A Backstepping Approach to Ship Course Control

Abstract

As an object of course control, the ship is characterised by a nonlinear function describing static manoeuvring characteristics that reflect the steady-state relation between the rudder deflection and the rate of turn of the hull. One of the methods which can be used for designing a nonlinear ship course controller is the backstepping method. It is used here for designing two configurations of nonlinear controllers, which are then applied to ship course control. The parameters of the obtained nonlinear control structures are tuned to optimise the operation of the control system. The optimisation is performed using genetic algorithms. The quality of operation of the designed control algorithms is checked in simulation tests performed on the mathematical model of a tanker. In order to obtain reference results to be used for comparison with those recorded for nonlinear controllers designed using the backstepping method, a control system with the PD controller is examined as well.

Designing a ship course controller by applying the adaptive backstepping method

“…Our results are a continuation of studies initiated earlier (Witkowska et al, 2007;Witkowska and Smierzchalski, 2009).…”

“…Genetic operations comprised classical selection, crossover and mutation. For more information about genetic operations, see the work of Witkowska et al (2007).…”

“…When designing the control law, we assume that we have precise information on the object, i.e., we consider the vector of parameters θ and the parameter c to be known in the adopted ship model. Then the ship course control law can be derived using the classical backstepping method, as was discussed in detail by Witkowska et al (2007), as well as Witkowska and Smierzchalski (2009).…”

“…For the variables and stabilizing functions defined as above, the derivatives of the components of the vector z take the following form (Witkowska et al, 2007;Witkowska and Smierzchalski, 2009):…”

Fault monitoring and fault recovery control for position-moored vessels

“…However, for certain faults, this controller cannot provide sufficiently good control. The nonlinear backstepping technique applied into the offshore vessel is found in the work of Witkowska et al (2007), and further research about sliding mode control on marine vessels is found in that by Tomera (2010).…”