Research On Stabilization Control Of Three-Degree-of-Freedom Ship-borne Stabilization Platform

Ships move in 6 degrees of freedom(DOF)including roll,pitch,yaw,sway,pitch and heave due to the ocean environment,which will seriously affect the safe operation of ship-borne equipment.The yaw,sway and surge of ships can be suppressed by dynamic positioning systems.The roll,pitch and heave of ships can be compensated using ship-borne stabilization platforms to isolate the effect of ships' motion on ship-borne equipment.However,ship-borne stabilization platforms are nonlinear and sub.ject to unmodeled dynamics and unknown time-varying environmental disturbances.Therefore,the research on stabilization control of ship-borne stabilization platforms has important theoretical significance and practical application value.In this paper,a dynamic model of 3 DOF ship-borne stabilization platforms is established applying Newton-Euler method.Then,in the presence of the unmodeled dynamics and unknown external environment disturbances caused by the wave-induced ship motion of 3 DOF ship-borne stabilization platforms,an extended state observer(ESO)is designed to online estimate the total disturbance combined by unmodeled dynamics and unknown external environment disturbance.Based on the above,a PID control law of the ship-borne stabilization platform is designed,the estimate of ESO is introduced into the PID control law to compensate the total disturbance for the stabilization control of the 3 DOF ship-borne stabilization platform.Further,a new finite-time robust control scheme is proposed by combining non-singular fast terminal sliding mode control with the finite-time ESO for the stabilization control of the 3 DOF ship-borne stabilization platform,where however,there exists the chattering problem of control input.To overcome this problem,the super twisting sliding mode method is employed to weaken the chattering of non-singular fast-terminal sliding mode method,and then a new finite-time robust control scheme is proposed combining the super twisting sliding mode control with the finite-time super twisting ESO for the stabilization control of the 3 DOF ship-borne stabilization platform.The simulation model of the ship-borne stabilization platform is established by MATLAB/Simulink.Simulations on a stabilization platform are carried out to demonstrate the effectiveness of the proposed control laws.