Using Mode Switch

1) Use the mode switch for the following purposes:

a) To prevent overshoot during acceleration or deceleration (for speed control).

b) To prevent undershoot during positioning in order to reduce settling time (for position control).

Speed

Overshoot

Actual motor operation

Reference

Time

Undershoot

Settling time

2) In other words, the mode switch is a function that automatically switches the speed con-trol mode inside the Servopack from PI concon-trol to P concon-trol while certain conditions are being established.

NOTE The mode switch is used to fully utilize performance of a servo drive to achieve very high-speed positioning. The high-speed response waveform must be observed to adjust the mode switch.

For normal use, the speed loop gain and position loop gain set by autotuning provide suf-ficient speed/position control.

Even if overshoot or undershoot occurs, they can be suppressed by setting the accelera-tion/deceleration time constant for the host controller, the soft start time constants (Cn-07, Cn-23), or smoothing time constant (Cn-26) for the Servopack.

TERMS From PI control to P control

PI control means proportional/integral control and P control means proportional control. In short, switching “from PI control to P control” reduces effective servo gain, making the servo system more stable.

3

3)Servopacks can use four types of mode switches (1 to 4). To select a mode switch, use the following memory switch. Note that the mode switch setting methods for speed/

torque control and position control are slightly different.

For Speed/

Torque Control (SGDA-jj

jS)

For Position Control (SGDA-jjjP)

Mode Switch Setting User Constant Unit Memory

Switch Cn-01

Memory Switch Cn-01

Mode Switch Setting User Constant Unit

Bit D Bit C Bit D Bit

C Bit B

1 1 − − 1 Does not use mode

switch.

0 0 0 0 0 Uses torque reference as

a detection point.

(Standard setting) Cn-0C Percentage of rated torque: %

0 1 0 1 0 Uses speed reference as

a detection point. Cn-0D Motor speed:

r/min

1 0 1 0 0 Uses acceleration

refer-ence as a detection point. Cn-0E

Acceleration reference in-side the Servo-pack:

10 (r/min)/s 1 1 0 Uses error pulse as a

detection point. Cn-0F Reference unit

When Torque Reference Is Used as a Detection Point of

Mode Switch (Standard

Setting) If a torque reference exceeds the torque value set

in user constant Cn-0C, the speed loop switches to P control.

The SGDA Servopack is factory set to this stan-dard mode (Cn-0C = 200).

Example of Use:

If a mode switch is not used and PI control is always performed, torque may enter a saturation state during acceleration or deceleration, causing the motor speed to have overshoot or undershoot.

Using the mode switch suppresses torque saturation and prevents the motor speed from having overshoot and undershoot.

Without mode switch With mode switch

3

Speed

Reference

speed Motor

speed

Internal torque reference Torque

PI control P control

PI control PI control P control

When Speed Reference Is Used as a Detection Point of Mode Switch If a speed reference exceeds the value set in user

constant Cn-0D, the speed loop switches to P control.

Example of Use:

The mode switch is used to reduce settling time.

Generally, speed loop gain must be increased to reduce settling time. Using the mode switch suppresses the occurrence of overshoot and undershoot when speed loop gain is increased.

Without mode switch Speed reference Motor

speed

Motor speed

Settling time is long

Increase speed loop gain

Without mode switch

Motor speed

Overshoot

Undershoot

Time

With mode switch

Motor speed

Settling time

Suppress the occurrence of overshoot and undershoot.

When Acceleration Is Used as a Detection Point of Mode

Switch (Standard

Setting) If motor acceleration exceeds the value set in user

constant Cn-0E, the speed loop switches to P control.

Example of Use:

If a mode switch is not used and PI control is always performed, torque may enter a saturation state during acceleration or deceleration, causing the motor speed to have overshoot or undershoot.

Using the mode switch suppresses torque saturation and prevents the motor speed from having overshoot and undershoot.

Without mode switch

Motor speed

Overshoot

Undershoot

Time

With mode switch

Motor speed

Time

3

Speed

Speed reference Motor

speed

PI control P control PI control

Speed

Reference

speed Motor speed

Motor acceleration Acceleration

PI control

P control P control PI control PI control

When Error Pulse Is Used as a Detection Point of Mode Switch For position control (SGDA-jjjP) only.

If an error pulse exceeds the value set in user constant Cn-0F, the speed loop switches to P con-trol.

Example of Use:

The mode switch is used to reduce settling time.

Generally, speed loop gain must be increased to reduce settling time. Using the mode switch suppresses the occurrence of overshoot and undershoot when speed loop gain is increased.

Without mode switch

Motor speed

Speed reference Motor speed

Settling time is long

Increase speed loop gain

Without mode switch

Motor speed

Overshoot

Undershoot

Time

Motor speed

Suppress the occurrence of overshoot and undershoot.

With mode switch

Settling time

4) The user constants required to set each mode switch are summarized as follows.

Cn-01Bit B Mode Switch ON/OFF Factory

Setting: 0 For Position Control Only

For position control (SGDA-jjjP) only.

This user constant is used to enable or disable the mode switch function.

Setting Meaning

0 Uses the mode switch function 1 Does not use the mode switch function

3

SGDA- P

Positions

Speed

Speed reference Motor

speed

Error pulse

PI control P control PI control

SGDA- P

Positions

Speed Reference Actual

motor operation

Time Settling time Mode switch is used to reduce settling time and suppress undershoot when the motor stops. It switches PI control to P control when certain conditions are met.

Cn-01 Bit C Mode Switch Selection Factory

Setting: 0 For Speed/Torque Control and Position Control Cn-01 Bit D Mode Switch Selection Factory

Setting: 0 For Speed/Torque Control and Position Control

Use the following user constants to set the mode switch to be used.

Memory Switch

Cn-01 Mode Switch Type

User Constant for Setting

Detection Bit D Bit C

Detection Point 0 0 Uses torque reference as a detection point. Cn-0C 0 1 Uses speed reference as a detection point. Cn-0D 1 0 Uses acceleration reference as a detection point. Cn-0E

1 1

For speed/

torque

con-trol Does not use mode switch.

For position

control Uses error pulse as a detection point. Cn-0F

Mode switch is used to reduce settling time and suppress undershoot when the motor stops. It switches PI control to P control when certain conditions are met.

3

Cn-0C

TRQMSW Mode Switch (Torque Reference)

Unit: % Setting Range: 0 toMaximum Torque

Factory Setting:

200

ForSpeed/Torque Control and Position Control

Cn-0D

REFMSW Mode Switch (Speed Reference)

Unit:

r/min Setting Range: 0 toMaximum Speed

Factory Setting: 0 For

Speed/Torque Control and Position Control

Cn-0E

ACCMSW Mode Switch (Acceleration Reference)

Unit: 10

(r/min)/s Setting Range: 0 to 3000

Factory Setting: 0 For

Speed/Torque Control and Position Control

Cn-0F

ERPMSW Mode Switch

(Error Pulse) Unit:

Refer-enceUnit

Setting Range: 0 to 10000

Factory Setting:

10000

For Position Control Only

Mode switch is used to reduce settling time and suppress undershoot when the motor stops. It switches PI control to P control when certain conditions are met.

The Servopack allows use of four different types of mode switch. To select a mode switch, set bits B, C and D of memory switch Cn-01.

Memory Switch

Cn-01 Mode Switch

Set-ting User Constant Unit

Bit D Bit C Bit B ting User Constant Unit

− − 1 Does not use

mode switch.

0 0 0 Uses torque refer-ence as a

detec-tion point. Cn-0C Percentage of rated

torque: %

0 1 0 Uses speed

refer-ence as a

detec-tion point. Cn-0D Motor speed: r/min

1 0 0 Uses acceleration

reference as a

detection point. Cn-0E Acceleration reference in-side the SGD Servopack:

10 (r/min)/s

1 1 0 Uses error pulse

as a detection

point. Cn-0F Reference unit

User constant Cn-0F is for position control (SGDA-jjjP) only. For speed/torque con-trol (SGDA-jjjS), Cn-0F is used to set a zero-clamp level.

3

Speed

Reference Actual motor operation

Time

Settling time

문서에서 USER'S MANUAL AC Servomotors and Drivers SGM/SGMP Servomotors SGDA Servopack (페이지 129-135)