
82
SM-Universal Encoder Plus User Guide
www.controltechniques.com
Issue Number: 6
encoders and this parameter has no effect. Any baud rate can be used when encoder
comms is used with a SINCOS encoder to obtain the absolution position during
initialisation.
When the encoder comms is used and the position within one turn can be obtained in
30
µ
s and the rest of the message including CRC within a further 30
µ
s (60
µ
s total) the
encoder position for control is taken during each level 1 interrupt (fast sampling).
If either of these conditions is not met the position is taken every 250
µ
s. The position
feedback used for speed control is taken every 250
µ
s irrespective of the encoder
message time. The comms message must not be longer than 200
µ
s otherwise position
feedback errors will occur. Compensation based on the speed over the previous 250
µ
s
is applied to correct the position so that it appears to have been taken at the encoder
datum used by all other encoder types.
If fast sampling is used the control position used to define the drive reference frame is
obtained every current/torque control sample (switching frequency selected dependant).
If slow sampling is used the control position is obtained every 200
µ
s.
When fast sampling is used the delay introduced into the control system by the encoder
is less, and so a higher control system bandwidth will be possible (position values from
the encoder could be used in a position control system).
The following encoders can be connected to the SM-Universal Encoder Plus.
0, Ab: Quadrature incremental encoder, with or without marker pulse
1, Fd: Incremental encoder with frequency and direction outputs, with or without
marker pulse
2, Fr: Incremental encoder with forward and reverse outputs, with or without
marker pulse
3, Ab.SErvo: Quadrature incremental encoder with commutation outputs, with or
without marker pulse
4, Fd.SErvo: Incremental encoder with frequency, direction and commutation
outputs, with or without marker pulse
5, Fr.SErvo: Incremental encoder with forward, reverse and commutation outputs,
with or without marker pulse
U, V, W commutation signals are required with an incremental type encoder when used
with a servo motor.
Pr value
Pr string
Baud rate
0
100
100k
1
200
200k
2
300
300k
3
400
400k
4
500
500k
5
1000
1M
6
1500
1.5M
7
2000
2M
Also refer to Chapter 8
on page 58, for further detailed information
on operation with encoder serial comms.
x.15
Encoder type
RW
Uni
US
Ú
0 to 12
Ö
0
Update rate: Background read
NOTE
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