Menu 13
Parameter
structure
Keypad and
display
Parameter
x.00
Parameter
description format
Advanced parameter
descriptions
Macros
Serial comms
protocol
Electronic
nameplate
Performance RFC mode
240
Unidrive SP Advanced User Guide
www.controltechniques.com Issue Number: 10
Rigid position control
In rigid position control the position error is always accumulated. This means that, if for example, the slave shaft is slowed down due to excessive
load, the target position will eventually be recovered by running at a higher speed when the load is removed.
Non-rigid position control
In non-rigid position control the position loop is only active when the 'At Speed' condition is met (see Pr
on page 53). This allows slippage to
occur while the speed error is high. It may be necessary to increase the ‘At Speed’ window in Pr
3.06
and Pr
3.07
with some lower resolution
feedback devices.
Velocity feed forward
The position controller can generate a velocity feed forward value from the speed of the reference encoder. The feed-forward value is passed to menu
1, and so ramps may be included if required. Because the position controller only has a proportional gain, it is necessary to use velocity feed-forward
to prevent a constant position error that would be proportional to the speed of the reference position.
If for any reason the user wishes to provide the velocity feed forward from a source other than the reference position, the feed forward system can be
made inactive, i.e. Pr
13.10
= 2 or 4. The external feed forward can be provided via Menu 1 from any of the frequency/speed references. However, if
the feed forward level is not correct a constant position error will exist.
Relative jogging
If relative jogging is enabled the feedback position can be made to move relative to the reference position at the speed defined by Pr
13.17
.
Orientation
If Pr
13.10
is 5 the drive orientates the motor following a stop command. If hold zero speed is enabled (Pr
6.08
= 1) the drive remains in position
control when orientation is complete and holds the orientation position. If hold zero speed is not enabled the drive is disabled when orientation is
complete.
If Pr
13.10
is 6 the drive orientates the motor following a stop command and whenever the drive is enabled provided that hold zero speed is enabled
(Pr
6.08
= 1). This ensures that the spindle is always held in the same position following the drive being enabled.
Parameter
value
Mode
Feed forward
active
0
Position controller disabled
1
Rigid position control
9
2
Rigid position control
3
Non-rigid position control
9
4
Non-rigid position control
5
Orientation on stop
6
Orientation on stop and when drive enabled
Speed
t
Reference
Actual
Equal Areas
Reference
Actual
Speed
Summary of Contents for unidrive sp
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