12.3 Nyquist Diagram In general, we are interested in a system with two terms G(s)-plant TF and H(s)-controller tF: CH(SHG(S) G(S) H(S) In both cases the stability is determined by the characteristic equation 1+G(s)H(S)=0 Thus we will be plotting the“ open loop TF”GsH(s)
12.3 Nyquist Diagram
In the most general case the open loop tf has the form G(SH(S) K∏+(+(25/,)+) +s+(2/0)s+/0) +slk We will first develop rules for plotting the individual factors in this expression, and later combine those in a single plot Case l: G(SH(s=K (0)H(0)=k Re q=∠K=0
Im Re 0 K