scholarly journals Inflight investigation of the effects of rotor state measurement and feedback on variable stability helicopters

2021 ◽  
Author(s):  
Marc David Alexander
Keyword(s):  
Flight Control ◽  
National Research Council ◽  
Likelihood Estimation ◽  
Flight Test ◽  
Flight Simulation ◽  
Tracking Accuracy ◽  
Response Dynamics ◽  
Control Laws ◽  
Systems Research ◽  
Model Following Control

This thesis describes a flight test evaluation of flight control laws applying rotor state measurements and feedback on the National Research Council Bell 412 Advanced Systems Research Aircraft (ASRA) and Bell 205A Airborne Simulator (AS). Parameter estimation of a higher-order mathematical model of the ASRA rotor dynamics was achieved by Maximum Likelihood Estimation (MLE) employing coupled rotor-body equations parameterized by explicit rotor and fuselage state measurements. Root Locus (RLM), Classical Multivariable (CMC), Eigenstructure Assignment (EAC), and Model Following control algorithms were implemented in Matlab/Simulink simulation for analysis of coupled rotor-body dynamics. Rotorcraft performance specifications were based on compliance with ADS-33E-PRF and Cooper Harper military handling qualities. Evaluated in desk-top and in-flight simulation, rotor state feedback of longitudinal and lateral disc tilt dynamics by modern multivariable control significantly improves inter-axis decoupling, disturbance rejection characteristics, rotor response dynamics, command tracking accuracy, and rigid-body bandwidth performance.

scholarly journals Inflight investigation of the effects of rotor state measurement and feedback on variable stability helicopters

2021 ◽  
Author(s):  
Marc David Alexander
Keyword(s):  
Flight Control ◽  
National Research Council ◽  
Likelihood Estimation ◽  
Flight Test ◽  
Flight Simulation ◽  
Tracking Accuracy ◽  
Response Dynamics ◽  
Control Laws ◽  
Systems Research ◽  
Model Following Control

This thesis describes a flight test evaluation of flight control laws applying rotor state measurements and feedback on the National Research Council Bell 412 Advanced Systems Research Aircraft (ASRA) and Bell 205A Airborne Simulator (AS). Parameter estimation of a higher-order mathematical model of the ASRA rotor dynamics was achieved by Maximum Likelihood Estimation (MLE) employing coupled rotor-body equations parameterized by explicit rotor and fuselage state measurements. Root Locus (RLM), Classical Multivariable (CMC), Eigenstructure Assignment (EAC), and Model Following control algorithms were implemented in Matlab/Simulink simulation for analysis of coupled rotor-body dynamics. Rotorcraft performance specifications were based on compliance with ADS-33E-PRF and Cooper Harper military handling qualities. Evaluated in desk-top and in-flight simulation, rotor state feedback of longitudinal and lateral disc tilt dynamics by modern multivariable control significantly improves inter-axis decoupling, disturbance rejection characteristics, rotor response dynamics, command tracking accuracy, and rigid-body bandwidth performance.

Rotorcraft Lateral-Directional Oscillations: The Anatomy of a Nuisance Mode

2021 ◽  
Author(s):  
Dheeraj Agarwal ◽  
Linghai Lu ◽  
Gareth D. Padfield ◽  
Mark D. White ◽  
Neil Cameron
Keyword(s):  
Simulation Model ◽  
Simulation Models ◽  
Flight Test ◽  
Flight Simulation ◽  
Stability And Control ◽  
Systems Research ◽  
Control Derivatives ◽  
Research Aircraft ◽  
Level Of Understanding ◽  
And Control

High-fidelity rotorcraft flight simulation relies on the availability of a quality flight model that further demands a good level of understanding of the complexities arising from aerodynamic couplings and interference effects. One such example is the difficulty in the prediction of the characteristics of the rotorcraft lateral-directional oscillation (LDO) mode in simulation. Achieving an acceptable level of the damping of this mode is a design challenge requiring simulation models with sufficient fidelity that reveal sources of destabilizing effects. This paper is focused on using System Identification to highlight such fidelity issues using Liverpool's FLIGHTLAB Bell 412 simulation model and in-flight LDO measurements from the bare airframe National Research Council's (Canada) Advanced Systems Research Aircraft. The simulation model was renovated to improve the fidelity of the model. The results show a close match between the identified models and flight test for the LDO mode frequency and damping. Comparison of identified stability and control derivatives with those predicted by the simulation model highlight areas of good and poor fidelity.

Design of Dynamic Inversion and Explicit Model Following Flight Control Laws for Quadrotor UAS

2020 ◽  
Vol 65 (3) ◽  
pp. 1-16
Author(s):  
Umberto Saetti ◽  
Joseph F. Horn ◽  
Sagar Lakhmani ◽  
Constantino Lagoa ◽  
Tom F. Berger
Keyword(s):  
Flight Control ◽  
Flight Test ◽  
Parametric Model ◽  
Unmanned Aerial Systems ◽  
Model Parameters ◽  
Dynamic Inversion ◽  
Explicit Model ◽  
Control Laws ◽  
Model Following ◽  
Novel Approach

The objectives of this paper are to advance dynamic inversion (DI) and explicit model following (EMF) flight control laws for quadrotor unmanned aerial systems (UAS) and to develop an efficient strategy to compute the stability and performance robustness statistics of such control laws given parametric model uncertainty. For this purpose, a parametric model of a quadrotor is identified from flight-test data. The identified model is validated both in frequency and time domains. Next, DI and EMF flight control laws are designed for both inner attitude and outer velocity loops. Finally, a novel approach based on an unscented transform is used to evaluate the statistics of the controller's performance based on the statistics of the uncertain model parameters.

Stalling transport aircraft

2013 ◽  
Vol 117 (1198) ◽  
pp. 1183-1206 ◽  
Author(s):  
P. J. Bolds-Moorehead ◽  
V. G. Chaney ◽  
T. Lutz ◽  
S. Vaux
Keyword(s):  
Wind Tunnel ◽  
Flight Control ◽  
Flight Test ◽  
High Angle ◽  
Flight Testing ◽  
Control Laws ◽  
Transport Aircraft ◽  
Wind Tunnel Data ◽  
Predictive Validation ◽  
Flight Deck

Abstract Airbus and Boeing are cooperatively presenting this topic dealing with transport aircraft stalls. The paper will begin by defining a stall, followed by a review of requirements, predictive validation and flight testing. There are various ways of designing modern jet transports for the stall regime such as aerodynamic approaches, flight deck indications, and augmentation control laws to deal with the high angle-of-attack (α) arena. The goal of augmented control laws for high α is common – no full aerodynamic stall or loss of climb performance should occur in the operational flight envelope, in Normal flight control modes. The validation techniques employed in preparation for a flight test campaign will follow. These include flight characteristic predictions based on wind-tunnel data as well as pilot-in-the-loop simulation rehearsals. The preparation for flight testing will be reviewed from both the engineer and pilot viewpoints. This will be followed by a review of various flight testing that has been conducted. The paper will close with a brief foray into what the future of transport stalls could be – perhaps protection features in degraded flight control modes? What are the benefits as well as drawbacks to increased augmentation for high α?

scholarly journals Validation of Aero-Load Estimator for Convair 880 Aircraft Flight Simulator Benchmark with Electro-Hydrostatic Actuators

2021 ◽  
Vol 13 (3) ◽  
pp. 13-27
Author(s):  
Yamina BOUGHARI ◽  
Ruxandra Mihaela BOTEZ ◽  
Amir BANIAMERIAN ◽  
Ehsan SOBHANI TEHRANI ◽  
Armineh GARABEDIAN
Keyword(s):  
Flight Control ◽  
Flight Test ◽  
Flight Simulation ◽  
High Fidelity ◽  
Aerodynamic Coefficient ◽  
Lookup Tables ◽  
Calculation Methodology ◽  
Geometrical Data ◽  
And Control ◽  
Control Surfaces

Simulating an aircraft model using of high fidelity models of subsystems for its primary and secondary flight control actuators requires measuring or estimating aero-load data acting on flight control surfaces. One solution would be to incorporate the data recorded from flight tests, which is a time-consuming and costly process. This paper proposes another solution based on the validation of an aero-loads estimator or on the hinge moments predictor for fully electrical aircraft simulator benchmark. This estimator is based on an aerodynamic coefficient calculation methodology, inspired by Roskam’s method that uses the geometrical data of the wing and control surfaces airfoils. The hinge moment values are found from two-dimensional lookup tables where the deflections of the control surfaces, aircraft altitude, and aircraft angles of attack are the input vectors of the tables; and the resulting hinge moment coefficients are the output vectors. The resulting hinge moment coefficients of the Convair 880 primary flight control surfaces are compared to those of its recorded flight test data; the results from the new software solution were found to be very accurate. Hinge moment lookup tables are integrated in the Convair 880 high fidelity flight simulation benchmark using mathematical models of energy-efficient Electro-Hydrostatic Actuators (EHA). Autopilot controls are designed for the roll, pitch, attitude and yaw damper motions using Proportional Integral (PI) controller scheduled for different flight conditions. Several different aircraft simulation scenarios are evaluated to demonstrate the efficacy and accuracy of the predicted hinge moment results.

Understanding the Effect of Rotor-to-Rotor Interference on CH-47D Helicopter Dynamics

2021 ◽  
Author(s):  
Feyyaz Guner ◽  
David G. Miller ◽  
J. V. R. Prasad
Keyword(s):  
Flight Control ◽  
Influence Factors ◽  
Flight Test ◽  
Flight Simulation ◽  
Flight Control System ◽  
Pressure Potential ◽  
Handling Qualities ◽  
Helicopter Flight ◽  
Lateral Inflow ◽  
Lateral Axis

During the development of the Boeing CH-47D helicopter flight simulation model, test pilots reported mismatch between the flight simulator results and flight test data of the hover and low-speed lateral axis handling qualities, especially for the case without the automatic flight control system. In addressing the observed mismatch, the gains of the longitudinal and lateral components of the inflow model were selected to be significantly higher than their theoretical values. In this study, a detailed understanding of the rotor-to-rotor inflow interference is pursued using a recently developed multi-rotor pressure potential superposition inflow model. It is shown that the coupling between the inflow gradients of individual rotors exists in a tandem rotor, which can be approximated by using higher values for the longitudinal and lateral inflow gains of individual rotors. Further, it is shown that the need for empirical tuning of aerodynamic hub moment influence factors can be eliminated by properly accounting for the rotor-to-rotor interference in the inflow model.

scholarly journals Historical Overview of Research in Reconfigurable Flight Control

2005 ◽  
Vol 219 (4) ◽  
pp. 263-275 ◽  
Author(s):  
M Steinberg
Keyword(s):  
Intelligent Control ◽  
Flight Control ◽  
Flight Test ◽  
Historical Overview ◽  
Reconfigurable Control ◽  
Control Laws ◽  
Loop Control ◽  
Software Algorithms ◽  
Lifting Surfaces ◽  
Initial Research

This article presents a historical overview of research in reconfigurable flight control. For the purpose of this article, the term ‘reconfigurable flight control’ is used to refer to software algorithms designed specifically to compensate for failures or damage of flight control effectors or lifting surfaces, using the remaining effectors to generate compensating forces and moments. This article will discuss initial research and flight testing of approaches based on explicit fault detection, isolation, and estimation, as well as later approaches based on continuously adaptive and intelligent control algorithms. In addition, approaches for trajectory reshaping of an impaired aircraft with reconfigurable inner loop control laws will be briefly discussed. Finally, there will be some discussion on current implementations of reconfigurable control to improve safety on production and flight test aircraft and remaining challenges to enable broader use of the technology, such as the difficulties of flight certification of these types of approaches.

DEVELOPMENT AND FLIGHT TEST OF A REAL-TIME ENERGY MANAGEMENT DISPLAY / REALAUS LAIKO ENERGIJOS VALDYMO MONITORIAUS KŪRIMAS IR BANDYMAS SKRYDŽIO METU

Aviation ◽  
2012 ◽  
Vol 15 (4) ◽  
pp. 83-91 ◽  
Author(s):  
Isaac Atuahene ◽  
Stephen Corda ◽  
Rapinder Sawhney
Keyword(s):  
Real Time ◽  
Energy Management ◽  
Energy State ◽  
Flight Test ◽  
Flight Simulation ◽  
Point Of View ◽  
Labview Software ◽  
Systems Research ◽  
Excess Power ◽  
Real Time Information

A real-time energy management display is developed and evaluated, and the feasibility and utility of the display in providing real-time guidance and information on an aircraft's energy state is investigated. Flight simulations were conducted with the UTSI's Aviation Systems research flight simulator to validate the display and to evaluate its utility for flying along constant specific excess power (PS) contours and for directly obtaining PS contours from level acceleration flight test. This study considers the energy state of the aircraft from the point of view of the relation that exists between specific excess power, PS, and the forces in flight. The approach yields as one result a cubic function for the PS of the aircraft. We then directly solve for velocity, V, as the control parameter for a given PS as a function of altitude, H. Using LabView software, this technique is used to build a real-time energy management display which provides guidance and real-time information on the aircraft's energy state. Flight simulation results proved the display to be successful in obtaining direct PS contours from level acceleration flight tests and in providing guidance for flights along constant PS contours at low airspeeds, although it was difficult to keep the PS constant. Santrauka Sukurtas ir įvertintas realaus laiko energijos valdymo monitorius, ištirtos jo galimybės ir panaudojimas informacijai apie energijos būklę teikti. Skrydžio simuliacijos rodo, kad monitorius sėkmingai gauna tiesioginį PS kontūrą greitėjančio skrydžio metu ir gali nukreipti skrydžius palei nuolatinį PS kontūrą, esant nedideliam greičiui, nors ir sunku išlaikyti nuolatinį PS.

Design and flight test of active flutter suppression on the X-56A multi-utility technology test-bed aircraft

2016 ◽  
Vol 120 (1228) ◽  
pp. 893-909 ◽  
Author(s):  
E. L. Burnett ◽  
J. A. Beranek ◽  
B. T. Holm-Hansen ◽  
C. J. Atkinson ◽  
P. M. Flick
Keyword(s):  
Flight Control ◽  
Flight Test ◽  
Test Bed ◽  
Control Laws ◽  
Control Approach ◽  
Mode Control ◽  
Flying Qualities ◽  
Technical Challenges ◽  
Long Endurance ◽  
Aircraft Configurations

ABSTRACTEfforts to develop the next generation of aircraft with ever-increasing levels of performance – higher, farther, faster, cheaper – face great technical challenges. One of these technical challenges is to reduce structural weight of the aircraft. Another is to look to aircraft configurations that have been unrealizable to date. Both of these paths can lead to a rigid flex coupling phenomenon that can result in anything from poor flying qualities to the loss of an aircraft due to flutter. This has led to a need to develop an integrated flight and aeroelastic control capability where structural dynamics are included in the synthesis of flight control laws. Studies have indicated that the application of an integrated flight and aeroelastic control approach to a SensorCraft high-altitude long-endurance vehicle would provide substantial performance improvement(1,2). Better flying qualities and an expanded flight envelope through multi-flutter mode control are two areas of improvement afforded by integrated flight and aeroelastic control. By itself, multi-flutter mode control transforms the flutter barrier from a point of catastrophic structural failure to a benign region of flight. This paper discusses the history and issues associated with the development of such an integrated flight and aeroelastic control system for the X-56A aircraft.

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