B. Basic controlling principles
B−44
Festo P.BE−CPX−CMA X−CONTROL−EN en 0908NH
B.8.5 Individual value mode
The individual value mode can be used in record select oper
ating mode and in direct mode.
After the force command has started, the controller starts to
build up the force according to the specified target force and
force ramp.
If the drive is not faced with any counteracting force, the force
initiates
a drive movement. This can be the case when the
workpiece is movable or yielding, or if there is no workpiece.
If the drive exceeds the setpoint speed in this case, the con
troller automatically switches to position control (see section
B.8.6). In this the hardware end position in the direction of
force
effect is used as the setpoint position and the setpoint
speed of the record or the speed parameter in direct mode
(PNU 406 or 554) is used as the speed.
If you want to prevent reversing to position control, the set
point speed must be set to 0.000 m/s.
In order to prevent
too much kinetic energy, the maximum
permissible value for the speed is limited to 0.500 m/s.
Reversing to position control permits a workpiece to start
moving. The typical process in an application is:
1. Record 1: Fast approach to a preliminary position near the
workpiece (e.g. −10 mm)
2. Record 2: Start force control. The CMAX automatically
switches to position control
until the workpiece has been
reached. This prevents strong acceleration of the drive in
the event of no workpiece". The drive simply moves right
up to the software end position or to the configured
stroke limit and stops there.
With the help of record sequencing, it is possible to switch
between position control
and force control anytime.
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