Gain Adjustment; Current Loop Gain; Speed Loop Gain - Mitsubishi Electric MELDAS MDS-B-SVJ2 Series Specifications And Instruction Manual

5-2 Gain adjustment

5-2-1 Current loop gain

No. Abbrev. Parameter name
SV009 IQA Current loop q axis lead
compensation
SV010 IDA Current loop d axis lead
compensation
SV011 IQG Current loop q axis gain
SV012 IDG Current loop d axis gain

5-2-2 Speed loop gain

(1) Setting the speed loop gain
The speed loop gain (SV005: VGN1) is an important parameter for determining the
responsiveness of the servo control. During servo adjustment, the highest extent that this value
can be set to becomes important. The setting value has a large influence on the machine cutting
precision and cycle time.
To adjust the VGN1 value, first obtain the standard VGN1 to judge how much VGN1 is required
for the machine load inertia.
The standard VGN1 is the value that corresponds to the size of the machine load inertia shown in
the graph in section 4-2-3. If the load inertia is not clear, estimate it using the following procedure.
① Set the VGN1 of a level where acceleration/deceleration operation is possible. (Set a slightly
lower value so resonance does not occur.)
② Set SV037 = 100, SV043 = 600, and SV044 = 0 in the servo parameters. Carry out a return
operation within the range where the axis can operate smoothly. At this time, set the
acceleration/deceleration time constant so the acceleration/deceleration torque equals or
exceeds (is 100% or higher than) the stall (rated) torque.
③ Observe the estimated disturbance using the D/A output, and increase the SV037 value until
the disturbance torque during acceleration/deceleration becomes smaller (cannot be
observed).
(The unbalance torque is observed as an estimated disturbance torque in the vertical and
slanted axes, so ignore this amount or set the torque offset (SV032) and adjust. The friction
torque is also observed in the same way for axes having a large amount of friction, but this
should be ignored. Refer to section "5-3-3 (3) Disturbance observer" for details.)
④ The SV037 setting where the disturbance torque becomes the smallest during the estimated
acceleration/deceleration is the machine's total load inertia magnification including the motor
inertia. Obtain the standard VGN1 from the graph in section 4-2-3 based on this value.
<When machine resonance does not occur at the standard VGN1>
Set the standard VGN1. Use the standard value if no problem (such as machine resonance)
occurs. If sufficient cutting precision cannot be obtained at the standard VGN1, do not raise the
VGN1 further above the standard value. Instead, use the disturbance observer and adjust.
Basically, there is no need to set a value higher than the standard value in VGN1.
<When machine resonance occurs at the standard VGN1>
Machine resonance is occurring if the shaft makes abnormal sounds when operating or stopping,
and a fine vibration can be felt when the machine is touched while stopped. Machine resonance
occurs because the servo control responsiveness includes the machine resonance points.
(Speed control resonance points occur, for example, at parts close to the motor such as ball
screws.) Machine resonance can be suppressed by lowering VGN1 and the servo control
responsiveness, but the cutting precision and cycle time are sacrificed. Thus, set a vibration
suppression filter and suppress the machine resonance (Refer to section "5-3-2 Vibration
suppression measures"), and set a value as close as possible to the standard VGN1. If the
machine resonance cannot be sufficiently eliminated even by using a vibration suppression filter,
then lower the VGN1.
No. Abbrev. Parameter name
SV005 VGN1

Speed loop gain

POINT
Chapter 5 Adjustment
This setting is determined by the motor's electrical
characteristics.
Set the standard parameters for all parameters.
(These are used for maker adjustments.)
Set this according to the motor inertia size.
If vibration occurs, adjust by lower the setting by 20% to 30% at a time.
The final VGN1 setting value should be 70 to 80% of the largest value at which
machine resonance does not occur.
If the vibration suppression functions are used to suppress the resonance and
the VGN1 setting value is raised, the subsequent servo adjustment becomes
more favorable.
Explanation
Explanation
5-4
Setting range
1 ~ 20480
1 ~ 20480
1 ~ 2560
1 ~ 2560
Setting range
1 ~ 999