Design of digital set-point tracking PID controllers for warships

In order to circumvent the need for mathematical models of multivariable plants expressed in either state-space or transfer function matrix form, tunable digital PID controllers were introduced by Porter and Jones (1986). The controller matrices can be directly determined from open-loop tests performed on asymptotically stable plants. However, although such controllers are intrinsically robust, some degradation in closed-loop behaviour inevitably occurs in the case of large plant parameter variations. In order to avoid such performance degradation, adaptive digital PID controllers were therefore introduced by Jones and Porter (1987). Such controllers incorporate fast online recursive identifiers which provide updated step-response matrices for inclusion in control laws with the structure of the earlier controllers. The effectiveness of these controllers is illustrated by examples of tunable and adaptive digital set-point tracking PID controllers for a three-input/three-output dynamically complex warship