ramping the speed of a step motor while it is running

[lalitha]

I would like to run my step motor at as fast a speed as possible ( considering motor limitations) through my labview program. but I find that a step motor can be started only a low speed and the speed can only be ramped up to higher values after the motor ahs started to run. so how do I implement this program ? can I have 2 porgrams running the step motor simultaneously with the second one having a 'delay until ms' attached to it so that it starts only after the first program stops. I want the step motor to start and run at a low speed for a very small time - maybe 100 ms or less, before I ramp it up. ( again I have ti actually test motor run to see if 100 ms would be enough for the motor to overcome its inertia.)


so is this 100 ms or lower delay possible to be implemented int he method I outlined? or is there a better way to do it ?

thank you
Lalitha.

p.s. I am attaching a copy of my step motor program also.

[Brent_R]

The behivior you are describing is correct for stepper motors. They can only accelerate at a certain rate which is limited by the available torque. If you try to accelerate more quickly, the motor will skip and lose step. I see that you are trying to control the motor with a counter output. This is possible, however the control will not be extremely precise or smooth. You will need to gradually ramp up the pulse frequency at a rate that is suitable for your motor.

The easiest way to accomplish this would be to use a NI 7334 motion controller. With this controller, you can easily specify position, velocity, acceleration, and even jerk. You do not need to calculate the pulse frequency and man
ually ramp up the rate. The board handles all of the calculations automatically and makes programming moves very straightforward.

Regards,

Brent R.
Applications Engineer
National Instruments

[lalitha]

thanks Brent. really appreciate the quick reply,

lalitha.

[Gurdas]

Brent,

I have a similar question which has been posted at:
http://exchange.ni.com/servlet/ProcessRequest?RHIVEID=101&RPAGEID=135&HOID=50650000000800000069EF0000&USEARCHCONTEXT_CATEGORY_0=_30_%24_12_&USEARCHCONTEXT_CATEGORY_S=0&UCATEGORY_0=_30_%24_12_&UCATEGORY_S=0

Could you please look into this?

Thanks,
Gurdas