Emerson SI-Universal User Manual page 64

There must be one period of the commutation signals for each pole pair for a rotary motor (i.e. 3
commutation signal periods per revolution for a 6 pole motor), or one period of the commutation
signals must be equal to the motor pole pitch for a linear motor.
1
It should be noted that for a movement of up to / of the commutation signal period after position
3
feedback Initialization the maximum motor torque is limited to 0.866 of the maximum possible
torque.
Incremental SINCOS
An incremental SINCOS encoder can be used in the same way as an AB incremental encoder,
except that the position resolution is increased with interpolation. These devices are suitable for
motor control in RFC-A mode. They can also be used for RFC-S mode, but some form of phasing
auto-tune is required each time the position feedback is initialized.
Absolute comms with incremental SINCOS
The absolute position is obtained after position feedback Initialization via the comms interface and
then after that point by tracking the incremental change from the sine wave signals. Interpolation is
used to increase the position resolution. The comms interface can be used to check the position
derived from the sine waves. It can also be used for bi-directional transfer of data between the drive
and encoder (except SSI comms). These devices can be used for motor control in RFC-A or RFC-
S modes.
Absolute comms
The absolute position is obtained at all times via the encoder comms. The comms interface can
also be used for bi-directional transfer of data between the drive and the encoder (except SSI
mode). These devices can be used for motor control in RFC-A or RFC-S modes.
Communications:
Hiperface
Hiperface is an asynchronous bi-directional communications protocol that is only used with
incremental sine waves. Therefore it can be used to check the position derived from the sine waves
or for bi-directional transfer of data between the drive and encoder. A checksum is provided for
error checking.
EnDat 2.1
EnDat 2.1 is a synchronous bi-directional communications protocol that is intended to be used with
incremental sine waves. Therefore it can be used to check the position derived from the sine waves
or for bi-directional transfer of data between the drive and encoder. It can be used as an absolute
comms only type position feedback interface, but the resolution of the position feedback using this
method may be limited. If it is used in this way it is not possible to use the position feedback via
comms at the same time as communicating with the encoder for data transfer. A CRC is provided
for error checking.
EnDat 2.2
EnDat 2.2 is a synchronous bi-directional communications protocol that is intended to be used
alone. It is possible to obtain position feedback at the same time as communicating with the
encoder for data transfer. A CRC is provided for error checking.
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SI-Universal Encoder User Guide
Issue: 2