Study On Model-free Adaptive Vector Control Strategy Of Propulsion Motor In Dynamic Positioning System

The dynamic positioning system is the key driving device of marine intelligent vehicles.However,the previous control algorithms are still focused on the trajectory tracking control of the dynamic positioning system,and the complex nonlinear dynamics characteristics of the propulsion system have not been covered.In recent years,the AC technology of propulsion motor has been developed rapidly,and the internal structure of the propeller are becoming more and more complex.As the main propulsion device of the ship dynamic positioning system,the podded propulsion control system needs to overcome the influence of the complex dynamic characteristics of the propeller,and convert the power of the operating ship into thrust in order to realize the tracking control for the dynamic positioning.When the ship dynamic positioning system is manoeuvring at sea,it not only has to face the uncertainty of model parameters and the disturbance of its own noise,but also has to solve the problem of the influence of external disturbance on the propulsion system.In this paper,the model-free adaptive vector control strategy of propulsion motor in dynamic positioning system is studied considering the uncertain factors such as the complex nonlinear dynamic characteristics of propulsion system and the disturbance effect.The significant contributions are as follows1.Considering the complex nonlinear dynamic characteristics of the propeller in dynamic positioning system,the method of combining PI control and model-free adaptive control in the propulsion motor vector control system is studied,and the control effects of PI vector control scheme and model-free adaptive vector control scheme are compared.The feasibility of two propulsion motor control schemes are verified by simulation experiments.2.A cascade model-free adaptive vector control method is proposed to improve the control accuracy of propulsion motor due to noise generated by propeller during hull vibration.The model-free adaptive control algorithm is utilized in the outer speed loop and the inner current loop to construct a new control method for the inner and outer loops,so as to suppress the influence of noise effectively and improve the control accuracy and response speed of the control system.3.The model-free adaptive sliding mode vector control system for propulsion motor is proposed for solving the uncertainty influence problem of the propulsion motor speed control which caused by the uncertainty propeller load by introducing sliding mode observer to observe the load disturbance that combining the model-free adaptive control,sliding mode control and vector control system.The robust performance of the dynamic positioning propulsion motor control system can be improved by the proposed method.4.The anti-disturbance performance of model-free adaptive sliding mode vector control system is researched for the unknown disturbance of load and measurement disturbance in the propulsion control system which leading to the problem of frequent action for the controller.The simulation experiment are compared with PI vector control system,and the effectiveness of the control scheme for anti-disturbance is verified,the reference value for ship application is provided.