velocity override command not working

[Nandkumar]

I am using ni pci-7334 stepper motion control board.
flex_set_velocity_override command is not working in VB6. the selected axis gets killed?

Please reply.

Regards

[JB]

With LabVIEW, there is a function called Load Velocity Override.flx. It works without any problem. However the percentage of the override is limited between 0 to 150%. This is probably the same with flex_set_velocity_override in VB and a value out of these limits may be the source of the problem. Just an idea...

[Nandkumar]

I am using NI-PCI7334 card with Visual Basic.
I am giving command as follows

status = flex_load_velocity_override(boardID%,NIMC_AXIS1,100,&hFF)

After the command is executed the selected axis, vector space stops moving ( Gets Killed ). The state continues until flex_find_reference command.

If possible please send sample coding

Regards,
Nandkumar

[DJ_L.]

Hey Nandkumar,

First, it should be stated that you can not load velocity override on contouring moves, so if you are doing contouring moves, this function (flex_set_velocity_override) will not work properly.
If you are not doing a contour move, then there might be something else going on. Can you please provide some more information about your code, like what else you are doing before and/or after you call this function? Have you tried to use this function in a more simple application with just one axis? Can you provide more information about your overall set up, like how many axes are you using and what version of the driver are you using? Please add any more information that you think might help.

Thanks,

DJ
Applications Engineer
National Instruments

[Nandkumar]

dear DJ

I am surprised to know that override will not work in countouring, as it is expected to be used mostely in contouring moves.

Anyway i also have tried same command on single axis but still it is killing the selected axis.

Additionaly I changed override setting on MAX and it is working OK in MAX,

I am expecting the command to function while moving & not moving as it is mentained in manual that this command is nonbuffered & acts immadiately.

I am using VB6.0 for programming in Windows XP. The project uses Four Stepper axis control in closed loop. & one axis in Open loop which is controlled by additional DAQ (pci6601) card.

Everything except above is working perfectly OK.

Regards.
nandkumar

[DJ_L.]

Hey Nandkumar,

The velocity of a contoured move is not determined by the velocity parameter but by the distance between the position points in the contour array. Thus, in this case, the velocity parameter has no effect and flex_load_velocity_override() doesn't change the velocity of contoured moves. The velocity override command does work with straight line moves, arc moves, and other moves, just not with contouring moves, because the contour moves set their velocities in a different way. Please refer to the following discussion forum link Using velocity override in absolute contouring mode for more information on why this function doesn't work with contouring moves. Also, in this discussion forum there is somewhat of a work around.

I hope this helps. Please let me know if you have any further questions on this. Thanks and have a great day.

Regards,
DJ
Applications Engineer
National Instruments