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6.3 Torque Control

Last modified by Wecon on 2025/09/03 21:03

The current of the servo motor has a linear relationship with the torque. Therefore, the control of the current could achieve the control of the torque. Torque control refers to controlling the output torque of the motor through a torque reference. Torque reference could be given by internal command and analog voltage.

The torque control block diagram is as follows:

1617847486252-505.png

Torque Reference Input Setting

6.3 Torque Control Mode_html_2421a7c916f19e0c.jpg

Torque reference source

In the torque control mode, there are two sources of torque reference, which could be set through [P1-7]. Relevant function codes:

Code

Parameter Name

Property

Effective

Time

Range

Function

Unit

Default

P1-7

Torque reference source

At stop

Immediate

0~1

0: Internal torque command.

1: AI_1 analog input.

-

0

Digital setting

The source of the torque reference is an internal command, which is set through function code [P1-8]. Relevant function codes:

Code

Parameter Name

Property

Effective

Time

Range

Function

Unit

Default

P1-8

Torque reference keyboard set value

During running

Immediate

-3000~3000

-300.0%～300.0%

0.1%

0

Analog voltage setting

Code

Function

Unit

Format

U0-21

AI1 input voltage value

V

decimal(3 decimal digits)

U0-22

AI2 input voltage value

V

decimal(3 decimal digits)

Code

Parameter Name

Property

Effective

Time

Range

Function

Unit

Default

P5-1

AI_1 input bias

During running

Immediate

-5000~5000

Set AI_1 channel analog offset value

mv

0

P5-2

AI_1 Input filter constant

During running

Immediate

0~65535

AI_1 channel input first-order low-pass filtering time constant

ms

200

P5-3

AI_1 dead zone

During running

Immediate

0~1000

Set AI_1 channel analog dead zone value

mv

20

P5-4

AI_1 zero drift

During running

Immediate

-500~500

Automatic calibration zero drift inside the driver.

mv

0

P5-5

AI_2 input bias

During running

Immediate

-5000~5000

Set AI_2 channel analog offset value

mv

0

P5-6

AI_2 Input filter constant

During running

Immediate

0~60000

AI_2 channel input first-order low-pass filtering time constant

ms

200

P5-7

AI_2 dead zone

During running

Immediate

0~1000

Set AI_1 channel analog dead zone value

mv

20

P5-8

AI_2 zero drift

During running

Immediate

-500~500

Automatic calibration zero drift value inside the driver

mv

0

P5-9

Analog 10V for speed value

At stop

Immediate

1000~4500

Set the speed value corresponding to analog 10V

rpm

3000

P5-10

Analog 10V for torque value

At stop

Immediate

0~3000

Set the torque value corresponding to analog 10V

0.1%

1000

Code

Parameter Name

Property

Effective

Time

Range

Function

Unit

Default

P4-4

Torque filter time constant

During running

Immediate

10~2500

When [Auto-tuning mode] is set as 1, or 2, this parameter is set automatically

0.01

0.5

Take the analog voltage signal outputs by the host controller or other equipment as a speed reference.

Operation flowchart of setting torque reference by analog voltage:

6.3 Torque Control Mode_html_ef2192af77e6a43.jpg

flowchart of setting torque reference by analog voltage

Zero drift: value of the servo drive sampling voltage relative to GND when the input voltage of the analog channel is zero

Offset: input voltage value of the analog channel when the sampling voltage is zero after zero drift correction

Dead zone: input voltage range of the analog channel when the sampling voltage is zero

6.3 Torque Control Mode_html_36f93e692c0b4cfe.jpg

                                 Analog signal waveform after-offset

After completing the correct settings, user could view the input voltage values of AI_1 and AI_2 through [U0-21] and [U0-22]

Relevant function codes:

Torque Reference Filter

In the torque mode, the servo drive could realize low-pass filtering of the torque command, which reduces the vibration of the servo motor.

Relevant function codes:

6.3 Torque Control Mode_html_7d09455d975ba974.jpg

Diagram of torque reference first-order filter

If the setting value of the filter time constant is too large, the responsiveness would be reduced. Please set it while confirming the responsiveness.

Torque Reference Limit

When the absolute value of the torque reference input from the host controller or output by the speed regulator is larger than the absolute value of the torque reference limit, the actual torque reference of the servo drive is restricted to the torque reference limit. Otherwise, the torque reference input from the host controller or output by the speed regulator is used.

Only one torque reference limit is valid at a moment. Both positive and negative torque limits does not exceed the maximum torques of the servo drive and motor and ±300.0% of the rated torque.

6.3 Torque Control Mode_html_13fea7aee44e606e.jpg

                           Torque setting and limit

Torque Limit Source

Code

Parameter Name

Property

Effective

Time

Range

Function

Unit

Default

P1-14

Torque limit source

At stop

Immediate

0~1

0: Internal value

1: AI_2 analog input

-

0

The torque limit source is set in[P1-14]. After the torque limit is set, the servo drive torque reference is restricted to be within the torque limit. After the torque reference reaches the limit, the motor runs according to the torque limit. The torque limit must be set according to the load conditions. If the setting is very small, it may cause longer acceleration/decelleration time of the motor, and the actual motor speed may not reach the required value at constant speed running.

Relevant code:

When [P1-14]= 0: internal torque limit

The torque reference limit value is determined by the internal function codes [P1-15] and [P1-16]

Relevant code:

Code

Parameter Name

Property

Effective

Time

Range

Function

Unit

Default

P1-15

Forward rotation torque limit

during

Immediate

0~3000

When [P1-14] selects internal torque limit, this function code value is used as the forward torque limit value

0.1%

3000

P1-16

Reverse torque limit

during

Immediate

0~3000

When [P1-14] selects internal torque limit, this function code value is used as the reverse torque limit value

0.1%

3000

Torque Limit DO Signal

When the torque reference reaches the torque limit value, the driver outputs a torque limit signal (138-T-LIMIT torque limit) to the host controller and determines the DO terminal logic.

Relevant code:

CodeParameter NameProperty

Effective

Time

RangeFunctionUnitDefault
P6-26DO_1 function selection During runningPower on again128~142138-T-LIMIT torque limit-138

Torque related DO output function

The feedback value of the torque reference is compared with different thresholds, and the DO signal could be output to the host controller to use. Assign the DO terminals of the servo drive to different functions and set the valid logic.

Torch reach signal

6.3 Torque Control Mode_html_9354fe306cbd5794.jpg

                                            Torch reach signal waveform

Relevant function code:

Code

Parameter Name

Property

Effective

Time

Range

Function

Unit

Default

P5-20

Torque reached threshold

During running

Immediate

0~300

The torque reached threshold needs to be used in conjunction with [torque reached hysteresis value]:

When the actual torque reaches [torque reached threshold] + [torque reaches hysteresis], the torque reached DO becomes effective.

When the actual torque decreases below [Torque reached threshold] + [Torque reached hysteresis], the torque reached DO becomes invalid.

%

100

P5-21

Torque reached hysteresis

During running

Immediate

10~20

[Torque reached hysteresis value] Need to be used together with [Torque reached threshold]

%

10

P6-26

DO_1 function selection

During running

Immediate

128~142

138-T-COIN Torch reach

-

138