from 0.000 to 2.000 (i.e. the change of position input value is added without scaling if Pr 12.13 is 0.000). The remainder from the scaling division is

stored and then added at the next sample to maintain an exact ratio between the position input and the position output, provided the speed input is

zero. The controller only takes the change of position from the input source parameter, and not the absolute value, so that when the controller is first

made active the output does not jump to the source position, but only moves with any changes of source position after that point in time.

The range of the output of the accumulator is 0.00% and 100.00%. Unlike other functions the value is not simply limited, but rolls under or over

respectively. Although the output destination can be any parameter it is intended to be used with a position value that has a range from 0 to 65535.

The speed input defines a speed offset with a resolution of 0.1rpm. Full scale of the source parameter corresponds to 1000.0rpm. Scaling may be

applied using Pr 12.14 to give a full scale value of 4000.0rpm. The speed input is added to the accumulator to move the output position forwards or

backwards with respect to the position input.

This sample time for this function is 4ms x number of menu 9 and 12 functions active. Extending the sample time does not cause any overflow errors

within the function, however, care must be taken to ensure that the input or output positions do not change by more than half a revolution within the

sample time, i.e for a sample time of 4ms the input or output speed should not exceed 7500rpm, for a sample time of 8ms the speed should not

exceed 3750rpm, etc. If the output of this function is to supply a reference to the position controller in menu 13 it must be the only user function in

menu 9 or 12 enabled. If another function is enabled the input to the position controller will only change every 8ms (i.e. every 2 samples of

the position controller) and the speed reference applied to the drive could be very noisy.

The diagram below shows how the variable selector in Sectional control mode can be used to provide a position reference for the drive and act as a

source for encoder simulation to give the position reference for the next drive in the system.

Input

SM-Universal

reference

Encoder Plus

module

Output

reference

The input reference is provided by the previous drive in the system via the SM-Universal Encoder Plus module and is used as the position source

(Pr 12.08) for the variable selector. The destination of the variable selector is the local position reference for the menu 13 position controller

(Pr 13.21). Pr 13.21 counts up or down based on the delta position from the variable selector and rolls over or under at 65535 or 0. If the controller is

set up to ignore the local reference turns then Pr 13.21 can be used as the position controller reference. If Pr 13.21 is also used as the encoder

simulation source the local reference can also be used to give the reference for the next drive in the system. With this arrangement a ratio is provided

between the input reference and output reference within the variable selector. An addition ratio can be provided within the position controller between

the position in Pr 13.21 and the position reference used by the position controller. The variable selector speed reference can be used to move the

position reference forwards or backwards with respect to the input reference.

Mentor MP Advanced User Guide

Issue Number: 1

Parameter description

Parameter x.00

format

Source

12.08

=Pr

x.05

Variable selector