Output feedback pole placement in the design of suboptimal linear quadratic regulators†

A design oriented methodology is presented for the construction of low-order, suboptimal, output feedback compensators. The design is suboptimal in the sense that it retains an l-dimensional eigenspace from a reference optimal state-feedback linear quadratic regulator problem. If r is the number of outputs, then for fixed l > r, it is known that the design requires a dynamic compensator of dimension l — r. The parameters of the compensator are determined by the solution of an associated output feedback pole placement problem. Using iterative, dyadic pole placement, a procedure is given which determines the solution of this problem, without a priori assumptions on the dimension of the compensator. The design is also extended to the class of stabilizable systems, and the resulting compensator is shown to possess a separation property.