User Manual

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Sinusoidal Commutation

Advanced Digital Motor Controller User Manual 105

Or by sending the conﬁguration command:

^BPOL channel nn

Entering a negative number of pole pairs will reverse the measured speed and the count

direction. It is useful when operating the motor in closed loop speed mode and if other-

wise a negative speed is measured when the motor is moved in the positive direction.

Conﬁguring Number of Sensor Poles

Single pole absolute sensors like Resolvers, sin/cos and SSI encoders typically return an

angular value that is equal to the mechanical angle. The controller then converts the mea-

sured angle into the electrical angle for its internal operation, using the formula:

Electrical Angle = (Sensor Angle * Number of Poles) modulo 360

When used on motors with a high number of pole pairs, single pole sensors will measure

the electrical angle with degrading resolution as the number of motor poles is higher. For

example, a single pole sensor with 1o resolution on a 10 pole motor will produce an elec-

tric angle evaluations with 10o resolution, which will result in less than optimal operation.

To resolve this problem, some absolute sensors are available in multiple pole versions.

In that case, the sensor will outputs a 0-360 angle value multiple times during a full turn.

Note that the controller will not work if the number of sensor poles is higher than the

number of motor poles.

Enter the number of Sensor Poles in the SinCos/SSI Sensor Poles conﬁguration menu in

the Roborun PC utility.

Or by sending the conﬁguration command:

^SPOL ch poles

You can determine or verify the number of sensor poles by following these steps:

1 Set Motor Poles to 1

2 Launch the Calibration/Setup

3 Make one full rotation of the motor shaft by hand and monitor the Angle value reported

in Roborun Utility.