I am controlling the speed of dc shunt motor using labview and DAq card some one help me?

i need to design a pid controller using labview


and the output is controling a circuit that control the speed of the dc motor


i need to make the speed don't change


even if i changed the loadI am controlling the speed of dc shunt motor using labview and DAq card some one help me?
Do you measure the speed?


In that case a feed back loop should be easy to make with Labview:


measure the speed, and *slowly* change the current according to the difference with the requested value.





You can measure the speed by counting light pulses from a light seen through a hole mounted on the motor (or the object your driving with the motor).