Manogna Ammalladene-Venkata, Omkar Halbe, Christian Seidel, Christine Groitl, Lothar Kramel, Christoph Stahl, Heiko Seidel
Aviation statistics identify collision with terrain and obstacles as a leading cause of helicopter accidents. Assisting helicopter pilots in detecting the presence of obstacles can greatly mitigate the risk of collisions. However, only a limited number of helicopters in operation have an installed helicopter terrain awareness and warning system (HTAWS), while the cost of active obstacle warning systems remains prohibitive for many civil operators. In this work, we apply machine learning to automate obstacle detection and classification in combination with commercially available airborne optical sensors. While numerous techniques for learning-based object detection have been published in the literature, many of them are data and computation intensive. Our approach seeks to balance the detection and classification accuracy of the method with the size of the training data required and the runtime. Specifically, our approach combines the invariant feature extraction ability of pretrained deep convolutional neural networks (CNNs) and the high-speed training and classification ability of a novel, proprietary frequency-domain support vector machine (SVM) method. We describe our experimental setup comprising the CNN + SVM model and datasets of predefined classes of obstacles—pylons, chimneys, antennas, TV towers, wind turbines, helicopters—synthesized from prerecorded airborne video sequences of low-altitude helicopter flight. We analyze the detection performance using average precision, average recall, and runtime performance metrics on representative test data. Finally, we present a simple architecture for real-time, onboard implementation and discuss the obstacle detection performance of recently concluded flight tests.
{"title":"Deep Learning Based Obstacle Awareness from Airborne Optical Sensors","authors":"Manogna Ammalladene-Venkata, Omkar Halbe, Christian Seidel, Christine Groitl, Lothar Kramel, Christoph Stahl, Heiko Seidel","doi":"10.4050/jahs.68.042012","DOIUrl":"https://doi.org/10.4050/jahs.68.042012","url":null,"abstract":"Aviation statistics identify collision with terrain and obstacles as a leading cause of helicopter accidents. Assisting helicopter pilots in detecting the presence of obstacles can greatly mitigate the risk of collisions. However, only a limited number of helicopters in operation have an installed helicopter terrain awareness and warning system (HTAWS), while the cost of active obstacle warning systems remains prohibitive for many civil operators. In this work, we apply machine learning to automate obstacle detection and classification in combination with commercially available airborne optical sensors. While numerous techniques for learning-based object detection have been published in the literature, many of them are data and computation intensive. Our approach seeks to balance the detection and classification accuracy of the method with the size of the training data required and the runtime. Specifically, our approach combines the invariant feature extraction ability of pretrained deep convolutional neural networks (CNNs) and the high-speed training and classification ability of a novel, proprietary frequency-domain support vector machine (SVM) method. We describe our experimental setup comprising the CNN + SVM model and datasets of predefined classes of obstacles—pylons, chimneys, antennas, TV towers, wind turbines, helicopters—synthesized from prerecorded airborne video sequences of low-altitude helicopter flight. We analyze the detection performance using average precision, average recall, and runtime performance metrics on representative test data. Finally, we present a simple architecture for real-time, onboard implementation and discuss the obstacle detection performance of recently concluded flight tests.","PeriodicalId":50017,"journal":{"name":"Journal of the American Helicopter Society","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136374774","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Nick J. Weinzapfel, Nathan W. Bolander, Tanmay D. Mathur, Hans DeSmidt, Edward C. Smith
Performance of ball bearings in the motion converter subassembly of an internally driven, single-speed, torque-split, twin configuration pericyclic transmission prototype is evaluated to extend the analytical knowledge base on this innovative transmission concept. A dynamic model of the transmission is developed with high-fidelity models of the installed rolling element bearings to determine their reactions. Attention is focused on the pair of ball bearings supporting the motion converter subassembly which are subjected to a complex combination of loads, including radial and axial forces, moments, carrier motion, and possibly internal preload. Then the influence of internal axial clearance and preload on the behavior of the rolling elements is analyzed with a fully dynamic ball bearing model. Provisions to consider the carrier motion and a robust integration algorithm for component orientations are presented. Finally, a microstructure-based fatigue life simulation of the critical bearing component is performed to demonstrate the effect of clearance/preload on bearing reliability.
{"title":"Dynamic Load Analysis of Motion Converter Ball Bearings in a Pericyclic Transmission","authors":"Nick J. Weinzapfel, Nathan W. Bolander, Tanmay D. Mathur, Hans DeSmidt, Edward C. Smith","doi":"10.4050/jahs.68.042005","DOIUrl":"https://doi.org/10.4050/jahs.68.042005","url":null,"abstract":"Performance of ball bearings in the motion converter subassembly of an internally driven, single-speed, torque-split, twin configuration pericyclic transmission prototype is evaluated to extend the analytical knowledge base on this innovative transmission concept. A dynamic model of the transmission is developed with high-fidelity models of the installed rolling element bearings to determine their reactions. Attention is focused on the pair of ball bearings supporting the motion converter subassembly which are subjected to a complex combination of loads, including radial and axial forces, moments, carrier motion, and possibly internal preload. Then the influence of internal axial clearance and preload on the behavior of the rolling elements is analyzed with a fully dynamic ball bearing model. Provisions to consider the carrier motion and a robust integration algorithm for component orientations are presented. Finally, a microstructure-based fatigue life simulation of the critical bearing component is performed to demonstrate the effect of clearance/preload on bearing reliability.","PeriodicalId":50017,"journal":{"name":"Journal of the American Helicopter Society","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136119100","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A potential flow model was developed for rotors hovering in-ground-effect above a heaving surface using a similar methodology to classical, analytical, static ground effect models. Experimental performance measurements for rotors hovering above a surface undergoing single degree-of-freedom heaving motion were used for model validation, and potential mission trends were generated for a representative naval helicopter. Unlike prior empirical models, the current model was able to capture the effect of rotor hub height as well as ground motion parameters. A new thrust ratio was proposed that compared the thrust produced in-ground-effect above a heaving surface to that produced above a static surface. Better agreement was found to occur at the higher collective pitch settings and hub heights, with the model predicting the classical thrust ratio within 5% of the measured value for approximately 75% of the test points. The thrust ratio relative to a static surface was found to produce better agreement, and approximately 80% of the experimental tests points were predicted within 5% of the measured value.
{"title":"Analytical Model Development for Rotors Hovering Above Heaving Surfaces","authors":"Joseph Milluzzo, John K. Tritschler, Scott Davids","doi":"10.4050/jahs.68.042007","DOIUrl":"https://doi.org/10.4050/jahs.68.042007","url":null,"abstract":"A potential flow model was developed for rotors hovering in-ground-effect above a heaving surface using a similar methodology to classical, analytical, static ground effect models. Experimental performance measurements for rotors hovering above a surface undergoing single degree-of-freedom heaving motion were used for model validation, and potential mission trends were generated for a representative naval helicopter. Unlike prior empirical models, the current model was able to capture the effect of rotor hub height as well as ground motion parameters. A new thrust ratio was proposed that compared the thrust produced in-ground-effect above a heaving surface to that produced above a static surface. Better agreement was found to occur at the higher collective pitch settings and hub heights, with the model predicting the classical thrust ratio within 5% of the measured value for approximately 75% of the test points. The thrust ratio relative to a static surface was found to produce better agreement, and approximately 80% of the experimental tests points were predicted within 5% of the measured value.","PeriodicalId":50017,"journal":{"name":"Journal of the American Helicopter Society","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136259941","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This paper presents a systematic investigation of high-speed rotorcraft pitch-axis response types, command models, and handling qualities specifications. The investigation was done using two future vertical lift-relevant rotorcraft configurations—a lift offset coaxial helicopter with a pusher propeller and a tiltrotor. Five response types were investigated, consisting of a pitch rate-command/attitude-hold response type typically used for rotorcraft, a pitch rate-command/attitude-hold response type using a higher-order command model based on the conventional airplane pitch rate transfer function, a normal acceleration command/angle-of-attack hold response type, a flight path rate command/flight path hold response type, and a "blended" flight path rate command response type which varies the command model bandwidth based on stick input size. Designs of varying levels of pitch attitude bandwidth, flight path bandwidth, control anticipation parameter, and pitch attitude dropback were evaluated in a piloted simulation experiment conducted at the Penn State Flight Simulator facility using two high-speed mission task elements. The results of the piloted simulation suggest that both the pitch attitude bandwidth and the pitch attitude dropback requirements must be met for Level 1 handling qualities. A set of recommended specifications and associated updated level boundaries is provided in the Appendix.
{"title":"High-Speed Rotorcraft Pitch Axis Response Type Investigation","authors":"Tom Berger, Mark B. Tischler, Joseph F. Horn","doi":"10.4050/jahs.68.032001","DOIUrl":"https://doi.org/10.4050/jahs.68.032001","url":null,"abstract":"This paper presents a systematic investigation of high-speed rotorcraft pitch-axis response types, command models, and handling qualities specifications. The investigation was done using two future vertical lift-relevant rotorcraft configurations—a lift offset coaxial helicopter with a pusher propeller and a tiltrotor. Five response types were investigated, consisting of a pitch rate-command/attitude-hold response type typically used for rotorcraft, a pitch rate-command/attitude-hold response type using a higher-order command model based on the conventional airplane pitch rate transfer function, a normal acceleration command/angle-of-attack hold response type, a flight path rate command/flight path hold response type, and a \"blended\" flight path rate command response type which varies the command model bandwidth based on stick input size. Designs of varying levels of pitch attitude bandwidth, flight path bandwidth, control anticipation parameter, and pitch attitude dropback were evaluated in a piloted simulation experiment conducted at the Penn State Flight Simulator facility using two high-speed mission task elements. The results of the piloted simulation suggest that both the pitch attitude bandwidth and the pitch attitude dropback requirements must be met for Level 1 handling qualities. A set of recommended specifications and associated updated level boundaries is provided in the Appendix.","PeriodicalId":50017,"journal":{"name":"Journal of the American Helicopter Society","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136311069","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Analysis of a hingeless rotor with a single wing on the retreating side for lift compounding was conducted. The goals included validation of performance and load predictions with wind tunnel test data, study of the impact of different aerodynamic inflow models, and understanding of benefits by lift compounding with a single wing on the retreating side. The three primary test cases include collective sweeps of the isolated rotor, and the rotor with the wing, at two different incidence angles. The comprehensive analysis was able to accurately predict the performance and blade structural loads of both the isolated rotor and rotor plus wing configurations. Overprediction of propulsive force leads to underprediction of lift-to-drag ratio in several cases. The normal bending moments were well captured for all cases, while the chord bending moment predictions had a phase offset from the test data, but magnitude and harmonics were captured. Comparing inflow models found that dynamic inflow and vortex wake (prescribed and free) models provided similar results. At these advance ratios, prescribed and free wake models showed almost no differences. Additionally, the vortex particle method showed an overprediction of thrust and greater rotorto-wing aerodynamic interference compared to test data. The addition of the wing on the retreating side provided dual benefits of increasing maximum lift-to-drag ratio and reduction of structural loads for a given total thrust. These effects are a result of both lift share between the rotor and wing, and lift offset, the rotor carries a roll moment to balance the wing's roll moment.
{"title":"Performance and Loads of a Wing-Offset Compound Helicopter","authors":"Daniel Escobar, Hyeonsoo Yeo","doi":"10.4050/jahs.68.032002","DOIUrl":"https://doi.org/10.4050/jahs.68.032002","url":null,"abstract":"Analysis of a hingeless rotor with a single wing on the retreating side for lift compounding was conducted. The goals included validation of performance and load predictions with wind tunnel test data, study of the impact of different aerodynamic inflow models, and understanding of benefits by lift compounding with a single wing on the retreating side. The three primary test cases include collective sweeps of the isolated rotor, and the rotor with the wing, at two different incidence angles. The comprehensive analysis was able to accurately predict the performance and blade structural loads of both the isolated rotor and rotor plus wing configurations. Overprediction of propulsive force leads to underprediction of lift-to-drag ratio in several cases. The normal bending moments were well captured for all cases, while the chord bending moment predictions had a phase offset from the test data, but magnitude and harmonics were captured. Comparing inflow models found that dynamic inflow and vortex wake (prescribed and free) models provided similar results. At these advance ratios, prescribed and free wake models showed almost no differences. Additionally, the vortex particle method showed an overprediction of thrust and greater rotorto-wing aerodynamic interference compared to test data. The addition of the wing on the retreating side provided dual benefits of increasing maximum lift-to-drag ratio and reduction of structural loads for a given total thrust. These effects are a result of both lift share between the rotor and wing, and lift offset, the rotor carries a roll moment to balance the wing's roll moment.","PeriodicalId":50017,"journal":{"name":"Journal of the American Helicopter Society","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136311057","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The paper discusses the synthesis of linear and nonlinear observers to estimate rotor states from fuselage state measurements alone. First, the paper reviews two forms of the classical Luenberger linear observer applied to the rotor state estimation problem and identifies some limitations thereof. Thereafter, the paper proposes a new robust nonlinear discontinuous observer based on the sliding mode theory to simultaneously estimate rotor flapping and lead-lagging states from fuselage state measurements. For this new nonlinear observer, the paper presents stability analyses to determine conditions that guarantee rotor state estimation accuracy despite unknown but bounded turbulence input. The nonlinear observer also lends itself to the online and real-time estimation of the unknown turbulence input. Simulation results in calm and turbulent air conditions highlight the efficacy and performance of the nonlinear discontinuous observer. Such rotor state observers could provide an independent source of online and real-time rotor states estimates to complement or supplement in situ rotor state measurement apparatus for various flight control and health-monitoring functions.
{"title":"Observers for Robust Rotor State Estimation","authors":"Omkar Halbe, Manfred Hajek, Florian Holzapfel","doi":"10.4050/jahs.68.032005","DOIUrl":"https://doi.org/10.4050/jahs.68.032005","url":null,"abstract":"The paper discusses the synthesis of linear and nonlinear observers to estimate rotor states from fuselage state measurements alone. First, the paper reviews two forms of the classical Luenberger linear observer applied to the rotor state estimation problem and identifies some limitations thereof. Thereafter, the paper proposes a new robust nonlinear discontinuous observer based on the sliding mode theory to simultaneously estimate rotor flapping and lead-lagging states from fuselage state measurements. For this new nonlinear observer, the paper presents stability analyses to determine conditions that guarantee rotor state estimation accuracy despite unknown but bounded turbulence input. The nonlinear observer also lends itself to the online and real-time estimation of the unknown turbulence input. Simulation results in calm and turbulent air conditions highlight the efficacy and performance of the nonlinear discontinuous observer. Such rotor state observers could provide an independent source of online and real-time rotor states estimates to complement or supplement in situ rotor state measurement apparatus for various flight control and health-monitoring functions.","PeriodicalId":50017,"journal":{"name":"Journal of the American Helicopter Society","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136261124","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Ariel Walter, Michael McKay, Robert Niemiec, Farhan Gandhi, Tom Berger
Hover analysis is performed on a 1200-lb gross weight UAM-scale quadcopter with both variable rotor speed and collective pitch control. With these redundant controls, the hover performance and flight dynamics are considered at three trim points, where power consumption can be increased to improve authority of the pitch inputs for changes in rotor thrust. An explicit model following control laws is optimized using CONDUIT R to meet ADS-33E-PRF handling qualities specifications, with design margin optimization on each axis. The responses of the linearized system are examined with either control type, and pitch control is shown to outperform RPM-control in heave, while the opposite is true for yaw. Trim in axial climb is simulated, where the collective pitch can be scheduled with the climb rate to maintain effective stall margin. Hybrid control mixing is implemented using a complementary filter, allowing the aircraft to use pitch control for short-term responses and RPM control for trim. The benefits of this hybrid control scheme are demonstrated through simulation of hot/high/heavy conditions, where trimming with RPM control allows the pitch actuators to maintain margin for maneuvers. It is concluded that hybrid control allows the aircraft to reap the benefits of pitch control for maneuverability while maintaining stall margin by using RPM control for trim.
{"title":"Hover Dynamics and Flight Control of a UAM-Scale Quadcopter With Hybrid RPM and Collective Pitch Control","authors":"Ariel Walter, Michael McKay, Robert Niemiec, Farhan Gandhi, Tom Berger","doi":"10.4050/jahs.68.022012","DOIUrl":"https://doi.org/10.4050/jahs.68.022012","url":null,"abstract":"Hover analysis is performed on a 1200-lb gross weight UAM-scale quadcopter with both variable rotor speed and collective pitch control. With these redundant controls, the hover performance and flight dynamics are considered at three trim points, where power consumption can be increased to improve authority of the pitch inputs for changes in rotor thrust. An explicit model following control laws is optimized using CONDUIT R to meet ADS-33E-PRF handling qualities specifications, with design margin optimization on each axis. The responses of the linearized system are examined with either control type, and pitch control is shown to outperform RPM-control in heave, while the opposite is true for yaw. Trim in axial climb is simulated, where the collective pitch can be scheduled with the climb rate to maintain effective stall margin. Hybrid control mixing is implemented using a complementary filter, allowing the aircraft to use pitch control for short-term responses and RPM control for trim. The benefits of this hybrid control scheme are demonstrated through simulation of hot/high/heavy conditions, where trimming with RPM control allows the pitch actuators to maintain margin for maneuvers. It is concluded that hybrid control allows the aircraft to reap the benefits of pitch control for maneuverability while maintaining stall margin by using RPM control for trim.","PeriodicalId":50017,"journal":{"name":"Journal of the American Helicopter Society","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135224711","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Aishwerya S. Gahlot, Ritu M. Eshcol, Lakshmi N. Sankar, Richard E. Kreeger
There is a significant interest in improving the performance of rotors under adverse operating conditions. However, there is a very limited understanding of the performance implications on two-dimensional (2D) airfoils and rotor blades under adverse effects of rainfall. Furthermore, the fundamental physical phenomena causing the loss in performance are not clearly understood. In this study, low-fidelity models are first developed to rapidly estimate the water layer formation on 2D airfoils and assess the resulting impact on lift and drag characteristics. The low-fidelity simulations are also useful to obtain quick estimates of water layer thickness as a function of liquid water content and droplet diameter. Subsequently, computational fluid dynamics studies for 2D airfoils and a small-scale rotor in hover are done to obtain more accurate estimates of the effects of rain on airfoil performance and match test data where available. Higher fidelity parametric studies for various airfoils were conducted by varying angles of attack, the liquid water content in the rain droplets, and the droplet diameters to capture trends in performance degradation. The resulting trends match the trends from the test data reasonably well. The higher fidelity airfoil loads are subsequently used within a classical combined blade element-momentum model to assess the loss of performance attributable to rain for a small-scale rotor. The present studies indicate a significant loss in thrust production, a rise in the power requirement, and a reduction in the figure of merit for small-scale rotors caused by rain.
{"title":"Numerical Simulations of the Adverse Effects of Rain on Airfoil And Rotor Aerodynamic Characteristics","authors":"Aishwerya S. Gahlot, Ritu M. Eshcol, Lakshmi N. Sankar, Richard E. Kreeger","doi":"10.4050/jahs.68.022004","DOIUrl":"https://doi.org/10.4050/jahs.68.022004","url":null,"abstract":"There is a significant interest in improving the performance of rotors under adverse operating conditions. However, there is a very limited understanding of the performance implications on two-dimensional (2D) airfoils and rotor blades under adverse effects of rainfall. Furthermore, the fundamental physical phenomena causing the loss in performance are not clearly understood. In this study, low-fidelity models are first developed to rapidly estimate the water layer formation on 2D airfoils and assess the resulting impact on lift and drag characteristics. The low-fidelity simulations are also useful to obtain quick estimates of water layer thickness as a function of liquid water content and droplet diameter. Subsequently, computational fluid dynamics studies for 2D airfoils and a small-scale rotor in hover are done to obtain more accurate estimates of the effects of rain on airfoil performance and match test data where available. Higher fidelity parametric studies for various airfoils were conducted by varying angles of attack, the liquid water content in the rain droplets, and the droplet diameters to capture trends in performance degradation. The resulting trends match the trends from the test data reasonably well. The higher fidelity airfoil loads are subsequently used within a classical combined blade element-momentum model to assess the loss of performance attributable to rain for a small-scale rotor. The present studies indicate a significant loss in thrust production, a rise in the power requirement, and a reduction in the figure of merit for small-scale rotors caused by rain.","PeriodicalId":50017,"journal":{"name":"Journal of the American Helicopter Society","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136261406","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
It is foreseen that in the upcoming application of (electric) urban air taxis, the comfort of ride and especially the experience of motion sickness will play a vital role in acceptance among passengers and therefore economic success of these vehicles. For this reason, accurate motion sickness prediction models are needed, which later can be employed for, for example, kinetosislow trajectory generation. Established motion sickness models like the ISO 2631 standard, however, only take into account the vertical translational axis and no rotational axis. For this reason, the 6-degrees-of-freedom Kamiji motion sickness model is selected and modified in order to circumvent unsatisfactory prediction results with this model. Subsequently, the parameters of this model are retuned by employing an optimization approach based on published experimental data. It is then shown that with this approach, the modified Kamiji model is better suited for predicting the motion sickness results of this dataset. In the future, this model shall be tested and validated via a series of flight tests with test subjects in DLR's BO-105 helicopter.
{"title":"Prediction of Motion Sickness Onset for Vertical Lift Applications","authors":"Philippe J. Petit","doi":"10.4050/jahs.68.022001","DOIUrl":"https://doi.org/10.4050/jahs.68.022001","url":null,"abstract":"It is foreseen that in the upcoming application of (electric) urban air taxis, the comfort of ride and especially the experience of motion sickness will play a vital role in acceptance among passengers and therefore economic success of these vehicles. For this reason, accurate motion sickness prediction models are needed, which later can be employed for, for example, kinetosislow trajectory generation. Established motion sickness models like the ISO 2631 standard, however, only take into account the vertical translational axis and no rotational axis. For this reason, the 6-degrees-of-freedom Kamiji motion sickness model is selected and modified in order to circumvent unsatisfactory prediction results with this model. Subsequently, the parameters of this model are retuned by employing an optimization approach based on published experimental data. It is then shown that with this approach, the modified Kamiji model is better suited for predicting the motion sickness results of this dataset. In the future, this model shall be tested and validated via a series of flight tests with test subjects in DLR's BO-105 helicopter.","PeriodicalId":50017,"journal":{"name":"Journal of the American Helicopter Society","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136261407","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The goal of this work is to characterize the ability of current numerical tools such as Comprehensive Analysis (CA) and computational fluid dynamics (CFD) to model the aeromechanics of a tiltrotor undergoing a transient conversion maneuver. First, a simplified model is used to quantify the differences in predicted loads between a simulation of a transient maneuver and those of several quasi-steady simulations. This analysis showed that quasi-steady simulations were an efficient and accurate method for modeling transient maneuvers. Next, the full XV-15 tiltrotor was studied using coupled CFD/CA quasi-steady and standalone CA transient maneuver simulations. Analysis and comparisons are made in terms of the rotor performance, trim, aerodynamic loads and interference, as well as the structural and vibrational loads. Nonlinear effects such as blade-wake interactions and aerodynamic interferences between the rotor and the wings were significant at the beginning and end of the conversion maneuver, respectively. As such, CA showed good agreement with CFD/CA at moderate airspeeds during conversion but struggled at low speeds and during cruise. Overall this work highlights the need for coupled CFD/CA analysis for capturing the complexities of tiltrotor conversion maneuvers. Coupled together, the simulations leverage the strengths offered by each tool and have the capability to accurately model the aerodynamic and structural dynamics of proprotors and tiltrotors at relevant operating conditions.
{"title":"Transient and Quasi-steady Numerical Simulations of Tiltrotor Conversion Maneuvers","authors":"Steven A. Tran, Hyeonsoo Yeo","doi":"10.4050/jahs.68.022003","DOIUrl":"https://doi.org/10.4050/jahs.68.022003","url":null,"abstract":"The goal of this work is to characterize the ability of current numerical tools such as Comprehensive Analysis (CA) and computational fluid dynamics (CFD) to model the aeromechanics of a tiltrotor undergoing a transient conversion maneuver. First, a simplified model is used to quantify the differences in predicted loads between a simulation of a transient maneuver and those of several quasi-steady simulations. This analysis showed that quasi-steady simulations were an efficient and accurate method for modeling transient maneuvers. Next, the full XV-15 tiltrotor was studied using coupled CFD/CA quasi-steady and standalone CA transient maneuver simulations. Analysis and comparisons are made in terms of the rotor performance, trim, aerodynamic loads and interference, as well as the structural and vibrational loads. Nonlinear effects such as blade-wake interactions and aerodynamic interferences between the rotor and the wings were significant at the beginning and end of the conversion maneuver, respectively. As such, CA showed good agreement with CFD/CA at moderate airspeeds during conversion but struggled at low speeds and during cruise. Overall this work highlights the need for coupled CFD/CA analysis for capturing the complexities of tiltrotor conversion maneuvers. Coupled together, the simulations leverage the strengths offered by each tool and have the capability to accurately model the aerodynamic and structural dynamics of proprotors and tiltrotors at relevant operating conditions.","PeriodicalId":50017,"journal":{"name":"Journal of the American Helicopter Society","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136261410","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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