Menu 13
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232
Unidrive SP Advanced User Guide
www.controltechniques.com Issue Number: 10
5.15 Menu 13: Position control
Menu 13 provides a position control system for the drive in open-loop mode and closed-loop modes (closed-loop vector and servo). The position
reference can be taken from the drive encoder, from a position feedback module or from a local reference defined in this menu. The reference
includes a relative jog function that can be used to advance or retard the position reference at a defined speed and a ratio that can scale the
reference. The feedback position can be taken from the drive encoder or from a position feedback module. As well as giving position control the
controller can provide shaft orientation within one revolution in conjunction with the drive sequencer (see section 5.8
page 134). The sample time for the position controller is 4ms and the output is supplied to the speed or frequency reference every 4ms.
Open–loop mode
The position controller outputs are a velocity feed forward and a speed reference (both in 0.1rpm units). When the position controller is selected (i.e.
Pr
13.10
is non-zero) these values are converted to 0.1Hz units and combined as shown below, before being written to the velocity feed forward
parameter (Pr
1.39
). The velocity feed forward select (Pr
1.40
) is always one when the position controller is selected. When the position controller is
de-selected (i.e. Pr
13.10
is changed to zero) Pr
1.39
and Pr
1.40
are set to zero. In open-loop mode the motor control must pass through the drive
ramp system, and so for stable operation short ramp times are normally required.
Closed-loop modes
The position controller outputs are a velocity feed forward and a speed reference (both in 0.1rpm units). When the position controller is selected (i.e.
Pr
13.10
is non-zero) these values are written directly to the velocity feed forward (Pr
1.39
) and hard speed reference (Pr
3.22
) respectively. Also the
hard speed reference select (Pr
3.23
) is forced to a one and the velocity feed forward select (Pr
1.40
) is set to one when a controller mode giving
velocity feed forward is selected. When the position controller is de-selected (i.e. Pr
13.10
is changed to zero) Pr
1.39
, Pr
1.40
, Pr
3.22
and Pr
3.23
are set to zero.
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