Active Surface Control Research Articles

Optimal Control of a Semi-Active Suspension System Collaborated by an Active Aerodynamic Surface Based on a Quarter-Car Model

This paper addresses the trade-off between ride comfort and road-holding capability of a quarter-car semi-active suspension system, collaborated by an active aerodynamic surface (AAS), using an optimal control policy. The semi-active suspension system is more practical to implement due to its low energy consumption than the active suspension system while significantly improving ride comfort. First, a model of the two-DOF quarter-car semi-active suspension in the presence of an active airfoil with two weighting sets based on ride comfort and road-holding preferences is presented. Then, a comprehensive comparative study of the improved target performance indices with various suspension systems is performed to evaluate the proposed suspension performance. Time-domain and frequency-domain analyses are conducted in MATLAB® (R2024a). From the time-domain analysis, the total performance measure is enhanced by about 50% and 35 to 45%, respectively, compared to passive and active suspension systems. The results demonstrate that a semi-active suspension system with an active aerodynamic control surface simultaneously improves the conflicting target parameters of passenger comfort and road holding. Utilizing the aerodynamic effect, the proposed system enhances the vehicle’s dynamic stability and passenger comfort compared to other suspension systems.

Aeroservoelastic Wind Tunnel Evaluation of Preview and Gust Load Alleviation

Studies of preview gust load alleviation and controllers via synthesis, simulation, wind tunnel tests, and test/simulation correlation are presented in this paper. University of Washington active aeroservoelastic wind tunnel model design, construction, and testing capabilities are used. The test article is a flexible half wing–body–tail model with active control surfaces of two ailerons and an elevator. The model moves in a combination of rigid-body and elastic motions. The commands of gust vanes are used both to generate gusts and to provide real-time preview gust encounter information. A discrete-time linear-time-invariant output feedback system is augmented with various preview lengths of information. The experimental results show that gust loads are reduced with gust preview information compared to feedback-only control and are halved with the fullest gust preview information compared to the open-loop case. The wind tunnel results validated the simulations and added insights to the performance of preview and control implementation. The closed-loop analysis quantified the margins and robustness of the systems and correlated with the time history of both simulations and experiments. This paper presents preview gust load alleviation robust control test results, not available so far, in a realistic experimental setting.

Gliding Motion Optimization for a Biomimetic Gliding Robotic Fish

In this paper, we present a gliding efficiency optimization strategy based on deep reinforcement learning (DRL) for a gliding robotic fish. For the gliding motion in shallow waters, the non-steady motion strongly impacts the gliding range and also reduces efficiency. This paper presents a concept of transient gliding motion and illustrates its importance for small-scale gliding robotic fish. For better gliding performance of active fins, several pectoral fins with different sizes are designed and their hydrodynamics and optimizing capabilities are analyzed by computational fluid dynamics (CFD) simulation. Then, a double deep Q network (DQN) based optimization strategy is proposed to improve gliding efficiency by active pectoral fins, in which an adversarial model and a two-stage reward function are presented for the adequate calculation of gliding range. Simulations are conducted to validate the convergence and effectiveness of the proposed strategy. The aquatic experiments are carried out to further verify the proposed strategy. The results reveal that the optimization strategy can save about 4.88% of energy and 19.45% of travel time. This study provides clues to the design of active control surfaces and improvement of gliding efficiency for underwater vehicles. Remarkably, the proposed strategy can significantly improve the duration and endow the robot with the potential to perform complex tasks.

A Micro Aircraft With Passive Variable-Sweep Wings

Traditional fixed-wing vehicles are equipped with multiple active aerodynamic surfaces for flight control. This inevitably necessitates several actuators, complicates the mechanical structure, and adversely impacts the flight efficiency, particularly for small aerial vehicles. As a lightweight and efficient solution, this work proposes to employ passive variable-sweep wings on a micro airplane to eliminate the need for active control surfaces while retaining effective pitch maneuverability. Depending on the thrust produced by the propellers, the wings passively sweep back and forth, relocating the center of pressure and affecting the pitch moment. The thrust-induced deformation substitutes the elevators for pitch control. Through aerodynamic modeling, the flight dynamics of the proposed vehicle is analyzed. The results show that the proposed design brings about amplified and accelerated pitch response. Lastly, a prototype was constructed to demonstrate and verify the enhanced aircraft’s pitch control ability.

Effect of stern appendages configurations on the course-keeping of ships in stern-quartering seas

Ships can experience serious difficulties in keeping a straight course when sailing in stern-quartering seas. Design modifications like the addition of stern passive fins, or the modification of active control surfaces, are common solutions to improve the ship course-keeping. However, the success of such design modifications depends on the delicate balance between the excitation forces induced by the waves on the appended hull, the stabilization forces provided by the lifting surfaces as appended fins, and the steering forces provided by the control surfaces. This research investigates which of these aspects of a ship design play a concrete role in improving the ship course-keeping in waves. The study is carried out with the intention of looking at the different behaviors of the ship originating from different stern appendages configurations. Three modifications of stern appendages on three different ship hulls were investigated in various mild-to-rough sea conditions. The behavior of the vessels were simulated using a time domain, boundary element potential method, with the addition of semi-empirical formulations for the modelling of the stern lifting surfaces. The simulations were carried out in long crested irregular waves at three different direction, using the JONSWAP spectrum. The results showed that although larger stern appendages improve the directional stability of relatively large and slow vessels, in most cases they worsen their course-keeping ability, increasing the yaw motions. For smaller and faster vessels instead, passive and active fins tend to improve the course-keeping, because at high speed the lift provided by the appendages stabilizes the vessel. This effect is compensated by the wave excitation force at lower speed. Similarly to yaw, the roll motions increases with larger stern appendages.

Testing high-precision electromechanical actuators used for adjustment of deployable antennas of astronomy space missions

Actuators for deployable space antennas operating under temperatures around the liquid helium point (~4.2 K) are in great demand since the number of space missions involving deployable mirrors is growing. We are suggesting a design of actuators to provide adjustment of mirrors with the active surface control system having in view the Millimetron observatory (Spektr-M space mission).Having defined the reference precision, power consumption, and resistance to vacuum and cryogenic temperatures of such actuators, we have analyzed probable solutions, and accordingly created our own cryogenic models based on a well-proven motor previously used for similar but non-cryogenic applications. We are suggesting that these models could be used as the developmental prototypes for batch production thus cutting possible costs.The cryogenic tests of our developmental prototypes have been conducted both in the boiling liquid nitrogen medium and under closest to open space conditions in the cryogenic vacuum chamber with the Cryomech closed-cycle cryorefrigerator PT-407 cooled down to the liquid helium point. The original test setups which were a challenge in itself, test algorithms, and the test results are being presented. The properties and electrical characteristics, and results of the tests of the actuators’ thermal behavior when adjusting a deployable mirror in emulated real-life situations mimicking the conditions of the Millimetron observatory are being discussed.

Error Sensing Strategy for Active Control of Low-Frequency Sound Absorption of Micro-Perforated Panel Absorber by Using a Point Force Controlled Thin Plate

This paper presents an analytical investigation on constructing an error sensing strategy of a new type of active MPPA. The proposed active MPPA is composed of MPP, air cavity, and point force-controlled backing panel, which can actively improve the low-frequency sound absorption of the MPPA. Constructing an appropriate error sensing strategy for obtaining an error signal that is highly correlated with the sound absorption coefficient of the active MPPA is a key problem encountered in practical implementation. The theoretical model of the active MPPA is firstly established using the modal analysis approach. Then, the active control performance and surface impedance characteristics in the controlled condition are analyzed in detail. Finally, the error sensing strategy of the active MPPA is constructed by measuring the surface average impedance ratio with an acoustic vector sensor (AVS). Simulation results show that, due to the antisymmetric property of the vibration of the backing panel on the resonant frequency, the surface impedance of the active MPPA after control also has symmetry or antisymmetry properties. Hence, the surface average impedance ratio of the active MPPA can be measured by using the limited number of acoustic vector sensors (sensing pressure and particle velocity). This variable is also highly correlated with the sound absorption coefficient of the active MPPA and thus can be used to construct the cost function (error signal). The active control result obtained by the proposed error sensing strategy is in good agreement with the theoretically optimal result, which validates the feasibility of this approach.

Numerical study of aeroelastic suppression using active control surfaces on a full-span suspension bridge

In this study, the aeroelastic active control of a suspension bridge was studied using both experimental and numerical methods. Two flat plates attached on either side of the suspension bridge were used as the control surfaces. With a suitable rotation of the control surfaces, the turbulent flow around the bridge was modified, thus addressing the problem of aeroelasticity. An appropriate feedback control law was determined using a two-dimensional numerical model. Next, a wind tunnel experiment was conducted to validate the numerical results. The numerical analysis was conducted for a suspension bridge with a span of 3000 m. The effectiveness of the control was considered based on the arrangement of the control wings along the span of the suspension bridge. The ratio between the total length of the control surfaces and the span length was investigated. The coupling of the modes of the suspension bridge also affected the control results. It was suggested that aerodynamic stability could be enhanced by using a partially installed control surface. Moreover, the buffeting responses of bending and torsion of the suspension bridge could be reduced.

Aeroelastic control of bridge using active control surfaces: Analytical and experiment study

An active control using a control surface system with winglets is described herein. Winglets help a long suspension bridge reach a stable state of flutter and buffeting. This system ensures the aerodynamic stability of a lightweight and economic stiffening girder without additional stiffening. Using a two-dimensional model, numerical and experimental studies were carried out to find a feedback control using winglets. In conclusion, a suitable control of the winglet motion can increase the flutter speed of a suspension bridge as the buffeting response moves in a contrasting manner.

Aerogami: Composite origami structures as active aerodynamic Ccontrol

This study explores the use of origami composite structures as active aerodynamic control surfaces. Towards this goal, two origami concepts were designed leveraging a combination of analytical and finite element modeling, and computational fluid dynamics simulations. Wind tunnel tests were performed at different dynamic pressures in conjunction with two different active control laws to test the capability of obtaining desired drag values. The experiments revealed excellent structural rigidity and folding characteristics under aerodynamic loading. These results are in very good agreement with one-way Fluid Structure Interaction (FSI) simulations, which show the potential of using high-fidelity modeling for the design and optimization of these structures.Future work will focus on developing advanced origami designs that allow for more deterministic folding as well as improved weight, stiffness, and fatigue characteristics in the use of materials.

A CFD-based numerical virtual flight simulator and its application in control law design of a maneuverable missile model

A CFD-based Numerical Virtual Flight (NVF) simulator is presented, which integrates an unsteady flow solver on moving hybrid grids, a Rigid-Body Dynamics (RBD) solver and a module of the Flight Control System (FCS). A technique of dynamic hybrid grids is developed to control the active control surfaces with body morphing, with a technique of parallel unstructured dynamic overlapping grids generating proper moving grids over the deflecting control surfaces (e.g. the afterbody rudders of a missile). For the flow/kinematic coupled problems, the 6 Degree-Of-Freedom (DOF) equations are solved by an explicit or implicit method coupled with the URANS CFD solver. The module of the control law is explicitly coupled into the NVF simulator and then improved by the simulation of the pitching maneuver process of a maneuverable missile model. A nonlinear dynamic inversion method is then implemented to design the control law for the pitching process of the maneuverable missile model. Simulations and analysis of the pitching maneuver process are carried out by the NVF simulator to improve the flight control law. Higher control response performance is obtained by adjusting the gain factors and adding an integrator into the control loop.

Active control of supersonic transport aeroelastic oscillations using high-fidelity equations

A higher order computational procedure to alleviate aeroelastic oscillations by using active control surfaces is addressed. Flow is modeled using the high-fidelity Navier–Stokes (NS) equations, compared to the current use of the low-fidelity linear theory to design active controls. An active control module is embedded into a general-purpose NS flow solver developed for full aircraft configurations. The structure is modeled using the modal equations of motion, and existing active control equations based on the energy approach are utilized. Previously established transonic small perturbation theory and wind tunnel experiments are considered for validating. The use of active controls for next generation supersonic transport aircraft is demonstrated.

Reduced-order model for robust aeroelastic control

The objective of aeroelastic control, i.e., aeroservoelasticity, is either suppression of instability, such as flutter, or impeding the effect of external excitation, e.g., due to a gust. In the present work, a robust active feedback controller for a NACA64A010 airfoil model under sub- and transonic flow conditions is designed to impede flutter. The airfoilmodel has an elastic heave and pitch suspension and is equipped with an active aerodynamic control surface. The control design is based on linear reduced-order models (ROM) derived from a coupled computational fluid dynamics (CFD)-computational structural mechanics (CSM) simulation environment. Because the control design should be robust across a range of flow conditions, a collection of ROMs, which span the desired operational envelope, is considered. For each condition, the stability region for a three-term controller is determined with a parameter space approach. Building the intersection area for certain flow regimes allows determining the area of robust stability. The possibility of shifting the flutter boundary with a robust controller compared to adaptive control designs is discussed. To determine finally a set of control parameters chosen from within the stabilizing area, an optimization approach is used. Comparisons of the response of the investigated airfoil model under control between ROM and CFD–CSM shows that the linear ROM is able to predict the response very accurately, despite nonlinearities due to shocks in the flow field.

FNN Approximation-Based Active Dynamic Surface Control for Suppressing Chatter in Micro-Milling With Piezo-Actuators

In this paper, an active dynamic surface control (DSC) to suppress regenerative chatter in micro-milling with nonlinear piezo-actuators (PZTAs) as active elements has been developed, where the hysteresis effects of two PZTAs are considered. The main features of the proposed approach are: 1) fuzzy neural networks (FNNs) are applied to approximate the unknown functions, including the uncertain dynamics of the high speed cutting system, the unknown bounding functions related to the time-delayed states, and the control errors introduced during the control design procedure; 2) to avoid the development of the adaptation law for each individual weight of the FNNs, the squared 2-norms of the weight vectors are constructed; 3) the utilization of two decreasing smooth performance functions ensures the boundedness of the tracking errors with the prescribed performance; 4) the Prandtl-Ishlinskii (PI) model is employed to depict the hysteresis effect of the active PZTAs and its inverse construction is adopted to mitigate the nonlinear influence; and 5) the Lyapunov-Krasovskii functional is used to cope with the time-delayed effect of chatter in micro-milling, which plays a pivotal role in developing the active control laws. The developed controller with the employments of Lyapunov-Krasovskii functionals, DSC and the adaptive FNN backstepping design can successfully suppress the chatter in micro-milling, guaranteeing all the signals of the closed-loop system are bounded. Simulation results are provided to verify the effectiveness of the proposed control approach.

Development of active surface technology of large radio telescope antennas

Aperture expanding and frequency upgrading of full steerable antennas make the electrical performance of the antennas difficult to guarantee, and that radio telescopes operate in a complex environment, so it has to improve the performance by some methods like mechanical or electronic compensation. To control the pointing accuracy and the detecting distance of antennas, we must adjust the position and the surface shape of shaped reflectors, in another word, the active surface adjustment is the most effective way. Therefore, this article describes the situation and status of applications of active surface adjustment. Then, it summarizes the basic principle and the applications of active surface adjustment and particularly analyzes the key technologies which include the calculation of actuator movement, the block design of main surface, the actuator design, the active surface control system and the surface profile measuring. The comparisons among four large radio telescopes of the world are discussed, which have used active surface technology. At last, it points out some suggestions on the future research of active surface technology of large radio telescopes such as QTT.

Morphing elastically lofted transition for active camber control surfaces

This paper introduces a compliant morphing flap transition that seeks to address a long-standing source of noise and drag in the design of aircraft wings – the gap present at the spanwise ends of the control surfaces. These gaps create large discontinuities in the flow and allow for pressure leakage from the lower to upper wing surface, generating significant amounts of vorticity, noise, and drag. The concept introduced here seals this gap with a smooth, three-dimensional morphing transition section that elastically lofts between the rigid wing and moving control surface in a passive and continuous manner. Previous transition concepts are first discussed, followed by establishment of an initial desired transition shape. Computational fluid dynamics analysis of the desired transition shape indicates both an increase in lift and a decrease in drag. The morphing, elastically lofted transition concept proposed here will then be introduced. In this concept, the complex three-dimensional shape change required is created with a novel structural architecture that combines material and geometric compliance with geometric bend-twist coupling. The concept design and operating principles will be introduced, relevant geometric parameters will be derived, and an initial prototype demonstrator capable of large deflections and smooth transition surfaces will be shown.

The design and realisation of the IXV Mission Analysis and Flight Mechanics

The Intermediate eXperimental Vehicle (IXV) is a suborbital re-entry demonstrator successfully launched in February 2015 focusing on the in-flight demonstration of a lifting body system with active aerodynamic control surfaces. This paper presents an overview of the Mission Analysis and Flight Mechanics of the IXV vehicle, which comprises computation of the End-to-End (launch to splashdown) design trajectories, characterisation of the Entry Corridor, assessment of the Mission Performances through Monte Carlo campaigns, contribution to the aerodynamic database, analysis of the Visibility and link budget from Ground Stations and GPS, support to safety analyses (off nominal footprints), specification of the Centre of Gravity box, selection of the Angle of Attack trim line to be flown and characterisation of the Flying Qualities performances. An initial analysis and comparison with the raw flight data obtained during the flight will be discussed and first lessons learned derived.

Shear stress and noise metric reduction using active vibration

The effects of active vibrational surface on wall shear stress and noise metric have been researched by the computational fluid dynamics method. The skin-friction drag and noise metric can be decreased by the active surface control. A sinusoidal vibration was imposed on the surface of a plate and the vibrational position located on downstream of the plate leading edge. The turbulence boundary layer was fully developed at the vibrational position. The downstream skin-friction drag exhibited a strong dependence on the control parameters (oscillation frequency and amplitude). A reduction in the trailing edge noise was obtained by the increasing of vibrational frequency and the appropriate choosing of amplitude. The maximum reduction in local skin friction drag is 64.3%. The noise metric can be decreased by 37.9 dB. Comparing the near-wall flow structures with and without control, it can be found that the turbulent kinetic energy and characteristic turbulence length scale were changed by the control.

Shear stress and noise metric reduction using active vibration

The effects of active vibrational surface on wall shear stress and noise metric have been researched by the computational fluid dynamics method. The skin-friction drag and noise metric can be decreased by the active surface control. A sinusoidal vibration was imposed on the surface of a plate and the vibrational position located on downstream of the plate leading edge. The turbulence boundary layer was fully developed at the vibrational position. The downstream skin-friction drag exhibited a strong dependence on the control parameters (oscillation frequency and amplitude). A reduction in the trailing edge noise was obtained by the increasing of vibrational frequency and the appropriate choosing of amplitude. The maximum reduction in local skin friction drag is 64.3%. The noise metric can be decreased by 37.9 dB. Comparing the near-wall flow structures with and without control, it can be found that the turbulent kinetic energy and characteristic turbulence length scale were changed by the control.

In brief

PAGE 18 Researchers in Korea have proposed a method to significantly reduce the computation complexity of a phase rotation beamforming technique commonly used in medical ultrasound scanners. They demonstrate that it can be implemented on smartphone hardware and that the technique doesn't sacrifice image quality, either analytically or experimentally. PAGE 29 Optical cloaking of arbitrary cross-section cylindrical structures using scattering cancellation is presented in work from Iran. The approach uses nano-strips of silver in a dielectric host as a cloaking shell around the object and the work explores the effect of the nano-strip parameters on the cloaking efficiency. The computational complexity of the technique is improved sufficiently to run in realtime on a smartphone without compromising quality PAGE 51 A compact Ka-band full bandwidth 3-dB waveguide hybrid has been designed by researchers in China. With high directivity over the full bandwidth of the WR-28 standard waveguide. The hybrid can also be used as a two-way power divider and can be made with excellent repeatability at low-cost. Optical cloaking of cylindrical objects of arbitrary cross-section PAGE 12 Researchers in China present a surface diagnosis approach for large reflector radio astronomy antennas with active surface control systems. Based on microwave holographic techniques, it allows far field patterns to be measured in focus by actively adjusting the primary surface. The 3-dB waveguide hybrid can be fabricated at low-cost with excellent repeatability PAGE 36 A robust, portable stereoscopic system for rapid identification of hidden objects using only a small number of X-ray projections has been demonstrated in work from the US. The system uses a single fixed sensor and obtains different angles using a motion-controlled single X-ray source. With a known system geometry, a series of depth planes can be computed to allow rapid object identification and realtime operation. The approach applies techniques from microwave holography to large reflector radio astronomy antennas The single source, single sensor, portable X-ray system allows rapid identification of hidden objects