Servo motor control systems with resonance often create difficult problems for designers because it causes the servo control system to over-shoot and oscillate.
An effective way to compensate for resonance in a servo system is the use of a notch filter in addition to the standard PID servo loop compensation. To understand the operation of a notch filter, note that every resonance is characterized by two parameters: the imaginary and the real part. The imaginary part sets the resonance frequency, whereas the real part sets the damping. The smaller the real part, the stronger the effect of the resonance.
