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Perfect P.,University of Liverpool | Perfect P.,Center for Engineering Dynamics | Perfect P.,Blue Bear Systems Research | Jump M.,University of Liverpool | And 3 more authors.
Journal of Guidance, Control, and Dynamics | Year: 2015

This paper describes the development of a methodology to assess the handling qualities requirements for vertical takeoff and landing-capable personal aerial vehicles. It is anticipated that such a personal aerial vehicle would be flown by a "flight-naïve" pilot who has received much less training than is typically received even by today's general aviation private pilots. The methodology used to determine handling requirements for a personal aerial vehicle cannot therefore be based entirely on existing best practice; the use of highly experienced test pilots in a conventional handling assessment limits the degree to which results apply to the flight-naïve pilot. Using rotary-wing handling qualities methods as a start point, this paper describes both existing and newly developed alternative methods to subjectively and objectively analyze the performance and workload of flight-naïve pilots in typical personal aerial vehicle tasks. A highly reconfigurable generic flight dynamics simulation model that has been used to validate the methodology is also described. Results that highlight the efficacy of the various methods used are presented, and their suitability for use with flight-naïve pilots demonstrated. Copyright © 2015 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.


Lu L.,University of Liverpool | Lu L.,Center for Engineering Dynamics | Jump M.,University of Liverpool | Jump M.,Center for Engineering Dynamics
Journal of Guidance, Control, and Dynamics | Year: 2014

This paper presents the development of a multiloop pilot model for use in boundary-triggered pilot-induced oscillation investigations. In doing so, the point-tracking and boundary-avoidance elements of the pilot control strategy are assumed to act simultaneously for a point-tracking-dominant task during a boundary-avoidance tracking event. The theoretical analysis indicates that the essence of the boundary-avoidance tracking phenomenon consists of an additional requirement for the pilot to provide lead equalization as the boundary is approached as the task transitions from a full-attention point-tracking task to both a point-tracking and boundary-avoidance task. This process leads to a narrower open-loop system bandwidth and a larger tracking error, or the triggering of a pilotinduced oscillation. It is also found that the severity of the boundary-avoidance influence can be reduced by including the effects of vestibular and proprioceptive cues into the model. The boundary-avoidance tracking pilot model exhibits pilot-vehicle responses that are consistent with those observed in a piloted-simulation study and can therefore be considered to be representative of pilot activity. Consideration of the results in the round indicates that the boundary-triggered pilot-induced oscillation can be categorized as Category III pilot-induced oscillation within the existing recognized taxonomy. Copyright © 2013 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.


Jones M.,University of Liverpool | Jones M.,Center for Engineering Dynamics | Jump M.,University of Liverpool | Jump M.,Center for Engineering Dynamics | And 2 more authors.
Journal of Guidance, Control, and Dynamics | Year: 2013

Significant effort has been expended to develop criteria to predict the susceptibility of an air vehicle to so-called pilot-induced oscillations . Much of this work has been carried out for fixed-wing aircraft and it is only recently that their applicability to rotorcraft has started to be assessed. Real time pilot-induced oscillation identification methods provide an alternative means to at least warn the pilot that a pilot-induced oscillation is in progress so that preventative action can be taken. Existing methods, however, have some limitations and have rarely been used for rotary-wing purposes. Specifically, the existing methods assessed in this paper do not provide an indication of the severity of the event and mask the underlying data that are being used to generate the warning. This paper proposes and presents a new method to identify pilot-induced oscillations, either in near real time or as a postprocessing aid for recorded flight-test data, that addresses both of these issues. The new method, entitled "phase-aggression criterion," is compared with current methods. It is shown, for a specific set of test cases and a limited test pilot population, that not only can it provide more information about the pilot-induced oscillation but it can also provide an earlier warning of its onset. Copyright © 2012 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.


Padfield G.D.,University of Liverpool | Padfield G.D.,Flight Science and Technology Research Group | Lu L.,University of Liverpool | Lu L.,Center for Engineering Dynamics | And 2 more authors.
Journal of Guidance, Control, and Dynamics | Year: 2012

Tau theory, introduced to the flight control discipline as a model for natural guidance, is shown to provide an approach to predicting a class of adverse aircraft-pilot couplings described as boundary-avoidance tracking events and pilot-induced oscillations. These have previously been modeled a posterior as discrete events using time-dependent feedback gains. Drawing on the prospective nature of the time-to-contact variable optical tau τ, a new method is proposed for modeling such phenomenon and also for determining the critical incipience for this class of aircraft-pilot coupling. In the present study, the approach has been applied to tau guidance in a rotorcraft trajectory tracking maneuver, to predict the conditions under which aircraft-pilot couplings may occur. In addition, a strong correlation between motion and control activity and the derivatives of tau adds substance to the hypothesis that the pilot's perceptual system works directly with invariants in the optical flow during visual guidance. Results from flight simulation tests conducted at the University of Liverpool and complementary flight tests carried out with the National Research Council (Canada) advanced systems research aircraft in-flight simulator support the tau control hypothesis. The theory suggests ways that pilots could be alerted to the impending threat of such adverse aircraft-pilot couplings. Copyright © 2011 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.


Papi M.,Catholic University of the Sacred Heart | Paoletti P.,Center for Engineering Dynamics | Geraghty B.,Center for Materials and Structures | Akhtar R.,Center for Materials and Structures
Applied Physics Letters | Year: 2014

We apply the PeakForce Quantitative Nanomechanical Property Mapping (PFQNM) atomic force microscopy mode for the investigation of regional variations in the nanomechanical properties of porcine sclera. We examine variations in the collagen fibril diameter, adhesion, elastic modulus and dissipation in the posterior, equatorial and anterior regions of the sclera. The mean fibril diameter, elastic modulus and dissipation increased from the posterior to the anterior region. Collagen fibril diameter correlated linearly with elastic modulus. Our data matches the known macroscopic mechanical behavior of the sclera. We propose that PFQNM has significant potential in ocular biomechanics and biophysics research. © 2014 AIP Publishing LLC.

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