Load Alleviation Flight Control Design using High-Order Dynamic Models

2020 ◽  
Vol 65 (3) ◽  
pp. 1-15
Author(s):  
Umberto Saetti ◽  
Joseph F. Horn
Keyword(s):  
Flight Control ◽  
State Feedback ◽  
Dynamic Models ◽  
Linear Time ◽  
Linear Quadratic Regulator ◽  
Linear Quadratic ◽  
Linear Time Invariant ◽  
Harmonic Decomposition ◽  
The Impact ◽  
Pseudo Inverse

The present study considers two notional rotorcraft models: a conventional utility helicopter, representative of an H-60, and a wing-only compound utility rotorcraft, representative of an H-60 with a wing similar to the X-49A wing. An explicit model following (EMF) control scheme is designed to achieve stability and desired rate command / attitude hold response around the roll, pitch, and yaw axes, while alleviating vibratory loads through both feed-forward and feedback compensation. The harmonic decomposition methodology is extended to enable optimization of primary flight control laws that mitigate vibratory loads. Specifically, linear time-periodic systems representative of the periodic rotorcraft dynamics are approximated by linear time-invariant (LTI) models. The LTI models are subsequently reduced and used in linear quadratic regulator (LQR) design to constrain the harmonics of the vibratory loads. Both fuselage state feedback and rotor state feedback are considered. A pseudo-inverse strategy is incorporated into the EMF scheme for redundant control allocation on the compound configuration. Simulations of the load alleviating controllers are compared to results from a baseline controller. Finally, an analysis is performed to assess the impact that load alleviating control action, rotor state feedback, and pseudo-inverse have on handling qualities in terms of ADS-33E specifications.

The Variations in Active Panel Location and Number for a Bioinspired Aircraft Gust Alleviation System

2012 ◽  
Author(s):  
Christopher J. Blower ◽  
Adam M. Wickenheiser
Keyword(s):  
Flight Control ◽  
Dynamic Models ◽  
Linear Quadratic Regulator ◽  
Control Surface ◽  
Linear Quadratic ◽  
Trailing Edge ◽  
Gust Alleviation ◽  
Wide Range ◽  
Trailing Edge Flaps ◽  
Global States

This paper presents the development of a biomimetic closed-loop flight controller that integrates gust alleviation and flight control into a single distributed system of feather-like panels over the upper and lower surfaces. This bio-inspired gust alleviation system (GAS) mimics the techniques used by birds to respond to turbulent and gusting airflow. The GAS design replicates the profile of a bird’s wing through the installation of feather-like panels across the upper and lower surfaces of the airfoil, and replacement of the trailing-edge flaps. While flying through gusts, the flight controller uses a linear quadratic regulator to perform continuous adjustments to the local states through active deflection of electromechanical feathers. This system consequently offers a wide range of flap configurations that enable the vehicle to perform gust response maneuvers unachievable by standard aircraft. The GAS is developed using a 2D adaptive panel method that enables analysis of the airfoil’s aerodynamic performance during all flap configurations. The airfoil’s dynamic model is simulated to calculate the disturbances incurred during gusting flows. The flight controller tracks the vehicles velocity, angle of attack and position, and continuously performs adjustment to the orientation of each flap to induce the corrective responses to inbound gusts. The replacement of standard single trailing edge profile with the integration of a dual trailing edge (DTE) configuration offers a reduction of the aircraft’s deviation from the target flight path through the introduction of aero-braking during strong longitudinal gusts. The introduction of 6 additional surface flaps offers new flap configurations capable of minimizing the disturbances in the aircraft’s global states. Non-linear and linear dynamic models of the 8-flap GAS are compared to a traditional single control surface baseline wing and the DTE configuration. The feedback loops synthesized depend on the inertial changes of the global states; however, variations in flap configuration are compared. The integration of an 8-flap GAS provides enhancements to maneuverability and stability in turbulent intensive environments.

An automatic system for a helicopter autopilot performance evaluation

2019 ◽  
Vol 91 (6) ◽  
pp. 880-885 ◽  
Author(s):  
Antoni Kopyt ◽  
Sebastian Topczewski ◽  
Marcin Zugaj ◽  
Przemyslaw Bibik
Keyword(s):  
Performance Evaluation ◽  
Flight Control ◽  
Automatic System ◽  
Control Algorithm ◽  
Linear Quadratic Regulator ◽  
Algorithm Analysis ◽  
Evaluation Methodology ◽  
Reference Trajectory ◽  
Linear Quadratic ◽  
Content Type

Purpose The purpose of this paper is to elaborate and develop an automatic system for automatic flight control system (AFCS) performance evaluation. Consequently, the developed AFCS algorithm is implemented and tested in a virtual environment on one of the mission task elements (MTEs) described in Aeronautical Design Standard 33 (ADS-33) performance specification. Design/methodology/approach Control algorithm is based on the Linear Quadratic Regulator (LQR) which is adopted to work as a controller in this case. Developed controller allows for automatic flight of the helicopter via desired three-dimensional trajectory by calculating iteratively deviations between desired and actual helicopter position and multiplying it by gains obtained from the LQR methodology. For the AFCS algorithm validation, the objective data analysis is done based on specified task accomplishment requirements, reference trajectory and actual flight parameters. Findings In the paper, a description of an automatic flight control algorithm for small helicopter and its evaluation methodology is presented. Necessary information about helicopter dynamic model is included. The test and algorithm analysis are performed on a slalom maneuver, on which the handling qualities are calculated. Practical implications Developed automatic flight control algorithm can be adapted and used in autopilot for a small helicopter. Methodology of evaluation of an AFCS performance can be used in different applications and cases. Originality/value In the paper, an automatic flight control algorithm for small helicopter and solution for the validation of developed AFCS algorithms are presented.

scholarly journals Identification of In-Flight Wingtip Folding Effects on the Roll Characteristics of a Flexible Aircraft

Aerospace ◽  
2019 ◽  
Vol 6 (6) ◽  
pp. 63 ◽  
Author(s):  
Gaétan Dussart ◽  
Sezsy Yusuf ◽  
Mudassir Lone
Keyword(s):  
Time Domain ◽  
Flight Control ◽  
Dynamic Models ◽  
Direct Connection ◽  
Reduced Order ◽  
Transport Aircraft ◽  
Flight Simulators ◽  
Induced Drag ◽  
Generic Polynomial ◽  
The Impact

Wingtip folding is a means by which an aircraft’s wingspan can be extended, allowing designers to take advantage of the associated reduction in induced drag. This type of device can provide other benefits if used in flight, such as flight control and load alleviation. In this paper, the authors present a method to develop reduced order flight dynamic models for in-flight wingtip folding, which are suitable for implementation in real-time pilot-in-the-loop simulations. Aspects such as the impact of wingtip size and folding angle on aircraft roll dynamics are investigated along with failure scenarios using a time domain aeroservoelastic framework and an established system identification method. The process discussed in this paper helps remove the need for direct connection of complex physics based models to engineering flight simulators and the need for tedious programming of large look-up-tables in simulators. Instead, it has been shown that a generic polynomial model for roll aeroderivatives can be used in small roll perturbation conditions to simulate the roll characteristics of an aerodynamic derivative based large transport aircraft equipped with varying fold hinge lines and tip deflections. Moreover, the effects of wing flexibility are also considered.

scholarly journals Robust Conditions for Iterative Learning Control in State Feedback and Output Injection Paradigm

2019 ◽  
Vol 2019 ◽  
pp. 1-10
Author(s):  
Muhammad A. Alsubaie ◽  
Mubarak KH. Alhajri ◽  
Tarek S. Altowaim ◽  
Salem H. Salamah
Keyword(s):  
Iterative Learning Control ◽  
State Feedback ◽  
Linear Time ◽  
Stability Margin ◽  
Learning Control ◽  
Iterative Learning ◽  
Delay Model ◽  
Linear Time Invariant ◽  
System Input ◽  
Linear Time Invariant Systems

A robust Iterative Learning Control (ILC) design that uses state feedback and output injection for linear time-invariant systems is reintroduced. ILC is a control tool that is used to overcome periodic disturbances in repetitive systems acting on the system input. The design basically depends on the small gain theorem, which suggests isolating a modeled disturbance system and finding the overall transfer function around the delay model. This assures disturbance accommodation if stability conditions are achieved. The reported design has a lack in terms of the uncertainty issue. This study considered the robustness issue by investigating and setting conditions to improve the system performance in the ILC design against a system’s unmodeled dynamics. The simulation results obtained for two different systems showed an improvement in the stability margin in the case of system perturbation.

scholarly journals Vision-based flight control in the hawkmoth Hyles lineata

2014 ◽  
Vol 11 (91) ◽  
pp. 20130921 ◽  
Author(s):  
Shane P. Windsor ◽  
Richard J. Bomphrey ◽  
Graham K. Taylor
Keyword(s):  
Flight Control ◽  
Insect Flight ◽  
Linear Time ◽  
Temporal Frequency ◽  
Sensory Modality ◽  
Flight Dynamics ◽  
Energetic Cost ◽  
Linear Time Invariant ◽  
Hyles Lineata ◽  
And Control

Vision is a key sensory modality for flying insects, playing an important role in guidance, navigation and control. Here, we use a virtual-reality flight simulator to measure the optomotor responses of the hawkmoth Hyles lineata , and use a published linear-time invariant model of the flight dynamics to interpret the function of the measured responses in flight stabilization and control. We recorded the forces and moments produced during oscillation of the visual field in roll, pitch and yaw, varying the temporal frequency, amplitude or spatial frequency of the stimulus. The moths’ responses were strongly dependent upon contrast frequency, as expected if the optomotor system uses correlation-type motion detectors to sense self-motion. The flight dynamics model predicts that roll angle feedback is needed to stabilize the lateral dynamics, and that a combination of pitch angle and pitch rate feedback is most effective in stabilizing the longitudinal dynamics. The moths’ responses to roll and pitch stimuli coincided qualitatively with these functional predictions. The moths produced coupled roll and yaw moments in response to yaw stimuli, which could help to reduce the energetic cost of correcting heading. Our results emphasize the close relationship between physics and physiology in the stabilization of insect flight.

Flight Control System Design for Propulsion-Controlled Aircraft

2005 ◽  
Vol 219 (4) ◽  
pp. 329-340 ◽  
Author(s):  
Y Ochi
Keyword(s):  
Flight Control ◽  
Linear Models ◽  
Control Method ◽  
Linear Quadratic Regulator ◽  
State Feedback Control ◽  
Longitudinal Motion ◽  
Linear Quadratic ◽  
Engine Thrust ◽  
Model Following Control ◽  
Flight Controls

The loss of an aircraft's primary flight controls can lead to a fatal accident. However, if the engine thrust is available, controllability and safety can be retained. This article describes flight control using engine thrust only when an aircraft has lost all primary flight controls. This is a kind of flight control reconfiguration. For safe return, the aircraft must first descend to a landing area, decelerate to a landing speed, and then be capable of precise flight control for approach and landing. For these purposes, two kinds of controllers are required: a controller for descent and deceleration and a controller for approach and landing. The former controller is designed for longitudinal motion using a model-following control method, based on a linear quadratic regulator. The latter is designed by an H∞ state-feedback control method for both longitudinal and lateral-directional motions. Computer simulation is conducted using linear models of the Boeing 747. The results indicate that flight path control, including approach and landing, is possible using thrust only; however, speed control proves more difficult. However, if the horizontal stabilizer is available, the airspeed can be reduced to a safe landing speed.

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