Stability Derivatives Research Articles

Study progress of supramolecular drug delivery system loading traditional Chinese medicine/natural anti-tumor products

Ingredients with the anti-tumor property from traditional Chinese medicine/natural products have effects in treating tumor by regulating immune function, inhibiting tumor cell growth, inducing apoptosis, and reversing multidrug resistance. However, the potential of clinical application was restricted by the low hydrophilicity, stability and bioavailability and the lack of targeting. The above problems can be solved through research and development of supramolecular chemistry based on the non-covalent interactions between molecules. The supramolecular macrocyclic host molecules are characterized by a special cavity structure, low toxicity, high stability and rich derivatives spot. The anti-tumor supramolecular drug delivery system loading traditional Chinese medicine/natural products were designed to solve the above problems. In this paper, different supramolecular macrocyclic molecules, including crown ethers, cyclodextrin, calixarene, cucurbituril and two new-type supramolecular macrocyclic hosts were introduced. Their inclusion in enhancing drug solubility and stability, targeting drug delivery, synergies, combinative administration and new-type therapies in different applications, as well as such drug load modes as supramolecular polymers, indirect combination drug mode and polyrotaxanes were also reviewed in this paper, in order to provide a new idea for effective drug utilization.

Derived Angle of Attack and Sideslip Angle Characterization for General Aviation

Proper exploitation of derived angle of attack (AOA) and sideslip angle from low-cost attitude heading reference system sensors found in general aviation aircraft is a candidate solution for improving flight safety. This approach uses equations for AOA and sideslip angle that are solved on board in real-time, using state data and information provided by sensors. These equations are a function of vehicle parameters and stability and control derivatives, in addition to the angular displacement and angular rate sensor outputs. This paper characterizes and evaluates the feasibility of derived AOA and sideslip angle for part 23 use cases of pilot displays, envelope protection, and fly-by-wire flight control systems. Standard AOA and sideslip angle equations and sensor models are implemented in a nonlinear six-degree-of-freedom simulation model of the Cessna 172. Piloted simulation inputs are used in a non-real-time Monte Carlo simulation to evaluate the effect of modeling uncertainties and sensor noise on derived AOA and sideslip angle. Results presented in the paper show the allowable bounds on aircraft model parametric uncertainties such as stability and control derivatives, in addition to sensor noise levels, that produce usable derived AOA and sideslip angle values.

Dynamics Modeling and Pitching Parameters Identification of a Novel Hybrid UAV

Unmanned Aerial Vehicle (UAV) is an appealing topic for aeronautical researchers due to its tremendous application in the world. To make controller design possible for a novel UAV design, dynamics modeling-a process of deriving a set of differential equations governing the motion of the aircraft-is essential. In this paper, we present a conceptual approach to obtain the parameterized dynamics equation based on application of Newton's second law and approximations of aerodynamics effects on the UAV. From there, two identification methods are introduced, one bases on maximum likelihood while the other employs linear regression to estimate the aircraft's dynamic parameters such as aerodynamic and control and stability derivatives through an example involving our new hybrid UAV developed from fixed wing aircraft and a tricopter. Wind tunnel tests for a one-third scaled model are carried out to receive outputs of the model, such as Euler angles and rotation rates, from prescribed input signals, which are rotors' speeds, then pitching parameters are identified. Estimated model would then be validated to another set of experiment to show the fitness, hence remarks regarding the accuracy of the dynamics model and the parameters themselves can be made. The articles show that for the derived mathematical model, the estimation results were well fitted, and cross-validation also indicates that the model was fine enough. The methods have strong implications about its generality that is applicable to other novel vehicle designs.

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.

Experimental Study of Aircraft Achieving Dutch Roll Mode Stability without Weathercock Stability

Weathercock stability is usually considered essential to achieve normal flight, while the Dutch roll mode stability can still be achieved without weathercock stability which has been algebraically proved. This paper proposed a flight experiment to investigate the characteristics of an airplane with Dutch roll mode stability but no weathercock stability. Firstly, the algebraic analysis based on a standard lateral-directional mode approximation was made to demonstrate the effect of yawing stability derivative Cnβ on the Dutch roll mode characteristics. The flight experiment was organized after that using a model glider which was modified to have zero Cnβ but with marginal change on Cyβ. The convergence of Dutch roll mode in flight meets the algebraic and numerical analysis as expected. However, the difference of handling characteristics between the original and modified configurations indicates some other roles the weathercock stability plays in flight as well as some limitations of utilizing mode criterion in flight quality analysis.

Aerodynamic and aeroacoustic investigation of an innovative regional turboprop scaled model: numerical simulations and experiments

An extensive aeroacoustic and aerodynamic investigation of an innovative regional turboprop aircraft has been carried out experimentally and numerically under the framework of two research projects funded by the European Union through the CleanSky Research Programme. Experimental tests have been performed in the RUAG Large Subsonic Wind Tunnel in Switzerland and CFD results have been validated against the experimental data. The A/C high-lift performance, stability and control derivatives, aerodynamic noise sources, and low-noise solutions for high-lift devices, have been investigated under representative conditions in cruise, take-off, and landing configurations. The aerodynamic and aeroacoustic investigation has been carried out parametrically, in terms of several reference quantities, including the propellers’ thrust and rpm, the speed of the air-flow, the incidence angle of the aircraft and the position of the microphone array used for the acoustic investigation. The present paper gives an overview of relevant results obtained for selected aircraft configurations which have been tested in the wind tunnel and analyzed through CFD simulations. The focus lies on the overall aerodynamic characterization and on the noise sources identification carried out using standard beamforming techniques.

SVR-ND Method for Online Aerodynamic Parameter Estimation

Online aerodynamic parameter estimation plays an important role in compensating control system of aircraft under parameter uncertainties and unknown disturbance. In this paper, stability and control derivatives of aircraft are estimated online via support vector regression-numerical differential(SVR-ND) method. Small-sample real-time flight data reflecting real-time aerodynamic characteristics of aircraft is processed as training samples. For the small-size training samples, SVR technique is used for aerodynamic modeling. To pursue good performance in both computation efficiency and estimation accuracy, offline parameter estimation simulations are performed to select training sample size. It is observed that parameter estimation accuracy is related to the number of training samples and the noise level of samples. After that, an empirical formula is proposed to select training sample size according to results of simulations. To adapt the variation of samples, empirical formulas to tune hyper-parameters of SVR are presented based on the estimation of noise variance of samples. Finally, aerodynamic parameters are obtained by numerical differential in real-time. In a simulated maneuver, the proposed method is applied to online aerodynamic parameter estimation, and a Monte Carlo simulation is carried out to validate the robustness of SVR-ND method. Results indicate that the proposed method could realize accurate and robust estimation of aerodynamic parameters online.

Helicopter stability and control derivatives identification in different flight conditions

Helicopter flight simulators require high-fidelity dynamic models based on a set of stability and control derivatives (SCDs). For different flight conditions, specific sets of SCDs must be identified and utilized in the flight simulator software. In this study, nine sets of SCDs of the AS 355 F2 helicopter have been estimated from experimental flight-testing data, considering different combinations of velocity, mass, and altitude. Linear dynamic models with eight states and four controls were determined for the different flight conditions, using the output-error method. The associated optimization problem was solved with the Gauss–Newton algorithm, and identification reliability was evaluated by the Cramer–Rao (CR) and relative correlation coefficient (RCC) indices. An instrumented AS 355 F2 Helicopter belonging to the Instituto de Pesquisas e Ensaios em Voo, Departamento de Ciencia e Tecnologia Aeroespacial, Sao Jose dos Campos, Brazil, was utilized for data collection in different flight conditions, totaling 16 test hours. The following natural dynamic modes have been excited: phugoid, short period, spiral and Dutch roll, by command inputs of the type: frequency sweep (sinusoidal), doublet pulse and 3-2-1-1. Considering CR and RCC criteria, the most appropriate maneuver for exciting each dynamic mode is suggested, and the sets of the nine flight conditions are SCDs reported.

복합관절 조류형 비행로봇 설계 및 비행동특성분석

This paper presents the design and flight verification of an articulated ornithopter-type flying robot that mimics the articulated wing structure of a bird. Key design parameters such as transmission angle, folding angle, and inner flapping angle were analyzed using flapping kinematics. The simulation results of the parameters were cross-compared using MATLAB and Solidworks and verified in the ground experiment facility where a motion capture camera system was equipped. The designed ornithopter-type flying robot is 0.7 m long and 1.5 m wide, and the maximum takeoff weight (MTOW) is less than 300 g. To reduce weight in the manufacturing process, the skeleton was made of lightweight carbon, and the skin made of expanded polypropylene (EPP). It is important to prevent warping of the main wing for proper thrust generation while flapping, so the gears were made of high-stiffness polyether ether ketone (PEEK) and the shaft made of titanium. A small and lightweight flight control computer was used to control the longitudinal and lateral motion of the flying robot and to acquire flight data. The flapping excitation frequency matches well with the design value via fast Fourier transform (FFT) analysis from the flight test. Dynamic analysis of the flying ornithopter was performed using a simplified longitudinal and lateral/directional dynamic model using stability and control derivatives from system identification method of the flight test data. The results of the parameter-optimization process demonstrate that the designed ornithopter has short-period and long-period longitudinal motion with stable but relatively low damping. Lateral/directional motion reveals slightly unstable slow dynamics and stable fast-roll modes.

날갯짓 기능을 가진 도약 로봇의 종방향 안정성 해석

Due to safety concerns, it is difficult for human beings to access a disaster area to rescue survivors. Even a robot may fail to conduct a rescue mission if it can use only one mode of transportation. A robot with multiple modes of transportation may have a greater chance to successfully search for survivors within the golden time. In previous work to develop a dual-mode mobile robot, we introduced a jumping robot assisted by flapping wings called Jump-flapper. The robot was equipped with one driving motor and dual transmissions to operate a winching mechanism for elastic energy storage used for jumping and flapping mechanisms to provide additional thrust in the air immediately after jumping. In this paper, we analyzed the stability of Jump-flapper using a linearized equation of motion. With commercial software ANSYS-Fluent, computational fluid dynamics were used to compute stability derivatives included in the system matrix. The eigenvalue analysis finds that the robot eventually becomes unstable due to two unstable oscillatory modes. For a more accurate estimation of vertical jumping height, the drag of the robot body was included in the equation. Consequently, the equation of motion became non-linear and we used the Euler method to solve the non-linear equation. The estimated vertical jumping height agreed with the prediction by a simple model and with the measured height from our previous work.

A Survey of Controller Designs for New Generation UAVs: The Challenge of Uncertain Aerodynamic Parameters

This paper presents a survey of controller design techniques aimed at autonomous navigation and control of Unmanned Aerial Vehicles (UAVs), focusing on the challenge of aerodynamic uncertainty. Although many roadblocks exist, the most significant and challenging task for UAV navigation and control is the one of aerodynamic/model uncertainty. Current autopilots and controller designs for autonomous airplanes are mainly concerned with the feature of constant, unknown aerodynamic parameters, i.e., control and stability derivatives of the platform. This research focuses on a thorough investigation of the related theory and its applicability, centering on specific techniques that are able to control UAVs with rapidly changing, time-varying aerodynamic characteristics during flight. The scientific merit of this work is the comprehensive overview provided and the technical study that is performed, highlighting the advantages and disadvantages for each technique with respect to its efficiency and performance.

A Full Hydrodynamic Consideration in Control System Performance Analysis for an Autonomous Underwater Vehicle

Autonomous underwater vehicles (AUVs) have important applications in several areas such as data collection, geological survey and exploration in underwater environment. The hydrodynamic forces acting on AUVs are highly nonlinear and the higher-order hydrodynamic coefficients should be taken into account to represent these nonlinear behaviors. Therefore, developing a suitable dynamic model of the AUV and also an accurate knowledge about the hydrodynamic parameters are important for proper design of the navigation and control system. The main goal of the present paper is to investigate the role of proper dynamic model for an AUV which includes different hydrodynamic stability derivatives coefficients. Design of proper actuator is also significant for the global performance of the system and the expenses of the plan. It is tried in the present paper to investigate the effect of full hydrodynamic coefficients on the design of actuators and control system performance analysis for an AUV which was ignored in the previous works. For this purpose, the effect of these parameters on the open loop characteristics of the AUV, its role in the control system design and the interaction of control system and actuator dynamics are considered in nonlinear time domain and frequency domain. It is shown that in a full hydrodynamic consideration for design of the AUV, the effect of control gains, system bandwidth and damping can be different in comparison with the cases which are not fully considered them. Finally, the design of optimum actuator and the effect of actuator natural frequency on the flight performance in the presence of full hydrodynamic coefficients are studied.

Analysis of Damping Derivatives for Delta Wings in Hypersonic Flow for Curved Leading Edges with Full Sine Wave

In this study, an attempt is made to evaluate the effect of first arched ends on the damping derived due to the pitch rate aimed at the variable sine wave bounty, flow deflection angle δ, pivot position, and the Mach numbers. Results show that with the escalation in the bounty of the complete sine wave (i.e., positive amplitude) there is an enlightened escalation in the pitch damping derivatives from h = 0, later in the downstream in the route of the sprawling verge it decreases till the location of the center of pressure and vice versa. At the location where the reasonable force acts, when we consider the stability derivatives in damping for the rate of pitch q, there is a rise in the numerical tenets of the spinoffs. This increase is non-linear in nature and not like for position near the leading edges. The level of the stifling derivatives owing to variations in Mach numbers, flow bend approach δ, and generosity of the sine wave remained in the same range.

Research on Damping Derivatives for Delta Wings in Hypersonic Flow for Curved Leading Edges with Full Sine Wave

In this study, an attempt is made to evaluate the effect of first arched ends on the damping derived due to the pitch rate aimed at the variable sine wave bounty, flow deflection angle δ, pivot position, and the Mach numbers. Results show that with the escalation in the bounty of the complete sine wave (i.e., positive amplitude) there is an enlightened escalation in the pitch damping derivatives from h = 0, later in the downstream in the route of the sprawling verge it decreases till the location of the center of pressure and vice versa. At the location where the reasonable force acts, when we consider the stability derivatives in damping for the rate of pitch q, there is a rise in the numerical tenets of the spinoffs. This increase is non-linear in nature and not like for position near the leading edges. The level of the stifling derivatives owing to variations in Mach numbers, flow bend approach δ, and generosity of the sine wave remained in the same range.

Nonlinear parameter estimation of airship using modular neural network

AbstractThe prime focus of this work is to estimate stability and control derivatives of an airship in a completely nonlinear environment. A complete six degrees of freedom airship model has its aerodynamic model as nonlinear functions of angle of attack. Estimating the parameters of aerodynamic model in a nonlinear environment is challenging as it demands an exhaustive dataset that could cover the entire regime of operation of airship. In this work, data generation is achieved by simulating the mathematical model of airship for different trim conditions obtained from continuation analysis. The mathematical model is simulated using predicted parameter values obtained using DATCOM methodology. A modular neural network is then trained using back-propagation and Adam optimisation algorithm for each of the aerodynamic coefficients separately. The estimated nonlinear airship parameters are found to be consistent with the DATCOM parameter values which were used for open-loop simulation. This validates the proposed methodology and could be extended to estimate airship parameters from real flight data.

Review of Numerical Simulations on Aircraft Dynamic Stability Derivatives

The dynamic stability derivatives of flight vehicle are directly related to unsteady aerodynamics during maneuverability, and are considered as key parameters to both the aerodynamics, control system design and flight qualities evaluation. As the rapid development of new conceptual aircraft configurations, higher precision and efficiency calculations of the dynamic stability derivatives are urgently required. Limited by high costs and risks, the traditional experimental ways of flight test and wind tunnel test cannot be widely used, thus the numerical calculation on dynamic stability derivatives have become the primarily approaches. This paper reviews the numerically methods applied in the estimation of aircraft dynamic stability derivatives, includes the early analytical method, the empirical and semi-empirical methods and the widely used modern time domain and frequency domain methods, deeply highlighting the advantages and drawbacks of these methods of the actual applications on various aircrafts. The early analytical method by using potential theory can be used to calculate dynamic stability derivatives and will never work for current geometries. The empirical and semi-empirical methods are available with simple mathematical model and existed data. They have the advantage to be simple and rapid to compute and can be well adapted for initial evaluation of aircraft conceptual design. The time domain analysis based on solving Euler or NS equations with CFD technique are the most widely used methods to obtain the aircraft dynamic stability derivatives. With a variety of different strategies, they can calculate the combined and single dynamic derivatives to satisfy the demand of aircraft design in each stage. Even they are accurate and better in adaptability, the huge time cost on the periodic unsteady flow limits the application. To overcome this problem, the frequency domain methods based on harmonic oscillation are developed. They only use the results at several sample points during the unsteady cycle to reconstruct the periodic unsteady flows to further efficiently obtain the dynamic stability derivatives. These frequency domain methods are currently available only in harmonic oscillation cases. This paper also discusses and analyses the existing problems and possible development directions of the numerical methods to calculate aircraft dynamic stability derivatives from four aspects: theory, calculating elaboration, efficiency and accuracy, and application.

Stability analysis for the Whipple bicycle dynamics

It has been known that bicycle stability is closely linked to a pair of ordinary differential equations (ODEs). The linearization technique used to derive these ODEs, nevertheless, has yet to be thoroughly examined. For this purpose, we conduct an analysis of the dynamics of the Whipple bicycle, starting with the contact kinematics, using the Gibbs–Appell method. The effort results in a complete nonlinear model with minimal dimensions, from which equilibrium points during the bicycle’s straight and circular motions can be determined. The model can be linearized around these points via a perturbation analysis under no additional assumptions. Given the non-hyperbolic nature of the equilibria, we apply the center manifold theorem to analyze their stability, offering a rigorous derivation of the (well-know) exponential stability of the bicycle in its leaning and steering motions. Finally, a dimensionless index is defined to characterize the influence of physical parameters on the bicycle stability.

Mathematical model derivation of an unmanned circulation control aerial vehicle UC2AV

This paper presents a system identification method to derive accurate mathematical models for an unmanned circulation control aerial vehicle (UC2AV) that account for the effects of circulation control (CC) on the vehicle dynamics. The X-plane flight simulator and the CIFER system identification software are utilized to first derive simulation models to verify and validate the proposed system identification methodology. This is followed by flight tests to derive mathematical models and stability derivatives for the aircraft with CC-on and CC-off. Flight tests indicate a nose down pitching moment effect induced by CC, which in turn alter the UAV trim values and dynamics. Analysis of the two sets of mathematical models reveal that CC changes the longitudinal trim values and improves the lateral maneuverability of the UAV. Verification experiments indicate an acceptable match between the derived models and UAV dynamics by calculating root mean square (RMS) error values and by quantifying the model predictive ability through calculating the Theil inequality coefficient (TIC).

A numerical algorithm based on modified extended B-spline functions for solving time-fractional diffusion wave equation involving reaction and damping terms

In this study, we have proposed an efficient numerical algorithm based on third degree modified extended B-spline (EBS) functions for solving time-fractional diffusion wave equation with reaction and damping terms. The Caputo time-fractional derivative has been approximated by means of usual finite difference scheme and the modified EBS functions are used for spatial discretization. The stability analysis and derivation of theoretical convergence validates the authenticity and effectiveness of the proposed algorithm. The numerical experiments show that the computational outcomes are in line with the theoretical expectations. Moreover, the numerical results are proved to be better than other methods on the topic.

Simulation and modelling of flight missile dynamics and autopilot analysis

In the current paper, nonlinear modelling and dynamical analysis of a surface to surface missile with both aerodynamic and thrust vector control is investigated. Aerodynamic force and moment modelling of the presented missile includes the challenging high angle of attack aerodynamics behaviour and the so-called hybrid control, which utilizes both tail fins for stabilization and rudder vanes as control surfaces. Then, concerning relative rotation between bodies, the missile aerodynamic model is built by Leabedev aerodynamic calculations software. After using the generated aerodynamic data obtained the required aerodynamic stability derivatives, the required transfer functions are resolute based on the equations of motion of the missile. The missile dynamic motion in pitch and roll channel are analysed. The guidance and control strategy are developed through an actuation system and autopilot design in the four channels based on the poles assignment technique. The roll autopilot is constructed to regulate the roll angle of the front body of the missile which is the controlled part, for the command signals generated by the guidance laws both pitch and yaw autopilots are designed to realize. The guidance command is in the form of rate of change of flight path angles of the missile with time.