Position Tracking/Measuring Gearbox - Siemens SINAMICS S120 Function Manual

Extended Functions

Position tracking/measuring gearbox

4.30 Position tracking/measuring gearbox
4.30.1 Description
If there is a mechanical gearbox (measuring gearbox) located between an end-
lessly rotating motor/load and the encoder and the position control is to be realized
using this absolute encoder, then depending on the gearbox ratio, at each encoder
overflow, an offset occurs between the zero position of the encoder and the motor/
load.
Fig. 4-39
In order to determine the position at the motor/load, in addition to the position
actual value of the absolute encoder, it is also necessary to have the number of
overflows of the absolute encoder.
If the power supply of the control module must be powered-down, then the number
of overflows must be saved in a non-volatile memory so that after powering-up the
position of the load can be uniquely and clearly determined.
Example: Gearbox ratio 1:3, absolute encoder can count 8 revolutions
Position
8
Position,
7
absolute encoder
6
5
4
3
2
1
0 1 2
Fig. 4-40
4-302
Motor/load
Position tracking
Load position
3
4 5 6 7 8 9
Offset for encoder overflow
Drive with an uneven gearbox and modulo axis
11 teeth
Encoders
19 teeth
Measuring gearbox
11
10 12 13 14 15 16 17
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SINAMICS S120 Function Manual, 03/2006 Edition
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Position
motor