Jinfu Feng

Longitudinal motion control of AUV based on fuzzy sliding mode method

According to the characteristics of AUV movement, a fuzzy sliding mode controller was designed, in which fuzzy rules were adopted to estimate the switching gain to eliminate disturbance terms and reduce chattering. The six-degree-of-freedom model of AUV was simplified and longitudinal motion equations were established on the basis of previous research. The influences of first-order wave force and torque were taken into consideration. The REMUS was selected to simulate the control effects of conventional sliding mode controller and fuzzy sliding mode controller. Simulation results show that the fuzzy sliding mode controller can meet the requirements and has higher precision and stronger antijamming performances compared with conventional sliding mode controller.

Covariance and crossover matrix guided differential evolution for global numerical optimization

Differential evolution (DE) is an efficient and robust evolutionary algorithm and has wide application in various science and engineering fields. DE is sensitive to the selection of mutation and crossover strategies and their associated control parameters. However, the structure and implementation of DEs are becoming more complex because of the diverse mutation and crossover strategies that use distinct parameter settings during the different stages of the evolution. A novel strategy is used in this study to improve the crossover and mutation operations. The crossover matrix, instead of a crossover operator and its control parameter CR, is proposed to implement the function of the crossover operation. Meanwhile, Gaussian distribution centers the best individuals found in each generation based on the proposed covariance matrix, which is generated between the best individual and several better individuals. Improved mutation operator based on the crossover matrix is randomly selected to generate the trial population. This operator is used to generate high-quality solutions to improve the capability of exploitation and enhance the preference of exploration. In addition, the memory population is randomly chosen from previous generation and used to control the search direction in the novel mutation strategy. Accordingly, the diversity of the population is improved. Thus, CCDE, which is a novel efficient and simple DE variant, is presented in this paper. CCDE has been tested on 30 benchmarks and 5 real-world optimization problems from the IEEE Congress on Evolutionary Computation (CEC) 2014 and CEC 2011, respectively. Experimental and statistical results demonstrate the effectiveness of CCDE for global numerical and engineering optimization. CCDE can solve the test benchmark functions and engineering problems more successfully than the other DE variants and algorithms from CEC 2014.

Investigation of water entry impact forces on airborne-launched AUVs

ABSTRACT Airborne-launched AUVs withstand great fluid impact force at the early stage when entering the water, which may cause damage to their structure and inner components in severe cases. Due to their large volume and mass, the major challenge involved in conducting experiments to measure the water entry impacts on real-life AUVs is the high demand for the experimental devices, finding a suitable site, and the cost of the experiments. Using a gas gun as launching device, water entry experiments using a full-size AUV model are conducted under various conditions. The axial and radial force changes that occur during the water entry process are obtained, and some accompanied phenomena such as cavitation and turnover under different water entry conditions are observed. Computational fluid dynamics (CFD) is used to simulate the water entry process of airborne-launched AUVs. The simulation results fit well with the experimental data, the latter of which show that both the water entry velocity and entry angle have a great influence on the impact load during the water entry process. These data can provide valuable reference information for AUV structure design and launch condition selection.

Water-Exit Process Modeling and Added-Mass Calculation of the Submarine-Launched Missile

Abstract In the process that the submarine-launched missile exits the water, there is the complex fluid solid coupling phenomenon. Therefore, it is difficult to establish the accurate water-exit dynamic model. In the paper, according to the characteristics of the water-exit motion, based on the traditional method of added mass, considering the added mass changing rate, the water-exit dynamic model is established. And with help of the CFX fluid simulation software, a new calculation method of the added mass that is suit for submarine-launched missile is proposed, which can effectively solve the problem of fluid solid coupling in modeling process. Then by the new calculation method, the change law of the added mass in water-exit process of the missile is obtained. In simulated analysis, for the water-exit process of the missile, by comparing the results of the numerical simulation and the calculation of theoretical model, the effectiveness of the new added mass calculation method and the accuracy of the water-exit dynamic model that considers the added mass changing rate are verified.

Overview on the development and key technologies of water-air UAV

The water-air UAV is a new kind of aircraft which cruises in the air on ordinary occasions. Specially, it can submerge for a short distance underwater and take off again when necessary. It has lots of superior performance and wide application fields for both military and civil users. Over the last decades, several vehicles like it have been developed for special uses. First, the research necessity and development history of water-air UAV and other similar vehicle are reviewed in this paper. Then, the involved key technologies and their application status, such as configuration, power, control and communication are introduced. It is certain that the water-air UAV will play an important role in the world ahead.

Research on the water-entry attitude of a submersible aircraft

BackgroundThe water entry of a submersible aircraft, which is transient, highly coupled, and nonlinear, is complicated. After analyzing the mechanics of this process, the change rate of every variable is considered. A dynamic model is build and employed to study vehicle attitude and overturn phenomenon during water entry. Experiments are carried out and a method to organize experiment data is proposed. The accuracy of the method is confirmed by comparing the results of simulation of dynamic model and experiment under the same condition.ResultsBased on the analysis of the experiment and simulation, the initial attack angle and angular velocity largely influence the water entry of vehicle. Simulations of water entry with different initial and angular velocities are completed, followed by an analysis, and the motion law of vehicle is obtained. To solve the problem of vehicle stability and control during water entry, an approach is proposed by which the vehicle sails with a zero attack angle after entering water by controlling the initial angular velocity. With the dynamic model and optimization research algorithm, calculation is performed, and the optimal initial angular velocity of water-entry is obtained.ConclusionsThe outcome of simulations confirms that the effectiveness of the propose approach by which the initial water-entry angular velocity is controlled.

Stability Control of Propeller Autonomous Underwater Vehicle Based on Combined Sections Method

Abstract Learning from the motion principle of quadrotor, a symmetric propeller AUV, which has small size and low velocity is designed. Compared with the AUV equipped with rudders, it has better maneuverability and manipulation at low velocity. According to the Newton-Euler method, the 6 DOF kinematic model and dynamic model of the propeller AUV are established. A stability controller that consists of 3 different PID controllers is designed. It makes the depth and attitude angle as trigger conditions, and the relevant controller is chosen in different moving process. The simulation experiments simulate ideal motion state and disturbed motion state, and experiments results show that the stability controller based on combined sections method can make the best of mature technology of PID, and meet the control requirements in different stages. It has a higher respond speed and accuracy, improving the stability of the propeller AUV under the disturbance of complex ocean currents.

Research on vertical air–water trans-media control of Hybrid Unmanned Aerial Underwater Vehicles based on adaptive sliding mode dynamical surface control

We address the problem of vertical air–water trans-media control of Hybrid Unmanned Aerial Underwater Vehicles in the presence of parameters uncertainty and disturbances. Hybrid Unmanned Aerial Underwater Vehicle suffers from huge changes of added mass, fluid drag force, and “ground effect” during crossing air–water surface, which easily lead to trans-media failure. A novel structure of Hybrid Unmanned Aerial Underwater Vehicle is built and introduced which adopts dual deck propellers including four air propellers and four water propellers. The dynamic model of trans-media process is developed for the trans-media process in condition that added mass, floatage, and drag force are linearized while linearization errors and “ground effect” are treated as disturbances. Attitude and altitude–depth controllers are designed based on Lyapunov stability theory and adaptive sliding mode dynamical surface control. The proposed controllers accomplish air, underwater, and “seamless” trans-media process integrated control without a priori boundary of disturbances, forcing the tracking errors to an arbitrarily small neighborhood of zero. Simulation results are presented to illustrate the control algorithm with good performance and robustness.

Simulation and experimental research on trans-media vehicle water-entry motion characteristics at low speed

The motion characteristics of trans-media vehicles during the water-entry process were explored in this study in an effort to obtain the optimal water-entry condition of the vehicle for developing a novel, single control strategy integrating underwater non-control and in-air control. A water-entry dynamics model is established by combining the water-entry motion characteristics of the vehicle in uncontrolled conditions at low speed with time-varying parameters (e.g. buoyancy, added mass). A water-entry experiment is designed to confirm the effectiveness of the established model. After that, by comparing the experimental results with the simulated results, the model is further modified to more accurately reflect water-entry motion. The change laws of the vehicle’s attitude and position during the water-entry process are also obtained by analyzing the simulation of the modified model under different velocity, angle, and angle of attack conditions. The results presented here have guiding significance for the future realization of reaching the stable underwater navigation state of the vehicle after water-entry process.

Water exit model and takeoff control for a morphing cross-media vehicle

Abstract The water exit of a morphing cross-media vehicle is a nonlinear, multi-coupled, physical process with strong disturbance. It severely affects the subsequent flight of the vehicle after leaving the water. Because of the short duration, it requires very fast response time from the controller. To overcome the shortcomings of existing research on the water exit process of morphing cross-media vehicles, a possible solution of uncontrolled water exit and controlled takeoff is proposed. A water exit dynamic model is established after properly simplifying the complexity and unpredictability of the underwater environment, in consideration of changing variables, such as buoyancy, wetted area, and added mass. A numerical simulation is conducted to prove the validity of the model. Furthermore, an improved sliding-mode controller is designed to ensure that the cross-media vehicle reaches the target conditions after leaving the water and to prevent the vehicle falling back into the water. Simulation results demonstrate the reasonability and feasibility of the proposed solution. These conclusions can provide valuable reference information for solving control problems in morphing cross-media vehicles.