Aerodynamic Fins Research Articles

Performance analysis of single cylinder engines with enhanced heat dissipation fins using computational fluid dynamics

Engine cooling plays a major role in engine performance. The expanded surfaces that aids to dissipate the engine’s heat are called fins, but their length is limited, which constrains the heat dissipation rate. The automotive industry as a whole works to increase the rate of heat dissipation so that engine efficiency may be increased. Current work aims to increase heat dissipation rate through these extended surfaces by varying the shape of the fins. Here, four different fins are considered, namely circular fins, rectangular fins, aerodynamic fins and curved fins for the analysis. Firstly, finite volume method (FVM) analysis was carried to obtain convective heat transfer coefficient “h” value for each fin shape in FLUENT software. These “h” values are imported for FEA thermal analysis and the result of temperature distribution across the engine cylinder fins and heat flux values at three different vehicle speeds are examined. The heat dissipation rates were observed low for circular fins at all speeds.

Research on the Stability of an Air-to-Air Missile Compound Control System with a Pulse Modulator

Based on pulse modulator, a method of lateral force and aerodynamic compound control system design in air-to-air missile and the stability is studied. First, the lateral force is assumed to be continuous and blended with aerodynamic fins accordding to a certain proportion, and the compound control is designed based on three-loop control method. Then the switch order of direct force device is obtained based on the pulse modulator. At last, the stability of control system is analysed based on describing function method, and then the parameter of pulse modulator is properly chosen. Simulation results show the validity of the proposed design.

Experimental study of Stagnation Pressure Reaction Control for mid-calibre non-spinning projectiles

Increased precision of gun-launched ammunition can reduce collateral damage and increase stand-off distance. It can maximize the tactical advantage of each shot and reduce the number of rounds needed to achieve mission success. Worldwide, technology for controlled smart munitions is being researched and demonstrated in various implementations. Although the use of aerodynamic control fins is an effective control means, such fins are complex to integrate with the projectile, they increase radar reflectivity (with associated risk of counter battery fire) and will reduce payload. The Netherlands Organisation for Applied Scientific Research has been developing a Stagnation Pressure Reaction Control technology without aerodynamic fins, for aerodynamically unstable projectiles. The on-off character of this control technology requires a tuned control algorithm in order to achieve stable and controllable projectile behaviour. This article discusses simulated projectile behaviour under different control algorithms and presents achieved test object performance in a supersonic wind tunnel experiment performed in 2018. The experiment demonstrated feasibility of the combination of the Stagnation Pressure Reaction Control Technology and the tuned control algorithm for a non-spinning, aerodynamically unstable test object, hinged through its centre of mass. In a Mach 2 wind tunnel flow, this test object was stabilized and put under a controlled angle of incidence up to 1.5 degrees with angular error bandwidths up to 0.3 degrees, requiring and realising actuator response times on the order of 2 ms. For higher stable angles of incidence, required for correcting disturbances such as wind gusts, the SPRC technology could be integrated into projectiles with a reduced margin of instability. The short response time would provide such a projectile with a high level of (end game) manoeuvrability, for instance against moving targets.

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.

Development of a piezoelectric energy-harvesting sensor: from concept to reality

This study focuses on the development and integrated design over a 24-month period of a high efficiency energy-harvesting (EH) temperature sensor, based on piezoelectric materials, with applications for the sustainability of smart buildings, structures and infrastructures. The EH sensor, harvests the airflow inside Heating, Ventilation and Air Conditioning (HVAC) systems, using a piezoelectric component and an appropriate customizable aerodynamic fin that takes advantage of specific air flow effects, and is implemented for optimizing the energy consumption in buildings. The project was divided in several work-packages (some running in parallel) that cover different aspects of the device development. Some of them focus on engineering aspects (starting from the numerical modeling, then prototyping, and concluding with experimental testing). Other aspects focus on the sensor promotion (including the development of a business plan, the intellectual property rights, the final design and the go-to-market actions). Considering the multidisciplinary character of the project (involving knowledge from fields such as wind engineering, electrical engineering, industrial design, entrepreneurship), this study tries to provide an insight on the complex design issues that arise when such complex, sometimes conflicting and overlapping aspects have to be managed within strict deadlines. In doing so, the most important design and development aspects are critically presented.

Nonlinear Model Predictive Control for Near-Space Interceptor Based on Finite Time Disturbance Observer

This paper proposes a novel nonlinear model predictive control design method based on the finite time disturbance observer (FTDO) and dynamic control allocation (DCA) algorithm for the near-space interceptor (NSI). First, the FTDO is introduced to estimate the mismatched system disturbance. The nonlinear model predictive control scheme based on the estimation value is proposed to obtain the virtual control command, and the mismatched disturbance can be effectively removed from the output channels of the NSI by designing a feed-forward disturbance compensation term with an appropriate compensation gain matrix. Moreover, a new DCA method is given to distribute the above virtual control command among the corresponding actuators (reaction jets and aerodynamic fins). Finally, numerical simulations illustrate that the proposed control scheme can track the command signal with high precision and have strong robustness against the mismatched disturbance.

Multi-Mode Electric Actuator Dynamic Modelling for Missile Fin Control

Linear first/second order fin direct current (DC) actuator model approximations for missile applications are currently limited to angular position and angular velocity state variables. Furthermore, existing literature with detailed DC motor models is decoupled from the application of interest: tail controller missile lateral acceleration (LATAX) performance. This paper aims to integrate a generic DC fin actuator model with dual-mode feedforward and feedback control for tail-controlled missiles in conjunction with the autopilot system design. Moreover, the characteristics of the actuator torque information in relation to the aerodynamic fin loading for given missile trim velocities are also provided. The novelty of this paper is the integration of the missile LATAX autopilot states and actuator states including the motor torque, position and angular velocity. The advantage of such an approach is the parametric analysis and suitability of the fin actuator in relation to the missile lateral acceleration dynamic behaviour.

Model tests of wind turbine with a vertical axis of rotation type Lenz 2

A building design of vertical axis wind turbines (VAWT) was presented in the article. The construction and operating principle of a wind turbine were described therein. Two VAWT turbine models were compared, i.a. Darrieus and Lenz2, taking their strengths and weaknesses into consideration. 3D solid models of turbine components were presented with the use of SolidWorks software. Using CFD methods, the air flow on two aerodynamic fins, symmetrical and asymmetrical, at different angles of attack were tested. On the basis of flow simulation conducted in FlowSimulation, an asymmetrical fin was chosen as the one showing greater load bearing capacities. Due to the uncertainty of trouble-free operation of Darrieus turbine on construction elements creating the basis thereof, a 3D model of Lenz2 turbine was constructed, which is more reliable and makes turbine self-start possible. On the basis of the research, components were designed and technical docu mentation was compiled.

Multi-model soft switching tracking control for near-space interceptor based on the disturbance observer

A disturbance observer–based multi-model soft switching tracking control design is proposed for the near-space interceptor. Initially, based on the Takagi–Sugeno modeling approach, a slow–fast loop soft switching model is employed to approximately describe the nonlinear dynamics of the near-space interceptor. Subsequently, a disturbance observer is constructed to estimate the unknown disturbance. Based on the disturbance observer, a descriptor system approach is proposed to solve the multi-model soft switching tracking control design problem. The suggested controller can not only ensure the stability of the closed-loop near-space interceptor system but also provide an upper bound of the cost function. Moreover, a robust least-squares weighted control allocation algorithm is employed to distribute the virtual control command among the redundant actuators (the aerodynamic fins and reaction jets). Finally, simulation results demonstrate the effectiveness of the proposed control scheme.

Observer-based adaptive sliding mode control and fuzzy allocation for aero and reaction jets’ missile

In this article, a novel control scheme is proposed to solve the problem of robust and fast tracking control for the longitudinal model of a dual-control missile steered by a combination of aerodynamic fins and reaction jets in the presence of model uncertainties and external disturbances. The control scheme contains two aspects, one is the observer-based adaptive sliding mode control law of the control moment and the other is the fuzzy allocation method which assigns the control moment to the fins and the reaction jets. The main contributions of the article are as follows: (1) to compensate the disturbances and uncertainties on the sliding mode surface and enhance the system robustness, an observer-based sliding mode surface is designed; (2) an adaptive sliding mode control scheme is proposed by introducing an adaptive term derived from radical basis function network, which does not require knowledge of the bound of the system uncertainties and external disturbances. Meanwhile, it eliminates the chattering phenomenon without deteriorating the system fast-response characteristic and robustness; (3) a control-moment allocator based on fuzzy reasoning is designed to make the system respond fast while avoiding wasting of the reaction jets. Simulation results demonstrate that the proposed control scheme is effective in improving control robustness and response rapidity.

Three-Dimensional Integrated Guidance and Control for Near Space Interceptor Based on Robust Adaptive Backstepping Approach

This study presents a novel integrated guidance and control method for near space interceptor, considering the coupling among different channels of the missile dynamics, which makes the most of the overall performance of guidance and control system. Initially, three-dimensional integrated guidance and control model is employed by combining the interceptor-target relative motion model with the nonlinear dynamics of the interceptor, which establishes a direct relationship between the interceptor-target relative motion and the deflections of aerodynamic fins. Subsequently, regarding the acceleration of the target as bounded uncertainty of the system, an integrated guidance and control algorithm is designed based on robust adaptive backstepping method, with the upper bound of the uncertainties unknown. Moreover, a nonlinear tracking differentiator is introduced to reduce the “compute explosion” caused by backstepping method. It is proved that tracking errors of the state and the upper bound of the uncertainties converge to the neighborhoods of the origin exponentially. Finally, simulations results show that, compared to the conventional guidance and control design, the algorithm proposed in this paper has greater advantages in miss distance, required normal overload, and flight stability, especially when attacking high-maneuvering targets.

Integrated Guidance and Control Design for the Near Space Interceptor

Considering the guidance and control problem of the near space interceptor (NSI) during the terminal course, this paper proposes a three-channel independent integrated guidance and control (IGC) scheme based on the backstepping sliding mode and finite time disturbance observer (FTDO). Initially, the three-channel independent IGC model is constructed based on the interceptor-target relative motion and nonlinear dynamic model of the interceptor, in which the channel coupling term and external disturbance are regarded as the total disturbances of the corresponding channel. Then, the FTDO is introduced to estimate the target acceleration and control system loop disturbances, and the feed-forward compensation term based on the estimated values is employed to effectively remove the effect of disturbances in finite time. Subsequently, the IGC algorithm based on the backstepping sliding mode is also given to obtain the virtual control moment. Furthermore, a robust least-squares weighted control allocation (RLSWCA) algorithm is employed to distribute the previous virtual control moment among the corresponding aerodynamic fins and reaction jets, which also takes into account the uncertainty in the control effectiveness matrix. Finally, simulation results show that the proposed IGC method can obtain the small miss distance and smooth interceptor trajectories.

Integrated guidance and control based on block backstepping sliding mode and dynamic control allocation

A novel integrated guidance and control (IGC) design method based on the block backstepping sliding mode and extended state observer is proposed for the near space interceptor (NSI) with aerodynamic fins and reaction jets. Initially, the IGC model is employed by combining the interceptor-target relative motion model with the nonlinear dynamic of the NSI. Subsequently, the ESO is constructed to estimate the target acceleration and autopilot loop disturbance. Based on the estimated value and block backstepping sliding mode method, the IGC algorithm is given to obtain the virtual control moment. The stability of the closed-loop IGC system is also proven based on the Lyapunov theory. Moreover, a new dynamic control allocation algorithm is proposed to distribute the previously virtual control moment among the redundant actuators, while the actuator saturation and rate constraints are also taken into account. Finally, simulation results demonstrate that the proposed IGC algorithm can not only obtain a small miss distance, but also ensure the stability of the NSI dynamic.

Disturbance-Observer-Based Robust H∞Switching Tracking Control for Near Space Interceptor

A novel robust <TEX>$H_{\infty}$</TEX> switching tracking control design method with disturbance observer is proposed for the near space interceptor (NSI) with aerodynamic fins and reaction jets. Initially, the flight envelop of the NSI is divided into small subregions, and a slow-fast loop polytopic linear parameter varying (LPV) model is proposed, to approximate the nonlinear dynamic of the NSI, based on the Jacobian linearization and Tensor-Product (T-P) model transformation approach. A disturbance observer is then constructed, to estimate the modeled disturbance. Subsequently, based on the descriptor system method, a robust switching controller is developed, to ensure that the closed-loop descriptor system is stable with a desired <TEX>$H_{\infty}$</TEX> disturbance attenuation level. Furthermore, the outcome of the proposed switching tracking control problem is formulated as a set of linear matrix inequalities (LMIs). Finally, simulation results demonstrate the effectiveness of the proposed design method.

A Blended Autopilot for Dual Control Missile Using Generalized Predictive and Adaptive Terminal Sliding Mode Control

A blended autopilot algorithm is developed using generalized predictive control and adaptive non-singular terminal sliding mode control, for dual control missile steered by combination of aerodynamic fins and reaction jets. The blended algorithm considers the reaction jets control design prior due to its inherent control error, and then treats the aerodynamic fin control on the basis of the reaction jets control results. The generalized predictive control method is applied to the reaction jets control, which could make the missile achieve desired performance with a small number of consumed reaction jets. Then a novel adaptive non-singular terminal sliding mode control method is proposed for the aerodynamic control system design, to meet the requirements of robustness and fast response for the control of the missile. The unknown bound of the uncertainties and disturbances is estimated adaptively in the control, which makes the control with better robustness. Using the Lyapunov stability theory, the finite time convergence in both reaching and sliding phases is achieved. Finally, the simulations are conducted on the nonlinear longitudinal missile model with uncertainties and disturbances, and the simulation results demonstrate the effectiveness of the blended autopilot algorithm.

Improving the Aerodynamic Performance of Flat-fronted Trains on Meter-gauge Railway Lines

Field measurements, wind tunnel experiments, and scale model launching experiments were conducted to improve the aerodynamic performance of flat-fronted trains on meter-gauge railway lines. The study centered mainly on the compression pressure waves generated by trains entering single-track tunnels and aerodynamic drag acting on the vehicle. Countermeasures to reduce the amplitude of the compression waves and their gradients and the aerodynamic drag were examined. Scale model launching experiments demonstrated that tunnel entrance hoods more than 8 m long - actual size - (about one and a half times the tunnel diameter) were an effective infrastructure measure for reducing the maximum compression wave pressure gradient (dp/dt)max by approximately 70% compared to tunnels with no hood. Running tests with real trains further demonstrated that attaching aerodynamic fins to the front end of a two-car test train traveling at 120 km/h was an effective onboard measure for reducing the separated flow region, (dp/dt)max by approximately 40%, and running resistance in the open environment by approximately 20%.

Vortex shedding induced energy harvesting from piezoelectric materials in heating, ventilation and air conditioning flows

A cantilevered piezoelectric beam is excited in a heating, ventilation and air conditioning (HVAC) flow. This excitation is amplified by the interactions between (a) an aerodynamic fin attached at the end of the piezoelectric cantilever and (b) the vortex shedding downstream from a bluff body placed in the air flow ahead of the fin/cantilever assembly. The positioning of small weights along the fin enables tuning of the energy harvester to operate at resonance for flow velocities from 2 to 5 m s−1, which are characteristic of HVAC ducts. In a 15 cm diameter air duct, power generation of 200 μW for a flow speed of 2.5 m s−1 and power generation of 3 mW for a flow speed of 5 m s−1 was achieved. These power outputs are sufficient to power a wireless sensor node for HVAC monitoring systems or other sensors for smart building technology.

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.

New Structure for an Aerodynamic Fin Control System for Tail Fin-Controlled STT Missiles

This paper presents a new design method for an aerodynamic fin-control system for tail-fin controlled skid to turn (STT) missiles. The performance of the actuation system plays a decisive role in determining the performance of the flight control system for a highly maneuverable missile. To control the missiles by aerodynamics, control surfaces, sometimes called fins, are used. Deflection angles of these fins are the control variables of aerodynamics, but aerodynamicists prefer to use analytic variables called aileron, elevator, and rudder instead of these physical variables because these three analytic variables dominantly influence the roll, pitch, and yaw motion of the missile, respectively; and each can be considered a linear combination of four fin deflection angles. On that basis, roll, pitch, and yaw autopilots for controlling the attitudes or lateral acceleration of the missile are designed, and aileron, elevator, and rudder commands, respectively, are generated as consequence outputs of each autopilot. In the existing fin-actuation control scheme for the typical tail-fin controlled cruciform missiles, these outputs are distributed to four fin defection commands. After that, the four fins are actuated by fin controllers so that their deflections follow the commands. This paper shows that such control schemes can cause a significant deterioration in flight control system performance when fin-actuators have certain physical constraints such as slew rate, voltage, or current limit, or have an uncertainty of actuator dynamics, and proposes a new control scheme that alleviates such problems. This scheme can be widely applied to various fin-actuation control systems. But in this paper, for convenience, a tail-fin controlled cruciform missile is used as the example, and the proposed control scheme is shown to give better performance than the existing one.