the ramp reaches :code:`sensorless_ramp.vel`, :code:`controller.input_vel` is automatically set to the same velocity, in [turns/s], and the state switches to closed loop control.
Sensorless mode starts by using open-loop control to spin up the motor to a desired speed, and then switches to closed loop control automatically.

The sensorless speed ramping parameters are in :code:`axis.config.sensorless_ramp`.

The :code:`vel` and :code:`accel` (in [radians/s] and [radians/s^2]) parameters control the speed that the ramp tries to reach and how quickly it gets there. Note that these are in **electric radians per second**

When the ramp reaches :code:`sensorless_ramp.vel`, :code:`controller.input_vel` is automatically set to the same velocity, (in [turns/s]), and the state switches to closed loop control.

If your motor comes to a stop after the ramp, try incrementally raising the :code:`vel` parameter.
The goal is to be above the minimum speed necessary for sensorless position and speed feedback to converge - this is not well-parameterized per motor.

If your motor comes to a stop after the ramp, try incrementally raising the :code:`vel` parameter.
The goal is to be above the minimum speed necessary for sensorless position and speed feedback to converge - this is not well-parameterized per motor.
The parameters suggested below work for the D5065 motor, with 270KV and 7 pole pairs.
If your motor grinds and skips during the ramp, lower the :code:`accel` parameter until it is tolerable.

Below are some suggested starting parameters that you can use for the ODrive D5065 motor.
Note that you **must** set the :code:`pm_flux_linkage` correctly for sensorless mode to work.
Motor calibration and setup must also be completed before sensorless mode will work.
The Motor calibration and setup must completed before sensorless mode will work.

Note that you **must** set the :code:`pm_flux_linkage` correctly for sensorless mode to work.

The parameters suggested below work for the D5065 motor, with 270KV and 7 pole pairs:

.. code:: iPython

odrv0.axis0.controller.config.vel_gain = 0.01
odrv0.axis0.controller.config.vel_integrator_gain = 0.05
odrv0.axis0.controller.config.control_mode = CONTROL_MODE_VELOCITY_CONTROL
odrv0.axis0.controller.config.vel_limit = <a value greater than axis.config.sensorless_ramp.vel / (2pi * <pole_pairs>)>
odrv0.axis0.motor.config.current_lim = 2 * odrv0.axis0.config.sensorless_ramp.current
odrv0.axis0.sensorless_estimator.config.pm_flux_linkage = 5.51328895422 / (<pole pairs> * <motor kv>)
odrv0.axis0.config.enable_sensorless_mode = True
odrv0.axis0.controller.config.vel_gain = 0.01
odrv0.axis0.controller.config.vel_integrator_gain = 0.05
odrv0.axis0.axis.config.sensorless_ramp.accel = 200
odrv0.axis0.controller.config.control_mode = CONTROL_MODE_VELOCITY_CONTROL
odrv0.axis0.controller.config.vel_limit = <a value greater than axis.config.sensorless_ramp.vel / (2pi * <pole_pairs>)>
odrv0.axis0.motor.config.current_lim = 2 * odrv0.axis0.config.sensorless_ramp.current
odrv0.axis0.sensorless_estimator.config.pm_flux_linkage = 5.51328895422 / (<pole pairs> * <motor kv>)


When ready, enable the sensorless mode and save the settings:

.. code:: iPython
odrv0.save_configuration()
odrv0.axis0.config.enable_sensorless_mode = True
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this should probably be one line above



To start the motor:

.. code:: iPython

odrv0.axis0.requested_state = AXIS_STATE_CLOSED_LOOP_CONTROL

odrv0.axis0.config.sensorless_ramp.vel = target_erps_velocity # in electric radians per second
odrv0.axis0.requested_state = AXIS_STATE_CLOSED_LOOP_CONTROL