Description - Siemens SINAMICS S120 Function Manual

Function modules
7.8 Closed-loop position control
7.8.2.2

Description

The position actual value conditioning implements the conditioning of the position actual
value in a neutral position unit LU (LENGTH UNIT). To do this, the function block uses the
encoder evaluation/motor control with the available encoder interfaces Gn_XIST1,
Gn_XIST2, Gn_STW and Gn_ZSW. These just provide position information in encoder
pulses and fine resolution (increments).
The position actual value is conditioned independently of whether the position controller is
enabled immediately after the system has booted and as soon as valid values are received
via the encoder interface.
Parameter p2502 (encoder assignment) is used to define from which encoder (1, 2 or 3), the
position actual value is sensed.
The following interconnections are automatically established after the assignment has been
made.
● p0480[0] (G1_STW) = encoder control word r2520[0]
● p0480[1] (G2_STW) = encoder control word r2520[1]
● p0480[2] (G3_STW) = encoder control word r2520[2]
Figure 7-7
The link between the physical variables and the neutral length unit LU is established via
parameter p2506 (LU per load revolution) for rotary encoders. Parameter p2506 mirrors,
together with p2504, p2505, the interrelationship between encoder increments and the
neutral position unit LU.
Example:
Rotary encoder, ball screw with a pitch of 10 mm/revolution. 10 mm should have a resolution
of 1 µm (i.e. 1 LU = 1 µm).
-> One load revolution corresponds to 10000 LU
-> p2506 = 10000
238
Position actual value sensing with rotary encoders
Function Manual, (FH1), 07/2007 Edition, 6SL3097-2AB00-0BP4
Drive Functions