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06/06/2019 TR - EMO - BA - DGB - 0019 - 08 Page 187 of 252
6.6 Rotary axis with modulo correction
The "rotary axis application" described below is only available for drives in which the
index of the firmware number at the penultimate position is ≥ 2.
Example: 0141x-xx2x.
6.6.1 Description
To realize a rotary axis application with continuous one-way positioning and a
mechanical gearbox with any reduction, a modulo correction algorithm is required.
This compensates for rounding errors and prevents the position value from drifting
away.
The following example illustrates the necessary modulo correction for a rotary table
application:
The encoTRive has A
M
= 4096 position units per revolution and drives a rotary table.
Between engine and application there is a gearbox with a reduction of i = 39/17. So
the table rotates 17 times while the motor turns 39 times. Thus, a table turn
corresponds to 4096 * 39/17, that is about 9396.70588 ..., in fact there are 9396 12/17
position units on the motor. To ensure that the rotary table is correctly positioned in
the starting position each time, 12 x 9396 and 17 x 9397 position units must be
alternately moved.
Figure 18: Modulo correction at rotary table application
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