Aircraft flight control in wind shear using sequential dynamic inversion

Abstract

Longitudinal wind shear flight control laws are developed for the dynamics of a twin-jet transport aircraft using nonlinear dynamic inversion. Time-scale decomposition simplifies controller design by partitioning it into slow and fast time scales. The effects of time-varying winds are explicitly considered in the derivation of the controllers. Three inverting controllers are developed and evaluated: airspeed/climb rate, groundspeed /climb rate, and throttle/climb rate. The implementation of a climb rate scheduling strategy makes it possible for the resultant flight paths to mimic the essential features of optimal escape trajectories developed in an earlier study, where altitude is exchanged for airspeed as a function of microburst strength. NomenclatureD = drag, Ibf E s = specific Energy, ft F = nondimensional wind shear hazard index g = acceleration due to gravity, ft/s 2 h = altitude, ft I yy = moment of inertia about body y axis, slug-ft 2 L = lift, Ibf M = pitching moment m = mass, slugs q = pitch rate, rad/s R = radius of downdraft column, ft r = rate of climb, ft/s s = Laplace variable T = engine thrust, Ibf t = time, s f^max = maximum horizontal wind speed, ft/s u = aircraft control vector V a = airspeed, ft/s Vi = groundspeed, ft/s W = weight, Ibf w x = wind component along the x axis, ft/s w h = wind component along the h axis, ft/s jc = distance along the x axis, ft x = aircraft state vector y = control system command vector Zmax = altitude of maximum outflow, ft a = angle of attack, rad y = flight-path angle, rad A* = range from core, ft 8 E = elevator deflection, deg 8 T = throttle setting, % 0 = pitch attitude, rad Subscripts a, A = air-mass referenced quantity c = commanded value i, I = inertially referenced quantity

Accommodation of unknown actuator faults using output feedback‐based adaptive robust control

“…Step 2: From (27), (14), (15) and rearrangement of (23)-(26), the derivative of 1 can be written as,˙…”

“…Note that in the context of aircraft control, many disturbances can be modeled using harmonic functions e.g. wind-shear [14] which corresponds to the y term. Also, rate-gyros which are used for measuring yaw-rates suffer from harmonic disturbances (see [15]) as well.…”

Aircraft flight characteristics in conditions of windshear and icing

“…Before the 1990s the linear method was playing a major role in the windshear researches. However, with the development and application of nonlinear inverse dynamics (NID) method (1,2) , more effective windshear penetration or escape strategies based on the physical essence of windshear have appeared in recent years (3)(4)(5)(6) . The NID method, by employing the localised information (like the wind velocity and its first and second order derivatives) for feedback, accomplishes the feedback decou-…”

Robust nonlinear flight control of a high-performance aircraft

“…The design of the controller structure is based on nonlinear dynamic inversion [2]- [9]. It is possible to separate system dynamics into two time scales if one subset of the state components (referred to as "fast dynamics") is known to evolve in a much faster time scale than the other subset (referred to as "slow dynamics").…”

“…The control laws must be designed at many operating points, and a great amount of assessment is required to ensure adequate stability and performance at off-design points. An alternative approach is to explore direct techniques for designing nonlinear control systems, such as dynamic inversion [2]- [9].…”