Feedback Compensation Using Derivative Signals I - Routh´s Criterion; Root Loci

Most signals used for feedback compensation may be treated mathematically as derivatives of the output signal. The gain associated with each derivative signal alters one or more coefficients of the characteristic equation of the closed-loop system, and may also affect the steady-state accuracy. The Routh test may be used in many simple cases to determine limiting values of the gains. In more complex cases manipulation of the characteristic equation provides a root locus assisting in design of compensation.