How can i blend a lot of very short moves?

[Falco]

Hi
I have the following problem on a gantry system: when i blend subsequent moves i have no problem until the moves are longer than 1 cm each.
Under 1 cm and going down until 1 tenth of a millimiter and below i have the gantry system going like... well my english is not so good but something like microstepping... it is not as fluid as when the steps are of 1cm but it's really nervous and very, very , very slow....
maybe the steps are too close and the 7344 cannot handle them?
i have to reach 1/100 of millimeter step and if someone can direct me in the right way....
Falco

[Jochen]

The frequency you can run blended moves with is limited by the communication speed between the host PC and your 7344. If your moves are too short the host PC can't send the new trajectory data and commands to the board fast enough.

As a solution you should consider using contouring instead. In contouring mode you can download complete or parts of 1D, 2D or 3D contours to the board. Please refer to the shipping contouring examples.

If you have any trouble finding the examples or any further questions please tell me which development environment you are using (LabVIEW, CVI, C,...) and which version of NI-Motion is installed on your PC.

Jochen Klier
NI-Germany

[Falco]

I'm using a PIV 2.0ghz so i think that communication should not be a real problem (but i can check). About the contour mode i have tried but it allway give me a following error and i really don't understand why. I'm using the last ni-motion library (6.1.3) and i don't use flexmotion but the c++ library with visual studio 2003. What I have noted is that i have a 'normal' respond with 1cm step, with 0.5 cm step until 1mm step and then from 0.5mm and below the machine goes very slow and it moves with 'tremour'... it was suggested to me to adjust the pid rate...

[Jochen]

The bottleneck of the communication with the 7344 is not the CPU speed of your PC but the CPU speed on the board. There is a 68331 processor on the board that amongst other tasks manages the communication with the PC. Even if your PC sends data and commands fast enough the 68331 limits the communication speed and there is no way around that issue.

Contouring should still be the solution. If you get following errors adjusting the PID parameters is not a bad suggestion. Can you run a standard example? If this is the case you need to check your contouring data.
In contouring mode the board tries to reach each of position sampling points within a fixed period of time (e. g. 10 ms). In order to generate a smooth acceleration you need to generate an a
rray with continuously increasing distances between consecutive position samples. If you start with too long distances between the samples you will also run into a following error as the motor can't reach the positions within the available time slot.

I hope this helps,

Jochen Klier
NI-Germany