NI-9516 Drive Command

[Microtec]

Hi,

I'd like to use a NI-9516 (Servo Module) through the SCAN interface, to drive my "servo driver".

My "servo driver" have three control inputs :

- A position control input (square stepper signal)

- A Velocity control input (+ / - 10 Volts)

- A Torque control input (+ / - 10 Volts)

I want to drive my "Servo Driver" in "Velocity" mode with NI-9516 module.

I saw in the documentation that only a torque control was possible (Drive Command output), I'm right ?

Is there a solution to control my "servo drive" in "Velocity" mode with NI-9516 module in SCAN mode ?

Thanks for your answer.

[Microtec]

Hi,

I'd like to use a NI-9516 (Servo Module) through the SCAN interface, to drive my "servo driver".

My "servo driver" have three control inputs :

- A position control input (square stepper signal)

- A Velocity control input (+ / - 10 Volts)

- A Torque control input (+ / - 10 Volts)

I want to drive my "Servo Driver" in "Velocity" mode with NI-9516 module.

I saw in the documentation that only a torque control was possible (Drive Command output), I'm right ?

Is there a solution to control my "servo drive" in "Velocity" mode with NI-9516 module in SCAN mode ?

[Microtec]

Thanks for your answer.

[PaulRB]

Hi Christophe,

You can run your servo drive in velocity mode when using the 9516. I know some people who think it is easier to tune the system when the velocity loop is running on the drive; my personal opinion is that it is easier to tune the system when the drive is in torque mode. You can try it both ways and see what works for you.

When you change the drive mode from torque to velocity, you will have to change the tuning values for the 9516. However, you should not have to make any other changes.

Can you tell me why you want to run the drive in velocity mode instead of torque mode?

Thanks,

[Microtec]

Hi Paul,

Thank you for your answers.

- For more information, we want to control a brushless motor in position with a one of three possible commands: Position (pulse), Speed (+ / - 10V) or Torque (+ / - 10V).

Can you tell me why you want to run the drive in velocity mode instead of torque mode?

=> I prefer to drive motor in "Velocity Mode", because I never drive motor in "Torque Mode".

- Can you tell me what is the advantage of a control in  "couple mode" over a "speed mode"?

- Is the block "Drive Command" only serves to condition/scale the analog output signal?

- Is the (position loop) functionality is to simply get measurement and commands, and generate analog output (drive command), according to the "position loop" scheme?

Thanks for your help,

Christophe B.

[PaulRB · Accepted solution]

Hi Christophe,

With the 9516, you will only be able to control the drive in torque or velocity mode; you need the 9512 to control the drive in position mode. 

Can you tell me what is the advantage of a control in  "couple mode" over a "speed mode"?

I'm not sure what you mean by 'couple mode'. If you mean torque mode, then there isn't really a difference between running the drive in torque mode or velocity mode. The only thing that changes is the location of the velocity loop. You may find that one of the two options makes tuning the system easier (I prefer torque mode but I know other people who have found velocity mode easier to tune). You also may find that using the drive in velocity mode will allow you to better utilize the peak torque of the drive.

Is the block "Drive Command" only serves to condition/scale the analog output signal?

You are correct. For most drives I've seen, the default values work fine. However, I have also seen some drives that only take a 0-10V drive command. In this case, you would change the negative torque limit to be 0.

Is the (position loop) functionality is to simply get measurement and commands, and generate analog output (drive command), according to the "position loop" scheme?

You are correct. The position loop gets a position setpoint from SoftMotion and feedback from an encoder and then uses a PID control loop to get a drive command signal. That drive command signal will either be a torque command (if the drive is in torque mode) or a velocity command (if the drive is in velocity mode).

Thanks,

[Microtec]

Hi Paul,

Thank you for your help on NI-9516 drive command.

Best Regards,

Christophe B.

[new_2_NI007]

how to perform a speed control of a servomotor in control system and design module, while using the drive command output of ni-9516

[PaulRB]

Can you explain what you mean by speed control? SoftMotion allows you to do pseudo speed control by doing a velocity move. Take a look at the Axis Velocity Override shipping example for how to do this.

Thanks,

[new_2_NI007]

I want to the implement the control diagram as attached in the .jpg image file, pfreferrably using control design &simulation module of labview. I have all the required software modules including real time module & NI-soft motion module. In the hardware i have a cRIO alongwith a NI-9516 c-series drive interface module, an AKD servodrive & an AKM servomotor