Problems programing blend move on a PCI7344

[cadet]

I have been trying to generate a blend motion of a 2D movement in a onboard program but the I have not had good results. I started from a simple Multiple vector moves in onboard program written in LabVIEW that I found in the website of NI. I included one blend motion and when I execute the program, this skips the trajectory that includes the blend move. What can i do to include blend moves in a onboard program?

Thanks for your attention,

Alberto

the program from i started is attached

[Jochen]

Hi Alberto,

1. Could you please provide information about the board type and the NI-Motion version?
   
   
2. In your vi you are using Start Motion all the time. For a blended move you need to use Start Motion only for the first move and Blend Motion for all consecutive moves. Waiting for Move Complete does also not work, as this will wait until a move is stopped, but at this point it's already to late to start a new blend operation. Please refer to the shipping examples that show how to implement a sequence of blended moves correctly.
   
   
3. I can't see any advantage why you would like to run blended move operations in an onboard program, instead of a running it on the host PC. Onboard programs don't execute faster than host programs. With today's PC performance, the only reasonable use cases for onboard-programming are additional safety features (e. g. stopping the motor after a torque limit is passed), that need to run independently from the PC.
   Please provide more information why you want to do this. Again: You won't get better performance or better determinism by using onboard programs.
   

Thanks and best regards,

Jochen Klier
National Instruments

[cadet]

Hi Jochen,

Could you please provide information about the board type and the NI-Motion version?

I´m develop an automated platform by means of stepper motors using the PCI 7344 board and the MID-7604. The NI-Motion version is 7.1 and the LabVIEW version is the 8.0.

In your vi you are using Start Motion all the time. For a blended move you need to use Start Motion only for the first move and Blend Motion for all consecutive moves. Waiting for Move Complete does also not work, as this will wait until a move is stopped, but at this point it's already to late to start a new blend operation. Please refer to the shipping examples that show how to implement a sequence of blended moves correctly.

I´m attaching the LabVIEW application that I performed to implement a sequence of blend moves. When I try to execute this application, the following error appears:

·         Error-70006 ocurred at Read Vector Space Position.flx

·         Possible reason: Motion: An invalid axis number or other resource ID (vector space, encoder,I/O port, and so on) was used. If you are using the NI SoftMotion Controller, this error indicates that the resource used in the operation is not configured.

I can't see any advantage why you would like to run blended move operations in an onboard program, instead of a running it on the host PC. Onboard programs don't execute faster than host programs. With today's PC performance, the only reasonable use cases for onboard-programming are additional safety features (e. g. stopping the motor after a torque limit is passed), that need to run independently from the PC.
Please provide more information why you want to do this. Again: You won't get better performance or better determinism by using onboard programs.

I thought that some interruptions of the PC operating system can interrupt the programming sequence, can it happen?

Thanks again and best regards

Alberto

[Jochen]

Alberto,

the reason why you get this error is the fact, that you have wired a wrong resource input of Read Vector Space Position.flx. You should use Vector Space 1 instead of Vector Space Control as input parameter.

In fact blending should work fine in a host program, as long as your moves are not extremely short. Jitter introduced by the OS is not a real problem for blended moves, as the board knows all the parameters and has already received the next blend command, before the first move has stopped. So everything is running in hardware even without an onboard program. If your moves are very short and/or fast, I strongly recommend using contouring instead of blending. Onboard programming shouldn't be necessary in any case.

Best regards,

Jochen