Author: Wei Guo
Publisher:
ISBN:
Category :
Languages : en
Pages : 121
Get Book Here
Book Description
Flight control design issues for rotorcraft with variable rotor speed are investigated, and new design methodologies are developed to deal with the challenges of variable rotor speed. The benefits of using variable rotor speed for rotorcraft are explored with a rotor speed optimization study using a modified GENHEL model of UH-60A Blackhawk. The optimization results recommend to use the optimal rotor speed in each flight condition to improve the helicopter performance. The efforts are made to accommodate the optimal rotor speed schedule into the flight control system design and also address the stability issues due to the rotor speed variation. The rotor speed optimization results show significant performance improvements can be achieved with moderate reductions in rotor speed. The objective of the control design is to accommodate these rotor speed variations, while achieving desired flying qualities and maneuver performance. A gain scheduled model following/model inversion controller is used to control the roll, pitch, yaw, heave, and rotor speed degrees of freedom. Rotor speed is treated as a redundant control effector for the heave axis, and different control allocation schemes are investigated. The controllers are evaluated based on step responses and the ADS-33E height response requirement. Results show that dynamic variation in rotor speed can improve maximum climb rate and flying qualities for moderate to large commands in vertical speed, but that non-linear effects present significant challenges when integrating control of the aircraft and the engine. The effects of reduced rotor speeds on stability margins, torque required, and stability issues are also studied. A power command system in the vertical axis is designed to incorporate variable rotor speed while handling torque limits and other constraints. The vertical axis controller uses a fixed nonlinear mapping to find the combination of collective pitch and rotor speed to optimize performance in level flight, climbing/descending flight, and steady turns. In this scheme, the controller is open-loop, making it an inexpensive and reliable solution. The mapping is designed to produce a desired power level for a given pilot input. Thus the mapping can take into account the performance limits associated with the vertical axis such as power limits, torque limits, and maximum rate of descent. A model following controller is implemented for the pitch, roll, and yaw axes. The piloted simulation was performed to evaluate the controller. The impact of variable rotor speed on closed loop stability of rotorcraft is discussed. The model following controller can provide high bandwidth control and improve performance using variable rotor speed. However, reduction of rotor speed can result in rotor body coupling and even instability. A rotor state feedback control law can be designed independently and easily integrated into the baseline model following control architecture. Simulations were performed to verify the effectiveness of RSF control to stabilize the rotorcraft dynamics or improve the command tracking performance in the presence of reduced rotor RPM.
Author: Stanford University. Department of Aeronautics and Astronautics
Publisher:
ISBN:
Category :
Languages : en
Pages : 246
Get Book Here
Book Description
Author: Brian L. Stevens
Publisher: John Wiley & Sons
ISBN: 1118870980
Category : Technology & Engineering
Languages : en
Pages : 768
Get Book Here
Book Description
Get a complete understanding of aircraft control and simulation Aircraft Control and Simulation: Dynamics, Controls Design, and Autonomous Systems, Third Edition is a comprehensive guide to aircraft control and simulation. This updated text covers flight control systems, flight dynamics, aircraft modeling, and flight simulation from both classical design and modern perspectives, as well as two new chapters on the modeling, simulation, and adaptive control of unmanned aerial vehicles. With detailed examples, including relevant MATLAB calculations and FORTRAN codes, this approachable yet detailed reference also provides access to supplementary materials, including chapter problems and an instructor's solution manual. Aircraft control, as a subject area, combines an understanding of aerodynamics with knowledge of the physical systems of an aircraft. The ability to analyze the performance of an aircraft both in the real world and in computer-simulated flight is essential to maintaining proper control and function of the aircraft. Keeping up with the skills necessary to perform this analysis is critical for you to thrive in the aircraft control field. Explore a steadily progressing list of topics, including equations of motion and aerodynamics, classical controls, and more advanced control methods Consider detailed control design examples using computer numerical tools and simulation examples Understand control design methods as they are applied to aircraft nonlinear math models Access updated content about unmanned aircraft (UAVs) Aircraft Control and Simulation: Dynamics, Controls Design, and Autonomous Systems, Third Edition is an essential reference for engineers and designers involved in the development of aircraft and aerospace systems and computer-based flight simulations, as well as upper-level undergraduate and graduate students studying mechanical and aerospace engineering.
Author: MB Tischler
Publisher: Routledge
ISBN: 135146843X
Category : Technology & Engineering
Languages : en
Pages : 450
Get Book Here
Book Description
This book provides a single comprehensive resource that reviews many of the current aircraft flight control programmes from the perspective of experienced practitioners directly involved in the projects. Each chapter discusses a specific aircraft flight programme covering the control system design considerations, control law architecture, simulation and analysis, flight test optimization and handling qualities evaluations. The programmes described have widely exploited modern interdisciplinary tools and techniques and the discussions include extensive flight test results. Many important `lessons learned' are included from the experience gained when design methods and requirements were tested and optimized in actual flight demonstration.
Author: Antonio Filippone
Publisher: Springer Nature
ISBN: 3031124375
Category : Technology & Engineering
Languages : en
Pages : 255
Get Book Here
Book Description
This textbook is a multi-disciplinary compendium that includes several aspects of rotorcraft technology. It introduces the reader to the aerodynamic aspects of rotary wings and presents experimental techniques for aerodynamics. The chapters also cover rotorcraft engines and rotorcraft steady-state flight performance and stability. It explores several aspects of the tiltrotor configuration and lists challenges in their design, modelling and simulation. The reader will also find an introductory overview of flight control systems for rotorcraft, as well as the conceptual and preliminary design concepts for a conventional helicopter. This textbook contains video recordings of computer simulations that can be used alongside the main text.
Author: James R. Mihaloew
Publisher:
ISBN:
Category : Helicopters
Languages : en
Pages : 40
Get Book Here
Book Description
Author: Adam Daniel Pechner
Publisher:
ISBN:
Category :
Languages : en
Pages : 214
Get Book Here
Book Description
Author: James R. Mihaloew
Publisher:
ISBN:
Category : Helicopters
Languages : en
Pages : 40
Get Book Here
Book Description
Author: Umberto Saetti
Publisher:
ISBN:
Category :
Languages : en
Pages :
Get Book Here
Book Description
The objective of this research effort is to develop rotorcraft flight control laws that minimize unsteady rotor loads by acting solely through the primary flight controls (first harmonic swashplate control). As opposed to Higher-Harmonic Control, this strategy does not affect stationary (periodic trim) loads, and is therefore effective only in maneuvering flight. However, such system could be readily integrated with existing or future Automatic Flight Control Systems (AFCS). The study considers control designs for both conventional and compound configurations.Starting from a non-linear simulation model of the rotorcraft developed in FLIGHTLAB, which includes sufficient fidelity to simulate rotor loads and vibrations, Linear Time-Periodic models (LTP) are derived via linearization. Next, the Harmonic Decomposition methodology is used to approximate the LTP systems with higher-order Linear Time-Invariant (LTI) systems. Reduced-order systems are subsequently obtained by using singular perturbation theory. By retaining the higher-harmonics of the rotor loads in the output, the reduced-order models are shown to accurately predicted the influence of the zeroth harmonics of the rigid-body and rotor flapping states on the higher-harmonics of the rotor loads. This way, previous limitations such as the reliance on non-physics-based models and curve fits to approximate rotor loads are lifted. Next, model following flight control laws are developed based on the reduced-order models. Parametric studies are performed to provide insights on how both the feed-forward and feedback paths of the model following control laws can be used to alleviate the rotor loads. Also, the impact of load alleviation on handling qualities is studied. It is shown that, for a standard helicopter configuration, load alleviation comes at the cost of a degradation in handling qualities. However, for the case of a compound rotorcraft, allocation of the control signal to the redundant control surfaces provides load alleviation without degradation in the handling qualities. The flight control laws are subsequently optimized using CONDUIT to meet a comprehensive set of stability, handling qualities, and performance specifications for specific mission task elements while minimizing the unsteady rotor loads. Finally, since industry will not only rely on LTP systems obtained from simulation models, a novel methodology is developed to identify LTP systems from flight test data. The methodology is successfully applied to JUH-60A Black Hawk flight test data using CIFER. The identified LTP systems capture the Nb/rev component of the rotorcraft dynamics. Further, it is shown how the higher-harmonics of the rotor states contribute to the overall rotorcraft dynamics for up to a 7%. On the other hand, the rigid-body states contribute to the overall rotorcraft dynamics almost entirely through their zeroth harmonic. Flight control design based on LTP systems identified from flight-test data could benefit the Future Vertical Lift (FVL) program. FVL is a plan to develop a new generation of military helicopters for the U.S. Army with increased capabilities in speed, range, and payload, and reduced maintenance and operational cost. Because these rotorcraft would operate at significantly higher speeds than the current helicopters, alleviation of the higher harmonic rotor loads and flight envelope protection are key elements to reduced maintenance cost. These rotorcraft are also likely to employ redundant control surfaces which, in connection with LTP-based flight control design, demonstrated outstanding effectiveness towards the alleviation of unsteady rotor loads.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 66
Get Book Here
Book Description
Advanced flight control system design, analysis, and testing methods are applied in an analytical and flight test evaluation of the Advanced Digital Optical Control System (ADOCS) demonstrator. This paper describes the knowledge gained about the implications of digital flight control system design for rotorcraft, and illustrates. The analysis of the resulting handling-qualities in the context of the proposed new handling-qualities specification for rotorcraft. Topics included are digital flight control design and analysis methods, flight testing techniques, ADOCS handling-qualities evaluation results, and correlation of flight test results with analytical models and the proposed handling- qualities specification. Evaluation of the ADOCS demonstrator indicated desirable response characteristics based on equivalent damping and frequency, but undesirably large effective time-delays. Piloted handling-qualities are desirable or adequate for all low, medium, and high pilot gain tasks; but handling-qualities are inadequate for ultra-high gain tasks such as slope and running landings. Correlation of these results with the proposed handling- qualities specification indicates good agreement for the bandwidth boundaries, but suggests the need for more stringent limits on allowable phase-delay. Analytical models based on emulation (s-plane) techniques compare favorably with flight extracted frequency-domain characteristics of the overall (end-to-end) ADOCS responses. Direct digital analysis procedures are necessary to characterize the intersample behavior of the actuator rate response.
