Name: Emerson unidrive sp
Brand: Emerson
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SM-Uni Enc Pl

Unidrive SP Advanced User Guide 265

Issue Number: 10 www.controltechniques.com

Linear EndAt encoders

The comms resolution is set to the number of bits required for the whole position within the position data messages from the encoder. The linear

encoder comms to sine wave ratio is calculated from the sine wave period and LS comms bit length. The encoder does not give the equivalent lines

per rev directly, but gives the length of a sinewave period in mm. Therefore the Solutions Module uses the pole pitch (Pr 5.36) and the number of

motor poles (Pr 5.11) for the motor to calculate the equivalent lines per revolution.

ELPR = Pole pitch x Number of motor pole pairs / Length of a sinewave

Normally the Number of motor poles will be set to 2, and so:

ELPR = Pole pitch / Length of a sinewave

It should be noted that the equivalent lines per revolution parameter is only updated when auto-configuration occurs, i.e. when the encoder is

initialized, and that it uses the pole pitch for the active motor. The value for Pole pitch x Number of motor pole pairs is limited to 655.35mm by the

drive. If the pole pitch is left at its default value of zero which would give ELPR = 0, or the result of the calculation is over 50000, the drive will initiate

an Enc15 trip.

The ELPR divider (Pr x.46) is returned to 1 if auto-configuration completes correctly.

Hiperface encoders

The Solutions Module can recognize any of the following devices: SCS 60/70, SCM 60/70, SRS 50/60, SRM 50/60, SHS 170, LINCODER, SCS-KIT

101, SKS36, SKM36, SEK52 and SEK53. If the Solutions Module cannot recognize the encoder type it will initiate 12 trip.

The ELPR divider (Pr x.46) is returned to 1 if auto-configuration completes correctly.

SC.SSI, SSI

SSI encoders normally use gray code data format. However, some encoders use binary format that may be selected by setting this parameter to one.

0 = 0ms, 1 = 1ms, 2 = 2ms, 3 = 4ms, 4 = 8ms, 5 = 16ms

A sliding window filter may be applied to the feedback. This is particularly useful in applications where the feedback is used to give speed feedback

for the speed controller and where the load includes a high inertia, and so the speed controller gains are very high. Under these conditions, without a

filter on the feedback, it is possible for the speed loop output to change constantly from one current limit to the other and lock the integral term of the

speed controller.

It should be noted that if this filter is used where the speed feedback is provided by an EndAt or SSI encoder connected directly to the module, it is

necessary for the encoder to provide at least 6 bits of turns information. This is not a problem when the position is defined by the absolute position

from the encoder at initialisation and then accumulated delta positions (Pr x.16=0), however, if the absolute position is taken directly from the encoder

(Pr x.16 > 0) the encoder must provide at least 6 bits of turns information. If this filter is not used (i.e. Pr x.19=0) turns information from the encoder is

not required.

The speed filter can be used to reduce resolution "stepping" problems with low line per revolution encoder inputs when used through the feedback

reference router also.

The resistance value of the thermistor input can be seen in Pr x.21. The motor thermistor resistance value shown in Pr x.21 is shown in 0.1% of 10kΩ

units. The position feedback when used as a reference can be viewed here.

x.19 Feedback filter

RW Uni US

0 (0), 1 (1), 2 (2), 4 (3), 8

(4), 16 (5) ms

0 (0)

Update rate: Background read

x.20 Maximum feedback reference