bnp-b2365(eng)b.pdf - 第232页

4. Servo Adjustment 4 - 33 4-4 Adjustment during full closed loop control 4-4-1 Outline (1) Full closed loop control The servo control is all closed lo op control using t he detector's fee dback. "Full closed l…

4. Servo Adjustment

4 - 32

[1] Confirm that the motor end circle accuracy measured with the NC sampling function is

appropriate.

[2] In this state, measure the tool end low-speed and high-speed circle path without tool end

compensation. The difference of the high-speed circle path and low-speed circle path is the

amount that path has swelled due to the spring effect of the machine system. Calculate the

SV065 setting value with the following expression using this amount as the compensation

amount.

SV065 =

Compensation amount [µm] × radius R [mm] ×10

(command speed F [mm/min])

[3] Set SV027/bit7 to 1, and input the value calculated in step 2 into SV065. Measure the

high-speed circle path. If the shape is still elliptical, adjust by increasing/decreasing the SV065

value in 1/10 units.

[4] Confirm that there is no problem with the low-speed circle path.

Example of low-speed and high-speed roundness measurement for adjusting tool end compensation

When using grid encoder When using DBB measurement Acceleration

Low speed (reference circle) R=25 [mm], F=500 [mm/min] R=100 [mm], F=1000 [mm/min] 0.00028G

High-speed (when adjusting

compensation amount)

R=25 [mm], F=10000 [mm/min] R=100 [mm], F=20000 [mm/min] 0.11G

No. Abbrev. Parameter name Explanation Setting range

SV027 SSF1 Servo function

selection 1 F E D C B A 9 8 7 6 5 4 3 2 1 0

aflt zrn2 afse ovs lmc omr zrn3 vfct upc vcnt

bit Meaning when "0" is set Meaning when "1" is set

7 omr Tool end compensation invalid Tool end compensation valid

SV065 TLC Tool end

compensation spring

constant

Set the spring constant of the tool end compensation.

In the semi-closed loop control, the tool end compensation amount is

calculated with the following equation.

Compensation amount =

Commanded speed F (mm/min)

SV065

Radius R (mm)

(µm)

When not using, set to "0".

-32768 to

32767

POINT

1. To confirm the machine's spring element, adjust the electrical end

roundness, and then tool end roundness while changing the cutting speed.

Confirm that the error increases with the speed.

2. The electrical end roundness will have an error on the inner side when tool

end compensation is used.

CAUTION

If an excessive value is set in the tool end compensation spring constant

(SV065), the machine could vibrate when stopping, resulting in a dangerous

state.

4. Servo Adjustment

4 - 33

4-4 Adjustment during full closed loop control

4-4-1 Outline

(1) Full closed loop control

The servo control is all closed loop control using the detector's feedback. "Full closed loop control"

is the system that directly detects the machine position using a linear scale, whereas the general

"semi-closed loop" is the one that detects the motor end position.

In a machine that drives a table with a ball screw, the following factors exist between the motor and

table end:

[1] Coupling or ball screw table bracket's backlash

[2] Ball screw pitch error

These can adversely affect the accuracy. If the table position, which is the tool end, is directly

detected with a linear scale, high-accuracy position control which is not affected by backlash or

pitch error is possible. However, with the full closed loop system, the machine system is also

directly included in the position loop control. Thus, if the machine's rigidity is not high, the gain

cannot be increased, and the required high accuracy cannot be attained.

The procedures for adjusting the servo with the full closed loop system are the same as the

semi-closed loop system. Vibration or overshooting will occur easily, so the position loop gain is

generally lower than the semi-closed loop.

(2) Overrun detection

With the full closed system, the tool end position feedback (FB) detected with the linear scale is

used for the position control. However, the motor end position FB is detected at the same time, and

the error of both FB is observed. If this FB error exceeds the servo parameter SV054 setting value,

alarm 43 will be detected and the system will stop to prevent overrunning due to a scale FB error

from occurring.

Overrun detection c ontrol

No. Abbrev. Parameter name Explanation Setting range

SV054 ORE Overrun detection

width in closed loop

control

Set the overrun detection width in the full-closed loop control.

If the gap between the motor end detector and the linear scale (tool end

detector) exceeds the value set by this parameter, it is judged to be

overrun and Alarm 43 will be detected.

When "-1" is set, the alarm detection won’t be performed. When "0" is

set, overrun is detected with a 2mm width.

-1 to 32767

(mm)

Position

command

PGN

FB error

Position droop

Servo-

motor

ENC

Linear scale

Table

Speed command

Machine end

osition FB

Motor end position FB

4. Servo Adjustment

4 - 34

4-4-2 Speed loop delay compensation

Generally, the tool end position follows the operation later than the motor end position. With full closed

loop position loop control, the tool end position is used for position feedback, so the motor end position

could advance too far and cause the tool end position to overshoot easily. Speed loop delay

compensation suppresses overshooting by weakening the speed loop PI control (weakening advance

compensation = delaying). If the compensation is too large and PI control is weakened too far, the

positioning time could increase, or the position droop will remain when the motor is stopped.

[1] Set the servo function selection 1 (SV027: SSF1)/bit1, bit0 to 10. (Select delay compensation

changeover type 2)

[2] Set the axis unbalance torque to the torque offset (SV032: TOF). (Refer to "4-3-5 (1) Unbalance

torque and frictional torque" for details on measuring the unbalance torque.)

[3] Observe the position droop waveform, and confirm the overshooting. Increase SV007 (VIL) in

increments of 5, and adjust so that the overshooting is improved. If set too high, the position

droop will remain when the axis is stopped.

No. Abbrev. Parameter name Explanation Setting range

Set this when the limit cycle occurs in the full-closed loop, or overshooting

occurs in positioning.

Select the control method with SV027 (SSF1)/bit1, 0 (vcnt).

Normally, use "Changeover type 2".

When you set this parameter, make sure to set the torque offset SV032

(TOF). When not using, set to "0".

SV007 VIL

Speed loop delay

compensation

Changeover type 2 When SV027 (SSF1)/ bit1, 0 (vcnt)=10

The delay compensation control works when the command from the

NC is "0" and the position droop is "0". Overshooting or the limit cycle

that occurs during pulse feeding or positioning can be suppressed.

0 to 32767

SV032 TOF Torque offset

Set the unbalance torque of vertical axis and inclined axis.

-100 to 100

(Stall [rated]

current %)

SV027 SSF1 Servo function

selection 1 F E D C B A 9 8 7 6 5 4 3 2 1 0

aflt zrn2 afse ovs lmc omr zrn3 vfct upc vcnt

bit Meaning when "0" is set Meaning when "1" is set

Set the execution changeover type of the speed loop delay

compensation.

vcnt

00:

Delay compensation changeover

invalid

10: Delay compensation

changeover type 2

01:

Delay compensation changeover

type 1

11: Setting prohibited

CAUTION

The position droop will remain if SV007 is set too high.