The following diagram represents the system:
The system input (ref or reference is zero). And actually the goal of the controller is to maintain the output of the system at zero.
In this system, there are also disturbance and noises. The disturbance has the shape of roughly a ramp, however by nature more like random events. The noises are band limited with bandwidth around 10Hz.
So the controller strives to compensate the influence from disturbance while get rid of noises.
As the noises are from sensors and I add a filter before the controller.
My questions are:
I was using simple FIR filters. The filter wait for, say, 5 seconds to get a batch of data and process them and pass the output to controller. The the controller controlls at 0.2Hz.
However, the bandwidth of 0.2Hz still brings too much noise to the system. If the controller waits 20 seconds for FIR, the system will be too slow. I was advised to use IIR, since it is online, instead of FIR for the filter to further reduce noises.
My question is: since IIR contains information of the past measurements, would the controller output still be accurate? It is supposed to adjust only for current errors! IIR brings past errors to the system!
Any other advice to reduce the noises further? Thanks!