WAGO-I/O-SYSTEM 750
Function Description
47
750-636/000-x00 DC Drive Controller 24V/5A
Manual
Version 2.1.0
4.12.3 Calculating a Swing-Back Drive
The target position of a swing-back drive is determined relative to the setpoint
position and the distance to the setpoint position is calculated from the sum of the
acceleration and braking distance (plus 10% safety margin). The braking distance
corresponds to the prestop and is determined separately for the negative and
positive rotation direction for each braking process. For a subsequent setpoint
position drive, it is always known at what distance the motor has to be shut down
before the setpoint position to come to a stop in the immediate area or at the
setpoint position exactly.
The swing-back drives to be used and described in chapter "Definition of the
Swing-Back Drives" ensure that the braking distance and subsequently
determined prestop stay nearly unchanged in the braking moment due to the ever-
constant speed.
However, if the mechanical damping of the system changes, a new prestop then
has to be determined. This situation is apparent by a swing-back drive occurring
after unsuccessfully completing a setpoint position drive. Ideally, the subsequent
drive should again hit the setpoint position. If the damping of the system changes
constantly, then a new prestop also has to be constantly determined.
If you now consider the second summand, the acceleration distance which
determines the total of a swing-back drive, then you have to proceed from the
same considerations as in considering the braking distance. The acceleration
distance is defined from the standstill to the end of the start ramp.
It certainly does not correspond to the real mechanical acceleration distance and
should be viewed as an acceptable compromise.