08.96 12 Functional Descriptions
12.31.2 Description of function
The reduction range represents a safety area. As soon as the following axis is positioned
in the reduction range, the path speed of the channels is reduced. Since the speed set for
the following axis in the next IPO cycle is not known, the path speed of the channels must
be restricted by means of the reduction range for safety reasons.
• Deadtime compensation
The setpoint position of the following axis is checked in every IPO cycle to establish
whether it is within the reduction range. The system is designed such that several IPO
cycles elapse before changes to the setpoints of a leading axis are output to the setpoint
controller of the following axis. To compensate this deadtime, the setpoint position is
corrected by the predicted path. The deadtime and thus also the compensation value are
dependent on the gear interpolation link type. The deadtime is 2 IPO cycles for the
setpoint link. A deadtime of 5.5 IPO cycles is recommended for the actual value link.
• Calculation of reduction factor
The distance between the deadtime-compensated setpoint position and the active
limitations is calculated. The active limitations are the innermost limit values as defined by
the working field boundary and the selected SW limit switch. If the distance d is smaller
than the reduction range, the braking operation must be initiated. For this purpose, a
permissible velocity value V
perm
calculated from the distance to the SW limit switch and
the max. acceleration value A
max
.
2 * d * A
max
V
perm
=
A reduction factor is calculated from V
perm
and V
max
and transmitted to the mode group
channels. In a similar way to an override, the reduction factor is included in the path
velocity calculation in all mode group channels.
Reduction factor= V
perm
/ V
max
* 100
Diagram showing reduction range in front of a limit switch:
Limit
switch
V
max
V
perm
Position
Reduction range
V
Setpoint position Corrected
setpoint
position
© Siemens AG 1992 All Rights Reserved 6FC5197- AA50
12–313
SINUMERIK 840C (IA)