New analogue-computer technique for automatic frequency-response locus plotting

A method is given for the automatic plotting of frequency-response loci for systems with poles or zeros in the right- or left-hand side of the s plane. A particular feature of the technique is that it is possible to plot loci for systems having pure time delays, and this is achieved without the necessity of providing a pure time-delay unit. The analogue-computer circuits are such that individual parameters of given transfer functions can readily be varied. Nyquist, Bode or other forms of locus can be plotted. The method can also be used to estimate transfer functions to fit experimentally obtained frequency-response data.