I am using the PID Tuner for the PID Controller Block in Simulink. I am particularly interested in the output disturbance BODE plot. I am trying to achieve an acceptable output disturbance with the follow requirements:
1. Attenuation of at least 10 dB with frequencies less than 0.5 Hz
2. Flat response (0 dB) at higher frequencies with no overshoot.
By raising the bandwidth of the controller, I am able to achieve the appropriate attenuation at < 0.5 Hz, but I am getting a nasty overshoot at 4 Hz, which is unacceptable. Lowering the bandwidth removes the overshoot but then I have poor attenuation.
I used the System Identification toolbox to model the plant using input/output data from a frequency response. The input was a chirp signal (0.1 - 3 Hz over 10 seconds) and the output was sampled at 20 Hz (fastest possible sampling rate).
The plant: G = (4.1s + 59.5)/(s^2 + 34.1s + 385.7) * exp(-0.5s)
Other than adjusting bandwidth and phase margin, is there anything else I can try to achieve both of these requirements?