Pub Date : 2021-05-10DOI: 10.4050/f-0077-2021-16852
Hsiang Chin, Charles Johnson, D. Mavris, A. Payan
Helicopters are used in a variety of operations and recent studies show that the number of accidents associated with helicopters is stagnating, if not increasing. Flight data monitoring (FDM) is a useful tool to review the data retrospectively for risk mitigation. Exceedance analyses are typically used in FDM for anomaly detection. However, they typically rely on pre-defined thresholds which might vary depending on the type of operations or vehicles considered. With recent advancements in data mining techniques, many efforts have been put into anomaly detection in the commercial fixed-wing aviation and this provides a new perspective beyond traditional methods. In this research, a sequential approach is proposed to detect anomalies in initial climb segments for helicopter operations. The stepwise methodology contains three elements: trajectory pattern mining, time series length analysis, and shape analysis for identifying different levels of anomalies. To ensure the effectiveness of the methods selected, synthetic and simulated data are used for testing before applying candidate methods to the actual initial climb segments. A specific group of initial climb segments is used to demonstrate the validity of the methods chosen in this study. Our tests show that functional principal component analysis and a convolutional variational autoencoder along with DBSCAN are capable of identifying shape anomalies in flight parameters. Although the detected anomalies might not directly be associated with hazardous events, it is useful to assist helicopter operators in discovering patterns not conforming to the norms.
{"title":"Anomaly Detection in Initial Climb Segments for Helicopter Operations","authors":"Hsiang Chin, Charles Johnson, D. Mavris, A. Payan","doi":"10.4050/f-0077-2021-16852","DOIUrl":"https://doi.org/10.4050/f-0077-2021-16852","url":null,"abstract":"\u0000 Helicopters are used in a variety of operations and recent studies show that the number of accidents associated with helicopters is stagnating, if not increasing. Flight data monitoring (FDM) is a useful tool to review the data retrospectively for risk mitigation. Exceedance analyses are typically used in FDM for anomaly detection. However, they typically rely on pre-defined thresholds which might vary depending on the type of operations or vehicles considered. With recent advancements in data mining techniques, many efforts have been put into anomaly detection in the commercial fixed-wing aviation and this provides a new perspective beyond traditional methods. In this research, a sequential approach is proposed to detect anomalies in initial climb segments for helicopter operations. The stepwise methodology contains three elements: trajectory pattern mining, time series length analysis, and shape analysis for identifying different levels of anomalies. To ensure the effectiveness of the methods selected, synthetic and simulated data are used for testing before applying candidate methods to the actual initial climb segments. A specific group of initial climb segments is used to demonstrate the validity of the methods chosen in this study. Our tests show that functional principal component analysis and a convolutional variational autoencoder along with DBSCAN are capable of identifying shape anomalies in flight parameters. Although the detected anomalies might not directly be associated with hazardous events, it is useful to assist helicopter operators in discovering patterns not conforming to the norms.\u0000","PeriodicalId":273020,"journal":{"name":"Proceedings of the Vertical Flight Society 77th Annual Forum","volume":"3 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-05-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131010374","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-05-10DOI: 10.4050/f-0077-2021-16831
R. Mckillip, T. Quackenbush, Michael K. Yu
This paper describes the continued development and validation of a multi-domain Eulerian/Lagrangian approach for modeling transient behavior of countermeasures released from tactical rotorcraft. The paper reviews the overall structure and background assumptions governing the model, includes recent correlations with public-domain chaff release data, and summarizes sensitivity studies to support real-time execution in flight simulation applications. The software is packaged as a Toolbox for operation in a MATLAB environment, though with modular elements – including industry-standard aerodynamic modeling - that can interact with other host software. The paper will describe some of the design tradeoffs in its realization, particularly as they impact features for manned flight simulation use. The ultimate goal of the analysis tool is to provide a variable level of fidelity that can trade off execution times with countermeasure response detail, so as to adjust the scope of the results to the auxiliary software that may interact with the simulation results.
{"title":"Rotorcraft Countermeasure Release Simulation","authors":"R. Mckillip, T. Quackenbush, Michael K. Yu","doi":"10.4050/f-0077-2021-16831","DOIUrl":"https://doi.org/10.4050/f-0077-2021-16831","url":null,"abstract":"\u0000 This paper describes the continued development and validation of a multi-domain Eulerian/Lagrangian approach for modeling transient behavior of countermeasures released from tactical rotorcraft. The paper reviews the overall structure and background assumptions governing the model, includes recent correlations with public-domain chaff release data, and summarizes sensitivity studies to support real-time execution in flight simulation applications. The software is packaged as a Toolbox for operation in a MATLAB environment, though with modular elements – including industry-standard aerodynamic modeling - that can interact with other host software. The paper will describe some of the design tradeoffs in its realization, particularly as they impact features for manned flight simulation use. The ultimate goal of the analysis tool is to provide a variable level of fidelity that can trade off execution times with countermeasure response detail, so as to adjust the scope of the results to the auxiliary software that may interact with the simulation results.\u0000","PeriodicalId":273020,"journal":{"name":"Proceedings of the Vertical Flight Society 77th Annual Forum","volume":"2 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-05-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133805389","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-05-10DOI: 10.4050/f-0077-2021-16813
R. Beggs
The American Helicopter Museum and Education Center opened to the public at the Brandywine Airport on October 18, 1996. This milestone was the realization of a vision adopted at a luncheon meeting hosted by the Philadelphia Chapter of the American Helicopter Society on July 30, 1993. Chapter leaders had previously brainstormed potential ideas for commemorating the upcoming 50th Anniversary of the American Helicopter Society in 1994, but recognized the need to engage a broader constituency to do something significant. With the goal of establishing a 50th Anniversary Committee, a luncheon was scheduled at Boeing Helicopters in Ridley Park, PA. Participants included the author, several Chapter officers and an invitation list that included Philadelphia area rotary-wing business leaders, industry pioneers and influencers. Attendees at that first meeting included Lee Douglas, Frank Duke, Vincent Genovese, Euan Hooper, Warren Jacobs, Wes Moore, Ren Pierpoint, John Schneider, George Townson, Edward B. Wilford III and Peter Wright, Sr. After debating multiple options for the commemoration, the idea of a museum was embraced when Peter Wright, then President of Keystone Helicopters, offered to donate several vintage helicopters if a museum was established. Two weeks later, the nascent 50th Anniversary Committee met again with a mission to: “Lay the foundation for a permanent rotary-wing restoration, conservation and exhibition facility in the Delaware Valley.” Referencing the documented minutes of the aforementioned meeting and that of subsequent meetings of the 50th Anniversary Committee, other documents and the recollections of the author, this paper will trace the formative years of the museum from July 1993 to October 1996. It will address the many challenges of founding an aviation museum including incorporation, location identification, building the collection and creating the exhibits and programs. It will recall the people involved and their significant contributions. This paper is particularly compelling to publish this year, recognizing the 25th anniversary of the American Helicopter Museum and Education Center on 18 October 2021.
{"title":"Preserve, Educate and Inspire - Founding the American Helicopter Museum and Education Center","authors":"R. Beggs","doi":"10.4050/f-0077-2021-16813","DOIUrl":"https://doi.org/10.4050/f-0077-2021-16813","url":null,"abstract":"\u0000 The American Helicopter Museum and Education Center opened to the public at the Brandywine Airport on October 18, 1996. This milestone was the realization of a vision adopted at a luncheon meeting hosted by the Philadelphia Chapter of the American Helicopter Society on July 30, 1993. Chapter leaders had previously brainstormed potential ideas for commemorating the upcoming 50th Anniversary of the American Helicopter Society in 1994, but recognized the need to engage a broader constituency to do something significant. With the goal of establishing a 50th Anniversary Committee, a luncheon was scheduled at Boeing Helicopters in Ridley Park, PA. Participants included the author, several Chapter officers and an invitation list that included Philadelphia area rotary-wing business leaders, industry pioneers and influencers. Attendees at that first meeting included Lee Douglas, Frank Duke, Vincent Genovese, Euan Hooper, Warren Jacobs, Wes Moore, Ren Pierpoint, John Schneider, George Townson, Edward B. Wilford III and Peter Wright, Sr. After debating multiple options for the commemoration, the idea of a museum was embraced when Peter Wright, then President of Keystone Helicopters, offered to donate several vintage helicopters if a museum was established. Two weeks later, the nascent 50th Anniversary Committee met again with a mission to: “Lay the foundation for a permanent rotary-wing restoration, conservation and exhibition facility in the Delaware Valley.”\u0000\u0000Referencing the documented minutes of the aforementioned meeting and that of subsequent meetings of the 50th Anniversary Committee, other documents and the recollections of the author, this paper will trace the formative years of the museum from July 1993 to October 1996. It will address the many challenges of founding an aviation museum including incorporation, location identification, building the collection and creating the exhibits and programs. It will recall the people involved and their significant contributions. This paper is particularly compelling to publish this year, recognizing the 25th anniversary of the American Helicopter Museum and Education Center on 18 October 2021.\u0000","PeriodicalId":273020,"journal":{"name":"Proceedings of the Vertical Flight Society 77th Annual Forum","volume":"57 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-05-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134110635","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-05-10DOI: 10.4050/f-0077-2021-16766
M. Favale, Ahmad Haidar, Nicola Donini, Cristian Lilliu, Giovanni Tovo, A. Trezzini
Part of the certification process of the Leonardo Helicopters AW609 – the first tiltrotor that is undergoing a civil certification process – is demonstrating that the aircraft is free from any aeroservoelastic instability by both analysis and flight test. Recently, one of the AW609 prototypes underwent an extensive certification flight flutter and ground stability test campaign. During these tests, the fundamental aircraft flutter mechanisms have been excited and demonstrated to meet the required stability margins foreseen by the certification basis. In this paper, the test methodology used to perform the tests and flight data processing techniques are detailed. The results are then presented in terms of frequency and damping and as a function of aircraft parameters such as airspeed and gross weight. The certification test results successfully establish that the AW609 is free from instability across the flight envelope and operating conditions with no detrimental damping trends.
{"title":"AeroServoElastic Test Campaign of the AW609 Civil Tilt-Rotor","authors":"M. Favale, Ahmad Haidar, Nicola Donini, Cristian Lilliu, Giovanni Tovo, A. Trezzini","doi":"10.4050/f-0077-2021-16766","DOIUrl":"https://doi.org/10.4050/f-0077-2021-16766","url":null,"abstract":"\u0000 Part of the certification process of the Leonardo Helicopters AW609 – the first tiltrotor that is undergoing a civil certification process – is demonstrating that the aircraft is free from any aeroservoelastic instability by both analysis and flight test. Recently, one of the AW609 prototypes underwent an extensive certification flight flutter and ground stability test campaign. During these tests, the fundamental aircraft flutter mechanisms have been excited and demonstrated to meet the required stability margins foreseen by the certification basis. In this paper, the test methodology used to perform the tests and flight data processing techniques are detailed. The results are then presented in terms of frequency and damping and as a function of aircraft parameters such as airspeed and gross weight. The certification test results successfully establish that the AW609 is free from instability across the flight envelope and operating conditions with no detrimental damping trends.\u0000","PeriodicalId":273020,"journal":{"name":"Proceedings of the Vertical Flight Society 77th Annual Forum","volume":"38 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-05-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133120197","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-05-10DOI: 10.4050/f-0077-2021-16882
Chris Stroncek, David Stephan, R. Benton, T. Hiros, D. Cripps, Edwin Martin
The U.S. Army's Future Vertical Lift (FVL) programs provide many opportunities and challenges for Vertical Flight Society members. The early stages of each FVL program are governed by principles that foster competition between companies, while requiring collaboration between the Army and each company. Down-selected companies competing for the Future Attack Reconnaissance Aircraft (FARA) Competitive Prototype (CP) possess unique capabilities and initiatives to help advance collaboration with the Army. Bell, with a long history of developing aircraft for commercial and military use, is one of five performers selected for Phase 1 of FARA CP, and one of two performers selected for phase 2. During phase 1, the Army began working with the Industry performers to exercise and adapt existing industry processes to collaborate with airworthiness representatives from the Army. The collaboration required for FARA CP also applies to another FVL Other Transaction Agreement (OTA). Concurrently, Bell was also selected as an OTA project agreement holder for the Future Long-Range Assault Aircraft (FLRAA) Competitive Demonstration and Risk Reduction (CD&RR) effort. The FARA CP and FLRAA CD&RR programs have introduced new types of agreements and new expectations in airworthiness paradigms that require greater collaboration between experienced industry and U.S. Army representatives.
{"title":"Streamlining Flight Safety Assurance Processes for Future Vertical Lift Development Programs through Government-Industry Collaboration","authors":"Chris Stroncek, David Stephan, R. Benton, T. Hiros, D. Cripps, Edwin Martin","doi":"10.4050/f-0077-2021-16882","DOIUrl":"https://doi.org/10.4050/f-0077-2021-16882","url":null,"abstract":"\u0000 The U.S. Army's Future Vertical Lift (FVL) programs provide many opportunities and challenges for Vertical Flight Society members. The early stages of each FVL program are governed by principles that foster competition between companies, while requiring collaboration between the Army and each company. Down-selected companies competing for the Future Attack Reconnaissance Aircraft (FARA) Competitive Prototype (CP) possess unique capabilities and initiatives to help advance collaboration with the Army. Bell, with a long history of developing aircraft for commercial and military use, is one of five performers selected for Phase 1 of FARA CP, and one of two performers selected for phase 2. During phase 1, the Army began working with the Industry performers to exercise and adapt existing industry processes to collaborate with airworthiness representatives from the Army. The collaboration required for FARA CP also applies to another FVL Other Transaction Agreement (OTA). Concurrently, Bell was also selected as an OTA project agreement holder for the Future Long-Range Assault Aircraft (FLRAA) Competitive Demonstration and Risk Reduction (CD&RR) effort. The FARA CP and FLRAA CD&RR programs have introduced new types of agreements and new expectations in airworthiness paradigms that require greater collaboration between experienced industry and U.S. Army representatives.\u0000","PeriodicalId":273020,"journal":{"name":"Proceedings of the Vertical Flight Society 77th Annual Forum","volume":"9 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-05-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116467779","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-05-10DOI: 10.4050/f-0077-2021-16836
Rhys M. Lehmann, David Howe
During conduct of clearance testing for the carriage of a heavy external load under a CH-47F aircraft, the Australian Army experienced an incident involving high frequency divergent oscillations in hover. Modelling and simulation was conducted in order to identify the likely source of the oscillations. In this paper, a high order 3 degree of freedom linear CH-47F helicopter model is coupled with a linearised model of an externally slung load in the dual point configuration. This is combined with a linearised version of the longitudinal flight control system to estimate the closed loop coupled helicopter/load dynamics. Analysis of predicted stability margins using the coupled model indicated that interactions between the load and the closed loop dynamics were likely in this configuration, with low airframe gross weight configurations contributing to the destabilisation of the system. The coupled linearised model approach is extended to facilitate parametric studies, allowing for analysis of the impact of configuration parameters and rigging geometry on the overall stability using root locus techniques. This paper presents the methods for generating the coupled linearised model and parametric analysis. It also highlights the importance of conducting stability margin analysis for external load configurations, particularly for high load-mass ratios and dual point configurations.
{"title":"Analysis of Helicopter Slung-Load Instabilities with AFCS Feedback using Coupled Linearised Models","authors":"Rhys M. Lehmann, David Howe","doi":"10.4050/f-0077-2021-16836","DOIUrl":"https://doi.org/10.4050/f-0077-2021-16836","url":null,"abstract":"\u0000 During conduct of clearance testing for the carriage of a heavy external load under a CH-47F aircraft, the Australian Army experienced an incident involving high frequency divergent oscillations in hover. Modelling and simulation was conducted in order to identify the likely source of the oscillations. In this paper, a high order 3 degree of freedom linear CH-47F helicopter model is coupled with a linearised model of an externally slung load in the dual point configuration. This is combined with a linearised version of the longitudinal flight control system to estimate the closed loop coupled helicopter/load dynamics. Analysis of predicted stability margins using the coupled model indicated that interactions between the load and the closed loop dynamics were likely in this configuration, with low airframe gross weight configurations contributing to the destabilisation of the system. The coupled linearised model approach is extended to facilitate parametric studies, allowing for analysis of the impact of configuration parameters and rigging geometry on the overall stability using root locus techniques. This paper presents the methods for generating the coupled linearised model and parametric analysis. It also highlights the importance of conducting stability margin analysis for external load configurations, particularly for high load-mass ratios and dual point configurations.\u0000","PeriodicalId":273020,"journal":{"name":"Proceedings of the Vertical Flight Society 77th Annual Forum","volume":"4 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-05-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116625085","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-05-10DOI: 10.4050/f-0077-2021-16695
J. Sagaga, Seongkyu Lee
In this paper, acoustic predictions are performed for the rotors of NASA’s side-by-side Urban Air Mobility (UAM) aircraft in hover. Investigations of the acoustics are performed on four overlap configurations, 0%, 5%, 15%, and 25%, in hover via high-fidelity Computational Fluid Dynamics (CFD) simulations. CFD simulations are carried out using the HPCMP CREATETM-AV Helios and acoustics calculations are conducted using PSUWOPWOP. Blade airloads and performance of the rotors are computed for this study. Predictions on the rotor airloads and wake geometry are compared for all overlap configurations at a collective pitch angle of 8°. It is shown that the 25% overlap configuration yields a higher overall sound pressure level (OASPL) than for the other overlap configurations, mainly due to stronger blade-vortex-interactions at the entrance and exit locations of the overlap region. It is found that the OASPL difference in hover is above 62 dB at an altitude of 500 ft (152.4 m), which is the UAM aircraft noise guideline suggested by Uber. Additionally, noise for all overlap cases are compared against various background noise levels. Results show that noise from the side-by-side rotor could not be fully concealed by the various background noise at an altitude of 500 ft (152.4 m).
本文对美国国家航空航天局(NASA)的并排城市空中机动飞机(UAM)的旋翼在悬停状态下进行了声学预测。通过高保真计算流体动力学(CFD)模拟，对悬停时的四种重叠配置(0%、5%、15%和25%)进行了声学研究。使用HPCMP CREATETM-AV Helios进行CFD模拟，使用PSUWOPWOP进行声学计算。本研究计算了叶片气动载荷和转子性能。对转子气动载荷和尾迹几何形状的预测进行了比较，所有重叠配置的集体俯仰角为8°。结果表明，25%的重叠配置比其他重叠配置产生更高的总声压级(OASPL)，这主要是由于重叠区域入口和出口位置的叶片-涡相互作用更强。研究发现，在Uber建议的UAM飞机噪声准则500 ft (152.4 m)高度，悬停时的OASPL差值在62 dB以上。此外，将所有重叠情况下的噪声与各种背景噪声水平进行比较。结果表明，在高度为500 ft (152.4 m)时，来自并排转子的噪声不能被各种背景噪声完全掩盖。
{"title":"Acoustic Predictions for the Side-by-Side Air Taxi Rotor in Hover","authors":"J. Sagaga, Seongkyu Lee","doi":"10.4050/f-0077-2021-16695","DOIUrl":"https://doi.org/10.4050/f-0077-2021-16695","url":null,"abstract":"\u0000 In this paper, acoustic predictions are performed for the rotors of NASA’s side-by-side Urban Air Mobility (UAM) aircraft in hover. Investigations of the acoustics are performed on four overlap configurations, 0%, 5%, 15%, and 25%, in hover via high-fidelity Computational Fluid Dynamics (CFD) simulations. CFD simulations are carried out using the HPCMP CREATETM-AV Helios and acoustics calculations are conducted using PSUWOPWOP. Blade airloads and performance of the rotors are computed for this study. Predictions on the rotor airloads and wake geometry are compared for all overlap configurations at a collective pitch angle of 8°. It is shown that the 25% overlap configuration yields a higher overall sound pressure level (OASPL) than for the other overlap configurations, mainly due to stronger blade-vortex-interactions at the entrance and exit locations of the overlap region. It is found that the OASPL difference in hover is above 62 dB at an altitude of 500 ft (152.4 m), which is the UAM aircraft noise guideline suggested by Uber. Additionally, noise for all overlap cases are compared against various background noise levels. Results show that noise from the side-by-side rotor could not be fully concealed by the various background noise at an altitude of 500 ft (152.4 m).\u0000","PeriodicalId":273020,"journal":{"name":"Proceedings of the Vertical Flight Society 77th Annual Forum","volume":"109 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-05-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132201251","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-05-10DOI: 10.4050/f-0077-2021-16906
Alexej Dikarew
Automatic helicopter flight in uncertain surroundings remains a challenging task due to sudden changes in environment, requiring fast response to guarantee safe and collision-free guidance. Increasing numbers of small unmanned aerial vehicles, which are not covered by air traffic control, pose a potential threat to rotorcraft operating in lower airspace. In order to provide collision avoidance in this scenario, the capability of reacting immediately to appearing obstacles and guiding the rotorcraft along feasible evasive trajectories is required. This paper presents an approach to short-term collision avoidance based on model predictive techniques. The proposed method, originally developed for automotive applications, finds optimal control inputs by predicting a set of trajectories utilizing a model resembling the helicopter dynamics. Compared to model predictive control no iterative optimization is adopted, resulting in deterministic execution time. The proposed method is evaluated by closed-loop simulations with a non-linear helicopter model. Additional hardware-in-the-loop simulations are conducted to examine the real-time capability of the approach.
{"title":"Model Predictive Approach for Short-Term Collision Avoidance","authors":"Alexej Dikarew","doi":"10.4050/f-0077-2021-16906","DOIUrl":"https://doi.org/10.4050/f-0077-2021-16906","url":null,"abstract":"\u0000 Automatic helicopter flight in uncertain surroundings remains a challenging task due to sudden changes in environment, requiring fast response to guarantee safe and collision-free guidance. Increasing numbers of small unmanned aerial vehicles, which are not covered by air traffic control, pose a potential threat to rotorcraft operating in lower airspace. In order to provide collision avoidance in this scenario, the capability of reacting immediately to appearing obstacles and guiding the rotorcraft along feasible evasive trajectories is required. This paper presents an approach to short-term collision avoidance based on model predictive techniques. The proposed method, originally developed for automotive applications, finds optimal control inputs by predicting a set of trajectories utilizing a model resembling the helicopter dynamics. Compared to model predictive control no iterative optimization is adopted, resulting in deterministic execution time. The proposed method is evaluated by closed-loop simulations with a non-linear helicopter model. Additional hardware-in-the-loop simulations are conducted to examine the real-time capability of the approach.\u0000","PeriodicalId":273020,"journal":{"name":"Proceedings of the Vertical Flight Society 77th Annual Forum","volume":"19 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-05-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132208621","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-05-10DOI: 10.4050/f-0077-2021-16805
Mike G. Sweet, Samuel Forgerson, Chad deMontfort
Mercer Engineering Research Center (MERC) developed a neural network-based regression method for predicting maximum stress per flight values at four structural tracking locations on the United States Air Force HH-60G helicopter airframe using Individual Vehicle Health and Usage Monitoring (IVHMS) data. Maximum stress per flight is utilized when evaluating a failure criterion within the HH-60G service life analysis, so an accurate, fleet-wide estimation of maximum stress magnitude and likelihood is critical for accurate service life determinations. The model was trained using parametric flight data time histories (from IVHMS) and stress time histories from a strain survey aircraft. The stress time histories were developed from the strain signals using two different methods depending on the location of strain gauges in the vicinity of the tracking locations. For two of the tracking locations, they were derived from a global finite element model using a collection of strain gauge signals throughout the strain survey aircraft. At the other two tracking locations, the strain time histories were derived from single strain gauges installed in close proximity to the tracking locations. Multiple regression methods and input data configurations were evaluated in order to identify an appropriate regression method that predicts a maximum stress per flight accurately without over-fitting the training data. MERC identified that the relationship between parametric flight data and aircraft component strain can be exploited to a high level of accuracy using machine learning regression tools. Achieving a high level of accuracy required an extensive review of independent and dependent variable data quality and thoughtful consideration of model inputs.
{"title":"Predicting a Maximum Stress using Machine Learning and Parametric Flight Data","authors":"Mike G. Sweet, Samuel Forgerson, Chad deMontfort","doi":"10.4050/f-0077-2021-16805","DOIUrl":"https://doi.org/10.4050/f-0077-2021-16805","url":null,"abstract":"\u0000 Mercer Engineering Research Center (MERC) developed a neural network-based regression method for predicting maximum stress per flight values at four structural tracking locations on the United States Air Force HH-60G helicopter airframe using Individual Vehicle Health and Usage Monitoring (IVHMS) data. Maximum stress per flight is utilized when evaluating a failure criterion within the HH-60G service life analysis, so an accurate, fleet-wide estimation of maximum stress magnitude and likelihood is critical for accurate service life determinations. The model was trained using parametric flight data time histories (from IVHMS) and stress time histories from a strain survey aircraft. The stress time histories were developed from the strain signals using two different methods depending on the location of strain gauges in the vicinity of the tracking locations. For two of the tracking locations, they were derived from a global finite element model using a collection of strain gauge signals throughout the strain survey aircraft. At the other two tracking locations, the strain time histories were derived from single strain gauges installed in close proximity to the tracking locations. Multiple regression methods and input data configurations were evaluated in order to identify an appropriate regression method that predicts a maximum stress per flight accurately without over-fitting the training data. MERC identified that the relationship between parametric flight data and aircraft component strain can be exploited to a high level of accuracy using machine learning regression tools. Achieving a high level of accuracy required an extensive review of independent and dependent variable data quality and thoughtful consideration of model inputs.\u0000","PeriodicalId":273020,"journal":{"name":"Proceedings of the Vertical Flight Society 77th Annual Forum","volume":"26 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-05-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133969543","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-05-10DOI: 10.4050/f-0077-2021-16791
S. Withrow-Maser, Carlos A. Malpica, K. Nagami
Control models of three NASA Urban Air Mobility (UAM) reference vehicles (the quadrotor, octocopter, and Lift+Cruise (LPC)) were created and compared to determine the effect of rotor number and disk loading on control margin and design. The heave and yaw axes demand more actuator usage than the roll and pitch axes. Between heave and yaw, heave was the more demanding of the two because of the dependence of heave on the engine speed controller (ESC). When the feedback gains for all three vehicles were optimized to Level 1 handling qualities (HQs) specifications using CONDUIT, the ESC for the octocopter was the most stable and had the highest rise time (time for the rotor to respond to an input), while the LPC ESC was the least stable and had the smallest rise time. Rise time corresponds to the time required for rotor response. When actuator usage was translated to current margin, torque margin, and power margin, heave was the most demanding axis, followed by yaw, roll, and then pitch for all three vehicles. The results emphasize the importance of an accurate motor model within the control system architecture.
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