In order to study the effects of geometric parameters of the rudder on the hydrodynamic performance of the propeller-rudder system,the surface panel method is used to build the numerical model of the steady interactio...In order to study the effects of geometric parameters of the rudder on the hydrodynamic performance of the propeller-rudder system,the surface panel method is used to build the numerical model of the steady interaction between the propeller and rudder to analyze the relevant factors.The interaction between the propeller and rudder is considered through the induced velocities,which are circumferentially averaged,so the unsteady problem is translated to steady state.An iterative calculation method is used until the hydrodynamic performance converges.Firstly,the hydrodynamic performance of the chosen propeller-rudder system is calculated,and the comparison between the calculated results and the experimental data indicates that the calculation program is reliable.Then,the variable parameters of rudder are investigated,and the calculation results show that the propeller-rudder spacing has a negative relationship with the efficiency of the propeller-rudder system,and the rudder span has an optimal match range with the propeller diameter.Futhermore,the rudder chord and thickness both have a positive correlation with the hydrodynamic performance of the propeller-rudder system.展开更多
Energy optimization is one of the key problems for ship roll reduction systems in the last decade. According to the nonlinear characteristics of ship motion, the four degrees of freedom nonlinear model of Fin/Rudder r...Energy optimization is one of the key problems for ship roll reduction systems in the last decade. According to the nonlinear characteristics of ship motion, the four degrees of freedom nonlinear model of Fin/Rudder roll stabilization can be established. This paper analyzes energy consumption caused by overcoming the resistance and the yaw, which is added to the fin/rudder roll stabilization system as new performance index. In order to achieve the purpose of the roll reduction, ship course keeping and energy optimization, the self-tuning PID controller based on the multi-objective genetic algorithm （MOGA） method is used to optimize performance index. In addition, random weight coefficient is adopted to build a multi-objective genetic algorithm optimization model. The objective function is improved so that the objective function can be normalized to a constant level. Simulation results showed that the control method based on MOGA, compared with the traditional control method, not only improves the efficiency of roll stabilization and yaw control precision, but also optimizes the energy of the system. The proposed methodology can get a better performance at different sea states.展开更多
The inherent nonlinearities of the rudder servo system(RSS) and the unknown external disturbances bring great challenges to the practical application of fault detection technology. Modeling of whole rudder system is a...The inherent nonlinearities of the rudder servo system(RSS) and the unknown external disturbances bring great challenges to the practical application of fault detection technology. Modeling of whole rudder system is a challenging and difficult task. Quite often, models are too inaccurate, especially in transient stages. In model based fault detection, these inaccuracies might cause wrong actions. An effective approach, which combines nonlinear unknown input observer(NUIO) with an adaptive threshold, is proposed. NUIO can estimate the states of RSS asymptotically without any knowledge of external disturbance. An adaptive threshold is used for decision making which helps to reduce the influence of model uncertainty. Actuator and sensor faults that occur in RSS are considered both by simulation and experimental tests. The observer performance, robustness and fault detection capability are verified. Simulation and experimental results show that the proposed fault detection scheme is efficient and can be used for on-line fault detection.展开更多
After the trajectory simulation model of rudder control rocket with six degrees of freedom is established by Matlab/ Simulink, the simulated targeting of rudder control rocket with rudder angle error and starting cont...After the trajectory simulation model of rudder control rocket with six degrees of freedom is established by Matlab/ Simulink, the simulated targeting of rudder control rocket with rudder angle error and starting control moment error is carried out respectively by means of Monte Carlo method and the distribution of impact points of rudder control rocket is counted from all the successful subsamples. In the case of adding interference errors associated with rudder angle error and starting time error, the simulation analysis of impact point dispersion is done and its lateral and longitudinal correction abilities at different targeting angles are simulated to identify the effects of these factors on characteristics and control precision of the rudder control rocket, which provides the relevant reference for high-precision design of rudder control system.展开更多
To analyse a possible way to improve the propulsion performance of ships,the unstructured grid and the Reynolds Average Navier-Stokes equations were used to calculate the performance of a propeller and rudder fitted w...To analyse a possible way to improve the propulsion performance of ships,the unstructured grid and the Reynolds Average Navier-Stokes equations were used to calculate the performance of a propeller and rudder fitted with additional thrust fins in the viscous flow field.The computational fluid dynamics software FLUENT was used to simulate the thrust and torque coefficient as a function of the advance coefficient of propeller and the thrust efficiency of additional thrust fins. The pressure and velocity flow behind the propeller was calculated. The geometrical nodes of the propeller were constituted by FORTRAN program and the NUMBS method was used to create a configuration of the propeller,which was then used by GAMMBIT to generate the calculation model. The thrust efficiency of fins was calculated as a function of the number of additional fins and the attack angles. The results of the calculations agree fairly well with experimental data,which shows that the viscous flow solution we present is useful in simulating the performance of propellers and rudders with additional fins.展开更多
The Reynolds-averaged Navier-Stokes (RANS) method, along with the Fluent software package, was used to study the steady and unsteady interaction of propellers and rudders with additional thrust fins.The sliding mesh m...The Reynolds-averaged Navier-Stokes (RANS) method, along with the Fluent software package, was used to study the steady and unsteady interaction of propellers and rudders with additional thrust fins.The sliding mesh model was employed to simulate unsteady interactions between the blades, the rudder and the thrust fins.Based on the numerical results, the pressure distribution on the propeller and the efficiency of the fins were calculated as a function of the attack angle.The RANS results were compared with results calculated by the potential method.It was found that the results for the potential method and the RANS method have good consistency, but they yield maximum efficiencies for the fins, and thus corresponding attack angles, that are not identical.展开更多
Roll motion of ships can be distinguished in two parts:an unavoidable part due to their natural movement while turning and an unwanted and avoidable part that is due to encounter with waves and rough seas in general.F...Roll motion of ships can be distinguished in two parts:an unavoidable part due to their natural movement while turning and an unwanted and avoidable part that is due to encounter with waves and rough seas in general.For the attenuation of the unwanted part of roll motion,ways have been developed such as addition of controllable fins and changes in shape.This paper investigates the effectiveness of augmenting the rudder used for rejecting part of the unwanted roll,while maintaining steering and course changing ability.For this purpose,a controller is designed,which acts through intentional superposition of fast,compared with course change,movements of rudder,in order to attenuate the high-frequency roll effects from encountering rough seas.The results obtained by simulation to exogenous disturbance support the conclusion that the roll stabilization for displacement can be effective at least when displacement hull vessels are considered.Moreover,robust stability and performance is verified for the proposed control scheme over the entire operating range of interest.展开更多
Given the uncertainty of parameters and the random nature of disturbances that effect a ships course, a robust course controller should be designed on the basis of rudder/flap vector control. This paper analyzes syste...Given the uncertainty of parameters and the random nature of disturbances that effect a ships course, a robust course controller should be designed on the basis of rudder/flap vector control. This paper analyzes system uncertainty, and the choice of weighting functions is also discussed. When sea waves operate on a ship, the energy-concentrating frequency varies with the angle of encounter. For different angles of encounter, different weighting functions are designed. For the pole of a nominal model existing in an imaginary axis, the bilinear-transform method is used. The "2-Riccati" equation is adopted to solve the H∞ controller. A system simulation is given, and the results show that, compared with a PID controller, this system has higher course precision and more robust performance. This research has significant engineering value.展开更多
Numerical simulation is carried out for jets arranged at 7 different positions for the same model and compared with non-jet flows.The total and rudder force and moment amplification is calculated and analyzed by the p...Numerical simulation is carried out for jets arranged at 7 different positions for the same model and compared with non-jet flows.The total and rudder force and moment amplification is calculated and analyzed by the pressure distribution on the surface and rudders of the simplified missile.Numerical results show that interactions take great effect on the configuration of the flow field around rudders and the pressure distribution on the missile surface.展开更多
The roll motions of ships advancing in heavy seas have severe impacts on the safety of crews,vessels,and cargoes;thus,it must be damped.This study presents the design of a rudder roll damping autopilot by utilizing th...The roll motions of ships advancing in heavy seas have severe impacts on the safety of crews,vessels,and cargoes;thus,it must be damped.This study presents the design of a rudder roll damping autopilot by utilizing the dual extended Kalman filter(DEKF)trained radial basis function neural networks(RBFNN)for the surface vessels.The autopilot system constitutes the roll reduction controller and the yaw motion controller implemented in parallel.After analyzing the advantages of the DEKF-trained RBFNN control method theoretically,the ship’s nonlinear model with environmental disturbances was employed to verify the performance of the proposed stabilization system.Different sailing scenarios were conducted to investigate the motion responses of the ship in waves.The results demonstrate that the DEKF RBFNN based control system is efficient and practical in reducing roll motions and following the path for the ship sailing in waves only through rudder actions.展开更多
The demands of aircraft quality design criterion on main control system failure and subsequently instantaneous response were analyzed.According to the simulation,the flight characteristics of an aircraft were studied ...The demands of aircraft quality design criterion on main control system failure and subsequently instantaneous response were analyzed.According to the simulation,the flight characteristics of an aircraft were studied in different angle of rudder seizure.It demonstrated that when rudder seizure with high angle and pilot could not take action immediately,the flight parameters would change sharply.The yaw angle increased 50 degrees in 5 minutes,side velocity could attain 40 meters per-second,the angle of attack and sideslip would surpass 30 degrees,roll rate would reach -20 degrees per second,side load would arrive 0.6g.Simultaneity the angle of attack exceeded the limited angle,the aircraft would stall.If control wasn't working,the disaster would happen.These phenomena supply the sufficient information of the rudder malfunction. The validity of correcting yaw moment by asymmetry thrust was testified,the simulation results showed that even rudder seizure in most serious conditions,adopting asymmetry thrust can correct yaw moment caused by the rudder seizure.The judgment standards of flight safety level for the state of malfunction were given.The safety level was assessed caused by the rudder seizure.For an aircraft with two engines on one side,the pilots need to adjust the 4 engines to balance the asymmetric moment,the work load is increased enormously.According the flight safety standards,the safety level is level Ⅲ.展开更多
基金Supported by the China Postdoctoral Science Foundation(Grant No.2012M512133)the National Natural Science Foundation of China(Grant NO.41176074)the Fundamental Research Funds for the Central University(Grant No.T013513015)
文摘In order to study the effects of geometric parameters of the rudder on the hydrodynamic performance of the propeller-rudder system,the surface panel method is used to build the numerical model of the steady interaction between the propeller and rudder to analyze the relevant factors.The interaction between the propeller and rudder is considered through the induced velocities,which are circumferentially averaged,so the unsteady problem is translated to steady state.An iterative calculation method is used until the hydrodynamic performance converges.Firstly,the hydrodynamic performance of the chosen propeller-rudder system is calculated,and the comparison between the calculated results and the experimental data indicates that the calculation program is reliable.Then,the variable parameters of rudder are investigated,and the calculation results show that the propeller-rudder spacing has a negative relationship with the efficiency of the propeller-rudder system,and the rudder span has an optimal match range with the propeller diameter.Futhermore,the rudder chord and thickness both have a positive correlation with the hydrodynamic performance of the propeller-rudder system.
基金Foundation item： Supported by the National Natural Science Foundation of China （Grant No. 61174047） and the Fundamental Research Funds for the Central Universities （HEUCF041406）.
文摘Energy optimization is one of the key problems for ship roll reduction systems in the last decade. According to the nonlinear characteristics of ship motion, the four degrees of freedom nonlinear model of Fin/Rudder roll stabilization can be established. This paper analyzes energy consumption caused by overcoming the resistance and the yaw, which is added to the fin/rudder roll stabilization system as new performance index. In order to achieve the purpose of the roll reduction, ship course keeping and energy optimization, the self-tuning PID controller based on the multi-objective genetic algorithm （MOGA） method is used to optimize performance index. In addition, random weight coefficient is adopted to build a multi-objective genetic algorithm optimization model. The objective function is improved so that the objective function can be normalized to a constant level. Simulation results showed that the control method based on MOGA, compared with the traditional control method, not only improves the efficiency of roll stabilization and yaw control precision, but also optimizes the energy of the system. The proposed methodology can get a better performance at different sea states.
基金Project(51221004)supported by the Science Fund for Creative Research Groups of National Natural Science Foundation of ChinaProject(51175453)supported by the National Natural Science Foundation of China
文摘The inherent nonlinearities of the rudder servo system(RSS) and the unknown external disturbances bring great challenges to the practical application of fault detection technology. Modeling of whole rudder system is a challenging and difficult task. Quite often, models are too inaccurate, especially in transient stages. In model based fault detection, these inaccuracies might cause wrong actions. An effective approach, which combines nonlinear unknown input observer(NUIO) with an adaptive threshold, is proposed. NUIO can estimate the states of RSS asymptotically without any knowledge of external disturbance. An adaptive threshold is used for decision making which helps to reduce the influence of model uncertainty. Actuator and sensor faults that occur in RSS are considered both by simulation and experimental tests. The observer performance, robustness and fault detection capability are verified. Simulation and experimental results show that the proposed fault detection scheme is efficient and can be used for on-line fault detection.
文摘After the trajectory simulation model of rudder control rocket with six degrees of freedom is established by Matlab/ Simulink, the simulated targeting of rudder control rocket with rudder angle error and starting control moment error is carried out respectively by means of Monte Carlo method and the distribution of impact points of rudder control rocket is counted from all the successful subsamples. In the case of adding interference errors associated with rudder angle error and starting time error, the simulation analysis of impact point dispersion is done and its lateral and longitudinal correction abilities at different targeting angles are simulated to identify the effects of these factors on characteristics and control precision of the rudder control rocket, which provides the relevant reference for high-precision design of rudder control system.
文摘To analyse a possible way to improve the propulsion performance of ships,the unstructured grid and the Reynolds Average Navier-Stokes equations were used to calculate the performance of a propeller and rudder fitted with additional thrust fins in the viscous flow field.The computational fluid dynamics software FLUENT was used to simulate the thrust and torque coefficient as a function of the advance coefficient of propeller and the thrust efficiency of additional thrust fins. The pressure and velocity flow behind the propeller was calculated. The geometrical nodes of the propeller were constituted by FORTRAN program and the NUMBS method was used to create a configuration of the propeller,which was then used by GAMMBIT to generate the calculation model. The thrust efficiency of fins was calculated as a function of the number of additional fins and the attack angles. The results of the calculations agree fairly well with experimental data,which shows that the viscous flow solution we present is useful in simulating the performance of propellers and rudders with additional fins.
基金Supported by the National Natural Science Foundation of China under Grant No.10702016the Fundamental Research Funds for the Central Universities No.HEUCFT1001
文摘The Reynolds-averaged Navier-Stokes (RANS) method, along with the Fluent software package, was used to study the steady and unsteady interaction of propellers and rudders with additional thrust fins.The sliding mesh model was employed to simulate unsteady interactions between the blades, the rudder and the thrust fins.Based on the numerical results, the pressure distribution on the propeller and the efficiency of the fins were calculated as a function of the attack angle.The RANS results were compared with results calculated by the potential method.It was found that the results for the potential method and the RANS method have good consistency, but they yield maximum efficiencies for the fins, and thus corresponding attack angles, that are not identical.
文摘Roll motion of ships can be distinguished in two parts:an unavoidable part due to their natural movement while turning and an unwanted and avoidable part that is due to encounter with waves and rough seas in general.For the attenuation of the unwanted part of roll motion,ways have been developed such as addition of controllable fins and changes in shape.This paper investigates the effectiveness of augmenting the rudder used for rejecting part of the unwanted roll,while maintaining steering and course changing ability.For this purpose,a controller is designed,which acts through intentional superposition of fast,compared with course change,movements of rudder,in order to attenuate the high-frequency roll effects from encountering rough seas.The results obtained by simulation to exogenous disturbance support the conclusion that the roll stabilization for displacement can be effective at least when displacement hull vessels are considered.Moreover,robust stability and performance is verified for the proposed control scheme over the entire operating range of interest.
文摘Given the uncertainty of parameters and the random nature of disturbances that effect a ships course, a robust course controller should be designed on the basis of rudder/flap vector control. This paper analyzes system uncertainty, and the choice of weighting functions is also discussed. When sea waves operate on a ship, the energy-concentrating frequency varies with the angle of encounter. For different angles of encounter, different weighting functions are designed. For the pole of a nominal model existing in an imaginary axis, the bilinear-transform method is used. The "2-Riccati" equation is adopted to solve the H∞ controller. A system simulation is given, and the results show that, compared with a PID controller, this system has higher course precision and more robust performance. This research has significant engineering value.
基金supported in part by Fundamental of Graduate Innovation Center in NUAA(No.kfjj20170122)the Fundamental Research Funds for the Central Universities
文摘Numerical simulation is carried out for jets arranged at 7 different positions for the same model and compared with non-jet flows.The total and rudder force and moment amplification is calculated and analyzed by the pressure distribution on the surface and rudders of the simplified missile.Numerical results show that interactions take great effect on the configuration of the flow field around rudders and the pressure distribution on the missile surface.
基金a part of the project titled ’Intelligent Control for Surface Vessels Based on Kalman Filter Variants Trained Radial Basis Function Neural Networks’ partially funded by the Institutional Grants Scheme(TGRS 060515)of Tasmania,Australia
文摘The roll motions of ships advancing in heavy seas have severe impacts on the safety of crews,vessels,and cargoes;thus,it must be damped.This study presents the design of a rudder roll damping autopilot by utilizing the dual extended Kalman filter(DEKF)trained radial basis function neural networks(RBFNN)for the surface vessels.The autopilot system constitutes the roll reduction controller and the yaw motion controller implemented in parallel.After analyzing the advantages of the DEKF-trained RBFNN control method theoretically,the ship’s nonlinear model with environmental disturbances was employed to verify the performance of the proposed stabilization system.Different sailing scenarios were conducted to investigate the motion responses of the ship in waves.The results demonstrate that the DEKF RBFNN based control system is efficient and practical in reducing roll motions and following the path for the ship sailing in waves only through rudder actions.
文摘The demands of aircraft quality design criterion on main control system failure and subsequently instantaneous response were analyzed.According to the simulation,the flight characteristics of an aircraft were studied in different angle of rudder seizure.It demonstrated that when rudder seizure with high angle and pilot could not take action immediately,the flight parameters would change sharply.The yaw angle increased 50 degrees in 5 minutes,side velocity could attain 40 meters per-second,the angle of attack and sideslip would surpass 30 degrees,roll rate would reach -20 degrees per second,side load would arrive 0.6g.Simultaneity the angle of attack exceeded the limited angle,the aircraft would stall.If control wasn't working,the disaster would happen.These phenomena supply the sufficient information of the rudder malfunction. The validity of correcting yaw moment by asymmetry thrust was testified,the simulation results showed that even rudder seizure in most serious conditions,adopting asymmetry thrust can correct yaw moment caused by the rudder seizure.The judgment standards of flight safety level for the state of malfunction were given.The safety level was assessed caused by the rudder seizure.For an aircraft with two engines on one side,the pilots need to adjust the 4 engines to balance the asymmetric moment,the work load is increased enormously.According the flight safety standards,the safety level is level Ⅲ.
