User Manual

Brushless Motor Connections and Operation
124 Advanced Digital Motor Controller User Manual V2.0, July 8, 2019
In the sensorless mode the motor will spin regardless of the phase wiring order. If the
motor spin in the opposite direction than the one desired, swap any two of the three mo-
tor wires, or change the motor direction to Inverted in the motor configuration..
The number of poles setting is not necessary in order for the motor to run. The number
of poles is only used to measure the motor’s rotation speed. Enter a negative number of
poles in order to change the speed polarity and count direction.
Sensorless PWM Frequency
PWM Frequency is variable when operating in sensorless mode. At startup and very
low speeds, the applied PWM Frequency is this from the configuration settings (16kHz
default). As the motor speeds up, the PWM Frequency is automatically increased up to
45kHz max. These settings work in practically all conditions and should be left unchanged
A low PWM Frequency improves the precision of the Back EMF measurement at very
slow speed. This in turn can help startup in difficult motor conditions. When lowering the
frequency, verify that the operation at maximum speed is not affected while the startup
improves. Do not go below the 6kHz minimum PWM frequency..
Sensorless Auto-tuning
An auto-tuning mechanism is provided for determining the BECC and SVT values. Beware
that the motor will reach maximum speed during calibration/auto-tuning. The auto-tuning
sequence lasts around one minute.
Make sure the controller is configured in open loop. Then, from the Diagnostics tab of
the Roborun+ Utility, click on the “Motor/Sensor Setup” button from the diagnostics tab
of the Roborun+ Utility. The motor will ramp up to two different speeds. If motor fails to
start, or starts unreliably, it may be necessary to adjust the Startup Frequency. See “Sen-
sorless Parameters” section above.
After the setup is complete, the motor will stop, BECC and SVT values will be printed on
the console and saved in the controller’s configurations flash memory.
In case BECC is reported as a negative number, the calibration will be treated as a failure,
and the error message “BEMF Integration Limit Detection FAILED!” will be displayed in
the console
If the calibration was successful, then motor is ready to use. Send motor commands in
open loop and verify that it runs in both direction with reliability startup.
Further verification is possible by using an oscilloscope connected to any of the motor
phases. Verify that the signal is symmetrical as shown in figure 8-5. If it is imbalanced,
this means that the Back EMF Integrator Limit (SVT) needs further adjustment. You can
change the value manually until the left and right ramps look symmetrical.
Important Warning
Beware that the motor will spin at maximum speed during calibration/auto-tuning.
Make sure it is safe to do so before initiating. Be ready to cut to power instantly at
any time during the tuning process.