Rudder Deflection Research Articles

Online Safe Flight Control Method Based on Constraint Reinforcement Learning

UAVs are increasingly prominent in the competition for space due to their multiple characteristics, such as strong maneuverability, long flight distance, and high survivability. A new online safe flight control method based on constrained reinforcement learning is proposed for the intelligent safety control of UAVs. This method adopts constrained policy optimization as the main reinforcement learning framework and develops a constrained policy optimization algorithm with extra safety budget, which introduces Lyapunov stability requirements and limits rudder deflection loss to ensure flight safety and improves the robustness of the controller. By efficiently interacting with the constructed simulation environment, a control law model for UAVs is trained. Subsequently, a condition-triggered meta-learning online learning method is used to adjust the control raw online ensuring successful attitude angle tracking. Simulation experimental results show that using online control laws to perform aircraft attitude angle control tasks has an overall score of 100 points. After introducing online learning, the adaptability of attitude control to comprehensive errors such as aerodynamic parameters and wind improved by 21% compared to offline learning. The control law can be learned online to adjust the control policy of UAVs, ensuring their safety and stability during flight.

Characteristics and optimization of multi-body separation in supersonic ground effects

The electromagnetic launch of aerospace vehicles is an option for reusable earth/orbit space transportation in the future. In contrast to open space, complex ground effects emerge in supersonic near-ground multi-body separations. Here, the separation processes between a supersonic aerospace vehicle (traveling at Mach 1.5) and an electromagnetic sled were studied with a focus on the characteristics of the flow evolution and aerodynamic interference. The results show that the evolution of the supersonic near-ground separation can be divided into three substages: choked flows in the narrow gap, multi-body shock interactions and independent ground effect interference. The aerodynamic loads of the vehicle strongly correspond to the separation stages. The high-pressure region at the leading edge of the electromagnetic sled continuously sweeps the vehicle abdomen and causes significant fluctuations in the aerodynamic lift and moment, which play a dominant role in the separation trajectory. The altitude of the vehicle that flies away from the electromagnetic sled is relatively stable when the preset attack angle is 0° Following this separation, the vehicle has a pitch angle of -0.25° and tends toward a negative angle of attack. A vertical distance of 4.2 m is insufficient for optimal separation. Thus, the separation characteristics were optimized by combining the preset rudder deflection angle of 0° and inclined track with a slope angle of 1.5° Following this separation, the pitch angle of the vehicle is 3.4°, and the vertical distance increases to 14.8 m, which significantly improves the separation safety.

Numerical Simulations of a Ship’s Maneuverability in Shallow Water

It is necessary to maintain maneuverability for ship navigation in shallow water, such as channels, ports and other confined waters. In this study, a turning circle maneuver with 35° rudder deflection and a 20/5 zigzag maneuver for KVLCC2 in shallow waters are tested numerically to directly predict the maneuverability of the ship in shallow water. A viscous in-house CFD solver is applied with the dynamic overset grid approach. The impacts of the water depth on the ship’s maneuverability in terms of turning and zigzag competence are evaluated, and the underlying mechanism is analyzed. The numerical method is validated by comparing it with experimental data on the turning indices, which shows good agreement. It is demonstrated that the turning capability become worse with a smaller depth–draft ratio, thus resulting in a lower yaw rate and a greater steady turning diameter. However, the drift angle and lateral speed are reduced with a smaller depth–draft ratio for zigzag maneuvers, but the overshoot angle and turn lag vary with the water depth non-monotonically.

Holistic collision avoidance decision support system for watchkeeping deck officers

The paper presents a 3-stage synthesis-based Decision Support System for watchkeeping deck officers. Its functional scope covers conflict detection, maneuver selection, and maneuver execution, all phases supplemented by collision alerts. First, a customized elliptic ship domain is used for checking if both OS and TS will have enough free space. A survey-based navigators’ declarative OS arena is then used to determine the time at which OOW would like to take evasive action. Next, a safety level is assigned to the current situation based on the predicted violations of the ship domain and the declarative arena. The safety levels are also attributed to potential evasive maneuvers (single actions combining course alteration and rudder deflection). For a selected maneuver, Collision Avoidance Dynamic Critical Area (CADCA) is displayed, which informs OOW about the time window when the maneuver remains feasible. All of the above contribute to a holistic system of multi-level safety assessment utilizing: empirical ship domain, survey-based declarative arena, and ship dynamics-based CADCA. These, in turn, take into account navigators’ knowledge and preferences, ship maneuverability, and the impact of environmental conditions. The system is presented in three real-life scenarios located in the southern part of the Baltic Sea around the Danish straits.

Predefined-Time Hierarchical Coordinated Neural Control for Hypersonic Reentry Vehicle.

This paper investigates the predefined-time hierarchical coordinated adaptive control on the hypersonic reentry vehicle in presence of low actuator efficiency. In order to compensate for the deficiency of rudder deflection in advantage of channel coupling, the hierarchical design is proposed for coordination of the elevator deflection and aileron deflection. Under the control scheme, the equivalent control law and switching control law are constructed with the predefined-time technology. For the dynamics uncertainty approximation, the composite learning using the tracking error and the prediction error is constructed by designing the serial-parallel estimation model. The closed-loop system stability is analyzed via the Lyapunov approach and the tracking errors are guaranteed to be uniformly ultimately bounded in a predefined time. The tracking performance and the learning accuracy of the proposed algorithm are verified via simulation tests.

Investigations on electromagnetic scattering characteristics of aircraft rudder considering electromagnetic discontinuities

This work investigates the scattering characteristics of the rudder structure of aircraft considering electromagnetic discontinuities through multi level fast multipole algorithm (MLFMA) of the computational electromagnetics. Firstly, the scattering characteristics of the rudder seam and its influence on the omnidirectional radar cross section (RCS) are performed. Based on the traditional high-frequency analysis theory, the source and spatial contribution distribution of seam scattering are further studied. Numerical results demonstrate that the sidewall of the rudder seam is an important scattering source, and the radar absorbing material (RAM) coated on the sidewall of the seam has a good RCS reduction effect. In addition, this work presents the influence of the rudder deflection on the stealth performance, analyzes the effect of the rudder movement of the ordinary aileron and the split drag rudder on the scattering characteristics of the whole aircraft. The common aileron has little effect on the stealth performance of the aircraft, and it only causes scattering peak in the direction opposite to the control surface. However, the split drag rudder has great damage to the opposite direction stealth performance of the aircraft. When its deflection angle is 45°, the mean value of the opposite direction RCS increases by about two orders of magnitude compared with the deflection angle 0° state. The results indicate that the structure of aircraft rudder has a significant impact on the RCS characteristics of the whole aircraft.

On the performance of different Deep Reinforcement Learning based controllers for the path-following of a ship

A set of continuous state-action space-based deep reinforcement learning algorithms are used for the path following of a ship in calm water and waves. The mathematical model of a KVLCC2 tanker represents the ship dynamics. The mathematical model includes the hull force, rudder force, propulsion force, and external wave forces. Look ahead distance-based guidance algorithm called Line of Sight (LOS) is used for computing the Cross Track Error (CTE) and Heading Error (HE). The reward function is designed based on HE and CTE. The created Environment is trained with four different Deep Reinforcement Learning (DRL) agents named Proximal Policy Optimization (PPO), Deep Deterministic Policy Gradients (DDPG), Twin-Delayed Deep Deterministic Policy Gradients (TD3), and Soft-Actor Critic (SAC). Common Neural Network architecture is used for all four agents. Yaw rate, HE, and CTE serve as input to the Neural Network, and the rudder deflection rate (δ°) corresponds to the action space (output). Computation time, average cross-track error, and rudder actuation are computed and compared for path-following scenarios. DDPG performs better with a minimum average CTE for all the simulated cases. However, SAC demands minimum rudder control effort to achieve the tasks. Finally, the trained agents are validated using Hardware In-Loop (HIL) simulation.

Command Filter AILC for Finite Time Accurate Tracking of Aircraft Track Angle System Based on Fuzzy Logic

In this paper, the longitudinal model of an uncertain aircraft is taken as the research object, and the aircraft path inclination is controlled by controlling the input rudder deflection angle. An adaptive iterative learning control (AILC) scheme is proposed to solve the accurate tracking control problem of the flight path inclination on a finite time interval. The aircraft track angle system is abstractly modeled to obtain a triangular model in the form of strict feedback. For the abstracted strict feedback model, the fuzzy logic is used to approximate the uncertain part of the model. A command filter and an error compensation mechanism are introduced to prevent the computational bloat problem caused by excessive system order, and a convergent series sequence is used to deal with the truncation error caused by the approximation of the fuzzy logic. Based on the Lyapunov stability theorem, all signals of the closed-loop system are bounded on the finite time interval 0 , T , and the output of the system can track the desired trajectory accurately. Finally, the feasibility and effectiveness of the method are verified by MATLAB simulation results.

Rudder hydrodynamics behind a propeller rotating ahead and astern

Ships sailing in harbour environments will experience four-quadrant manoeuvres, based on the direction of ship velocity and propeller rate. A better understanding of ship hydrodynamics in such manoeuvres will contribute to the navigation safety. Aimed at ships equipped with a conventional single propeller and single rudder, the hydrodynamic performance of a rudder with the engine ahead and astern is studied. The KP505 propeller and NACA 0018 semi-balanced rudder (from the KCS benchmark ship) are selected for numerical studies for extended experimental data published. After validating numerical methods with open-water test data for the single propeller and the single rudder, CFD simulations based on RANS methods are conducted for different advance ratios ahead and astern, with rudder deflections ranging from 0 to 15 degrees. To understand propeller impact on lift and drag forces of the rudder in different working conditions, inflow to the rudder in propeller slipstreams are analysed by extracting the flow field data in different profiles along the rudder span. Streamlines around the rudder and pressure distributions on the rudder surfaces, along with the turbulent kinematic energy distributions and the vortex structures visualised by Q-criterion, are compared to reveal propeller-rudder interaction mechanisms in ahead and astern conditions. The study shows that the propeller rotation mode has a significant impact on rudder inflow patterns, and induced rudder forces change in different trends with propeller loading variations.

A Modified Model-Free Adaptive Control Method for Large-Scale Morphing Unmanned Vehicles

This paper investigates the attitude control problem for large-scale morphing unmanned vehicles. Considering the rapid time-varying and strong aerodynamic interference caused by large-scale morphing, a modified model-free control method utilizing only the system input and output is proposed. Firstly, a two-loop equivalent data model for the morphing unmanned vehicle is developed, which can better reflect the practical dynamics of morphing unmanned vehicles compared to the traditional compact form dynamic linearization data model. Based on the proposed data model, a modified model-free adaptive control (MMFAC) scheme is proposed, consisting of an external-loop and an inner-loop controller, so as to generate the required combined control torques. Additionally, in light of the aerodynamic uncertainties of the large-scale morphing unmanned vehicle, a rudder deflection actuator control scheme is designed by employing the model-free adaptive control approach. Finally, the boundedness of the closed-loop system and the convergence of tracking errors are guaranteed, based on the stability analysis. Additionally, numerical examples are presented to demonstrate the effectiveness and robustness of the proposed control scheme in the case of the effect of large-scale morphing.

Upgraded design methodology for airframe/engine integrated full-waverider vehicle considering thrust chamber design

An upgraded airframe/engine integrated design approach for a full-waverider vehicle considering thrust chamber design is proposed. Compared with the existing design approach of the full-waverider vehicle, the isolator, the combustor, and the nozzle are designed complementally. First, the airframe and inlet are generated using the full-waverider theory, the isolator with the centroid offset variable cross-section is designed using the geometric morphing method, and the maximum thrust nozzle is obtained by the method of characteristics. Coupled with a circular cross-section combustor and air rudders, a complete full-waverider vehicle including the thrust chamber is generated. Second, the correctness and the availability of the design method is verified through numerical simulations under the design condition. Finally, the aerodynamic performance of the full-waverider vehicle is analyzed under a wide-speed range in the moment equilibrium state. The optimal lift-to-drag ratio of the entire vehicle is 4.03 appearing at 4° angle of attack. Owing to the rudder deflection, the optimal lift to drag ratio reduces from 4.03 to 2.44, and the corresponding angle of attack changes as well. Moreover, the inlet unstart phenomenon occurs with the decrease of the Mach number and with the increase of the angle of attack.

Fluidic-Oscillator-Based Pulsed Jet Actuation on a Vertical Tail

An industry-relevant vertical tail plane (VTP) model equipped with fluidic-oscillator-based pulsed jet actuators was tested with different active flow control (AFC) settings, rudder deflection, and sideslip angles at a chord Reynolds number of 1.3 million. In addition to pressure and force measurements, tuft visualizations and stereoscopic particle image velocimetry measurements were used to investigate AFC effects. With a total momentum coefficient of 1.5%, the control authority (lateral force) of the VTP was increased by a maximum of 34% when actuators were distributed along the rudder span. Additionally, flow control at dedicated positions on the rudder was investigated by using individual actuator segments. It was found that AFC is particularly effective at the position of the maximum load in the spanwise direction. The measurements also confirmed that local application of AFC actuators may simulate the effect of a boundary-layer fence. Finally, a comparison with existing results obtained with sweeping jet actuators shows that these two specific AFC implementations are most effective in different ranges of the momentum and the power coefficients.

함정의 평판형 방향타 캐비테이션 침식에 대한 모형 시험 연구

In the present study, a method of performing cavitation erosion test directly on the anodized surface of the rudder model is proposed, not applying ink or paint on its surface. An image processing technique is newly developed to quantitatively evaluate the erosion damages on the rudder model surface after erosion test. The preprocessing saturation image, image smoothing, adaptive hysteresis thresholding and eroded area detection algorithms are in the image processing program. The rudder cavitation erosion tests are conducted in the rudder deflection angle range of 0SUPo/SUP to -4SUPo/SUP, which is used to maintain a straight course at the highest speed of the targeted navy ship. In the case of the conventional flat-type full-spade rudder currently being used in the target ship, surface erosion can occur on the model rudder surface in the above rudder deflection angle range. The bubble type of cavitation occurs on rudder surface, which is estimated to be the main reason of erosion damage on the rudder surface.

Investigation on the flow around a submarine under the rudder deflection condition by using URANS and DDES methods

Considering the complex flow features of a submarine under the maneuvering condition and their close relationship with the maneuverability, a numerical study is performed for the flow around the submarine under the rudder deflection condition. Taking the submarine model DARPA SUBOFF as the study object, the rudder force test with a wide range of rudder angles is simulated based on the open source CFD platform OpenFOAM. Two numerical methods of Unsteady Reynolds-Averaged Navier-Stokes (URANS) method and Delayed Detached Eddy Simulation (DDES) method are employed. A systematic convergence study is performed to clarify the effect of grid spacing and time step on the numerical solution. The computed hydrodynamic forces are compared with the available experimental data, and the effectiveness of the adopted numerical methods is validated. Besides, the obtained rudder forces and rudder parameters are compared and discussed. Based on the obtained flow field details of vortex structures, velocity fields, streamline distribution, turbulence levels, and pressure distribution, the flow mechanisms of the deflected rudders are analyzed. Compared with URANS method, DDES method presents a better capability of capturing the flow field details around the submarine under the tight maneuvering condition, where remarkable flow separation is involved.

Hipersoničnu letelicu sa Airbreathing pogonom

The paper uses the state feedback technique to provide a control design method for a dynamic linear 6-degree-of-freedom (DOF) model of an Airbreathing Hypersonic Vehicle (AHV). A linear model of AHV with a state space model is developed for the open loop simulation for the level flight with Mach number 5 and a height of 65000 ft (19812 m). The dynamic stability of AHV is analyzed, and state feedback with the pole placement method is implemented for the controller design. The dynamic stability, response, and comparison for the PI and PID controller are presented for the aileron deflection da and rudder deflection dr for the AHV linear model.

Adaptive iterative learning control method for finite-time tracking of an aircraft track angle system based on a neural network

Based on a neural network, this paper presents a new adaptive iterative learning control method for the finite-time tracking control problem of an uncertain aircraft track angle system, which can control the aircraft track inclination through the designed control input rudder deflection angle, so that it can track the preset trajectory in a finite time interval. First, the flight path angle system of the aircraft is abstractly modeled by variable substitution to obtain a triangular model in the form of strict feedback. Second, radial basis function neural network approximation is used to model the uncertain part of the system, aiming at the abstract strict feedback model, and two virtual quantities are designed through the three-layer inversion design method, and then, Lyapunov functions are designed for each subsystem to derive virtual control laws, the actual control law, and the neural network weight adaptive laws. Through Lyapunov stability analysis, it can be seen that the designed controller and adaptive laws can make the whole closed-loop system tend to be stable and realize the tracking of a target trajectory in a finite time interval. Finally, the feasibility and effectiveness of the theory are verified by a simulation example.

A New Sliding Mode Control Algorithm of IGC System for Intercepting Great Maneuvering Target Based on EDO.

To intercept the great maneuvering target, combining with the sliding mode and the extended disturbance observer, a new control algorithm for integrated guidance and control (IGC) system is proposed in this paper. Firstly, the paper formulates the Missile–Target problem. Then the paper establishes an uncertain IGC dynamic model where the nonlinearities, the perturbations and the maneuvering of the target are regarded as disturbance. Secondly, a second-order disturbance observer is designed to estimate the disturbance and their derivatives.. After this, combining with the second-order disturbance observer, a modified sliding surface and the corresponding reaching law are designed to obtain the rudder deflection command directly. Thus, the real sense of IGC system is achieved. Next, the paper uses the Lyapunov stability theory to prove the stability of the system. Finally, the paper provides different simulation cases, which have different maneuver modes of the target, to demonstrate the superiority of the proposed method in reducing the response time, increasing the rudder response, and having a high interception probability.

A systematic investigation on the manoeuvring performance of a ship performing low-speed manoeuvres in adverse weather conditions using CFD

The International Maritime Organisation (IMO) requirements for the control of greenhouse gas (GHG) emissions of shipping have raised interest in ship manoeuvrability in adverse weather conditions when compliance is accomplished simply by reducing the main engine power. In response, the IMO has adopted the guidelines for determining minimum propulsion power to maintain the manoeuvrability of ships in adverse conditions. In the present paper, a systematic investigation on the manoeuvrability of a ship with different low advance speeds in adverse weather conditions was conducted by means of an unsteady Reynolds-Averaged Navier-Stokes solver. The numerical results demonstrated the contribution of low advance speeds to the course-keeping and turning circle manoeuvre, providing a practical insight into the manoeuvring performance of a ship with minimum propulsion power in adverse weather conditions. For the course-keeping control, the ship experienced more aggressive steering as the propeller revolution decreased in the oblique waves, while it appeared that the difference in the rudder deflection according to the change in the propeller speed in the head, beam, and following waves is negligible. The difficulty of the low speed turning manoeuvre was clearly noted when the direction of the incident wave was opposite to the direction towards which the ship intended to turn. It is believed that this paper can also be impactful in improving the guidelines of minimum powering of ships for safe navigation in adverse weather conditions.

RANS investigation of the hydrodynamic interactions between two approaching ships in shallow water considering the effects of drift motion and rudder deflection

There exists a high risk of collision between two approaching ships in the lightering operation. The investigations of the hydrodynamic interactions between such two ships are of great interest to ensure navigation safety. To this end, the RANS (Reynolds-Averaged Navier-Stokes) technique based on OpenFOAM is employed to simulate the flow around two approaching Wigleys in this work. The two Wigleys are identical. Due to the slow ship speed, the water-air flow is simplified as the double-body flow in the present consideration. The computed hydrodynamic side forces and yaw moments are compared with the available experimental data, and acceptable agreements are found. The effects of lateral distance between the two ships, water depth, rudder deflection, ship scale and drift motion on the hydrodynamic forces and moments on both ships are analyzed. This study shows that the suction forces and bow-out moments generally become larger as the water depth or lateral distance decreases, while the suction forces trends to become repulsion forces when both the water depth and lateral distance are very small. It is also found that the rudder deflection of one ship has a very little hydrodynamic disturbance on the other ship, rather than the drift motion which affects much the hydrodynamic forces and moments on the other ship especially in very shallow water.

Performance Analysis on the Small-Scale Reusable Launch Vehicle

According to the symmetrical characteristics of a new type of Reusable Launch Vehicle (RLV) in the recovery phase, we studied the basic aerodynamic model data of Starship and the aerodynamic data with rudder deflection, and the causes of its aerodynamic coefficients are expounded. At the same time, we analyzed its stability and maneuverability. According to the flying quality requirements, the lateral-directional model of Starship in the return phase at a high angle of attack is analyzed. Finally, we analyzed the lateral heading stability and control deviation of Starship by using the criterion and nonlinear open-loop simulations. The results show that the Starship has pitching and rolling stability, but it only has heading stability in some ranges of angle of attack, and there is no heading stability at a conventional large angle of attack. At the same time, after modal analysis and comparison of flight quality, it can be seen that the longitudinal long-period model of the starship degenerates into a real root and it is stable and convergent. The lateral heading roll mode is at level 2 flight quality, the helical mode is at level 1 flight quality, and the Dutch roll mode diverges, which needs to be stabilized and controlled later.