Songtao Zhang

Application of H ∞ Control Based on Mixed Sensitivity in the Electro-hydraulic Load Simulator

The electro-hydraulic load simulator is an essential rig for the performance and stability test of aircraft rudder system. Its function is to reproduce, under laboratory conditions, the aerodynamic load of the rudder system. The model of electro-hydraulic load simulator is developed and the affecting factors of extraneous force are determined. To replicate the wide spectrum of aerodynamic load when the load spring stiffness varies within a definite bound, a loading controller is designed with H∞ mixed sensitivity approach. Its solved by the linear matrix inequality algorithm through selecting the suitable weighted functions. Its testified by experiments that the proposed controller can satisfy robust stability and robust performance when the load spring stiffness varies. It also can eliminate extraneous force and improve the passive loading performance with the compensation networks based on the structure invariance principle.

Predictive control and stabilizing effect analysis of controlled passive tank

Controlled passive tank is able to achieve a more perfect stabilizing effect by extending the natural period of water tank with opening/closing the air-valves in accordance with the variation tendency of ships rolling. Two controlling parameters, which are most important, are the closing-time and closing time span. The determination of closing time span has a direct relation with the ships real-time rolling period. By adopting wavelet neural network to predict the ships rolling motion and real-time updating the closing time span of closing valves with the predicted values, meanwhile, real-time analysing the rolling power spectrum is applied before and after anti rolling according to the known input-output relation of anti-rolling tank model coupled with rolling. The paper shows this predictive control method which is more perfect than traditional anti rolling control effect and possess favourably practical value in engineering.

Research on hydrodynamic characteristics of Magnus rotor wing at medium/low speed

Magnus rotor wing is a novel roll reduction device that it generates anti-rolling force through the rotation of the rotor wing installed at the bilge of ship hull to reduce ships roll motion. It is effective at medium/low speed and at zero speed, which is different from fin stabilizer. This paper focuses on the situation that the rotor wing is perpendicular to ship hull. The lift generating and anti-rolling mechanism of Magnus rotor wing are analyzed based on Kutta-Joukowski theorem. The hydrodynamic characteristics of Magnus rotor wing at medium/low speed is achieved using CFD software Fluent. The relationship between the lift/drag of the rotor wing and its rotation speed at a certain sailing speed is analyzed and discussed in details. The numerical simulation results have a good correspondence with theory analysis results. Finally, The conclusion that Magnus rotor wing is more suitable for ship roll stabilization at medium/low speed is achieved.

Application of model predictive control technique for wave piercing catamarans ride control system

Large vertical acceleration induced by sea waves can severely affect the safety and comfort of passengers and crew for wave piercing catamarans(WPC). While WPC sailing in high speeds and high sea states, there are two motions that heave and pitch seriously affect the stability of ship. Under the low sea states and low navigational speeds conditions, the accurate linear ship motions model can be built because of the smaller ship motions. On the contrary, with the increase of the amplitude of the ship motions, the nonlinear characteristic is enhanced. However, the complexity of the non-linear model makes it unattractive for the purpose of designing a controller. As an application, model predictive algorithm is proposed which does not need to establish accurate ship motions model during high navigational speeds and high sea states. The T-foil and two trim flaps stabilizers combination control system is designed with model predictive algorithm controller(MPC). The results from simulations are given to testify the effectiveness of the controller.

Design a software real-time operation platform for wave piercing catamarans motion control using linear quadratic regulator based genetic algorithm

This work presents optimal linear quadratic regulator (LQR) based on genetic algorithm (GA) to solve the two degrees of freedom (2 DoF) motion control problem in head seas for wave piercing catamarans (WPC). The proposed LQR based GA control strategy is to select optimal weighting matrices (Q and R). The seakeeping performance of WPC based on proposed algorithm is challenged because of multi-input multi-output (MIMO) system of uncertain coefficient problems. Besides the kinematical constraint problems of WPC, the external conditions must be considered, like the sea disturbance and the actuators (a T-foil and two flaps) control. Moreover, this paper describes the MATLAB and LabVIEW software plats to simulate the reduction effects of WPC. Finally, the real-time (RT) NI CompactRIO embedded controller is selected to test the effectiveness of the actuators based on proposed techniques. In conclusion, simulation and experimental results prove the correctness of the proposed algorithm. The percentage of heave and pitch reductions are more than 18% in different high speeds and bad sea conditions. And the results also verify the feasibility of NI CompactRIO embedded controller.

Ride control method of wave-piercing catamaran with T-foil and flaps

A T-foil is installed at the bow and two flaps are installed at the stern transom to control the motion of a wave-piercing catamaran. The T-foil and flaps are controlled by a ride controller, so as to smoothen pitch and heave motions of the ship effectively. Firstly, the mathematical model to describe the ships vertical motion is constructed, and its coefficients are established from the Strip Theory. Then, the hydrodynamic characteristics of the T-foil and transom flaps are analyzed by employing CFD methods. A ride control system adopting LQG optimum control theory is designed and motions of a catamaran in different sea states are analyzed. The results show that it is feasible and effective to reduce pitch and heave motions by using the LQG controller.

Stabilizer fin effect on SWATH ship motions and disturbance observer based control design

This paper sets out to explore the stabilizer fin effect on SWATH ship motions. And control design based on disturbance observer are presented. Stabilizer fin effect on ship motions is studied by transforming into foil lift damping. Disturbance observer (DO) is present to study SWATH wave disturbances. It can be used compensate the wave disturbance by fins. In the controller design the optimal controller is designed firstly, then DO is used to achieve feedback compensation of wave disturbances, and to enhance the controller performance of the original controller. System stability is theoretically proved. Also motion induced sickness is presented to directly show the controller effect on human responses. Simulation results prove the method efficiency.

Loop shaping-based robust controlin hydraulic servo system

The swing bench of anti-rolling tanks is a hydraulic servo system achieving position following control, and aims to simulate ship motion. When the bench moves, there is inter-coupling between the two freedoms of rolling and swaying. The sloshing fluid in the tank could generate large disturbing force and torque, which lead to parameter uncertainty in system modeling. These factors will greatly affect the systems precision. The decoupling controlling is achieved by building a coupling motion model for swing benches, then loop shaping control strategy is introduced into controller designing. The simulations show that this system can accurately and rapidly follow up the dynamically inputted rolling and swaying displacement signals, achieve estimation and compensation of disturbance, improve the systems following speed and robustness, and more accurately validate the anti-rolling tanks performance. The method provides effective solutions for similar hydraulic servo systems in other fields.

Analysis of real time stabilization effect and parameter optimization of fin stabilizer

The mathematic model of an actually installed fin stabilizer system is developed and simulation model of the system is built using MATLAB/Simulink. The power spectral analysis is performed and the real time stabilizing effect of the fin stabilizer is obtained by calculating the rolling motion of the ship both in conditions that with and without fin stabilizer running. Then, an optimizing platform is developed using iSIGHT software package and optimized control parameter sets are obtained for different operation conditions. At last, DOE analysis is performed to analyze the influence of each control parameter on the stabilizing effect.

Simulation and experimental study on control strategy of zero-speed fin stabilizer based on disturbance and compensation

Zero-speed fin stabilizer is applied to reduce the roll motion of ships at zero speed. This paper aims to explore the control strategy of zero-speed fin stabilizer through a composite method of theoretical analysis, simulations and tank tests. The hydrodynamic force model is established using analytical approach and a simplified model is obtained by fitting the CFD simulation data. The control strategy of zero-speed fin stabilizer is obtained based on disturbance and compensation by analyzing the phase matching relationship between the wave disturbance, the roll motion of the ship, the movement of the fin and the fin-induced hydrodynamic force. Simulations and water tank tests are performed to verify the effectiveness and feasibility of the obtained control strategies. The results of simulations and tank tests show that the obtained control strategies of zero-speed fin stabilizer based on disturbance and compensation are effective and practical. The proposed method provides theoretical and experimental support for engineering application, and can also be a reference for the controller design of zero-speed fin stabilizers.