Effects of Heave Washout Settings in Aircraft Pitch Disturbance Rejection

Abstract

In most moving-base flight simulators, the simulated aircraft motion needs to be filtered with motion washout filters to keep the simulator within its limited motion envelope. Translational motion in particular requires filtering, as the low-frequency components of the vehicle motion tend to quickly drive simulators toward their motion bounds. Commonly, linear washout filters are therefore used to attenuate the simulated motion in magnitude and in phase. It is found in many studies that the settings of these washout filters affect pilot performance and control behavior. In most of these studies, no comparison to a case with one-to-one motion cues is performed as a result of the limited motion envelope of the simulators used. In the current study, an experiment was performed in the SIMONA Research Simulator at the Delft University of Technology to investigate the effects of heave washout settings on pilot performance and control behavior in a pitch attitude control task. In addition to rotational pitch motion, heave accelerations at the pilot station that result directly from aircraft pitch were evaluated. This heave motion component could be supplied one-to-one in the simulator due to the modest size of the aircraft model, a Cessna Citation I business jet. The experiment revealed that pilot performance and control activity both increased significantly with increasing heave motion fidelity. An analysis of pilot control behavior using pilot models indicated that the enhanced performance was caused by an increase in the magnitude with which pilots responded to visual and physical motion stimuli and a decrease in the amount of visual lead that was generated by the pilots. Nomenclature A = sinusoid amplitude, deg a z cg = c.g. heave acceleration, m s 2 a z = pitch-heave acceleration, m s 2 e = tracking error signal, deg f d = disturbance forcing function, deg f t = target forcing function, deg H nm = neuromuscular system dynamics H ol = open-loop response H sc = semicircular canal dynamics H p e = pilot visual response H p az = pilot heave motion response H p = pilot pitch motion response Hj! = frequency response function Hs = transfer function H ; e = controlled system dynamics j = imaginary unit, -K = gain, -K m = motion perception gain, -K v = visual perception gain, -k = sinusoid index, -l = pitch-heave arm length, m N = number of points, -n = forcing function frequency integer factor, -S = power spectral density s = Laplace variable T I = visual lag time constant, s T L = visual lead time constant, s T sc 1 , T sc 2 , T sc 3 = semicircular canal model time constants, s t = time, s u = pilot control signal, deg z = vertical position, m Symbols e = elevator deflection, deg = damping factor, -nm = neuromuscular damping, -= pitch angle, deg 2 = variance m = motion perception time delay, s v = visual perception time delay, s = sinusoid phase shift, rad ' m = phase margin, deg ! = frequency, rad s 1 ! c = crossover frequency, rad s 1 ! nm = neuromuscular frequency, rad s 1 ! sp = short period frequency, rad s 1 Subscri...

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