Research On Heave Motion Control Of Surface Effect Ships

A surface effect ship(SES) is a high performance vessel with high speed, excellent sea-keeping, high comfort and ride quality. The SES is widely used in offshore activities such as military operations, rescue activities, resources exploitation. However, heave motion of the SES can be easily influenced by wave while an SES at dock is used to transfer personnel or cargo to another ship or float platform. The heave motion control problem involves parameters’uncertainties and external disturbance. Therefore, it is necessary to control the heave motion actively to damp the amplitude of the heave motion to provide a safer environment for transfer.Sliding mode control which has extremely strong robustness can guarantee the system not be influenced by parameter perturbation and external disturbance. It provides an effective way to control heave motion of SES. This thesis’ main work is that: considering the heave motion control problem of surface effect ships with parameter uncertainties and time-variant wave disturbance, firstly, adaptive technique is applied to design adaptive laws to estimate the bound of compound disturbance including parameter uncertainties and time-variant wave disturbance. Based on the estimate, a robust adaptive sliding mode control law is designed to control the heave motion. The boundary layer method is introduced to eliminate the chattering phenomenon. Secondly, a sliding mode control law is designed with a disturbance observer which is proposed to estimate the compound disturbance to control the heave motion. Considering parameters of SES heave motion mathematical model are all unknown, a model-free sliding mode control law is designed with two radial basis function neural networks which are employed to approximate the equivalent control term of sliding mode control and the unknown wave disturbance. Since the outputs of the two neural networks are not able to approximate the equivalent control term and disturbance accurately, an error estimator is used to compensate the sum of the approximation errors in the control law design.At last, simulations on a Norwegian Navy’s surface effect ship are carried out and the simulation results illustrate the effectiveness of the three proposed control laws, respectively.