The design of autopilots using the pseudo-derivative feedback algorithm

Abstract

This paper is concerned with a simple method for the design of autopilots for ships. The method used is based on an automatic-control-design technique due to Phelan [1,2], based on physical arguments, and termed pseudo-derivative feedback control. When properly tuned (a comparatively easy task) such controllers are known to possess good transient behaviour when their set-point is altered and to be extremely good at alleviating output deviations due to step-changes imposed by external loads disturbing the system. This latter property appears to carry, over when the disturbances are sinusoidal in form and, by implication, stochastic in form. Such behaviour is achieved generally with modest amounts of final control-element (e.g. rudder) activity. Evaluation of the autopilot design has been done by simulation using mathematical models of the steering dynamics of a Mariner Class vessel. The evidence to date is that such autopilots may be expected to exhibit robust properties and warrant further detahed investigation.