Angle Of Attack Rate Research Articles

Preventing inlet unstart in air-breathing hypersonic vehicles using adaptive backstepping control with state constraints

Aiming at the problem that the inlet is prone to unstart during the flight of air-breathing hypersonic vehicles (AHV), an adaptive backstepping control method with state constraints is proposed to prevent the occurrence of inlet unstart. Firstly, a parametric model of AHV with velocity, flight path angle, angle of attack and angle of attack rate as state variables is derived. Then, adaptive dynamic inverse control is adopted for the velocity subsystem, and adaptive backstepping control with state C is adopted for the flight path angle subsystem. The tracking errors of angle of attack and angle of attack rate are constrained by asymmetric barrier Lyapunov function (ABLF) and symmetric barrier Lyapunov function (SBLF) respectively, and smooth saturation function is constructed to restrict the virtual control commands. Adaptive laws are used to handle parameter uncertainty. Finally, it is proved by Lyapunov theory that the states of the closed-loop system can be uniformly and ultimately bounded, and the constraints on angle of attack and angle of attack rate can be satisfied. The simulation results show that compared with the adaptive backstepping control method, the proposed method can guarantee that the angle of attack and angle of attack rate are always within the operating limits of scramjet engine, and effectively avoid the occurrence of inlet unstart.

Near-Optimal Guidance with Impact Angle and Velocity Constraints Using Sequential Convex Programming

This paper proposes a near-optimal air-to-ground missile guidance law with impact angle and impact velocity constraints based on sequential convex programming. A realistic aerodynamic model is introduced into the problem formulation, such that traditional optimization theory cannot obtain an analytical solution to the optimization problem under state constraints. The original problem is considered as an optimization problem, and the angle of attack is replaced with the angle of attack rate as a new control variable to reconstruct the problem and simplify the solving process. Next, the independent variable is changed in the differential equations to linearize and discretize the problem such that the reconstructed problem can be solved using sequential convex programming. The results obtained by numerical simulations confirmed that the proposed algorithm is valid and faster than the general-purpose nonlinear optimal control problem solver. Finally, it was verified that different impact angles and impact velocities were achieved.

A miniature seven-hole probe air data system and its application on spin prediction

A miniature air data system based on a seven-hole probe was developed for real-time, in-flight measurement of wind flow deviation angle and inertial parameters. The system is very small in size and weighs only 150 g, especially suitable for flight tests with miniature unmanned aerial vehicles (UAVs). It is capable of measuring angle of attack (AOA) and angle of sideslip (AOS), ranging up to ±78°. The exposed part is a slender probe fixed on the nose of the aircraft, which is only 4 mm in diameter. A spin flight test was conducted with a delta-wing, slender body unmanned aircraft; experimental results demonstrate the complete spinning process. The synchronized measurement of AOA, AOS and angular rate clearly revealed the different phases of spin entry. Furthermore, a spin prediction criterion based on the sideslip changes at high AOA is given. Flight test results show that the prediction approach based on air data can forecast spin entry earlier than the conventional approach based on angular rate, which makes incipient spin detection possible.

Altitude of Stabilization for Slowly Tumbling Re-Entry Vehicles

Abstract : An analysis is made to identify the parameters which determine the altitude of stabilization defined as the altitude at which the angle of attack rate first vanishes for slowly tumbling re-entry vehicles. The analysis is limited to small tumble rates and angles of attack which allow the assumptions of Cm = Cm and Cm = constant respectively. An expression is derived which implicitly relates the altitude of stabilization to (1) the initial descent velocity, VE sin , (2) the atmospheric scale height, (3) a vehicle stability parameter, Cm Al/I, and (4) the quantity ( o/ o). The important result is the fact that the initial angle of attack and initial tumble rate, i.e., o and o respectively, appear only as a ratio, o/ o, the remaining parametric quantities being properties of the vehicle, the atmosphere, and the trajectory.