Conventional Aerodynamic Surfaces Research Articles

Numerical Exploration of Transverse Sonic Jet In Hypersonic Cross-flow

At high altitudes, due to low air density, the control response of highly agile and manoeuvrable aerospace vehicles through conventional aerodynamic surfaces is rather slow and inadequate. The control demand of such vehicles can be met very effectively with high-pressure side jets positioned at different locations of the vehicle. Additionally, as none of the components of passive jet control intrudes in the flow path in a passive state, no additional drag is incurred. CFD methods are increasingly being used to characterize jet-controlled aerospace vehicles. Before using in the design exercise, CFD methods need to be validated against reliable experimental results to find its range of applications and error band. In this work, a recent experimental study of transverse sonic injection into Mach 5 hypersonic stream is numerically explored by solving three-dimensional Reynolds Averaged Navier Stokes (RANS) equations using a commercial CFD solver. The computed surface pressures show a reasonable match with experimental results for different momentum ratios of jet and free stream flows. The predictive capabilities of different turbulence models were assessed. The spreading and penetration characteristics of the injectant are analysed from the computed data. The computed penetration and spreading of the injectant depicts nearly linear dependence with the momentum ratio.

Minimum Parameters Learning-Based Dynamic Surface Control for Advanced Aircraft at High Angle of Attack

Aiming at the difficulty of post-stall maneuvering control modeling and control of advanced aircraft under unsteady aerodynamics, a control method with high control accuracy and fast computation speed is proposed based on Radial Basis Function (RBF) network with minimum parameters learning (MPL) and dynamic surface control (DSC) method. Firstly, the aerodynamic characteristics of post-stall maneuvers are analyzed based on the experimental data of large-scale oscillation wind tunnels, and the key factors affecting the unsteady aerodynamic forces are obtained. Then, an accurate unsteady aerodynamic model is established based on the improved extreme learning machine (ELM) method. Secondly, the influence of unsteady aerodynamic forces on the control of post-stall maneuvers is considered. For the uncertainty of advanced aircraft model, high angle of attack flight control laws based on RBF-DSC are designed. In order to improve the calculation speed of the above control law and optimize the parameters, a post-stall maneuver control law method based on MPL-RBF-DSC is designed, and the stability of the method is proved. The coordinated allocation of the conventional aerodynamic surfaces and thrust vectors is realized based on the daisy chain method. Finally, the typical maneuver simulation of “Cobra” is carried out, which highlights the advantages of the design method in this paper, such as high control accuracy, short calculation time and strong robustness.

Nonlinear H2 Lateral Control Design of Missiles

AbstractA novel nonlinear control law for the purpose of lateral control of a missile is presented in this paper. This approach can be applied to generate lateral control commands for a missile operating in flight regimes where the effectiveness of conventional aerodynamic surfaces is reduced (i.e. high angle of attack). The design objective is to specify one control law that satisfies the H2 performance for the nonlinear attitude tracking design of missiles. In general, it is hard to obtain the closed‐form solutions from this nonlinear attitude tracking problem. Fortunately, because of the adequate choice of state variable transformation, the nonlinear H2 attitude tracking problem of the missile can be reduced to solving one nonlinear time varying Riccati‐like equation. Furthermore, one closed‐form solution to this equation can be obtained in a very simple form for the preceding control design.

Simulator Investigation of the VTOL Transport

In order to explore the handling and performance qualities of a future civil VTOL aircraft some fairly extensive flight simulation trials have been carried out. The simulated aircraft was a slender delta fitted with four banks of lift engines representing sixteen lift fan engines located on both sides of the fuselage. Thrust vectoring and thrust modulation were assumed for aircraft control in VTOL phases of flight, and conventional aerodynamic surfaces in wingborne flight. The simulator cockpit was equipped with the conventional dual flying controls and instrument panels typical of current jet airliners, but with some minor modifications to suit the VTOL role. Engine controls were modified as necessary, and a simple head-up display was incorporated. An analogue computer having some 400 amplifiers was used, for aircraft simulation in six degrees of freedom. Test pilots with current jet VTOL aircraft and helicopter flying experience participated in the piloted trials. The results of these trials indicated that the introduction of fail-safe autostabilization system into VTOL transport may be necessary in roll, pitch, yaw and in height. Very steep and vertical flight profiles, considered necessary to meet noise abatement rules during city center operations were studied and these proved to be feasible. Double lift fan engine failures could be controlled providing, at least, attitude demand autostabilization system in roll and in pitch was available. Particular attention was given to the cockpit controls layout, and to head up display. A gradual