Application of the root locus technique to the closed-loop SO/sub 2/ pacemaker-cardiovascular system

A previously developed nonlinear model of the pacemaker-cardiovascular system (G.F. Inbar et al. ibid., vol.35, p.679-90, 1988) is converted to a linear model using a Taylor´s series expansion procedure. As the expansion is about a steady-state value, the linear model operates at specified exercise levels. Using the linear forward-loop transfer function a root locus plot of the closed-loop s-plane poles is obtained as a function of pacemaker controller gain. The unique feature of this root locus algorithm is that it allows for a time delay in the forward-loop transfer function. The simulation results presented show that the dynamics of the nonlinear model step responses correspond to the predicted performance from the location of the poles in the root locus plot.