User Manual

Sinusoidal Commutation
Advanced Digital Motor Controller User Manual 107
Incremental Encoder-Only
A quadrature encoder can be used to determine the rotor position. Enter the Encoder PPR
using the PC Utility.
Or by sending the configuration command:
^EPPR channel nn
Optimally, the encoder should have a PPR that is at least 128 x the number of pole pairs.
For example a motor with 4 pole pairs should have a 128 x 4 = 512 Pulse per revolution.
This will result in 2048 counts for a full turn of the rotor, and therefore the electrical angle
to be measured with 360 / 2048 * 4 = 0.7 degrees, resulting in a very smooth changing
sinusoidal drive to the motor. A significantly lower resolution encoder will results in a step-
ping sinusoid. A higher resolution encoder will not improve the waveform.
Since encoders do not give an absolute position, a reference search sequence is per-
formed automatically by the controller at every power up or when the controller switches
from a different mode to sinusoidal mode with encoder feedback
The search can also be forced manually by pressing the Sensor Setup button on the Diag-
nostic tab of the PC utility, or by sending the following maintenance command from the
console or the serial/USB port
%CLMOD 2 (for channel 1) or
%CLMOD 3 (for channel 2).
Before trusting that reference search will be successful at every power up, try repeated-
ly to send the sensor tuning (%CLMOD) command under real-life load conditions. After
reference search is completed, verify that the motor turns with the same efficiency in the
forward and reverse direction.
Proper operation of the encoder can be verified by viewing the counter with the query:
?C [channel]
And verifying that it increments by the Encoder’s CPR (counts per revolution, or PPR *4)
when making a full turn, and returns to its original value after a full turn in the reverse di-
rection.
Hall-Only
In this mode, the Hall sensors are used to determine the angular position of the rotor.
Since transitions of the Hall pattern occur at every 60 degrees only, the controller will
estimate the current angle by interpolating in between two transition based on the cur-
rent motor speed. This technique works well as long as speed is stable and changes are