The tau of flight control

Abstract

are described as 'τ guides'. In this context the author presents his perspective on flight control, briefly reviewing τ-theory and providing examples from research conducted at The University of Liverpool during the period 1999-2011, including the work of several PhD students. Concepts for guidance algorithms suitable for augmented manual or autonomous control are discussed and the implications for handling qualities developments, particularly relating to flight in degraded visual conditions, are presented. Some outstanding questions pointing directions for future research are raised. NOMENCLATURE a(t)acceleration during stopping manoeuvre (m/sec 2 , ft/sec 2 ) C a constant in power law relationship between two variables c, n constants in the relationship derived from the NASA approach test dataopen-loop crossover model transfer function between response error and response G CL closed-loop crossover model transfer function g gravitational acceleration (m/sec 2 , ft/sec 2 ) h height above ground in flare manoeuvre (m, ft) h e eye-height unit K pilot-aircraft gain in crossover model, gain in ball tracking dynamic model ABSTRACTWith this survey paper, the author proposes a new 'tao' -a new way of understanding -of how pilots do what they do. Research into the control of purposeful action in the natural world suggests that very rapid, efficient and 'instinctive' techniques have evolved based on the time to close on a goal, or close a gap, τ(t), and its derivatives. Purposeful actions involve the closure of one or more physical gaps, each with its own time to close, varying with time. Maintaining a constant rate of change of τ(t) with time (< 1) during an approach will ensure a successful arresting when the gap is closed, but an animal's strategy can be adapted to the circumstances to achieve either a hard stop (aggressive action with τ > 0⋅5), or a soft stop (gentle action with τ < 0⋅5). Synchronous coupling of two motions, x(t) and y(t), such that the times to close are coupled, τ x = kτ y , results in the motion gaps x(t) and y(t) being related through a power law, x = Cy 1/k , and closing smoothly together; examples of such coupling in the form of pursuit tracking in the natural world abound. Research has also shown that gaps can be closed by following 'intrinsic' guides, or self-generated mental models of desired motion, that have particular forms; for example, constant deceleration or constant acceleration. The gathering evidence from research into animal behaviour in the natural-world forms a background for the exploration of flight control in the man-made world. The implications for control theory, flight control developments and flight handling qualities, are considered to be profound. τ-theory suggests that natural control has a particular non-linear, albeit very simple, time varying form and that pilots learn control strategy skills by developing mental models, or internalised schemata, in the form of what

Development of a Generic Time-to-Contact Pilot Guidance Model

“…3, when the parameters of the controlled system are varied [3]. There were two requirements for this experiment.…”

“…[1][2][3]. The navigation function is a relatively long period, cognitive activity whilst the stabilization and guidance functions shape the pilot control inputs in the shorter term.…”

“…[3] it was suggested that pilots' τ-based actions effectively suppress the natural aircraft dynamics and this important aspect will be investigated in the present paper.…”

“…Previous work has assumed that the τ-guide is a learned response, a mental model, to closing the desired motion gap [3]. Its position at the perceptual level for flight control is still unclear, whether it be compensatory, pursuit, or precognitive [6].…”

Function of basal ganglia in tauG-guiding action

“…(The experiments were reported with τ G and τ D as the experimental variables rather than ρ G and ; however, since, ρ = 1/τ , the experimental results are directly translatable into ρ terms.) The experiments included newborn babies suckling ); infants catching (van der Meer et al 1994); adults reaching ), controlling gaze Lee 2005), intercepting moving objects (Lee et al 2001), putting at golf (Craig et al, 2000), flying aircraft (Padfield 2011), singing and playing music (Schogler et al 2008); hummingbirds aerially docking on a food source (Lee et al 1991;Delafield-Butt et al 2010); unicellular paramecia steering to an electric pole (Delafield-Butt et al 2012). There is also evidence for rho (tau) at a neural level -in the brains of locusts (Rind & Simmons 1999), pigeons (Sun and Frost 1998), monkeys (Merchant et al 2004;Merchant & Georgopoulos, 2006) and humans (Field & Wann, 2005;Tan et al, 2009;van der Weel et al 2009).…”