Bosch Rexroth IndraDrive MPH-02 Functional Description page 269

MPH-02, MPB-02, MPD-02
Determining the Critical
Proportional Gain
Determining the Critical Integral
Action Time
Characteristics of Controller
Speed controller
Application type proportional gain
feed axis at standard K
machine tool
feed axis at perforating K
machine or nibbling
machine
feed drive at following- K
on cutting devices
DOK-INDRV*-MP*-02VRS**-FK01-EN-P
To determine the "critical proportional gain" proceed as follows:
1. Let the drive move with low velocity after switching drive enable on:
• linear motor
• rotary motor
2. Increase value in parameter S-0-0100, Velocity loop proportional
gain until instable behavior (continuous oscillation) occurs.
3. Determine frequency of oscillation by oscilloscoping the actual
velocity (see also "Analog Outputs" or "Oscilloscope Feature"). When
frequency of oscillation is considerably higher than 500 Hz, increase
value in parameter P-0-0004, Velocity loop smoothing time
constant until oscillation diminishes. Then continue increasing the
value in parameter S-0-0100, Velocity loop proportional gain until
oscillation (instability) occurs again.
4. Reduce parameter S-0-0100, Velocity loop proportional gain until
permanent oscillation decreases automatically.
The value thus determined is the so-called "critical velocity loop
proportional gain".
Note: By using the filter cascade (P-0-1120, P-0-1121, P-0-1122,
P-0-1123) it is possible to activate a PT4-filter.
To determine the "critical integral action time" proceed as follows:
1. Set parameter S-0-0100, Velocity loop proportional gain =
0.5 * "critical proportional gain"
2. Reduce value in parameter S-0-0101, Velocity loop integral action
time, beginning with maximum value, until instable behavior
(continuous oscillation) occurs.
3. Increase value in parameter S-0-0101, Velocity loop integral action
time until continuous oscillation decreases automatically.
The value thus determined is the "critical integral action time". Usual
values are within the range from 5 to 20 ms!
From the determined critical values (see above) it is possible to derive a
Setting controller setting with the following characteristics:
• independent of changes at the axis because sufficient distance to
stability limit
• properties can be reliably reproduced in series machines
The following table contains some of the most common types of
application and the corresponding characteristics of the control loop
setting.
Speed controller
integral action time Notes
= 0.5 x K T = 2 x T
p pkrit n
= 0.8 x K T = 0
p pkrit n
= 0.5 x K T = 0
p pkrit n
Fig. 6-40: Characteristics of controller setting
→
1000 ... 2000 mm/min
→
10 ... 20 rpm
good load stiffness and good control
nkrit
performance
high proportional gain; no I-component in
order to obtain short response times
relatively non-dynamic controller setting
without I-component in order to keep the
material to be cut from getting distorted with
the cutting device
6-57
Drive Control