Design of adaptive digital PID controllers incorporating linear quadratic compensators

The problem of loss of co-primeness in recursively identified ARMA models is discussed, and its impact on a large class of multivariable pole-assignment controllers is elucidated. On this basis, an adaptive digital controller is proposed based on a multivariable PID controller incorporating an inner-loop linear quadratic compensator. This control-law circumvents the problems which can be experienced, due to loss of co-primeness of the identified ARMA model, using the adaptive PID controller incorporating inner-loop pole-assignment as proposed by B. Porter and C.L. Body (1989). The effectiveness of such an adaptive digital controller is illustrated by designing an adaptive set-point tracking controller for the F-16 aircraft in a flight condition for which this aircraft is open-loop unstable