4. Function overview
42
Festo P.BE-CMMP-AS-3A-HW-EN 0708NH
4.3.3
Absolute positioning
Here, the positioning target is moved to regardless of the current position. To be able to
execute absolute positioning we recommend first referencing the drive. With absolute
positioning the target position is a fixed (absolute) position relative to the zero point or
reference point.
4.3.4
Motion profile generator
With travel profiles, a distinction is made between time-optimised and jerk-limited posi-
tioning. With time-optimised positioning, motion occurs with the maximum specified ac-
celeration and braking. The drive moves to the target in the shortest possible time, the
speed sequence is trapezoidal and the acceleration sequence square. With jerk-limited
positioning, the acceleration is trapezoidal and the speed sequence is third-order. Since
the acceleration constantly changes, the drive moves in a manner that is especially gentle
to the mechanics.
a(t)
a(t)
a(t)
t
t
t
v(t)
t
v(t)
t
v(t)
t
at time optimal
jerk limit
jerk limit
Fig. 4.2 Travel profile with the CMMP-AS servo positioning controller. t
1
<t
2
<t
3,
when a
max 1,
a
max 2,
and a
max 3
are the same
4.3.5
Homing run
Every positioning controller requires a defined zero point at the start of operation, which is
determined by a homing run. The CMMP-AS servo positioning controller can independently
perform this homing run. It analyses various inputs for the reference signal, e.g. the limit
switch inputs.
A homing run can be started via a command over the communication interface or auto-
matically when the controller is enabled. The start can also optionally occur via a digital
input configured using the parameterising software, in order to perform a targeted homing
run independently of the controller enable. Among other operations, the controller enable
acknowledges error messages and can be switched off on an application-dependent basis
without requiring a new homing run when it is enabled once more. Since the existing digi-
tal inputs are usually occupied in normal applications, the analogue inputs AIN1 and AIN2
Summary of Contents for CMMP-AS-C2-3A
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