Biodynamic Modeling Techniques for Rotorcraft Comfort Evaluation

Abstract

This work shows how different occupant biodynamic modeling techniques are integrated in a rotorcraft design environment and discusses the resulting differences in comfort assessment. Three modeling techniques, that are used for biodynamic characterization, are considered: lumped parameter, finite element and multibody dynamics. These models are identified for the same gender, age, weight and height and then integrated into a virtual helicopter environment with a seat-cushion interface. A generic helicopter model is used to demonstrate the approach. For each of the three techniques, the vertical acceleration levels at the human-helicopter interface, as required by vibration regulations, and at the head are evaluated up to 30 Hz. At a first glance, it is observed that the lumped parameter is the easiest to implement in terms of model set-up. However, the use of lumped parameter models is limited to the population groups that they are identified from, and thus are not as flexible as the finite element and multibody ones in developing biodynamic models for individuals of an arbitrary population percentile. Furthermore, through numerical analysis it is found that the differences are not very significant in terms of accelerations at the human-seat interface. Therefore, for comfort related issues, the use of more complex models is not justified, unless complicated comfort assessments other than human interface accelerations are required. On the other hand, it is observed that the spine dynamics can play a significant role in estimating the acceleration of head; therefore, the sophisticated finite element and multibody dynamics models redeem their higher modeling cost and computation time when the head-neck health of occupants is considered.

A numerical study of vibration-induced instrument reading capability degradation in helicopter pilots

“…With regard to the above-mentioned features, MASST has proven its capabilities considering its efficient use in rotorcraft helicopter and tiltrotor aeroservoelasticity [18,21], vibration analysis [23], and handling of biodynamic models of the human body with increasing and arbitrary levels of complexity [24].…”

Multibody dynamics analysis of the human upper body for rotorcraft–pilot interaction

“…Fig. 2), for the purpose of rotorcraft comfort assessment: with respect to [46] the model presented in [21], the proposed model can capture the full 3D behaviour of the spine about a nominal reference condition.…”

Cabin Layout Optimization for Vibration Hazard Reduction in Helicopter Emergency Medical Service

“…The lumped parameter, finite element and multibody dynamics modeling techniques have gained acceptance in human biodynamics, mainly differing in the level of detail, versatility, and required input data [40]; all of them can be handled within MASST [41]. To present an example of the infrastructure for vibration rating, a lumped human model is considered in this work, since nonlinear and more complex models do not lead to significant changes when whole body vibration is calculated at the seat surface [41]. Among many others [42], the model proposed by Wan and Schimmels [43] is a classical four degree of freedom lumped model of human body vibration with linear springs and dampers that idealize the connections between the body parts.…”

“…The vertical accelerations are measured at the seat surface, as suggested in ISO-2631. It is worth mentioning that the proposed methodology can support increasingly complex biodynamics models [41], and respond to recent considerations about the comfort and health degradation due to vibrations of other body parts. For example, head accelerations [46] can be critical in helicopters due to the increasing use of helmets and night vision systems [47].…”