Why is the resulting amplitude smaller than the desired one?

[bbl]

I'm using the hardwares listed below and the example labview program downloaded from ni website (i.e. Analog Feedback Automatic), but it couldn't reach the voltage that I inputted in the front panel no matter how long I let it run or how fast the slew rate is.  I actually checked the analog output from the motion interface, it seems that the output stays the same with no increment even though the desired voltage hasn't been reached.  I've made sure the setting in MAX, the primary feedback is to AI1 and the primary output is to AO1(ie. ADChannel 1 and DAChannel 1).

Acutuator->Load Cell-->Strain Gage Conditioner-->Universal Motion Interface -->Servo Amplifier connected to FW-7344 Motion Controller (--->back to Actuator).

Thanks for your attention!

[Jochen]

This could be a tuning issue. E. g. if you only use Kp and leave Kd = Ki = 0 the control loop won't be able to eliminate the complete deviation. You should experiment with Kd and especially with Ki which eliminates deviations over the time by integrating them.

Best regards,

Jochen Klier
National Instruments Germany