Extremal pole placement in control systems with a low order controller

We develop an optimizational approach to the design of linear control systems with a low order controller. The objective function is given by the right boundary of the location of poles in the closed-loop system, which depends on the values of controller parameters. We specify the types of mutual pole placements (root diagrams) corresponding to singular manifolds of such functions in the space of parameters and, in particular, their critical points. We establish the exact number of critical root diagrams depending on the dimension of the parameter space. With the example of finding a stabilizing control for a triple mathematical pendulum, we demonstrate the algebraic approach to finding the global minimum of the objective function.