Watson-Marlow MM440 - Manual (Page 249)

Issue 10/06 3 Functions
MICROMASTER 440 Operating Instructions
6SE6400-5AW00-0BP0 249
If the moment of inertia was entered, the speed controller (K
p
,T
n
) can be calculated
using the automatic parameterization (P0340 = 4) (refer to Section 3.5.4). The
controller parameters are defined according to the symmetrical optimum as follows:
T
n
= 4 * T
σ
K
p
= ½ * r0345 / T
σ
= 2 * r0345 / T
n
T
σ
= sum of the low delay times
If oscillations occur with these particular settings, then the speed controller gain K
p
should be manually reduced. It is also possible to increase the speed actual value
smoothing (this is the usual procedure for gearbox play or high-frequency torsional
oscillations) and then re-call the controller calculation as the value is incorporated
in the computation of K
p
and T
n
.
The following interrelationships apply for the optimization routine:
¾
If K
p
is increased then the controller becomes faster and the overshoot is
reduced. However, the signal ripple and oscillations in the speed controller loop
are increased.
¾ If T
n
is reduced, then the controller also becomes faster. However, the
overshoot increases.
When manually adjusting the speed control, the simplest procedure is to initially
define the possible dynamic response using K
p
(and the speed actual value
smoothing) in order to then reduce the integral action time as far as possible. In
this case it is important to ensure that the closed-loop control must also remain
stable in the field-weakening range.
When oscillations occur in the closed-loop speed control, it is generally sufficient to
increase the smoothing time in P1452 for SLVC or P1442 for VC (or to reduce the
controller gain) in order to dampen oscillations.
The integral output of the speed controller can be monitored using r1482 and the
unlimited controller output can be monitored using r1508 (torque setpoint).
NOTE
When compared to closed-loop control with encoder (refer to Section 3.23.2.2), the
dynamic response for sensorless drives is significantly reduced. This is because
the speed can only be derived from the drive inverter output quantities for current
and voltage which have the appropriate noise level.