I am trying to control the diameter of a plastic bubble by controlling the speed of an outlet blower. There is an inlet blower and outlet. The inlet blower is fixed by the operator - manually. We measure the bubble diameter using ultrasonic sensors. The measurement is quite noisy due to fluctuations of the bubble.

I have been trying to research PID algorithms to do the control. I don't quite understand how they will cope with the measurement errors and also the process lag.

Any help greatly appreciated,
Michael.

 

Use a filter to reduce the noisy input signal. The filter should hold the last measured value for a period of time until a new measured value sustains beyond the filter period, say 1 - 3 seconds.

Since this filter will introduce more dead time into the control you may want to adjust your Reset (Integral) Time up, accordingly.

Consider running the controller in PI mode only or by adjusting the Derivative Time to zero. Derivative action may counteract noisy process conditions only to introduce more error to otherwise steady-state operations.