Can i use NI-7358 to implement a hybrid position force/torque control system?

[wlan]

Hello!

I have a manipulator with 5 joints. I will use the NI-7358 motion control card to control them. In my application i also want to implement a force control system by using a force/torque sensor.

Question:

Is it possible to use the NI-7358 to implement a force/torque control system? Can i use the analog input channel of the NI-7358 as the force feedback? How is the torque exactly controlled with this card? Do I need buy other hardware to realize the hybrid force/position control?

Thanks a lot!

WLAN

[Jochen]

Yes, you can use the analog inputs as feedback inputs for force control. The analog inputs of the 7358 provide 16-bit resolution. Thus you can resolve your feedback in 2^16 steps.  Controlling force works exactly like controlling positions. That means you use the same functions or vis to control the force as you would do for controlling the position. Please have a look at the attached document which explains how to do the correct settings in MAX and how to "translate" the terms of position control to the terms of force control.

I hope that helps,

Jochen Klier
National Instruments Germany

[wlan]

thanks for your answer, Jochen!

in the robotics, the end effector forces are related to the joint torques by the transpose of the manipulator Jacobian.

So i want to set the should-forces by giving the torques for all motors, i get the is-forces from a force-moment-sensor (analog inputs).

but i did not find how can i use the NI-7358 to control the torques for my motors? can you help me?

thanks!

WLAN 

[wlan]

i wanted to ask the people in "Machine Vision" group this question, but they have not answered yet, do you know that?

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recently i found this mini-camera (TransChip's CoderCam TC5740), its size and resolution should be ok for my vision-system.

see: http://www.transchip.com/content.aspx?id=49

Question:

which card can/must i use to acquire and process the images from this camera (perhaps two cameras for stereo-effect)?

thanks for your replies!

WLAN

[Jochen]

WLAN,

If you want to control the torque of the motor you will need an analog feedback signal that corresponds to the torque of each axis. If these signals are available you will be able to use the method that I have described in my last reply.
For the case that you only get the feedback from the force-moment-sensor(s) that return the effecitve forces caused by the joints the 7358 can't do the job as there is no way to implement the algorithms on the board that are needed to calculate the command voltages for the individual axes.

In the latter case you probably won't be able to use an out-of-the-box solution. NI provides other solutions based on LabVIEW Real-Time, LabVIEW FPGA and the NI SoftMotion Development Module to design your own motion control solution. Please look at this link for more information.

Jochen Klier
National Instruments Germany

[Jochen]

The device you are talking about is not a ready to use camera but a camera module with that should be implemented in some external circuitry. I haven't found out what protocol is used for the parallel and the serial data channel of the module. You might be able to use a PCI-1422 board but this is typically used to acquire uncompressed images. Your camera seems to create jpg images. Another option could be a general purpose high-speed digital I/O board like the PCI-6534 but in this case you will have to do the data handling to reconstruct the image by your own.

My best advice is not to use this module but a real camera with a standardized output (e. g. IEEE-1394, camera link or analog (e. g. CCIR, NTSC, PAL,...)). This will allow you to use off-the-shelf solutions. Please have a look at this link for further information.

Best regards,

Jochen Klier
National Instruments Germany

[wlan]

thank for your answers Jochen!

You mean that it is impossible to set the torque-value for the individual motors? What did you mean torque-control then? To keep the actual torque? I did not completely understand it...

Can you help me?

WLAN

[Jochen]

WLAN,

you can control the torque of each individual axis but you need an analog torque feedback signal from each axis to do so. If I understand you correctly you don't have these signals but only a signal of the resulting forces. In this case you can't use these signals as direct feedback signals as you would need to do some calculations on them in order to take the geometrie of your mechanical setup into account. And as I have already said these calculations can't be run on the 7358.

Jochen Klier
National Instruments Germany

[wlan]

thank you Jochen, i have two ways to get the torque values for each axis:

1. by using a force-sensor on each axis. (direct, very precise)

2. by using the Jacobian of my manipulator structure to calculate the torques (indirect, not precise, maybe correction needed)

do u mean i must  use option "1" as feedback (hardware dependent)? how can i increase or reduce the torque when i use the force-feedback and the NI PCI-7358?

still a question:

the motors that i am using are:

Motor:              3x Faulhaber 3564 024B DC-Servomotor

                         2x Faulhaber 2036 012B DC-Servomotor

Encoder:         1x HEDM 5500 B14

can i use the Faulhaber BLD 5606 http://www.faulhaber.de/zip_pdf/produkte/kat_2000/10_steuerungen/dBLD5603_06.pdf Motor Driver with the NI PCI-7358 together (with UMI)?

Can u take a look?

Thanks for your help!

WLAN

[Jochen]

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@wlan wrote:

thank you Jochen, i have two ways to get the torque values for each axis:

1. by using a force-sensor on each axis. (direct, very precise)

2. by using the Jacobian of my manipulator structure to calculate the torques (indirect, not precise, maybe correction needed)

do u mean i must  use option "1" as feedback (hardware dependent)? (JK: yes, that's the only option with the 7358. The other option will require the use of another approch like LV RT or LV FPGA as discussed before) how can i increase or reduce the torque when i use the force-feedback and the NI PCI-7358? (JK: please refer to the document about analog feedback that I have attached to my first answer. With analog feedback you can set torque values exactly the same way as you set target positions).

still a question:

the motors that i am using are:

Motor:              3x Faulhaber 3564 024B DC-Servomotor

                         2x Faulhaber 2036 012B DC-Servomotor

Encoder:         1x HEDM 5500 B14

can i use the Faulhaber BLD 5606 http://www.faulhaber.de/zip_pdf/produkte/kat_2000/10_steuerungen/dBLD5603_06.pdf Motor Driver with the NI PCI-7358 together (with UMI)?

(JK: The PDF doesn't contain a schematic of the pinout but telling from the table this combination should work. Please make sure that you limit the output voltage of the 7358 to +-5 V as this is the voltage input range for the command input of the BLD 5606. This can be done in MAX)

Can u take a look?

Thanks for your help!

WLAN

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