Rudder Roll Stabilization of Ships Subject to Input Rate Saturation Using a Gain Scheduled Control Law

This paper describes a new gain scheduling algorithm for handeling the problem of hard nonlinearities like input rate and magnitude saturations. The proposed algorithm was originally designed for stabilization of integrator chains with input rate saturation. Here it is shown that the gain scheduler also is eeective for rudder roll control systems. The approach is to reduce the controller gains of a linear controller on-line in an computational eeective way. A simulation study comparing the algorithm with the Automatic Gain Controller (AGC) of Van der Klugt (1987) is included. Abstract. This paper describes a new gain scheduling algorithm for handeling the problem of hard nonlinearities like input rate and magnitude saturations. The proposed algorithm was originally designed for stabilization of integrator chains with input rate saturation. Here it is shown that the gain scheduler also is eeective for rudder roll control systems. The approach is to reduce the controller gains of a linear controller on-line in an computational eeective way. A simulation study comparing the algorithm with the Automatic Gain Controller (AGC) of Van der Klugt (1987) is included. 1. INTRODUCTION Besides controlling the heading of a ship it is often desirable to reduce the rolling motion induced by waves. The main reasons for introducing a roll damping system are to prevent cargo damage and to increase crew eeectiveness and passenger comfort. Criteria for the maximum roll angle are given in Faltinsen (1990), and they suggest that the root mean square of the roll angle should be less than 6 degrees for light manual work and 3 degrees for intellectual work. There are several approaches that can be used to reduce the roll motion, e.g. bilge keels, anti-rolling tanks, n stabilizers and rudder roll stabilizers (RRS). For a detailed discussion of the different roll stabilizers, see Fossen (1994) and the references therein. Here we discuss the rudder roll damping approach which is attractive, since existing equipment can be used and thus it is a relative inexpensive solution. The drawbacks of a RRS are the requirement of a high-speed steering machine and the ineeectiveness of the rudder at low ship speed. Successful implementation of full-scale RRS system were rst reported in Baitis (1980) and later in e.g. KK allstrr om (1987) and Van Amerongen et al. (1990). A nonlinear stability analysis of ships in coupled sway, roll and yaw is given by Fossen and Lauvdal (1994), whereas the design of a …