Large Flight Envelope Research Articles

Asynchronous H∞ control for unmanned aerial vehicles: switched polytopic system approach

This study is concerned with the H∞ control for the full-envelope unmanned aerial vehicles (UAVs) in the presence of missing measurements and external disturbances. With the dramatic parameter variations in large flight envelope and the locally overlapped switching laws in flight, the system dynamics is modeled as a locally overlapped switched polytopic system to reduce designing conservatism and solving complexity. Then, considering updating lags of controller's switching signals and the weighted coefficients of the polytopic subsystems induced by missing measurements, an asynchronous H∞ control method is proposed such that the system is stable and a desired disturbance attenuation level is satisfied. Furthermore, the sufficient existing conditions of the desired switched parameter-dependent H∞ controller are derived in the form of linear matrix inequality (LMIs) by combining the switched parameter-dependent Lyapunov function method and average dwell time method. Finally, a numerical example based on a highly maneuverable technology (HiMAT) vehicle is given to verify the validity of the proposed method.

An overview on flight dynamics and control approaches for hypersonic vehicles

With the capability of high speed flying, a more reliable and cost efficient way to access space is provided by hypersonic flight vehicles. Controller design, as key technology to make hypersonic flight feasible and efficient, has numerous challenges stemming from large flight envelope with extreme range of operation conditions, strong interactions between elastic airframe, the propulsion system and the structural dynamics. This paper briefly presents several commonly studied hypersonic flight dynamics such as winged-cone model, truth model, curve-fitted model, control oriented model and re-entry motion. In view of different schemes such as linearizing at the trim state, input-output linearization, characteristic modeling, and back-stepping, the recent research on hypersonic flight control is reviewed and the comparison is presented. To show the challenges for hypersonic flight control, some specific characteristics of hypersonic flight are discussed and the potential future research is addressed with dealing with actuator dynamics, aerodynamic/reaction-jet control, flexible effects, non-minimum phase problem and dynamics interaction.

Collaborative Deformation Design Using Control Integrated Analysis Methods for Hypersonic Waverider

Hypersonic waveriders have a large flight envelope, leading to the difficulty in keeping overall flight stability for a fixed geometry. Accordingly, hypersonic waveriders can be considered to design as a morphing vehicle such that the flight range is expanded for waveriding stability. To this end, this paper investigates the collaborative deformation design using control integrated analysis methods for the hypersonic waverider. Firstly, a parametric model is applied to combine the shape deformation with the geometrical properties. Secondly, the morphing process with regard to the change in a single geometric parameter and the static and dynamic characteristics affected by this deformation are analyzed. Afterwards, the collaborative relations are discussed for the changes in the lower forebody angle and elevon area. Furthermore, a flight control law is designed to guarantee flight stability while implementing the collaborative deformation, and the morphing results are evaluated based on the control-oriented idea. Finally, a simulation example is used to verify the effectiveness of the proposed methods for the hypersonic waverider.

Nonlinear Multivariate Spline-Based Control Allocation for High-Performance Aircraft

High-performance flight control systems based on the nonlinear dynamic inversion principle require highly accurate models of aircraft aerodynamics. In general, the accuracy of the internal model determines to what degree the system nonlinearities can be canceled; the more accurate the model, the better the cancellation, and with that, the higher the performance of the controller. In this paper, a new control system is presented that combines nonlinear dynamic inversion with multivariate simplex spline-based control allocation. Three control allocation strategies that use novel expressions for the analytic Jacobian and Hessian of the multivariate spline models are presented. Multivariate simplex splines have a higher approximation power than ordinary polynomial models and are capable of accurately modeling nonlinear aerodynamics over the entire flight envelope of an aircraft. This nonlinear spline based controller is applied to control a high-performance aircraft (F-16) with a large flight envelope. The simulation results indicate that perfect feedback linearization can be achieved throughout the entire flight envelope, leading to a significant increase in tracking performance compared with ordinary polynomial-based nonlinear dynamic inversion.

An Improved Nonlinear Flight Controller Design Using Active Disturbances Rejection Control Method

An improved large envelope nonlinear flight control method using active disturbances rejection control (ADRC) method and wavelet neural network is approved in this paper. Wavelet neural network is used to realize the inversion of the 6-DOF nonlinear airplane model. The wavelet neural network is optimized using simulated annealing particle swarm optimization algorithm to improve the approach precision. In order to improve the robustness and control performance in all disturbances, ADRC is used to realize the high precision flight control. The simulation results show that the large envelope flight controller has excellent control performance.

A Robust Large Envelope Flight Controller Design Method Based on the Particle Swarm Optimization Algorithm

A robust flight control method based on the particle swarm optimization (PSO) algorithm is approved in this paper. Because of non-modeling dynamic character and parameter uncertainty are taken into consideration during the controller design process, the flight controller has strong robustness, excellent control performance and one robust controller could realize the large envelope flight control. In order to design the robust flight controller automatically and rapidly, the particle swarm optimization algorithm is used to select the weighting function. The simulation result shows that the weighting function could be designed automatically and rapidly, the flight controller has good performance and robustness.

Nonlinear system modeling and identification of small helicopter based on genetic algorithm

PurposeThe purpose of this paper is to build nonlinear model of a small rotorcraft‐based unmanned aerial vehicles (RUAV), using nonlinear system identification method to estimate the parameters of the model. The nonlinear model will be used in robust control system design and aerodynamic analysis.Design/methodology/approachThe nonlinear model is built based on mechanism theory, aerodynamics and mechanics, which can reflect most dynamics in large flight envelop. Genetic algorithm (GA) and time domain flight data is adopted to estimate unknown parameters of the model. The flight data were collected from a series of fight tests. The identification results were also analyzed and validated.FindingsThe nonlinear model of RUAV has better accuracy, the parameters are physical quantities, and having distinctly recognizable values. The GA is suitable for nonlinear system identification. And the results proved the identified model can reflect the dynamic characteristics in extensive area of flight envelop.Research limitations/implicationsThe GA requires much more computing power, to identify 12 unknown parameters with 30 iterations, will takes more than 18 hours of a four cores desktop computer. Because of this is an off‐line identification process, and has more accuracy, extra time is acceptable.Originality/valueGA method has significantly increased the accuracy of the model. The previous work of system identification used a ten states linear model, and using PEM identified 23 coefficients. By carefully building the nonlinear model, it has only 21 unknown parameters, but if the model is linearized, it will get a linear model more than 35 states, which shows nonlinear model contain more dynamics than linear model.

Some Control Problems for Near Space Hypersonic Vehicles

摘要: 近空间高超声速飞行器的特点给其建模和控制带来了新的问题.本文 首先分析高超声速飞行器的特点,进一步给出 大包络飞行的统一模型.其次,总结了高超声速飞行器巡航控 制、再入姿态控制研究的现状,强调了弹性、非最小相位、再入制导控制一体化设计等问题. 最后,结合高超声速飞行器的发展,阐述了高超声速目标的拦截问题,提供未来可供研究的方向. 关键词: 高超声速飞行器 / 特性分析 / 巡航控制 / 再入控制 / 拦截

Feedback linearization-based robust nonlinear control design for hypersonic flight vehicles

A new approach to designing a robust nonlinear controller for longitudinal flexible body models of canard configured air-breathing hypersonic flight vehicles with significant couplings and interactions is presented. The methodology uses a robust feedback linearization method to feedback linearize the nonlinear air-breathing hypersonic flight vehicle model with 24 uncertainty parameters. Using this approach, a linearized uncertainty model of the air-breathing hypersonic flight vehicle is obtained in the first step by considering an upper bound on each uncertain parameter. In the second step, a minimax linear quadratic regulator-based velocity and altitude robust tracking controller is synthesized for the linearized model. Simulation studies are conducted using the original nonlinear model of the air-breathing hypersonic flight vehicle with a large flight envelope and time-varying uncertainties. Simulation results show that the feedback linearization-based minimax linear quadratic regulator controller effectively achieves the tracking requirement and robustly stabilizes the air-breathing hypersonic flight vehicle.

Design of Neutral Network–Sliding Model Based Large Envelope Flight Control Law

Applying neutral network-sliding model control design methods to large envelope flight control law of aircraft whose model parameter varies greatly with flight condition was studied in this paper. Neural network theory is used to approximately linearize the nonlinear system and cancel the errors brought with approximate inversion, and the residual error is solved by sliding model control. So it can approximate the nonlinear model accurately, and improve robustness and anti-jamming capability of the flight control system. Simulation results show the design neural network – sliding model large envelope flight controller has excellent control performance.

Optimal Design of Configuration Change Program for Tactical Missile with Morphing Wings

The flight Performance of missile can be improved by adaptive morphing wing serving as main lift surface. A novel compounded morphing missile, a complicated nonlinear and non-analytical multivariable constrained optimization problem, is modeled to design adaptive program of the wing geometry versus flight states. Based on reformed optimal algorithms such as Monte Carlo and Particle Swarm Optimization (PSO), a set of integrated approach is developed to optimize the shape change program of wings by interactively reading and writing data files from missile DATCOM. The simulation results show that the proposed algorithms can be used to obtain an optimal missile configuration over large flight envelope, characterized by maximal lift-to-drag ratio and a required normal overload.

可倾转双旋翼微型飞行器飞行力学模型研究 Flight Dynamic Mathematical Model of Tilt Dual Rotor Micro Aerial Vehicle

微型飞行器(MAV)非线性飞行力学模型研究是MAV设计中的一个重要环节。可倾转双旋翼微型飞行器的非常规气动布局和大飞行包线使得其空气动力学特性与常规飞行器有很大差异。以理论计算为基础，在MATLAB/Simulink环境下建立了双旋翼微型飞行器的飞行力学模型。在建模过程中，采用非定常叶素理论计算旋翼的气动力，采用升力线理论计算机翼、尾翼和机身的气动力。对于气动干扰的问题，则着重考虑了螺旋桨滑流对机翼的影响。最后计算了MAV在不同飞行模式下的飞行性能和配平结果。结果表明，在整个飞行包线中，升降舵有足够的操纵权限来进一步改变MAV的飞行状态，MAV可以悬停，以直升机模式低速前飞，而且能以飞机模式快速前飞。 Research on nonlinear dynamic model of Micro Air Vehicle (MAV) plays an important role in MAV design. Its special design in configuration and large flight envelope make it more different from other aircrafts in aerodynamic characteristics. The flight dynamic model of the dual rotor MAV was established in MATLAB/Simulink environment based on research to the aerodynamic of the rotor and wing. Unsteady ele-ment theory was used to analyze the lift, drag, and moment of the rotor. The lift line theory was used to re-search the aerodynamics of the wing, fuselage, horizontal and vertical tails. The aerodynamic interference between propeller and wing was considered. At last, the MAV flight performance was calculated and trimmed in various flight modes. The results show that elevator has enough control authority to change the flight con-dition in the whole flight envelop and the MAV can hover, fly slowly in helicopter mode and fly rapidly in wing-borne mode.

Linear, parameter-varying control of a supercavitating vehicle

A systematic approach to parameter-dependent control synthesis of a high-speed supercavitation vehicle (HSSV) is presented. The aim of the control design is to provide robust reference tracking across a large flight envelope, while directly accounting for the interaction of liquid and gas phases with the vehicle. A nonlinear dynamic HSSV model is presented and discussed relative to the actual vehicle. A linear, parameter-varying (LPV) controller is synthesized for angle rate tracking in the presence of model uncertainty. The control design takes advantage of coupling in the governing equations to achieve improved performance. Multiple LPV controllers synthesized for smaller overlapping regions of the parameter space are blended together, providing a single controller for the full flight envelope. Time-domain simulations implemented on high-fidelity simulations, provide insight into the performance and robustness of the proposed scheme.

Model reference adaptive switching control of a linearized hypersonic flight vehicle model with actuator saturation

In order to address the control of an air-breathing hypersonic flight vehicle (AHFV) with actuator saturation, a model reference adaptive switching control (MRASC) approach is proposed. The design of the MRASC system is centred around a linearized longitudinal-motion flexible model at a Mach 8, altitude of 10 000 ft, and dynamic pressure of 1017 lb/ft2 flight condition. A switched reference system (SRS) is established to describe the desired dynamics of the AHFV with/without actuator saturation, and correspondingly, a switched adaptive controller (SAC) is constructed utilizing the hyperstability method. By switching between the subsystems of the SRS and the corresponding subcontrollers of the SAC, the MRASC system achieves the desired performance and is globally asymptotically stable under limited disturbances, provided that a simple linear-matrix-inequality-based sufficient condition holds. Although it is too early to say that the proposed scheme gives desired anti-saturation performance with respect to large disturbances, within a large flight envelope, there are still some advantages that will improve performance.

Modeling and attitude control analysis of a ducted-fan micro aerial vehicle

This paper deals with the aerodynamic modeling of a ducted fan Vertical TakeOff and Landing (VTOL) Unmanned Aerial Vehicle (UAV) and the problem of attitude stabilization when the vehicle is remotely controlled by a human pilot in presence of crosswind. The main aerodynamic elements, which are inherent to the presence of the duct and explain the flight dynamics of this kind of vehicle, are first presented. Then, an attitude control is designed from a linearization of the dynamic model around the hovering flight equilibrium. As the vehicle is axis-symmetric, the pitch and the roll dynamics have a similar expression. For this reason, the presentation is focused on the design of the pitch controller. Similar results can be directly deduced for the roll. Experiments, led on the HoverEye platform designed by Bertin Technologies, show that the proposed attitude control is sufficient to open a large secure flight envelope.

Robust terminal area energy management guidance using flatness approach

This study deals with the design of a guidance scheme based on flatness theory and dedicated to the terminal area energy management phase of a reusable launch vehicle. The proposed guidance strategy is based on a non-linear dynamic inversion technique to handle the large flight envelope that characterises the reentry mission. This inversion takes advantage of a particular choice of linearising terms called flat outputs, that are used to perform an input-to-state linearisation. First, it is shown that the coupled in-plane and out-of-plane vehicle dynamics admits a set of flat outputs. The flatness property of this model is then used to compute the nominal control input profiles corresponding to a single reference trajectory computed off-line. Based on the linearised model obtained by dynamic inversion, a linear tracking controller is then designed so as to circumvent off-nominal flight conditions. Finally, robustness and performances of the proposed guidance scheme are assessed by performing Monte Carlo runs within an industrial simulation environment.

Novel Control Scheme for Helicopter Flight: Fuzzy Immune Adaptive Model Inversion Control

A novel control scheme, fuzzy immune adaptive model inversion control, was put forward, aiming at the large flight envelope curve control problem of helicopter. The proposed scheme was designed based on model inversion theory, biology immune response mechanism and fuzzy control method. It could achieve effective control throughout large flight envelope curve via the design of fuzzy immune online-compensation element, only needing a static inverse model on the basis of a single flight condition. Simulation results comparing with the neural network adaptive control method show the system based on the proposed scheme has better real-time performance. It can offer adaptive compensation in time for model inverse errors caused by the changes of flight conditions and achieve accurate commands tracking. Stronger robustness has been demonstrated in the case of control surface damage and sensor output noise. Good three-axis uncoupled performance has also been shown.

NONLINEAR ROBUST MODEL PREDICTIVE CONTROL FOR LIFTING BODY RE-ENTRY FLIGHT ATTITUDE CONTROL

The dynamics of re-entry vehicles are time varying and notoriously nonlinear due to the large flight envelope and nonlinear aerodynamic flow phenomena. Accuracy of guidance and control of the re-entry vehicle along a predefined trajectory is crucial because of operational and safety considerations. This paper presents the design of a nonlinear attitude controller based on a Robust Model Predictive Controller (RMPC) combined with Feedback Linearization of the vehicle dynamics. Since the re-entry vehicle model contains uncertainties, FBL will not fully linearize the system. This, combined with its constraint handling capabilities, is the motivation for the application of RMPC. The uncertainty is modeled as perturbations of the aerodynamic parameters within a given percentage of their nominal value. The designed controller was tested using the GESARED simulation toolbox and shows excellent performance. The state and input constraints are satisfied, and the robustness of the controller to variations in the aerodynamic parameters has increased significantly compared to a nominal, non-robust controller.

ON THE DESIGN OF A FLATNESS-BASED GUIDANCE ALGORITHM FOR THE TERMINAL AREA ENERGY MANAGEMENT OF A WINGED-BODY VEHICLE

This paper suggests a flatness theory-based guidance scheme dedicated to the Terminal Area Energy Management (TAEM) guidance of a Reusable Launch Vehicle. The suggested guidance strategy is based on a Nonlinear Dynamic Inversion (NDI) by flatness approach adapted to the large flight envelope that characterizes the RLV reentry. By this way, after having demonstrated the flatness property of the coupled in-plane and out-of-plane vehicle dynamics, a linear tracking controller is added to the flat model so as to circumvent off-nominal flight conditions. Eventually, the robustness and performances of the considered TAEM guidance scheme are assessed using Monte Carlo simulations under a dedicated simulation tool.

Application of quantitative feedback theory to a class of missiles

A control design problem is investigated for a class of missiles that exhibits unstable and nonminimum phase behavior over a large flight envelope. Traditional control design for this class consists of a set of controllers, designed at different operating points within the flight envelope, which are implemented using the gain-scheduling method. The quantitative feedback theory is proposed for this class to overcome certain control design and implementation difficulties related to gain scheduling. In particular, the advantages in using quantitative feedback theory are that 1) it is possible to investigate the feasibility of fixed controllers for the whole flight envelope, and 2) it reveals tradeoffs between the size of flight envelope, controller complexity, and closed-loop specifications. These advantages are illustrated using a control design for the longitudinal dynamics of a Vanguard missile.