Tailless Aircraft Research Articles

Flight Dynamics and Control of a Vertical Tailless Aircraft

The present work aims at studying a new concept of a vertical tailless aircraft provided with a morphing tail solution with the purpose of eliminating the drag and weight created by the vertical tail structure. The solution consists on a rotary horizontal tail with independent left and right halves to serve as control surfaces. Different static scenarios are studied for different tail configurations. The proposed morphing configurations are analyzed in terms of static and dynamic stability and compared with a conventional configuration. The stability derivatives defining the limits of static stability are calculated for the whole range of tail rotation angles. The aircraft’s dynamic model is developed and feedback control systems are implemented. A sideslip suppression system, a heading control system and a speed and altitude hold system are studied for three different configurations, MC1, MC2 and MC3 configurations. Static results show that the aircraft is longitudinally stable for a wide range of tail rotation angles. Variation of tail dihedral and rotation angles are two mechanisms able to maintain directional and lateral stability but only the last is able to produce lateral force and yawing moment. Dynamic stability results demonstrate no spiral nor Dutch-roll modes due to the absence of the vertical stabilizer. The increase in tail rotation produces an appearance of the spiral mode and an unstable Dutch-roll mode that quickly degenerates into two unstable real roots with the increase in tail rotation. The addition of dihedral to the tail increases the stability of the overall modes while decreasing their variation amplitude with the tail rotation. The morphing tail configuration proved to be a feasible control solution to implement in an aircraft such as a small UAV, with the MC1 configuration being the most simple of the three morphing configurations and also the most reliable one.

Drag Reduction Methodology for Adaptive Tailless Aircraft

An approach is presented for determining optimum lift distributions for adaptive tailless aircraft. In this study, wing adaptation is achieved using multiple trailing-edge flaps that are used to optimally distribute the lift of the wing such that drag is minimized. For tailless aircraft that are stable in pitch, the lack of a secondary lifting surface makes it necessary that the lift distribution on the wing also satisfies a pitching-moment constraint to ensure trim. The current work implements a numerical approach that solves for the optimal scheduling of multiple trailing-edge flaps on the wing of a tailless aircraft for various flight conditions with a pitching-moment constraint to reduce both induced and profile drag. The approach uses superposition to construct the spanwise lift distribution from basic and additional loadings, and decomposes the flap-angle distribution into mean and variation distributions. Together, these elements enable the solution of the problem using semi-analytical methods that also provide insight. The results are presented for a planar, swept, tapered wing with two airfoil-section choices to verify the theory and provide insight for trade studies.

Flight mechanics of a tailless articulated wing aircraft

This paper investigates the flight mechanics of a micro aerial vehicle without a vertical tail in an effort to reverse-engineer the agility of avian flight. The key to stability and control of such a tailless aircraft lies in the ability to control the incidence angles and dihedral angles of both wings independently. The dihedral angles can be varied symmetrically on both wings to control aircraft speed independently of the angle of attack and flight path angle, while asymmetric dihedral can be used to control yaw in the absence of a vertical stabilizer. It is shown that wing dihedral angles alone can effectively regulate sideslip during rapid turns and generate a wide range of equilibrium turn rates while maintaining a constant flight speed and regulating sideslip. Numerical continuation and bifurcation analysis are used to compute trim states and assess their stability. This paper lays the foundation for design and stability analysis of a flapping wing aircraft that can switch rapidly from flapping to gliding flight for agile manoeuvring in a constrained environment.

Trim Optimizations of an Adaptive Tailless Aircraft with Composite Wing

This paper investigates aeroelastic tailoring and optimal trailing edge control surface deflection to minimize induced drag for a HALE UAV flying wing configuration. The analysis process is conducted on the Finite Element(FE) model of a composite slender wing. Genetic Algorithm(GA) is employed to aeroelastically tailor the wing by setting the composite ply orientation. The study examined conformal and traditional flaps and explored two optimization formulations to minimize drag. The impacts of the conformal control surface are recognized as required deflection saving which can be translated to drag reduction. The results also show that the control demands for the optimal trim can be further reduced if the wing is properly tailored.

Flight Control Design for a Tailless Aircraft Using Eigenstructure Assignment

We apply eigenstructure assignment to the design of a flight control system for a wind tunnel model of a tailless aircraft. The aircraft, known as the innovative control effectors (ICEs) aircraft, has unconventional control surfaces plus pitch and yaw thrust vectoring. We linearize the aircraft in straight and level flight at an altitude of 15,000 feet and Mach number 0.4. Then, we separately design flight control systems for the longitudinal and lateral dynamics. We use a control allocation scheme with weights so that the lateral pseudoinputs are yaw and roll moment, and the longitudinal pseudoinput is pitching moment. In contrast to previous eigenstructure assignment designs for the ICE aircraft, we consider the phugoid mode, thrust vectoring, and stability margins. We show how to simultaneously stabilize the phugoid mode, satisfy MIL-F-8785C mode specifications, and satisfy MIL-F-9490D phase and gain margin specifications. We also use a cstar command system that is preferable to earlier pitch-rate command systems. Finally, we present simulation results of the combined longitudinal/lateral flight control system using a full 6DOF nonlinear simulation with approximately 20,000 values for the aerodynamic coefficients. Our simulation includes limiters on actuator deflections, deflection rates, and control system integrators.

Potential Effects of Blended Wing Bodies on the Air Transportation System

Flying wings in various layouts (blended wing body, C-wing, tail-less aircraft, etc.) are among the most promising concepts in the foreseeable scenario of air traffic increase and very demanding noise and emission regulations. Published literature shows that these aircraft will exhibit considerable gains in field length and cruise performance with respect to conventional airplanes and could be less harmful in terms of emissions and noise. The objective of this study is to present the beneficial effects that blended wing bodies would have on the air transportation system: specifically, on four relevant aspects of airport capacity, community noise, air space capacity, and emissions.

Yaw Control of a Tailless Aircraft Configuration

The yaw control of a tailless aircraft configuration is investigated. The four trailing-edge control surfaces are actuated using electrical servos which are controlled using a custom designed Ether ...

Neurobiologically Inspired Control of Engineered Flapping Flight

This article presents a new control approach and a dynamic model for engineered flapping flight with many interacting degrees of freedom. This paper explores the applications of neurobiologically inspired control systems in the form of Central Pattern Generators (CPG) to control flapping flight dynamics. A rigorous mathematical and control theoretic framework to design complex three dimensional wing motions is presented based on phase synchronization of nonlinear oscillators. In particular, we show the flapping flying dynamics without a tail or traditional aerodynamic control surfaces can be effectively controlled by a reduced set of CPG parameters that generate phase-synchronized or symmetry-breaking oscillatory motions of two main wings. Furthermore, by using Hopf bifurcation, we show that tailless aircraft alternating between flapping and gliding can be effectively stabilized by smooth wing motions driven by the CPG network. Results of numerical simulation with a full six degree-of-freedom flight dynamic model validate the effectiveness of the proposed neurobiologically inspired control approach.

Multidisciplinary Considerations in the Design of Wings and Wing Tip Devices

Conceptual wing design analysis methods are combined with numerical optimization to find minimum-drag wings subject to constraints on lift, weight, pitching moment, and stall speed. Tip extensions and winglets designed for minimum drag achieve similar performance, with the optimal solution depending on the ratio of the maneuver lift coefficient to the cruise lift coefficient. The results highlight the importance of accounting for the depth of the wing structural box in the weight model and including constraints on stall speed. For tailless aircraft, C-wings show a slight performance advantage over wings with winglets when longitudinal trim and stability constraints are considered. This performance advantage is more significant for span-constrained or low-sweep designs. Finally, to demonstrate other possible applications of the method, planar wings with active load alleviation are optimized, showing drag savings on the order of 15%.

Lateral Stability and Control of a Tailless Aircraft Configuration

The aerodynamics of a generic aircraft configuration known as Swing was investigated. The configuration used had two trailing-edge flaps on each wing used for control around all three stability axes included pitch, roll, and yaw. Tests are done in the low-speed wind tunnel L2000 at a freestream velocity of 30 m/s corresponding to a Reynolds number of 6.9 · 105 was applied. A NACA-66009 airfoil was used for the wing, and the outer wing section was twisted up 5° around the leading-edge point of the wing. Asymmetric deflections with the same amplitude for both flaps on each wing were applied for roll control. The deflection of the flaps was recorded with a motion capture system. The infrared light was emitted from four cameras and the light was reflected back to the cameras with a scan rate of 100 Hz and the system computed the distance to the markers. The results revealed that a sudden increase in pitch moment were observed at angles of attack above 10° and the flaps deflected with the same amplitude.

ℒ 1 adaptive controller for tailless unstable aircraft in the presence of unknown actuator failures

This article considers application of ℒ1 adaptive controller to multi-input multi-output open loop unstable unmanned military aircraft. The control is designed to accommodate and to be robust to actuator failures as well as to pitch break uncertainty, which is used to model uncertain aerodynamics. Results of using the ℒ1 adaptive controller are compared with the conventional model reference adaptive control scheme to show improved transient command tracking as well as guaranteed time-delay margin.

Pitch Handling Qualities Investigation of the Tailless Gull-Wing Configuration

A handling quality analysis of the tailless swept gull-wing configuration is presented here. This aircraft configuration is defined, for the purpose of this discussion, as one having multiple sweep and dihedral angles. The effects of changes in the static margin and of gusts on handling qualities were investigated for this new configuration. The Exulans, an aircraft currently under development, was used as a representative example of a tailless swept gull-wing configuration. The Exulans uses variable outboard wing sweep as a means of static margin control. This is achieved by a sweep hinge located at semispan. The pilot can change the outboard wing sweep angle for purposes of pitch trim. The Exulans is a research test bed that is being used to investigate the possibility of designing a tailless aircraft with both good handling qualities and a high Oswald efficiency. The handling qualities investigation was limited to the longitudinal plane. A Neal-Smith handling quality analysis was used to investigate handling qualities at different static margins, and a Monnich-Dalldorff analysis was used to investigate gust handling qualities. Time domain simulations were also used to investigate the aircraft gust response. It is shown that the gull-wing configuration promises to have satisfactory handling qualities for a region of center of gravity locations, for which good Oswald efficiency can also be achieved. A satisfactory gust response can also be achieved.

Adaptive Synthetic Jet Actuator Compensation for A Nonlinear Aircraft Model at Low Angles of Attack

A new technology for the control of next-generation airplanes using virtual wing shaping with synthetic jet actuators is presented. In this approach, an array of actuators is used to modify the aerodynamic performance of a wing and mimic control surface deflections. In the model, the control effect is represented with a nonlinear, parameterized model, derived from experimental data. An adaptive compensation scheme for the implementation of such actuator arrays on a nonlinear tailless aircraft model at low angles of attack has been developed. Adaptive inverse arrays (set of adaptive inverse models of the actuators) are employed for cancelling the effect of the jet nonlinearities. A nonlinear state feedback control law is designed, wherein a set of intermediate states are used as controls for other aircraft states. Parameter projection-based adaptive laws are used to ensure desired closed-loop stability.

Effective Design of Highly Maneuverable Tailless Aircraft

The correct design of unusual aircraft configurations is critical to achieving proper closed-loop flight dynamics. This paper is a guide based on decades of design experience on how the proper incorporation of yaw control power effects (their magnitude and bandwidth) within the iterative conceptual design process is critical to a successful aircraft design from a dynamics standpoint. Also critical is the open-loop level of stability. Factors that must be accounted for in designing tailless aircraft are also covered. These include the use of high-fidelity simulations with higher-order actuator models, time delays, and frequently excluded second-order effects for effective vehicle modeling and simulation.

Robust Controller Design to Uncertain Nonlinear Tailless Aircraft

The vertical tail of an aircraft produces a large radar signature and the requirement for stealth in new military aircraft necessitates the design of tailless aircraft. Without the vertical tail results in lateral-directional response characteristics which are a great deal different from those of conventional aircraft. In this paper, a robust controller designed for the tailless aircraft is presented. The controller's basic structure consists of an inner-loop DI controller wrapped around an outer-loop robust µ-synthesis controller. The inner-loop controller equalizes the tailless aircraft dynamics across the flight envelope, and the outer-loop controller addresses the issues of stability, performance, and robustness to tailless aircraft uncertainties.

Constrained Control Allocation for Linear Systems with Internal Dynamics

This paper presents a new control allocation design method for overactuated linear systems with internal dynamics and input constraints. The control inputs are designed to implement constrained control allocation and guaranteed stability of the closed-loop system. An LMI-based sufficient condition is provided to solve the control allocation problem. The proposed approach is demonstrated by a linear tailless aircraft model.

Flying Wings. A New Paradigm for Civil Aviation?

Over the last 50 years, commercial aviation has been mainly based what is currently called the conventional layout, characterized by a slender fuselage mated to a high aspect ratio wing, with aft-tail planes and pod-mounted engines under the wing. However, it seems that this primary configuration is approaching an asymptote in its productivity and performance characteristics. One of the most promising configurations for the future is the flying wing in its distinct arrangements: blended-wing-body, C-wing, tail-less aircraft, etc. These layouts might provide significant fuel savings and, hence, a decrease in pollution. This configuration would also reduce noise in take-off and landing. All this explains the great deal of activity carried out by the aircraft industry and by numerous investigators to perform feasibility and conceptual design studies of this aircraft layout to gain better knowledge of its main characteristics: productivity, airport compatibility, passenger acceptance, internal architecture, emergency evacuation, etc. The present paper discusses the main features of flying wings, their advantages over conventional competitors, and some key operational issues, such as evacuation and vortex wake intensity.

Non-linear anti-windup for manual flight control

In this paper we address the windup problem arising from actuator magnitude and rate saturation for the linearized longitudinal short-period dynamics of a tailless aircraft model around any trim flight condition. The proposed anti-windup scheme allows for more aggressive manoeuvres than the standard “command limiting” approach. Moreover, the compensation law guarantees stability of the controlled aircraft for any pilot command and enforces flight quality specifications whenever they are achievable within the given control constraints. “Pilot-in-the-loop” simulations confirm the effectiveness of the control strategy.

Modified Pseudoinverse Redistribution Methodsfor Redundant Controls Allocation

Introduction I N recent years, control allocation problems have been intensively studied following the work of Durham.1−3 There are several solution methods: direct control allocation,1−3 daisy chaining,4 a linearprogramming (LP) method,5−6 a quadratic-programming (QP) method,7−11 and a pseudoinverse-redistribution (PIR) method.10−13 In this Note, a PIR method is discussed. A pseudoinverse has been used as a selector or a distributor.14 Shtessel et al. applied a pseudoinverse to the control allocation problem for a tailless aircraft.15 However, it is fixed, and it does not consider the control surfaces’ limits. Virnig and Bodden developed a PIR method for a short takeoff and vertical landing aircraft and then demonstrated the algorithm by means of a simulator.12 The PIR method repeats the process of calculating a pseudoinverse and a control vector by setting the saturated elements of a control vector to their limit values until a solution is obtained or there is no unsaturated element. Bordignon and Bessolo developed a modified method and applied it to the X-35 aircraft’s control allocation problem.16 Although the PIR method sets the saturated control elements to their limit values, the modified method selects only one saturated element and sets it to its limit value during the redistribution process. The purpose of this Note is to propose other modified methods and to compare them with the conventional PIR method and Bordignon and Bessolo’s method. A different selection of one saturated element results in a difference in performance. For this purpose, two different selections are proposed. The performance metrics of concern are the calculation times, the percentage of times that a method converges to an optimal solution, and the characteristics of the errors between the optimal solutions and the redistributed solutions. Numerical examples are presented for comparisons.

1101 ANSYSによる無尾翼滑空機の研究(GS-5 翼・ポンプ,研究発表講演)

For challenging the Birdman rally with a tailless aircraft, the design of aircraft which can fly a longer distance was investigated using ANSYS. First of all, we propose the aerodynamic design for the tailless aircraft to fly with stability by adjusting the position of center of gravity of the airframe, and then build the base to use ANSYS in other fields. Based on securing stability, which is the most important problem, the analysis on the fluid mechanics of the tailless aircraft was almost completed in this investigation.