W.E.ST. MDR-133-U Technical Documentation Manual page 32

FAULT
ENABLE and START are
active, the READY LED is
active, and the pressure
control loop works. Lower
pressure at the beginning
causes that the system is
not actuated and that no
pressure build-up occurs.
ENABLE and START (PIN
6) are active, the READY
LED is active, the pres-
sure control loop works,
but the pressure is oscillat-
ing or the pressure UP
and DOWN time is too
slow.
ENABLE is active, the
READY LED is active and
the pressure is instable.
7
The limit value should be higher than the remaining control range (100 % - C:SC), additionally you have to add a value to
compensate the non-linearity of the valve.
8
Optimizing in steps is a general description. Our experience: you can change the parameters in steps from +20 % or ra-
ther -20 % for a rough adjustment of the actual value. For a fine adjustment you can select smaller steps.
9
Maybe you have to adjust / optimize the solenoid control loop (P and I).
10
In most applications (particularly pressure-actuated pumps) with pressure valves a lower PWM-frequency is the better
solution.
Page 32 of 42
CAUSE / SOLUTION
In this case, the integrator threshold (activation point of the integrator) in combination
with the controller setting is too high. The parameter LIM: S should be reduced.
The capability of the hydraulic system has to be checked. Deactivate PIN 6 for open
loop control and check the pressure build up and down time. If the system is in open
loop still instable, check the hydraulic and the dither/ PWM setup first.
1. Check the parameters C:I, C:P and C:SC.The parameter C:SC has the following
relevance:
With this parameter you can increase or decrease the feed forward gain to the
valve. C:SC 8000 (80 %) means, the remaining 20 % must be provided by the PID
compensator. The integrator limitation should be set to 2500... 3500 (25 % ... 35
7
%) .
2. The C:P (P-gain) is to increase in steps
to be instable. At this point, C:P should be decreased for 30... 50 % to get an ef-
fectual stability margin.
3. The integrator time constant C:I fixes the static error. Typical values are: 100 ms
to 1200 ms. Optimize this parameter by monitoring the transient response.
In many cases you may have a hydraulic problem.
Electrical problems may be:

Electrical noise at the wire of the power supply.

Very long solenoid wiring (> 40 m), disturbance in the current control loop

Instable current control loop. The adjustments of the PWM-frequency and the
dither (frequency and amplitude) have to be checked carefully. Good experi-
ences are made with:
a. PWM-frequency = 2600 Hz (higher frequency), the dither has to be aligned
to the valve (amplitude and frequency).
PWM-frequency = 100... 400 Hz (lower frequency), the dither amplitude is
b.
set to 0 % (disabled)
MDR-133-*-2030
8
to the point where the pressure is going
10
.
9
.
29.08.2019