Analysis of Handling Qualities Design Criteria for Active Inceptor Force-Feel Characteristics

The force-feel system characteristics of the cyclic inceptors of most helicopters are set based on the characteristics of the mechanical components in the control system (mass, springs, friction dampers, etc.). For these helicopters, the force-feel characteristics typically remain constant over the entire flight envelope, with perhaps a trim release to minimize control forces while maneuvering. With the advent of fly-by-wire control systems and active inceptors in helicopters, the force-feel characteristics are now determined by the closed-loop response of the active inceptor itself as defined by the inertia, force/displacement gradient, damping, breakout force and detent shape configuration parameters in the inceptor control laws. These systems give the flexibility to dynamically prescribe different feel characteristics for different control modes or flight conditions, and the ability to provide tactile cueing to the pilot through the actively controlled side-stick or center-stick cyclic inceptor. For rotorcraft, a few studies have been conducted to assess the effects of cyclic force-feel characteristics on handling qualities in flight. An early study provided valuable insight into the static force-deflection characteristics (force gradient) and the number of axes controlled by the side-stick controller for the U.S. Army's Advanced Digital/Optical Control System (ADOCS) demonstrator aircraft [1]. The first of a series of studies providing insight on the inceptor dynamic force-feel characteristics was conducted on the NASA/Army CH-47B variable-stability helicopter [2]. This work led to a proposed requirement that set boundaries based on the cyclic natural frequency and inertia, with the stipulation of a lower damping ratio limit of 0.3 [3]. A second study was conducted by the Canadian Institute for Aerospace Research using their variable-stability Bell 205A helicopter [4]. This research suggested boundaries for stick dynamics based on natural frequency and damping ratio. While these two studies produced boundaries for acceptable/unacceptable stick dynamics for rotorcraft, they were not able to provide guidance on how variations of the stick dynamics in the acceptable region impact handling qualities. More recently, a ground based simulation study [5] suggested little benefit was to be obtained from variations of the damping ratio for a side-stick controller exhibiting high natural frequencies (greater than 17 rad/s) and damping ratios (greater than 2.0). A flight test campaign was conducted concurrently on the RASCAL JUH-60A in-flight simulator and the ACT/FHS EC-135 in flight simulator [6]. Upon detailed analysis of the pilot evaluations the study identified a clear preference for a high damping ratio and natural frequency of the center stick inceptors. Side stick controllers were found to be less sensitive to the damping. While these studies have compiled a substantial amount of data, in the form of qualitative and quantitative pilot opinion, a fundamental analysis of the effect of the inceptor force-feel system on flight control is found to be lacking. The study of Ref. [6] specifically concluded that a systematic analysis was necessary, since discrepancies with the assigned handling qualities showed that proposed analytical design metrics, or criteria, were not suitable. The overall goal of the present study is to develop a clearer fundamental understanding of the underlying mechanisms associated with the inceptor dynamics that govern the handling qualities using a manageable analytical methodology

Impact of scalar mixing uncertainty on the predictions of reactor-based closures: Application to a lifted methane/air jet flame

This work is devoted to quantify the predictive uncertainty in RANS simulation of a non-premixed lifted flame due to uncertainty in the model parameters of the scalar dissipation rate transport equation. The uncertainty propagation and the global sensitivity analysis of the effect of such parameters on the quantities of interest (QoIs) is performed employing Polynomial Chaos Expansions as surrogate models of the uncertain response. This approach is applied on a lifted methane-air jet flame in vitiated coflow, already experimentally investigated by Cabra et al [1]. The results show the effectiveness of the approach to provide predictions with estimates of uncertainty. It is shown that the the uncertainty in the mixture fraction and temperature is negligible as long as only pure mixing happens, then it becomes significant in the regions where ignition begins, starting from z/D=30. Of the four parameters considered, i.e., CD1, CD2, CP1 and CP2, main and total effect sensitivity indices show that the largest contribution to the uncertainty in the flame temperature is given by the two dissipation parameters CD1 and CD2, while the production parameter CP2 has almost negligible impact on the predictions. Lastly, the surrogate models are used to determine an optimum set of parameters that minimizes the distance with the experimental measures, leading to improved predictions of the QoIs

Rotorcraft Flight Dynamics and Controls Research at NASA

In recent years, NASA has invested in key activities in the areas of flight controls, handling qualities and operations of rotorcraft for civilian applications. More specifically, the flight dynamics and control discipline has focused on analyzing the unique flight control and handling qualities challenges of large rotary wing vehicles anticipated for future passenger service, and examining the effect of control system augmentation on handling qualities for current civilian helicopters in order to improve safety and reduce accident rates. This paper highlights two recent research efforts in these areas. The first is an examination of flight control and handling qualities aspects of large rotorcraft. A series of experiments were performed in the large-motion Vertical Motion Simulator at NASA Ames Research Center to quantify the effects of vehicle size on flight control requirements and piloted handling qualities. These experiments used a large tilt-rotor concept (~100 passengers) to also investigate the control augmentation required to obtain Level 1 handling qualities for a vehicle of this size. The second is an examination of the effect of control system augmentation on handling qualities for current civil rotorcraft, like those currently used for Emergency Medical Service type operations. Many current civilian helicopters have rate response type control systems and little or no control system augmentation, although current technologies allow helicopters to be fitted with stability augmentation systems, either as standard equipment or aftermarket options. A simulation experiment was conducted in the Vertical Motion Simulator to quantify the effects of advanced control modes available with a partial authority stability augmentation system on task performance and handling qualities in both good and degraded visual conditions. In addition to providing an overview of the rotary wing flight dynamics and controls research at NASA, this paper will provide an overview of these two research activities along with key results and conclusions

Rotorcraft Flight Dynamics and Controls Research at NASA

In recent years, NASA has invested in key activities in the areas of flight controls, handling qualities and operations of rotorcraft for civilian applications. More specifically, the flight dynamics and control discipline has focused on analyzing the unique flight control and handling qualities challenges of large rotary wing vehicles anticipated for future passenger service, and examining the effect of control system augmentation on handling qualities for current civilian helicopters in order to improve safety and reduce accident rates. This paper highlights two recent research efforts in these areas. The first is an examination of flight control and handling qualities aspects of large rotorcraft. A series of experiments were performed in the large-motion Vertical Motion Simulator at NASA Ames Research Center to quantify the effects of vehicle size on flight control requirements and piloted handling qualities. These experiments used a large tilt-rotor concept (~100 passengers) to also investigate the control augmentation required to obtain Level 1 handling qualities for a vehicle of this size. The second is an examination of the effect of control system augmentation on handling qualities for current civil rotorcraft, like those currently used for Emergency Medical Service type operations. Many current civilian helicopters have rate response type control systems and little or no control system augmentation, although current technologies allow helicopters to be fitted with stability augmentation systems, either as standard equipment or aftermarket options. A simulation experiment was conducted in the Vertical Motion Simulator to quantify the effects of advanced control modes available with a partial authority stability augmentation system on task performance and handling qualities in both good and degraded visual conditions. In addition to providing an overview of the rotary wing flight dynamics and controls research at NASA, this paper will provide an overview of these two research activities along with key results and conclusions

Multimodality in {VR}: {A} Survey

Virtual reality has the potential to change the way we create and consume content in our everyday life. Entertainment, training, design and manufacturing, communication, or advertising are all applications that already benefit from this new medium reaching consumer level. VR is inherently different from traditional media: it offers a more immersive experience, and has the ability to elicit a sense of presence through the place and plausibility illusions. It also gives the user unprecedented capabilities to explore their environment, in contrast with traditional media. In VR, like in the real world, users integrate the multimodal sensory information they receive to create a unified perception of the virtual world. Therefore, the sensory cues that are available in a virtual environment can be leveraged to enhance the final experience. This may include increasing realism, or the sense of presence; predicting or guiding the attention of the user through the experience; or increasing their performance if the experience involves the completion of certain tasks. In this state-of-the-art report, we survey the body of work addressing multimodality in virtual reality, its role and benefits in the final user experience. The works here reviewed thus encompass several fields of research, including computer graphics, human computer interaction, or psychology and perception. Additionally, we give an overview of different applications that leverage multimodal input in areas such as medicine, training and education, or entertainment; we include works in which the integration of multiple sensory information yields significant improvements, demonstrating how multimodality can play a fundamental role in the way VR systems are designed, and VR experiences created and consumed

Crossmodal perception in virtual reality

With the proliferation of low-cost, consumer level, head-mounted displays (HMDs) we are witnessing a reappearance of virtual reality. However, there are still important stumbling blocks that hinder the achievable visual quality of the results. Knowledge of human perception in virtual environments can help overcome these limitations. In this work, within the much-studied area of perception in virtual environments, we look into the less explored area of crossmodal perception, that is, the interaction of different senses when perceiving the environment. In particular, we look at the influence of sound on visual perception in a virtual reality scenario. First, we assert the existence of a crossmodal visuo-auditory effect in a VR scenario through two experiments, and find that, similar to what has been reported in conventional displays, our visual perception is affected by auditory stimuli in a VR setup. The crossmodal effect in VR is, however, lower than that present in a conventional display counterpart. Having asserted the effect, a third experiment looks at visuo-auditory crossmodality in the context of material appearance perception. We test different rendering qualities, together with the presence of sound, for a series of materials. The goal of the third experiment is twofold: testing whether known interactions in traditional displays hold in VR, and finding insights that can have practical applications in VR content generation (e.g., by reducing rendering costs)

Los Sistemas de Información Geográfica en salud ambiental

This paper gives a brief introduction to the Geographic Information Systems (GIS) and its applications to the field of Environmental Health (EH). It starts with a conceptual exposition in order to show the potential of GIS’s as an space temporal analysers, and as an aids to take decisions. Some specific cases are analysed, these cases represent success applications of new technology to EH. A brief survey of the more popular software for GIS, free and commercial, is presented. It is also shown the connexion of this software with statistical software and other kind of specialize software in order to build computer tools for working in EH. Finally, some strategies are given for a deepen involvement of GIS in EH.En esta ponencia se presenta una breve introducción a los Sistemas de Información Geográfica (GIS, Geographic Information System) y sus aplicaciones en el área de Salud Ambiental (SA). Se inicia con una exposición conceptual para mostrar el potencial de los GIS como analizadores espacio-temporales, y como ayudas a la toma de decisiones. Se analizan algunos casos concretos, que han resultado un éxito, en la aplicación de las nuevas tecnologías en SA. También se hace una breve revisión del software más popular para un GIS, comercial y libre, y su conexión con otro software estadístico y especializado para construir herramientas informáticas apropiadas con las que trabajar en SA. Finalmente, se ofrecen algunas estrategias para logra una mayor utilización de los GIS en SA

A spatial contextual postclassification method for preserving linear objects in multispectral imagery

Classification of remote sensing multispectral data is important for segmenting images and thematic mapping and is generally the first step in feature extraction. Per-pixel classification, based on spectral information alone, generally produces noisy classification results. The introduction of spatial information has been shown to be beneficial in removing most of this noise. Probabilistic label relaxation (PLR) has proved to be advantageous using second-order statistics; here, we present a modified contextual probabilistic relaxation method based on imposing directional information in the joint probability with third-order statistics. The proposed method was tested in synthetic images and real images; the results are compared with a "Majority" algorithm and the classical PLR method. The proposed third-order method gives the best results, both visually and numerically

Physics-informed Bayesian inference of external potentials in classical density-functional theory

The swift progression of machine learning (ML) has not gone unnoticed in the realm of statistical mechanics. ML techniques have attracted attention by the classical density-functional theory (DFT) community, as they enable discovery of free-energy functionals to determine the equilibrium-density profile of a many-particle system. Within DFT, the external potential accounts for the interaction of the many-particle system with an external field, thus, affecting the density distribution. In this context, we introduce a statistical-learning framework to infer the external potential exerted on a many-particle system. We combine a Bayesian inference approach with the classical DFT apparatus to reconstruct the external potential, yielding a probabilistic description of the external potential functional form with inherent uncertainty quantification. Our framework is exemplified with a grand-canonical one-dimensional particle ensemble with excluded volume interactions in a confined geometry. The required training dataset is generated using a Monte Carlo (MC) simulation where the external potential is applied to the grand-canonical ensemble. The resulting particle coordinates from the MC simulation are fed into the learning framework to uncover the external potential. This eventually allows us to compute the equilibrium density profile of the system by using the tools of DFT. Our approach benchmarks the inferred density against the exact one calculated through the DFT formulation with the true external potential. The proposed Bayesian procedure accurately infers the external potential and the density profile. We also highlight the external-potential uncertainty quantification conditioned on the amount of available simulated data. The seemingly simple case study introduced in this work might serve as a prototype for studying a wide variety of applications, including adsorption and capillarity