{"title":"Erratum to: Analytical Estimate of Rotor Controls Required for a Straight Vortex Disturbance Rejection","authors":"B. G. Wall","doi":"10.4050/JAHS.66.028011","DOIUrl":"https://doi.org/10.4050/JAHS.66.028011","url":null,"abstract":"Correction to:Journal of the American Helicopter Society, Vol. 62, (1), January 2017, pp. 1-4,http://dx.doi.org/10.4050/JAHS.62.015001","PeriodicalId":50017,"journal":{"name":"Journal of the American Helicopter Society","volume":"1 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70215277","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}
Rotorcraft symbology can provide pilots with the flight information necessary to replace the visual cues lost when operating in degraded visual environments. However, tuning symbology for effective use is a time-consuming process as it generally requires considerable in-flight testing and extensive trial and error. In this work, two experiments are conducted to assess how changes in the display scaling of a position–velocity–acceleration architectured symbology set affects pilot performance and workload. In the first experiment, participants attempt a modified single-axis precision hover using a simulated helicopter and nonconformal symbology set while display parameters relating to acceleration, velocity, and position cue scaling are varied. Performance is measured using the root mean square of the position error relative to a target location, and participant workload is assessed using their cyclic control activity and Bedford ratings. In the second experiment, an analytical pilot-in-the-loop simulation is conducted to validate the performance results obtained in the first experiment and to investigate the underlying system characteristics that contribute the observed trends. For the implemented symbology and Bell UH-1H model, the results from both experiments concur that a combination of low-to-mid range acceleration cue scaling and mid-to-high range position cue scaling enable strong performance without inflating workload. Results indicate an insensitivity to velocity vector scaling, likely due to the symbology architecture and nature of the control task. The results of these experiments establish a predictable relationship between display scaling and pilot response, which can aid in streamlining the tuning process for similarly-styled symbology, helicopter and task envelope combinations.
{"title":"Effects of Hover Symbology Display Scaling on Performance and Workload","authors":"F. Erazo, S. Jennings, K. Ellis, J. Etele","doi":"10.4050/JAHS.66.022002","DOIUrl":"https://doi.org/10.4050/JAHS.66.022002","url":null,"abstract":"Rotorcraft symbology can provide pilots with the flight information necessary to replace the visual cues lost when operating in degraded visual environments. However, tuning symbology for effective use is a time-consuming process as it generally requires considerable in-flight testing and extensive trial and error. In this work, two experiments are conducted to assess how changes in the display scaling of a position–velocity–acceleration architectured symbology set affects pilot performance and workload. In the first experiment, participants attempt a modified single-axis precision hover using a simulated helicopter and nonconformal symbology set while display parameters relating to acceleration, velocity, and position cue scaling are varied. Performance is measured using the root mean square of the position error relative to a target location, and participant workload is assessed using their cyclic control activity and Bedford ratings. In the second experiment, an analytical pilot-in-the-loop simulation is conducted to validate the performance results obtained in the first experiment and to investigate the underlying system characteristics that contribute the observed trends. For the implemented symbology and Bell UH-1H model, the results from both experiments concur that a combination of low-to-mid range acceleration cue scaling and mid-to-high range position cue scaling enable strong performance without inflating workload. Results indicate an insensitivity to velocity vector scaling, likely due to the symbology architecture and nature of the control task. The results of these experiments establish a predictable relationship between display scaling and pilot response, which can aid in streamlining the tuning process for similarly-styled symbology, helicopter and task envelope combinations.","PeriodicalId":50017,"journal":{"name":"Journal of the American Helicopter Society","volume":"1 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70215298","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 methods of using the viscous vortex particle method, dynamic inflow, and uniform inflow to conduct whirl-flutter stability analysis are evaluated on a four-bladed, soft-inplane tiltrotor model using the Rotorcraft Comprehensive Analysis System. For the first time, coupled transient simulations between comprehensive analysis and a vortex particle method inflow model are used to predict whirl-flutter stability. Resolution studies are performed for both spatial and temporal resolution in the transient solution. Stability in transient analysis is noted to be influenced by both. As the particle resolution is refined, a reduction in simulation time-step size must also be performed. An azimuthal time step size of 0.3 deg is used to consider a range of particle resolutions to understand the influence on whirl-flutter stability predictions. Comparisons are made between uniform inflow, dynamic inflow, and the vortex particle method with respect to prediction capabilities when compared to wing beam-bending frequency and damping experimental data. Challenges in assessing the most accurate inflow model are noted due to uncertainty in experimental data; however, a consistent trend of increasing damping with additional levels of fidelity in the inflow model is observed. Excellent correlation is observed between the dynamic inflow predictions and the vortex particle method predictions in which the wing is not part of the inflow model, indicating that the dynamic inflow model is adequate for capturing damping due to the induced velocity on the rotor disk. Additional damping is noted in the full vortex particle method model, with the wing included, which is attributed to either an interactional aerodynamic effect between the rotor and the wing or a more accurate representation of the unsteady loading on the wing due to induced velocities.
{"title":"On the Influence of Inflow Model Selection for Time-Domain Tiltrotor Aeroelastic Analysis","authors":"Ethan Corle, M. Floros, S. Schmitz","doi":"10.4050/JAHS.66.032009","DOIUrl":"https://doi.org/10.4050/JAHS.66.032009","url":null,"abstract":"The methods of using the viscous vortex particle method, dynamic inflow, and uniform inflow to conduct whirl-flutter stability analysis are evaluated on a four-bladed, soft-inplane tiltrotor model using the Rotorcraft Comprehensive Analysis System. For the first time, coupled transient simulations between comprehensive analysis and a vortex particle method inflow model are used to predict whirl-flutter stability. Resolution studies are performed for both spatial and temporal resolution in the transient solution. Stability in transient analysis is noted to be influenced by both. As the particle resolution is refined, a reduction in simulation time-step size must also be performed. An azimuthal time step size of 0.3 deg is used to consider a range of particle resolutions to understand the influence on whirl-flutter stability predictions. Comparisons are made between uniform inflow, dynamic inflow, and the vortex particle method with respect to prediction capabilities when compared to wing beam-bending frequency and damping experimental data. Challenges in assessing the most accurate inflow model are noted due to uncertainty in experimental data; however, a consistent trend of increasing damping with additional levels of fidelity in the inflow model is observed. Excellent correlation is observed between the dynamic inflow predictions and the vortex particle method predictions in which the wing is not part of the inflow model, indicating that the dynamic inflow model is adequate for capturing damping due to the induced velocity on the rotor disk. Additional damping is noted in the full vortex particle method model, with the wing included, which is attributed to either an interactional aerodynamic effect between the rotor and the wing or a more accurate representation of the unsteady loading on the wing due to induced velocities.","PeriodicalId":50017,"journal":{"name":"Journal of the American Helicopter Society","volume":"1 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70215747","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}
Robotic landing gear enhances the landing capabilities of vertical take-off and landing aircraft on sloped, rough, and even moving landing surfaces. This research demonstrates the integration and systematic testing of a robotic landing gear system for the commercial S-100 Camcopter, expanding the aircraft’s landing capabilities to currently inaccessible terrains with slopes at and above 15°. An overview of the mechanical design, sensors, and controller as integrated into the S-100 rotorcraft is provided along with expected landing performance from simulations tools. The system is then demonstrated using ground and flight experiments, and performance metrics are found to match design metrics. An asymmetry in left and right leg landings during flight testing is observed and analyzed. Lastly, cross-coupling of pitch and roll rates induced by the rotor is discussed as a cause of the asymmetry on this three-legged rotorcraft.
{"title":"Ground and Flight Tests of an Unmanned Rotorcraft with Cable-Driven Robotic Landing Gear","authors":"Benjamin L. Leon, J. Rimoli, Claudio V. Di Leo","doi":"10.4050/jahs.66.042003","DOIUrl":"https://doi.org/10.4050/jahs.66.042003","url":null,"abstract":"Robotic landing gear enhances the landing capabilities of vertical take-off and landing aircraft on sloped, rough, and even moving landing surfaces. This research demonstrates the integration and systematic testing of a robotic landing gear system for the commercial S-100 Camcopter, expanding the aircraft’s landing capabilities to currently inaccessible terrains with slopes at and above 15°. An overview of the mechanical design, sensors, and controller as integrated into the S-100 rotorcraft is provided along with expected landing performance from simulations tools. The system is then demonstrated using ground and flight experiments, and performance metrics are found to match design metrics. An asymmetry in left and right leg landings during flight testing is observed and analyzed. Lastly, cross-coupling of pitch and roll rates induced by the rotor is discussed as a cause of the asymmetry on this three-legged rotorcraft.","PeriodicalId":50017,"journal":{"name":"Journal of the American Helicopter Society","volume":"1 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70216011","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 deals with finite element analysis of helicopter blades with single and double swept geometries made by metallic and composite materials. First, classical and refined beam theories are combined at the element level via a nodedependent kinematic (NDK) concept, which was recently introduced by the authors. Such an NDK approach enables the accuracy/efficiency ratio of the solution to be tuned according to the level of fidelity required by the design phase. Second, one-dimensional NDK models are combined with the possibility to introduce solid elements in those regions of the blade with a sharp variation of the geometries. The numerical examples consider a swept-tip rectangular beam and a doubleswept helicopter blade with a realistic airfoil. Natural frequencies and through-the-layer stress distributions are reported to demonstrate the flexibility and computational efficiency of the proposed methodology.
{"title":"Node-Dependent Kinematics and Multidimensional Finite Elements for the Analysis of Single/Double Swept, Composite Helicopter Blades","authors":"M. Filippi, E. Carrera, D. Giusa, E. Zappino","doi":"10.4050/JAHS.66.032005","DOIUrl":"https://doi.org/10.4050/JAHS.66.032005","url":null,"abstract":"This paper deals with finite element analysis of helicopter blades with single and double swept geometries made by metallic and composite materials. First, classical and refined beam theories are combined at the element level via a nodedependent kinematic (NDK) concept, which was recently introduced by the authors. Such an NDK approach enables the accuracy/efficiency ratio of the solution to be tuned according to the level of fidelity required by the design phase. Second, one-dimensional NDK models are combined with the possibility to introduce solid elements in those regions of the blade with a sharp variation of the geometries. The numerical examples consider a swept-tip rectangular beam and a doubleswept helicopter blade with a realistic airfoil. Natural frequencies and through-the-layer stress distributions are reported to demonstrate the flexibility and computational efficiency of the proposed methodology.","PeriodicalId":50017,"journal":{"name":"Journal of the American Helicopter Society","volume":"1 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70216049","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 investigates structural coupling problems for tiltrotors, considering not only the interaction of the flight control system with the flexible structure but also the potentially adverse effects on the aeroservoelastic stability that may be caused by the pilot's involuntary, high-frequency, biodynamic response. The investigation is focused on the analysis of the side effects that could appear at high speed in the airplane flight regime, where the whirl flutter boundaries may be significantly reduced. A detailed tiltrotor model, representative of the Bell XV-15 and of a flight control system has been built and joined with a pilot biodynamic model acting on the power-lever and on the center stick, available in the literature. Additionally, a modified version of the XV-15 using differential collective pitch for yaw control in airplane mode instead of rudder has been investigated to show the effect of different yaw control designs. The stability analyses presented demonstrate that the structural coupling analysis and the flutter boundaries for tiltrotors must be evaluated not only considering the closed loop created by the flight control system but also the effect of involuntary pilot response. Sensitivity analyses examine the most critical parameters impacting tiltrotor aeroservoelastic stability. Finally, the employment of notch filters as a means of prevention is discussed.
{"title":"Structural Coupling and Whirl-Flutter Stability with Pilot-in-the-Loop","authors":"V. Muscarello, G. Quaranta","doi":"10.4050/JAHS.66.032003","DOIUrl":"https://doi.org/10.4050/JAHS.66.032003","url":null,"abstract":"This paper investigates structural coupling problems for tiltrotors, considering not only the interaction of the flight control system with the flexible structure but also the potentially adverse effects on the aeroservoelastic stability that may be caused by the pilot's involuntary, high-frequency, biodynamic response. The investigation is focused on the analysis of the side effects that could appear at high speed in the airplane flight regime, where the whirl flutter boundaries may be significantly reduced. A detailed tiltrotor model, representative of the Bell XV-15 and of a flight control system has been built and joined with a pilot biodynamic model acting on the power-lever and on the center stick, available in the literature. Additionally, a modified version of the XV-15 using differential collective pitch for yaw control in airplane mode instead of rudder has been investigated to show the effect of different yaw control designs. The stability analyses presented demonstrate that the structural coupling analysis and the flutter boundaries for tiltrotors must be evaluated not only considering the closed loop created by the flight control system but also the effect of involuntary pilot response. Sensitivity analyses examine the most critical parameters impacting tiltrotor aeroservoelastic stability. Finally, the employment of notch filters as a means of prevention is discussed.","PeriodicalId":50017,"journal":{"name":"Journal of the American Helicopter Society","volume":"1 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70215520","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}
Rotorcraft brownout is an in-flight visibility restriction caused by clouds of sand and dust particles during landing, takeoff, and near-ground flight operations in arid desert terrain. This complex phenomenon is caused by the entrainment of dust, sand, and ground particles by rotor downwash and is compounded by fuselage geometry and its orientation with respect to the ground. Highly unsteady wind velocities are common in near-ground operations and play a significant role in the particulate cloud’s behavior that creates the brownout condition. Experiments and flight tests to understand brownout are challenging, expensive, and risky. Alternatively, computational fluid dynamics (CFD) has been used extensively over the past few decades to study rotorcraft aerodynamics. However, there are additional computational challenges associated with modeling the dust particle transport in a brownout. In this work, a computationally efficient Eulerian-based framework has been developed to model rotorcraft brownout. The flowfield is modeled by Reynolds averaged Navier–Stokes (RANS) equation and is solved using the SIMPLER algorithm. Turbulence properties are modeled using Realizable k – ε equations, while the rotor is modeled as a momentum source to focus on the global flowfield rather than the flow near the rotors. The Eulerian approach for both the flowfield and the dust transport allows computationally efficient and rapid analysis, taking an order of few hours in a single CPU to a fraction of an hour using GPU-based computation. In this work, results from two sets of experiments are presented. At first, a study on the fuselage’s effect on brownout with respect to height for a single-rotor configuration in hover is demonstrated. Next, a study on the brownout characteristics of three rotor–fuselage configurations in hover, namely single-rotor, tandem-rotor, and quad-rotor, is presented. It has been observed that the ground friction velocity profile and flowfield vorticity around the rotorcraft play a significant role in dust cloud behavior. Additionally, the body forces and interference due to the fuselage plays a vital role in the formation of brownout dust clouds. The experiments showed that the quad-rotor is worst affected in terms of size and height of the dust clouds. However, the tandem-rotor has been found to be worst in the terms of average dust density.
旋翼机熄火是在干旱的沙漠地带着陆、起飞和近地飞行时，由沙尘颗粒云引起的飞行中能见度限制。这种复杂的现象是由转子下冲带来的灰尘、沙子和地面颗粒的夹带引起的，并且由于机身的几何形状及其相对于地面的方向而更加复杂。高度不稳定的风速在近地作业中很常见，并且在微粒云的行为中起着重要作用，从而产生了电力不足的情况。实验和飞行测试是有挑战性的，昂贵的，有风险的。在过去的几十年里，计算流体动力学(CFD)被广泛应用于旋翼飞行器的空气动力学研究。然而，在停电情况下，还有与模拟尘埃颗粒传输相关的额外计算挑战。在这项工作中，一个计算效率高的基于欧拉的框架已经开发出来，以模拟旋翼机熄火。流场采用Reynolds平均Navier-Stokes (RANS)方程建模，采用simple算法求解。湍流特性使用Realizable k - ε方程建模，而转子作为动量源建模，以关注全局流场而不是转子附近的流动。对于流场和粉尘传输的欧拉方法允许计算效率和快速分析，在单个CPU上花费几个小时的数量级，使用基于gpu的计算只需一小时的几分之一。本文给出了两组实验的结果。首先，研究了悬停时单旋翼构型的机身对高度的影响。其次，研究了单旋翼、串联旋翼和四旋翼三种旋翼-机身构型悬停时的减光特性。研究发现，旋翼机周围的地面摩擦速度分布和流场涡量对尘云的特性有重要影响。此外，机体力和机身的干扰在停电尘埃云的形成中起着至关重要的作用。实验表明，四旋翼飞行器受尘云大小和高度的影响最大。然而，串联转子在平均粉尘密度方面被发现是最差的。
{"title":"A Computational Study on Rotor and Fuselage Configuration Effect on Rotorcraft Brownout","authors":"Sayan Ghosh, R. Rajagopalan","doi":"10.4050/jahs.67.012001","DOIUrl":"https://doi.org/10.4050/jahs.67.012001","url":null,"abstract":"Rotorcraft brownout is an in-flight visibility restriction caused by clouds of sand and dust particles during landing, takeoff, and near-ground flight operations in arid desert terrain. This complex phenomenon is caused by the entrainment of dust, sand, and ground particles by rotor downwash and is compounded by fuselage geometry and its orientation with respect to the ground. Highly unsteady wind velocities are common in near-ground operations and play a significant role in the particulate cloud’s behavior that creates the brownout condition. Experiments and flight tests to understand brownout are challenging, expensive, and risky. Alternatively, computational fluid dynamics (CFD) has been used extensively over the past few decades to study rotorcraft aerodynamics. However, there are additional computational challenges associated with modeling the dust particle transport in a brownout. In this work, a computationally efficient Eulerian-based framework has been developed to model rotorcraft brownout. The flowfield is modeled by Reynolds averaged Navier–Stokes (RANS) equation and is solved using the SIMPLER algorithm. Turbulence properties are modeled using Realizable k – ε equations, while the rotor is modeled as a momentum source to focus on the global flowfield rather than the flow near the rotors. The Eulerian approach for both the flowfield and the dust transport allows computationally efficient and rapid analysis, taking an order of few hours in a single CPU to a fraction of an hour using GPU-based computation. In this work, results from two sets of experiments are presented. At first, a study on the fuselage’s effect on brownout with respect to height for a single-rotor configuration in hover is demonstrated. Next, a study on the brownout characteristics of three rotor–fuselage configurations in hover, namely single-rotor, tandem-rotor, and quad-rotor, is presented. It has been observed that the ground friction velocity profile and flowfield vorticity around the rotorcraft play a significant role in dust cloud behavior. Additionally, the body forces and interference due to the fuselage plays a vital role in the formation of brownout dust clouds. The experiments showed that the quad-rotor is worst affected in terms of size and height of the dust clouds. However, the tandem-rotor has been found to be worst in the terms of average dust density.","PeriodicalId":50017,"journal":{"name":"Journal of the American Helicopter Society","volume":"1 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70216200","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 predictions of an upgraded UMARC comprehensive analysis are compared to experimental lift offset rotor results. The experiments cover a range of collective pitch angles (θ°) from 2° to 10°, advance ratios (μ) from 0.21 to 0.53, and lift offset from 0% to 20%. The experimental model rotors are from a system of coaxial hingeless rotors, with two blades each, and a first flap frequency of approximately 1.6/rev. The simulation is compared with isolated rotor performance and controls with lift offset, loads, and pitch link forces. Increasing efficiency with increasing lift offset, the impact of lift offset on different loads, and the dependence of pitch link loads on pitch bearing damping are identified in the experiment and correlated with the simulation.
{"title":"Performance and Loads of a Lift Offset Rotor, Part II: Prediction Validations with Measurements","authors":"J. Schmaus, I. Chopra","doi":"10.4050/jahs.67.012004","DOIUrl":"https://doi.org/10.4050/jahs.67.012004","url":null,"abstract":"The predictions of an upgraded UMARC comprehensive analysis are compared to experimental lift offset rotor results. The experiments cover a range of collective pitch angles (θ°) from 2° to 10°, advance ratios (μ) from 0.21 to 0.53, and lift offset from 0% to 20%. The experimental model rotors are from a system of coaxial hingeless rotors, with two blades each, and a first flap frequency of approximately 1.6/rev. The simulation is compared with isolated rotor performance and controls with lift offset, loads, and pitch link forces. Increasing efficiency with increasing lift offset, the impact of lift offset on different loads, and the dependence of pitch link loads on pitch bearing damping are identified in the experiment and correlated with the simulation.","PeriodicalId":50017,"journal":{"name":"Journal of the American Helicopter Society","volume":"1 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70216314","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 an approach to reframe the sizing problem for vertical-lift unmanned aerial vehicles (UAVs) as an optimization problem and obtains a weight-optimal solution with up to two orders of magnitude of savings in wall clock time. Because sizing is performed with higher fidelity models and design variables from several disciplines, the Simultaneous Analysis aNd Design (SAND) approach from fixed-wing multidisciplinary optimization literature is adapted for the UAV sizing task. Governing equations and disciplinary design variables that are usually self-contained within disciplines (airframe tube sizes, trim variables, and trim equations) are migrated to the sizing optimizer and added as design variables and (in)equality constraints. For sizing consistency, the iterative weight convergence loop is replaced by a coupling variable and associated equality consistency constraint for the sizing optimizer. Cruise airspeed is also added as a design variable and driven by the sizing optimizer. The methodology is demonstrated for sizing a package delivery vehicle (a lift-augment quadrotor biplane tailsitter) with up to 39 design variables and 201 constraints. Gradient-based optimizations were initiated from different starting points; without blade shape design in sizing, all processes converged to the same minimum, indicating that the design space is convex for the chosen bounds, constraints, and objective function. Several optimization schemes were investigated by moving combinations of relevant disciplines (airframe sizing with finite element analysis, vehicle trim, and blade aerodynamic shape design) to the sizing optimizer. The biggest advantage of the SAND strategy is its scope for parallelization, and the inherent ability to drive the design away from regions where disciplinary analyses (e.g., trim) cannot find a solution, obviating the need for ad hoc penalty functions. Even in serial mode, the SAND optimization strategy yields results in the shortest wall clock time compared to all other approaches.
{"title":"A MultiDisciplinary Optimization Approach for Sizing Vertical Lift Aircraft","authors":"A. Sridharan, B. Govindarajan","doi":"10.4050/jahs.67.022004","DOIUrl":"https://doi.org/10.4050/jahs.67.022004","url":null,"abstract":"This paper presents an approach to reframe the sizing problem for vertical-lift unmanned aerial vehicles (UAVs) as an optimization problem and obtains a weight-optimal solution with up to two orders of magnitude of savings in wall clock time. Because sizing is performed with higher fidelity models and design variables from several disciplines, the Simultaneous Analysis aNd Design (SAND) approach from fixed-wing multidisciplinary optimization literature is adapted for the UAV sizing task. Governing equations and disciplinary design variables that are usually self-contained within disciplines (airframe tube sizes, trim variables, and trim equations) are migrated to the sizing optimizer and added as design variables and (in)equality constraints. For sizing consistency, the iterative weight convergence loop is replaced by a coupling variable and associated equality consistency constraint for the sizing optimizer. Cruise airspeed is also added as a design variable and driven by the sizing optimizer. The methodology is demonstrated for sizing a package delivery vehicle (a lift-augment quadrotor biplane tailsitter) with up to 39 design variables and 201 constraints. Gradient-based optimizations were initiated from different starting points; without blade shape design in sizing, all processes converged to the same minimum, indicating that the design space is convex for the chosen bounds, constraints, and objective function. Several optimization schemes were investigated by moving combinations of relevant disciplines (airframe sizing with finite element analysis, vehicle trim, and blade aerodynamic shape design) to the sizing optimizer. The biggest advantage of the SAND strategy is its scope for parallelization, and the inherent ability to drive the design away from regions where disciplinary analyses (e.g., trim) cannot find a solution, obviating the need for ad hoc penalty functions. Even in serial mode, the SAND optimization strategy yields results in the shortest wall clock time compared to all other approaches.","PeriodicalId":50017,"journal":{"name":"Journal of the American Helicopter Society","volume":"1 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70216703","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 real-time flight simulation for multirotor unmanned aerial vehicles (UAV) is performed in combination with dynamic inflow aerodynamics. The present combination procedure includes rotor/fuselage aerodynamics and trim analysis. The rotor aerodynamics is based on dynamic inflow aerodynamics, which is appropriate for the analysis of multirotor UAVs. The present simulation uses an appropriate formulation for fuselage aerodynamics. Trim analysis was conducted for climb and forward flight to determine the physical constraints of the UAV. Based on this procedure, a simulation was performed and validated against the flight test. It was found that the accuracy of flight simulation increased if the simulation is performed in combination with dynamic inflow aerodynamics. Using this methodology, the dynamic characteristics that affect the performance of UAVs were investigated.
{"title":"Real-Time Flight Simulation for Multirotor UAV Integrated with the Dynamic Inflow Aerodynamics","authors":"S. Park, JeongUk Yoo, Sihun Lee, Sang-Joon Shin","doi":"10.4050/jahs.66.042008","DOIUrl":"https://doi.org/10.4050/jahs.66.042008","url":null,"abstract":"A real-time flight simulation for multirotor unmanned aerial vehicles (UAV) is performed in combination with dynamic inflow aerodynamics. The present combination procedure includes rotor/fuselage aerodynamics and trim analysis. The rotor aerodynamics is based on dynamic inflow aerodynamics, which is appropriate for the analysis of multirotor UAVs. The present simulation uses an appropriate formulation for fuselage aerodynamics. Trim analysis was conducted for climb and forward flight to determine the physical constraints of the UAV. Based on this procedure, a simulation was performed and validated against the flight test. It was found that the accuracy of flight simulation increased if the simulation is performed in combination with dynamic inflow aerodynamics. Using this methodology, the dynamic characteristics that affect the performance of UAVs were investigated.","PeriodicalId":50017,"journal":{"name":"Journal of the American Helicopter Society","volume":"36 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70216086","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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