Improved set-points tracking of remotely operated underwater vehicles through a supervised pid control scheme

This paper considers the position control problem of an underwater vehicle used in the exploitation of combustible gas deposits at great water depths. The use of a single, time invariant PID controller may result in an unsatisfactory set-point tracking. To cope with this problem, a globally non-linear regulator given by the connection of a supervisor with a finite family of properly chosen PID controllers is here proposed. Each PID is designed to obtain a specific desired feature of the step response and the supervisor governs the switching among them to obtain an overall time-varying control law yielding a globally satisfactory output behaviour. The switching logic is driven by the numerical values assumed by some suitably defined cost functionals of output prediction errors. The performance of the switched controller so obtained is evaluated by numerical simulations.