bnp-b2365(eng)b.pdf - 第220页
4. Servo Adjustment 4 - 21 (3) Inductive voltage compensation The current loop response is improved by co mpensating th e back electromotive force element induced by the motor rotation. This i mproved the current com man…
4. Servo Adjustment
4 - 20
(2) Acceleration feed forward
Vibration may occur at 10 to 20 Hz during acceleration/deceleration when a short time constant of
30 ms or less is applied, and a position loop gain (PGN1) higher than the general standard value or
SHG control is used. This is because the torque is insufficient when starting or when starting
deceleration, and can be resolved by setting the acceleration rate feed forward gain (SV015: FFC).
This is also effective in reducing the peak current (torque).
While measuring the current command waveform, increase FFC by 50 to 100 at a time and set the
value where vibration does not occur.
No FFC setting With FFC setting
Acceleration rate feed forward gain means that the speed loop gain during
acceleration/deceleration is raised equivalently. Thus, the torque (current command) required
during acceleration/deceleration starts sooner. The synchronization precision will improve if the
FFC of the delayed side axis is raised between axes for which high-precision synchronous control
(such as synchronous tapping control and superimposition control).
No. Abbrev. Parameter name Explanation Setting range
SV015 FFC Acceleration rate
feed forward gain
When a relative error in the synchronous control is large, apply this
parameter to the axis that is delaying. The standard setting value is "0". For
the SHG control, set to "100".
To adjust a relative error in acceleration/deceleration, increase the value
by 50 to 100 at a time.
0 to 999
(%)
POINT
Overshooting occurs easily when a value above the standard value is set during
SHG control.
Current
command
(%)
200
100
0
100
806040
20 0
Time (ms)
200
100
0
100
8060 40
200
Time (ms)
4. Servo Adjustment
4 - 21
(3) Inductive voltage compensation
The current loop response is improved by compensating the back electromotive force element
induced by the motor rotation. This improved the current command efficiency, and allows the
acceleration/deceleration time constant to the shortened.
<Adjustment method>
1. While accelerating/decelerating at rapid traverse, adjust the inductive voltage compensation
gain (SV047: EC) so that the current FB peak is a few % smaller than the current command
peak.
Inductive voltage compensation
No. Abbrev. Parameter name Explanation Setting range
SV047 EC Inductive voltage
compensation gain
Set the inductive voltage compensation gain. Set to "100" as a standard.
If the current FB peak exceeds the current command peak, lower the gain.
0 to 200
(%)
POINT
If the current FB peak becomes larger than the current command peak (over
compensation), an overcurrent (alarm 3A) will occur easily. Note that over
compensation will occur easily if the load inertia is large.
0
0
3000
200
-200
-3000
Speed command
(r/min)
Current
command
(Rated current %)
No inductive voltage
compensation
With inductive
voltage
compensation
Time
Time
4. Servo Adjustment
4 - 22
4-3-5 Improvement of protrusion at quadrant changeover
The response delay (caused by dead band from friction, torsion, expansion/contraction, backlash, etc.)
caused when the machine advance direction reverses is compensated with the lost motion compensation
(LMC compensation) function.
With this, the protrusions that occur at the quadrant changeover in the DBB measurement method, or
the streaks that occur when the quadrant changes during circular cutting can be improved.
The following three compensation types are available for lost motion compensation (LMC compensation).
[1] LMC compensation type 1
This is a backward compatible (for older models) compensation type. Either type 2 or type 3 should
be used on new models.
[2] LMC compensation type 2
Performs servo internal PI control response delay compensation for the frictional torque reversing
condition that occurs during servo reverse travel. Reverse response delay is compensated with
adding the torque command set by parameter when a speed and direction change occurs.
LMC compensation type 2 adjustments should be performed with reference to the following items.
(1) Unbalance torque and frictional torque
(2) LMC compensation type 2 setting and adjustment
(3) Lost motion compensation timing adjustment
(4) Adjustment at feed forward control
[3] LMC compensation type 3
In addition to frictional torque influence, this type compensates torsion and expansion/contraction
influences in the machine system in which compensation amount is changed by travel speed. A
mechanical system viscosity coefficient setting further enhances the compensation accuracy even
if the travel speed is changed. Adjustment requires a machine end roundness measurement.
LMC compensation type 3 adjustments should be performed with reference to the following items.
(1) Unbalance torque and frictional torque
(2) LMC compensation type 3 setting and adjustment
Circle cutting path before compensation
Compensation
Cutting
direction
DBB: Double Ball Bar
Circle cutting path after compensation