Adaptive control of nonminimum phase systems subject to unknown bounded disturbances

This paper presents a robust adaptive pole placement control scheme for continuous-time systems with bounded disturbances. The system may possibly be nonminimum phase and unstable. It is shown that for arbitrary bounded disturbances, a global asymptotical bounded-input/bounded-output (BIBO) stability is established through pole placement techniques without either introducing persistent excitation probing signals into the system or assuming any a priori knowledge on the plant parameters. Moreover, the disturbance upper bound is not assumed to be known. The system order is the only a priori knowledge required on the plant. The adaptive control law is free from singularities in the sense that the estimated plant model is always controllable.