when iam using analog feedback for PCI7342 my velocity given by card is not correct

[gopi]

Hai
Iam using PCI7342 card for my motion control application. Iam givinng analog feed back as position. My maximum count is 4095 and minimum count is 0. Iam controlling my servo motor with external control and ginving position feedback to the card. In this condition in MAX iam able to read my popsition perfectly but whatever the velocity it is showing is not correct i.e. it is varying randomly. Even though iam rotating my motor at fixed speed and position reading is very uniform it is gving random readings in velocity. If any one knows please explain me what could be the reason.

One more doubt is iam having motion assistant software with me. as i previously mentioned my maximum count is 4095 and minimum count is zero. I want to rotate my motor at a maximum speed of 100counts/sec. in motion assistant acceleration and deacceleration are not allowed to program beyond 4000counts/sec. Why? if any one know please show me a way to feed some lesser value.

[Irene B]

Hi gopi,

I believe there is another India applications engineer who is working on your exact issue and according to the notes, the motor is now able to be controlled at the specified counts/sec.  If you are not the same customer, just let me know and I will contact the other applications engineer to find out what work they did on the Motion system.  Otherwise, please do respond back with additional information about your motor, how the velocity profile differs from expected (screenshots would be helpful), how many axes you are controlling, what version of NI-Motion you are using, and what type of move (contoured, PVT, or trapezoidal/s-curve).

Thanks,
Irene Chow
National Instruments
Applications Engineer

[gopi]

Hi Irene Chow

Thank you for response. Yes Mr Sujeeth of NI India is working on my application. My application is little bit different to the usual applications. I want to control the movement of an antenna with NI motion control card. Iam having a 1900RPM servo AC motor and iam having 450:1 gearing ratio. So my antenna will be rotating at a maximum speed of 4RPM.
When iam loading velocity iam able to load whatever the value iwant. But in acceleration and deacceleration values are limited to minimum of 4000rpm. Wheras my motor is rotating at a maximum speed of 400 counts/sec. is there any way of reducing still slow counts/sec.
Eventhough iam able to raotate my motor at required counts/sec velocity showing is not correct. and the moment is very jerky because of which my gear wheels are getting effected. I want to smoothen the DAC output. what are all the parameters i need to paly with in control loop.
Is there any way to control the dac output at fixed voltage level with specified acceleration and deacceleration atleast in velocity mode so that i can minimize variations in DAC voltage i.e. may be bypassing PID loop.

Sujeeth had sent me links for tuning servo motor, i will go through them and i will try. if anyone has already faced this problem please suggest me the solution.

Gopi Chand