A practical biodynamic feedthrough model for helicopters

Abstract

Biodynamic feedthrough (BDFT) occurs when vehicle vibrations and accelerations feed through the pilot's body and cause involuntary motion of limbs, resulting in involuntary control inputs. BDFT can severely reduce ride comfort, control accuracy and, above all, safety during the operation of rotorcraft. Furthermore, BDFT can cause and sustain Rotorcraft-Pilot Couplings (RPCs). Despite many studies conducted in past decades -both within and outside of the rotorcraft community -BDFT is still a poorly understood phenomenon. The complexities involved in BDFT have kept researchers and manufacturers in the rotorcraft domain from developing robust ways of dealing with its effects. A practical BDFT pilot model, describing the amount of involuntary control inputs as a function of accelerations, could pave the way to account for adversive BDFT effects. In the current paper, such a model is proposed. Its structure is based on the model proposed by Mayo [1], its accuracy and usability are improved by incorporating insights from recently obtained experimental data. An evaluation of the model performance shows that the model describes the measured data well and that it provides a considerable improvement to the original Mayo model. Furthermore, the results indicate that the neuromuscular dynamics have an important influence on the BDFT model parameters.

Mathematical Biodynamic Feedthrough Model Applied to Rotorcraft

“…Experimental data were obtained using a method elaborately described in [10]. This section provides a brief description of the experimental design, for details the reader is referred to [10].…”

“…From these, it has become clear that biodynamic feedthrough is a complex process, in which many different factors play a role of which the influence is often only poorly understood. BDFT dynamics depend on vehicle dynamics and control device dynamics [9], but also on factors such as seating dynamics, disturbance direction [10], disturbance frequency [11], and the presence of seat belts, and arm rests [12], [13].…”

“…Recent studies have been conducted in the context of the GARTEUR HC-AG16 project (e.g., [16]) and the ARISTOTEL project (e.g., [10], [17] and [18]). These projects mainly investigate rotorcraftpilot couplings [(RPCs), which were until the mid 1990s referred to as pilot induced/assisted oscillations (PIOs/PAOs)], i.e., oscillations or divergent vehicle responses, originating from adverse pilot-vehicle couplings.…”

“…For rotorcraft, a simple BDFT model was proposed in [6], incorporating between-subject variability by providing different parameter sets for two different body types. In [21], this model was extended by providing parameter sets for three different body types and for different settings of the neuromuscular system, including both between-and within-subject variability. It was noted that in some conditions the model was unable to describe BDFT effects at higher frequencies, which highlights one of the possible weaknesses of a simple model structure; it may not be suitable to describe all relevant dynamics.…”

“…Typically, with these models the BDFT dynamics can be described more accurately and understood physically in more detail [23]. A drawback of these models is that their parameters are often difficult to estimate, rendering them unwieldy and hard to use in practical situations [21].…”