Lateral Thrusters Research Articles

Compound Control Design of Near-Space Hypersonic Vehicle Based on a Time-Varying Linear Quadratic Regulator and Sliding Mode Method

The design of a hypersonic vehicle controller has been an active research field in the last decade, especially when the vehicle is studied as a time-varying system. A time-varying compound control method is proposed for a hypersonic vehicle controlled by the direct lateral force and the aerodynamic force. The compound control method consists of a time-varying linear quadratic regulator (LQR) control law for the aerodynamic rudder and a sliding mode control law for the lateral thrusters. When the air rudder cannot continuously produce control force and torque, the direct lateral force is added to the system. To solve the problem that LQR cannot directly obtain the analytical solution of the time-varying system, a novel approach to approximate analytical solutions using Jacobi polynomials is proposed in this paper. Finally, the stability of the time-varying compound control system is proven by the Lyapunov–Krasovskii functional (LKF). The simulation results show that the proposed compound control method is effective and can improve the fast response ability of the system.

Research on the induced vibration force characteristics of lateral propulsion propeller

Abstract This article conducts unsteady numerical calculations on lateral thrusters under arrival conditions, revealing the induced unsteady force characteristics under the interference between lateral thrusters and pod packages. The calculation results show that the lateral force and torque of the lateral propeller point towards the bow of the ship, and the main characteristic frequencies of pressure pulsation are blade frequency and its harmonics; The thrust and torque pulsation of the side thrusters on the bow side of the ship have maximum values; The bottom of the lateral thrust channel exhibits stronger pressure pulsation compared to other positions. The calculation results of this article determine the position and characterization form of the excitation force of the lateral thruster, providing a basis for the design of low-noise lateral thrusters.

Study on Fault Diagnosis Technology for Efficient Swarm Control Operation of Unmanned Surface Vehicles

The purpose of this study is to design a Swarm Control algorithm for the effective mission performance of multiple unmanned surface vehicles (USVs) used for marine research purposes at sea. For this purpose, external force information was utilized for the control of multiple USV swarms using a lead–follow-formation technique. At this time, to efficiently control multiple USVs, the LSTM algorithm was used to learn ocean currents. Then, the predicted ocean currents were used to control USVs, and a study was conducted on behavioral-based control to manage USV formation. In this study, a control system model for several USVs, each equipped with two rear thrusters and a front lateral thruster, was designed. The LSTM algorithm was trained using historical ocean current data to predict the velocity of subsequent ocean currents. These predictions were subsequently utilized as system disturbances to adjust the controller’s thrust. To measure ocean currents at sea as each USV moves, velocity, azimuth, and position data (latitude, longitude) from the GPS units mounted on the USVs were utilized to determine the speed and direction of the hull’s movement. Furthermore, the flow rate was measured using a flow rate sensor on a small USV. The movement and position of the USV were regulated using an Artificial Neural Network-PID (ANN-PID) controller. Subsequently, this study involved a comparative analysis between the results obtained from the designed USV model and those simulated, encompassing the behavioral control rules of the USV swarm and the path traced by the actual USV swarm at sea. The effectiveness of the USV mathematical model and behavior control rules were verified. Through a comparison of the movement paths of the swarm USV with and without the disturbance learning algorithm and the ANN-PID control algorithm applied to the designed simulator, we analyzed the position error and maintenance performance of the swarm formation. Subsequently, we compared the application results.

Improved line-of-sight nonlinear trajectory tracking control of autonomous underwater vehicle exposed to high variable speed ocean currents

In this paper, a new controller is proposed to help AUV (Autonomous Underwater Vehicle) track ideal trajectory in the high speed and variable speed ocean current environment. The kinematic and dynamic model of AUV under current interference is derived in the defined coordinate system. For the observation of variable speed current, the proposed controller proposes an improved extended state observer based on ADCP (Acoustic Doppler Current Profiler) sensor and fuzzy control. In order to resist the interference of high speed current, the proposed controller introduces an auxiliary lateral thruster to improve the anti-current capability of AUV. In order to coordinate the path tracking performance and current interference resistance of AUV, the proposed controller proposes an improved line of sight method, where observer gain is selected through fuzzy control. The improved line of sight method compensates for the prediction error of the state observer and the error in the AUV speed regulation process through the switching symbol function term in the sliding film control. The AUV's speed gradually reaches the ideal speed calculated by the navigation law through the dynamic controller, which is designed based on the backstepping method. Finally, the proposed controller is theoretically proved by the Lyapunov stability criterion and tested by comparison simulation in various working environments and controllers.

Research on Heading Control of USV with the Lateral Thruster

In order to solve the problem of low speed and stable course tracking of the small unmanned surface vessel (USV), the lateral thruster are added to the driving structure of the USV, and a backstepping control method is designed. By introducing the Lyapunov function, the course tracking error can converge to the region near the desired course and meet the transient and steady performance of the system at the same time. The adaptive control is applied to the lateral thrust control and the closed-loop system remains stable for a finite time. The Lyapunov direct method is used to prove the controller, which greatly simplifies the tedious parameter adjustment problem in traditional control. The simulation results show that the designed controller can make the USV track the specified value stably at low speed and meet the requirements of the USV heading robustness under dynamic conditions.

Sensitivity Analysis and Flight Tests Results for a Vertical Cold Launch Missile System

In vertical cold launch the missile starts without the function of the main engine. Over the launcher, the attitude of the missile is controlled by a set of lateral thrusters. However, a quick turn might be disturbed by various uncertainties. This study discusses the problem of the influences of disturbances and the repeatability of lateral thrusters’ ignition on the pitch maneuver quality. The generic 152.4 mm projectile equipped in small, solid propellant lateral thrusters was used as a test platform. A six degree of freedom mathematical model was developed to execute the Monte-Carlo simulations of the launch phase and to prepare the flight test campaign. The parametric analysis was performed to investigate the influence of system uncertainties on quick turn repeatability. A series of ground laboratory trials was accomplished. Thirteen flight tests were completed on the missile test range. The flight parameters were measured using an onboard inertial measurement unit and a ground vision system. It was experimentally proved that the cold vertical launch maneuver could be realized properly with at least two lateral motors. It was found that the initial roll rate of the projectile and the lateral thrusters ‘igniters’ uncertainties could affect the pitch angle achieved and must be minimized to reduce the projectile dispersion.

Parametric Study of Guidance of a 160-mm Projectile Steered with Lateral Thrusters

The development of projectile guidance requires consideration of a large number of possible flight scenarios with various system parameters. In this paper, the Monte-Carlo parametric study for a 160 mm artillery rocket equipped with a set of 34 small, solid propellant lateral thrusters located before the center of mass was evaluated to reduce projectile dispersion and collateral damage. The novelty of this paper lies in the functionality of modifying the shape of the trajectory in the terminal phase using lateral thrusters only. A six degree of freedom mathematical model implemented in MATLAB/Simulink was used to investigate the influence of numerous parameters on the resulting accuracy at several launch elevation angles. Augmented impact point prediction guidance was applied in the descending portion of the flight trajectory to achieve the trajectory shaping functionality. The optimum combination of thruster magnitude and algorithm parameters was obtained. The real data from the LN200 inertial measurement unit were used to investigate the influence of noise on the resulting accuracy. It was shown that with the proposed guidance method, the dispersion could be reduced by more than 250 times and the projectile impact angle might be increased when compared to an unguided projectile.

Spinning gasodynamic projectile system identification experiment design

PurposeThe purpose of this paper is to present the methodology that was used to design a system identification experiment of a generic spinning gasodynamic projectile. For this object, because the high-speed spinning motion, it was not possible to excite the aircraft motion along body axes independently. Moreover, it was not possible to apply simultaneous multi-axes excitations because of the short time in which system identification experiments can be performed (multi-step inputs) or because it is not possible to excite the aircraft with a complex input (multi-sine signals) because of the impulse gasodynamic engines (lateral thrusters) usage.Design/methodology/approachA linear projectile model was used to obtain information about identifiability regions of stability and control derivatives. On this basis various sets of lateral thrusters’ launching sequences, imitating continuous multi-step inputs were used to excite the nonlinear projectile model. Subsequently, the nonlinear model for each excitation set was identified from frequency responses, and the results were assessed. For comparison, the same approach was used for the same projectile exited with aerodynamic controls.FindingsIt was found possible to design launching sequences of lateral thrusters that imitate continuous multi-step input and allow to obtain accurate system identification results in specified frequency range.Practical implicationsThe designed experiment can be used during polygonal shooting to obtain a true projectile aerodynamic model.Originality/valueThe paper proposes a novel approach to gasodynamic projectiles system identification and can be easily applied for similar cases.

Impact point prediction guidance parametric study for 155 mm rocket assisted artillery projectile with lateral thrusters

Impact point prediction guidance parametric study for 155 mm rocket assisted artillery projectile with lateral thrusters

Finite-time blended control for air-to-air missile with lateral thrusters and aerodynamic surfaces

This paper investigates the tracking control problem for the air-to-air missile with lateral thrusters and aerodynamic surfaces. An integral sliding mode manifold which is suitable for solving the problem of the input constraint is first given based on the saturation function. By using the integral sliding mode manifold, a finite-time controller without singularity is designed to deal with the input saturation and bounded disturbances. Then, the control moment is mapped to the control commands for the aerodynamic deflector and thrust engine array respectively, by using the dynamic control allocation. Finally, theoretical analysis and numerical simulations are presented to prove that the robust controller can make the missile follow a reference signal in finite time.

Attitude Blended Control for Aerospace Vehicle with Lateral Thrusters and Aerodynamic Fins

A finite-time blended control strategy is proposed for the reentry phase attitude control of the aerospace vehicle (ASV) based on the neural network, sliding mode control theory and control allocation. Firstly, a finite-time neural networks sliding mode controller is designed based on the attitude model of the ASV in the reentry phase to obtain the virtual control moments which can make the attitude error converge to the equilibrium point in finite time. Secondly, the desired control moments are mapped into the control commands on the aerodynamic deflectors and the reaction control system (RCS) by using the control allocation. Finally, simulation results are provided to demonstrate the effectiveness of the attitude blended control strategy proposed.

Autopilot Design for a Compound Control Small-Scale Solid Rocket in the Initial Stage of Launch

In this paper, an autopilot design method for a compound control small-scale solid rocket is proposed. The rocket has multiple actuators, including a flexible nozzle for pitching and yawing channels, aerodynamic fins for rolling channel, and lateral thrusters which work in on-off mode for all three channels. In order to keep the aircraft steady in the initial stage of launch when the dynamic pressure is low, the autopilot is aimed at optimizing the cooperation among the actuators. Firstly, without considering the discontinuous lateral thrust, the control law for flexible nozzle and aerodynamic fins is achieved via the sliding mode control approach. On this basis, an object to be controlled with choiceness is obtained for the lateral thrusters controlled loop. Secondly, the operation logic of lateral thrusters is programmed, regarding rolling moment as priority. Thirdly, after a continuous controller is obtained, a discretization method for the lateral thrusters control law is designed combining the characteristics of sliding mode control and Lyapunov’s stableness theorem. Finally, the fundamental cause why compound control improves the system stability is given theoretically. Simulation results validate the improved response performance and robustness against uncertainties and disturbance of the autopilot.

Horizontal Parking Control of Autonomous Underwater Vehicle, FOLOGA

Abstract In this study, a velocity field control algorithm and an optimal autopilot algorithm are developed for horizontal parking system motion of Fologa which is an autonomous unmanned underwater survey vehicle and manufactured by Graaltech Ltd., Genoa, Italy. Firstly, a nonlinear mathematical model for Fologa is obtained. The structure of the mathematical model of the vehicle comes from a Newton-Euler formulation. The resultant nonlinear system is then controlled by PID controllers. These PID controllers are designed for horizontal parking motion which is realized by a suitable combination of rear and front lateral thrusters. The velocity field control and optimal control problem is that the vehicle is supposed to reach the desired position and rotation by consuming minimum energy. Velocity field control is solved with developed velocity field vector notation. Optimal control problem is solved with a genetic algorithm. The performance and consuming energy of velocity field control and optimal control are compared. All of this study is performed in a Matlab/Simulink environment.

Quantifying the extent of niche areas in the global fleet of commercial ships: the potential for “super-hot spots” of biofouling

Niche areas of ships, such as lateral thruster tunnels, sea chests, and propellers, are often hot spots for the accumulation of biofouling organisms, a potential source of aquatic invasive species. Yet, the relative importance of different niche areas is poorly resolved, in terms of both total surface area and the associated biota (i.e., the species of organisms and their abundances). To address this information gap, a method was developed to estimate the extent of various niche areas in the global fleet of 120,252 commercial ships active between 1999 and 2013. The total niche area for these vessels was estimated to be 32,996 × 103 m2, representing approximately 10% of the total wetted surface area (WSA) available for colonization by biota. Considering the portion of niche areas relative to the total WSA, it was highest for passenger vessels (27%), followed by tugs (25%), and fishing vessels (21%), with niche areas representing a small portion of the WSA for bulk carriers and tankers (7–8%). Examining the different types of niche areas, thruster tunnels had the greatest total extent (10,189 × 103 m2), representing a disproportionately large contribution (>50%) of the total niche area for passenger vessels and tugs compared to other vessel types. This result, combined with the use and cleaning of thrusters, may render them “super-hot spots” of biofouling. The uneven distribution and extent of niche areas across vessels has implications for transfers of organisms and management strategies to reduce invasions associated with the surfaces of ships.

Thermo-mechanical analysis of first-stage-adjustment thruster propelled by explosive pressure

A lateral jet thruster operates at high temperature and high pressure, which causes ablation at the nozzle neck and malfunction of the nozzle system. The function of the solid propulsion system's nozzle is to provide thrust to the system by effectively utilising the high temperature gas that is generated in the combustion chamber. The requirements of the lateral propulsion system have to be taken into account in nozzle design, as well as the structural safety of the nozzle itself. An accurate stress analysis therefore needs to be conducted beforehand, simultaneously taking into account the thermal stress caused by the heat transfer between the high temperature gas and the wall, and the mechanical stress resulting from the pressure in the flow path. This study examined nozzle safety according to thruster operating time, where high temperature and high pressure combustion gas explodes to propel the prototype lateral thruster.

Development of a core mathematical model for arbitrary manoeuvres of a shuttle tanker

A 3DOF still-water manoeuvring mathematical model embracing all regimes of motion of a single-screw shuttle LNG carrier has been developed. Besides four-quadrant models for hull forces, main propeller and the rudder, the model describes also the action of a lateral thruster and of assisting tug boats. Environmental factors include constant wind and constant current. Results of off-line simulations partly compared with available trial data are given.

Design of Missile Autopilot with Aerodynamic Lift and Reaction Jets Based on Auto Disturbance Rejection Controller

First a new autopilot design model is presented for the interceptor missile with the blended aerodynamic lift and reaction jet. The reaction jet can improve the response speed, but the structure of control system becomes more complex. Therefore how to design control strategy properly is an urgent problem. Second, considering the discrete property of the lateral pulse jet thrusters and the continuous property of the aerodynamic fins, a kind of ADRC (active disturbance rejection control) autopilot system was designed for the aerodynamic lift/reaction jet missile. Finally, through a testing in the simulation of MATLAB, it is shown that, due to the sufficient utilization of the reaction jet, there is a significant improvement in the fast response and robust performance of the proposed controller. It is applicable to design the autopilot of aerodynamic lift and reaction jet blended missile.

A vision-based autopilot for a miniature air vehicle: joint speed control and lateral obstacle avoidance

In our project on the autonomous guidance of Micro-Air Vehicles (MAVs) in confined indoor and outdoor environments, we have developed a vision based autopilot, with which a miniature hovercraft travels along a corridor by automatically controlling both its speed and its clearance from the walls. A hovercraft is an air vehicle endowed with natural roll and pitch stabilization characteristics, in which planar flight control systems can be developed conveniently. Our hovercraft is fully actuated by two rear and two lateral thrusters. It travels at a constant altitude (∼2 mm) and senses the environment by means of two lateral eyes that measure the right and left optic flows (OFs). The visuo-motor control system, which is called LORA III (Lateral Optic flow Regulation Autopilot, Mark III), is a dual OF regulator consisting of two intertwined feedback loops, each of which has its own OF set-point and controls the vehicle’s translation in one degree of freedom (surge or sway). Our computer-simulated experiments show that the hovercraft can navigate along a straight or tapered corridor at a relatively high speed (up to 1 m/s). It also reacts to any major step perturbations in the lateral OF (provided by a moving wall) and to any disturbances caused by a tapered corridor. The minimalistic visual system (comprised of only 4 pixels) suffices for the hovercraft to be able to control both its clearance from the walls and its forward speed jointly, without ever measuring speed and distance. The non-emissive visual sensors and the simple control system developed here are suitable for use on MAVs with a permissible avionic payload of only a few grams. This study also accounts quantitatively for previous ethological findings on honeybees flying freely in a straight or tapered corridor.

A new strategy for lunar soft landing

A new strategy based on a windlass device is proposed to deal with the terminal descent of a lunar soft landing mission in this paper. The lunar lander considered here consists of a rover and an assist module (AM) which is equipped with three decelerating thrusters and a lateral thruster. The rover and the AM are connected by a tether (mass is negligible) which winds around the windlass. The dynamics of the terminal descent process is modeled. The guidance laws for the terminal descent phase are derived. Both fuel optimality and lander safety are considered. The design of the terminal guidance laws in this paper are separated into three stages: firstly, finding the activation point of the decelerating thrusters to minimize fuel consumption; secondly, determining the tensile force of the tether for deployment; and finally, designing the tether’s tensile force to make the rover track the desired velocity-altitude profile. The proposed soft landing strategy needs only the measurements of altitude and vertical velocity. Therefore, it is easy to implement. It effectively prevents the decelerating thrusters’ plume from damaging the lander due to ground interference. Moreover, it is robust against the uncertainties of initial altitude and vertical velocity. Numerical simulation results illustrate the feasibility of the proposed soft landing strategy.

Full Scale Identification Method of Four-Quadrant Hull Hydrodynamic Coefficients in Ship Manoeuvring

A new identification method of four-quadrant hull manoeuvring hydrodynamics (temporarily called a “2×LT method”), as essentially based on recording the manoeuvring motions excited by two fixed-point lateral forces, is presented in detail, including the concept formulation and simulated results (proving the method's potential). There is, namely, a significant lack of published data in this context, which are necessary e.g. to run the low-speed harbour manoeuvring and berthing simulation. This rather simple and cheap solution can be easily used for full scale ships, that are intended to be the primary field of application, where two fore and aft pushing tugs are required. Also free-running models, after installing two mobile lateral thrusters, are a successful option, though being subject to some scale effects.