Siemens SINAMICS S120 Function Manual page 458

Function modules
7.8 Basic positioner
STOP cam
A traversing range can, on the one hand, be limited per software using the software limit
switches and on the other hand, the traversing range can be limited per hardware. In this
case, the functionality of the STOP cam (hardware limit switch) is used. The function of the
STOP cams is activated by the 1 signal on the binector input p2568 (activation of STOP
cams).
Once enabled, the activity of binector inputs p2569 (STOP cam, minus) and p2570 (STOP
cam, plus) is checked. These are low active; this means if a 0 signal is present at binector
input p2569 or p2570, then these are active.
When a STOP cam (p2569 or p2570) is active, the current motion is stopped with OFF3 and
the appropriate status bit r2684.13 (STOP cam minus active) or r2684.14 (STOP cam plus
active) is set.
When an axis has approached a STOP cam, only motion that allows the axis to move away
from the cam is permitted (if both STOP cams are actuated, then no motion is possible).
When the STOP cam is exited, this is identified by the 0/1 edge in the permitted traversing
direction which means that the corresponding status bits (r2684.13 or r2684.14) are reset.
Jerk limitation
Acceleration and deceleration can change suddenly if jerk limiting has not been activated.
The diagram below shows the traversing profile when jerk limitation has not been activated.
The maximum acceleration (a
drive accelerates until the target speed (v
velocity phase.
Figure 7-15
Jerk limitation can be used to achieve a ramp-like change of both variables, which ensures
"smooth" acceleration and braking as shown in the diagram below. Ideally, acceleration and
deceleration should be linear.
456
) and deceleration (d
max
Without jerk limitation
) are effective immediately. The
max
) is reached and then switches to the constant
target
Function Manual, (FH1), 01/2013, 6SL3097-4AB00-0BP3
Drive functions