Adaptive/self-tuning PID control by frequency loop-shaping

Addresses issues arising in the online adaptation of PID controller parameters. With frequency loop-shaping principles as the underlying controller design approach, the PID parameter adaptation can be performed directly by minimizing a suitable estimation error with standard least-squares algorithms. A variant of such an algorithm is also proposed in an effort to approximate the minimization of the H-infinity norm of the error operator. A numerical example is used to illustrate the implementation of the algorithm