Design of a Haptic Feedback System for Flight Envelope Protection

Abstract

Several modern aircraft use a passive control manipulator: a spring-damper system that generates command signals to the flight control computers in combination with a flight envelope protection system that limits pilot inputs when approaching the aircraft limits. This research project aims to increase pilot awareness of this protection system through the use of force feedback on the control device, that is, haptics. This paper describes in detail how the haptic feedback works and when it triggers; another paper will discuss the results of an experimental evaluation. With the current haptic design, pilots can get five cues: first, a discrete force cue when approaching the limits; second, an increased spring coefficient for control deflections that bring the aircraft closer to its limits; third, a stick shaker for low velocities; fourth, if a low-velocity condition requires an input, the stick is moved forward to the desired control input; and finally, the stick follows the automatic Airbus "pitch-up" command during an overspeed condition. This novel system is expected to help pilots correctly assess the situation and decide upon the right control action. It will be evaluated in two scenarios close to the flight envelope limits: a windshear and an icing event. Nomenclature a = acceleration, m∕s 2 C L = lift coefficient D = drag, N F = force, N g = gravitational acceleration, m∕s 2 K = gain k = spring, N∕rad L = lift, N m = mass, kg n = load factor, g q = pitch rate, rad∕s S = surface, m 2 T = thrust, N t = time, s V = velocity, m∕s W = weight, N α = angle of attack, rad β = sideslip angle, rad γ = flight path angle, rad δ = control device deflection, rad θ = pitch angle, rad ρ = density, kg∕m 3 φ = roll angle, rad Subscripts br = breakout max = maximum value min = minimum value nom = nominal value np = neutral point prot = protected region value

Flight safety warning of iced aircraft based on reachability analysis and fuzzy inference

“…The key to calculating flight safety set is to determine the boundary conditions f 0 (x) and seek the optimal solution of equation (11). Suppose the flight states are confined to a rectangular area K = ½V min , V max 3 ½a min , a max 3½u min , u max 3½q min , q max , then the boundary conditions f 0 (x) : R 3 !…”

“…The flight safety warning system evaluates the safety of the flight state and feeds safety information back to the pilot in some way. In Van Baelen et al, 11 , the risk-evolution analysis is used determine whether a flight state is safe or not, and the safety of the whole flight space is presented in the form of a cloud chart, which provides vivid and predictive information for the pilot by means of computational flight dynamics. In Van Baelen et al, 11 a haptic feedback system is designed by using force feedback through the control device to provide intuitive information on the state of the aircraft relative to the flight envelope protection.…”

Flying by Feeling: Communicating Flight Envelope Protection through Haptic Feedback

“…Exploratory research first investigated a system which provided a change in force gradient near the flight envelope limits, and pilots indicated that it lacked discrete information, a 'tick-on-the-stick', indicating when the protections become active (Lombaerts et al, 2017). Therefore, the first design iteration involved both guidance and discrete haptic feedback (Van Baelen et al, 2020). Although one should ideally feel haptic feedback, the working principles are visualized in this paper using the haptic profile, i.e., the amount of force required on the side stick, to move that side stick to a certain deflection.…”

Evaluating Stick Stiffness and Position Guidance for Feedback on Flight Envelope Protection

“…Full details are given in our earlier work, see Ref. [15], only the relevant elements for understanding the current experiment will be explained in this section. Two designs are elaborated which use haptic feedback to communicate the flight envelope protection limits by changing the feel on the control device.…”