Effects of rotor blade-tip geometry on helicopter trim and control response

2017 ◽  
Vol 121 (1239) ◽  
pp. 637-659 ◽  
Author(s):  
M. Rohin Kumar ◽  
C. Venkatesan
Keyword(s):  
Equations Of Motion ◽  
Rotor Blades ◽  
Equilibrium Equations ◽  
Aerodynamic Model ◽  
Nonlinear Equilibrium ◽  
Control Response ◽  
Blade Tip ◽  
Nonlinear Equations Of Motion ◽  
The Cost ◽  
And Control

ABSTRACTFor performance improvement and noise reduction, swept and anhedral tips have been incorporated in advanced-geometry rotor blades. While there are aerodynamic benefits to these advanced tip geometries, they come at the cost of complicated structural design and weight penalties. The effect of these tip shapes on loads, vibration and aeroelastic response are also unclear. In this study, a comprehensive helicopter aeroelastic analysis which includes rotor-fuselage coupling shall be described and the analysis results for rotor blades with straight tip, tip sweep and tip anhedral shall be presented and compared. The helicopter modelled is a conventional one with a hingeless single main rotor and single tail rotor. The blade undergoes flap, lag, torsion and axial deformations. Tip sweep, pretwist, precone, predroop, torque offset and root offset are included in the model. Aerodynamic model includes Peters-He dynamic wake theory for inflow and the modified ONERA dynamic stall theory for airloads calculations. The complete 6-dof nonlinear equilibrium equations of the fuselage are solved for analysing any general flight condition. Response to pilot control inputs is determined by integrating the full set of nonlinear equations of motion with respect to time. The effects of tip sweep and tip anhedral on structural dynamics, trim characteristics and vehicle response to pilot inputs are presented. It is shown that for blades with tip sweep and tip anhedral/dihedral, the 1/rev harmonics of the root loads reduce while the 4/rev harmonics of the hub loads increase in magnitude. Tip dihedral is shown to induce a reversal of yaw rate for lateral and longitudinal cyclic input.

scholarly journals A Simulation Model for Computing the Loads Generated at Landing Site During Helicopter Take-Off or Landing Operation

2019 ◽  
Vol 2019 (2) ◽  
pp. 59-75
Author(s):  
Jarosław Stanisławski
Keyword(s):  
Equations Of Motion ◽  
Landing Site ◽  
Simulation Method ◽  
Rigid Bodies ◽  
Landing Gear ◽  
Rotor Blades ◽  
Wind Gust ◽  
The Galerkin Method ◽  
Lumped Masses ◽  
And Control

Summary The paper presents simulation method and results of calculations determining behavior of helicopter and landing site loads which are generated during phase of the helicopter take-off and landing. For helicopter with whirling rotor standing on ground or touching it, the loads of landing gear depend on the parameters of helicopter movement, occurrence of wind gusts and control of pitch angle of the rotor blades. The considered model of helicopter consists of the fuselage and main transmission treated as rigid bodies connected with elastic elements. The fuselage is supported by landing gear modeled by units of spring and damping elements. The rotor blades are modeled as elastic axes with sets of lumped masses of blade segments distributed along them. The Runge-Kutta method was used to solve the equations of motion of the helicopter model. According to the Galerkin method, it was assumed that the parameters of the elastic blade motion can be treated as a combination of its bending and torsion eigen modes. For calculations, data of a hypothetical light helicopter were applied. Simulation results were presented for the cases of landing helicopter touching ground with different vertical speed and for phase of take-off including influence of rotor speed changes, wind gust and control of blade pitch. The simulation method may help to define the limits of helicopter safe operation on the landing surfaces.

Direct Linearization of Continuous and Hybrid Dynamical Systems

2009 ◽  
Vol 4 (3) ◽  
Author(s):  
Julie J. Parish ◽  
John E. Hurtado ◽  
Andrew J. Sinclair
Keyword(s):  
Dynamical Systems ◽  
Nonlinear Equations ◽  
Equilibrium Configuration ◽  
Equations Of Motion ◽  
Hybrid Dynamical Systems ◽  
Linearized Equations ◽  
Direct Linearization ◽  
Taylor Series Expansions ◽  
Nonlinear Equations Of Motion ◽  
And Control

Nonlinear equations of motion are often linearized, especially for stability analysis and control design applications. Traditionally, the full nonlinear equations are formed and then linearized about the desired equilibrium configuration using methods such as Taylor series expansions. However, it has been shown that the quadratic form of the Lagrangian function can be used to directly linearize the equations of motion for discrete dynamical systems. This procedure is extended to directly generate linearized equations of motion for both continuous and hybrid dynamical systems. The results presented require only velocity-level kinematics to form the Lagrangian and find equilibrium configuration(s) for the system. A set of selected partial derivatives of the Lagrangian are then computed and used to directly construct the linearized equations of motion about the equilibrium configuration of interest, without first generating the entire nonlinear equations of motion. Given an equilibrium configuration of interest, the directly constructed linearized equations of motion allow one to bypass first forming the full nonlinear governing equations for the system. Examples are presented to illustrate the method for both continuous and hybrid systems.

scholarly journals An Enhanced Message Distribution Mechanism for Northbound Interfaces in the SDN Environment

2021 ◽  
Vol 11 (10) ◽  
pp. 4346
Author(s):  
Chenhui Wang ◽  
Hong Ni ◽  
Lei Liu
Keyword(s):  
Control Plane ◽  
Message Queue ◽  
Ip Network ◽  
Data Plane ◽  
Control Response ◽  
Basic Functions ◽  
The Cost ◽  
New Generation ◽  
And Control ◽  
High Degree

Software-Defined Network (SDN), which is recommended as a new generation of the network, a substitute for TCP/IP network, has the characteristics of separation of data plane and control plane. Although the separation of the control plane brings a high degree of freedom and simple operation and maintenance, it also increases the cost of north–south communication. There are many additional modules for SDN to modify and enhance the basic functions of SDN. This paper proposes a message queue-based northbound communication mechanism, which pre-categorizes messages from the data plane and accurately pushes them to the apps potentially interested. This mechanism improves the efficiency of northbound communication and apps’ execution. Furthermore, it supports both OpenFlow and the protocol-independent southbound interface, and it has strong compatibility. Experiments have proved that this mechanism can reduce the control-response latency by up to 41% when compared with the normal controller northbound communication system, and it also improves the network situation of the data plane, such as real-time bandwidth.

Vibration Analysis of Vertical-Axis Wind-Turbine Blades

2016 ◽  
Author(s):  
Fatemeh Afzali ◽  
Onur Kapucu ◽  
Brian F. Feeny
Keyword(s):  
Equations Of Motion ◽  
Turbine Blades ◽  
Vertical Axis ◽  
Vertical Axis Wind Turbine ◽  
Wind Turbine Blades ◽  
Aerodynamic Model ◽  
Vibration Model ◽  
Nonlinear Equations Of Motion ◽  
Energy Equations ◽  
Twisting Deformation

In this work the derivation of a vibration model for an H-rotor/Giromill blade is investigated. The blade is treated as a uniform straight elastic Euler-Bernoulli beam under transverse bending and twisting deformation. The derivation of the energy equations for the bending and twisting blade and a simplified aerodynamic model is issued. Lagrange’s equations are applied to assumed modal coordinates to obtain nonlinear equations of motion for bend and twist. A single quasi-steady airfoil theory is applied to obtain the aeroelastic loads. The behavior of the linearized equation for bend only is examined.

scholarly journals Modeling and control of a spherical rolling robot: a decoupled dynamics approach

Robotica ◽  
2011 ◽  
Vol 30 (4) ◽  
pp. 671-680 ◽  
Author(s):  
Erkan Kayacan ◽  
Zeki Y. Bayraktaroglu ◽  
Wouter Saeys
Keyword(s):  
Feedback Linearization ◽  
Equations Of Motion ◽  
Longitudinal Axis ◽  
Radius Of Curvature ◽  
Modeling And Control ◽  
Modeling Analysis ◽  
Highly Nonlinear ◽  
Nonlinear Equations Of Motion ◽  
And Control ◽  
Rolling Robot

SUMMARYThis paper presents the results of a study on the dynamical modeling, analysis, and control of a spherical rolling robot. The rolling mechanism consists of a 2-DOF pendulum located inside a spherical shell with freedom to rotate about the transverse and longitudinal axis. The kinematics of the model has been investigated through the classical methods with rotation matrices. Dynamic modeling of the system is based on the Euler–Lagrange formalism. Nonholonomic and highly nonlinear equations of motion have then been decomposed into two simpler subsystems through the decoupled dynamics approach. A feedback linearization loop with fuzzy controllers has been designed for the control of the decoupled dynamics. Rolling of the controlled mechanism over linear and curvilinear trajectories has been simulated by using the proposed decoupled dynamical model and feedback controllers. Analysis of radius of curvature over curvilinear trajectories has also been investigated.

Helicopter Rotor Noise Prediction and Control

1969 ◽  
Vol 14 (3) ◽  
pp. 38-47
Author(s):  
Ronald G. Schlegel ◽  
William E. Bausch
Keyword(s):  
Sound Pressure ◽  
Rotor Blades ◽  
Helicopter Rotor ◽  
Noise Prediction ◽  
Spectrum Shape ◽  
Rotor Noise ◽  
Blade Area ◽  
Prediction And Control ◽  
Blade Tip ◽  
And Control

This paper summarizes the results of Sikorsky Aircraft's research in the prediction and control of helicopter rotor noise. The work to he discussed was partly funded by the U.S. Army Aviation Material Laboratories under Contracts DA 44‐177‐AMC‐141(T) and DA 44‐177‐AMC‐448(T). An improved procedure has been developed for the prediction of main rotor vortex noise under conditions of uniform inflow for a single rotor helicopter. Both the overall sound pressure level and the spectrum shape of the vortex noise from square tipped blades can be calculated as a function of tip speed, blade area, and thrust. The geometry of the blade tip can alter both levels and spectrum shape appreciably. The USAAVLABS contracts also resulted in two computerized analyses for rotational noise prediction. Both analyses extend the work of Gutin to include the noise produced by harmonics of airload acting on the rotor blades. These analyses have demonstrated the importance of the higher harmonics of airload and the chordwise distribution of loading for accurate rotational noise prediction.

Modelling the flight dynamics of the hang glider

2006 ◽  
Vol 110 (1103) ◽  
pp. 1-20 ◽  
Author(s):  
M. V. Cook ◽  
M. Spottiswoode
Keyword(s):  
Complex Geometry ◽  
Equations Of Motion ◽  
Linear Equations ◽  
Control Analysis ◽  
Stability And Control ◽  
Aerodynamic Model ◽  
Directional Control ◽  
Weight Shift ◽  
Control Derivatives ◽  
And Control

AbstractThe development of the non-linear equations of motion for the hang glider from first principles is described, including the complex geometry of control by pilot ‘weight shift’. By making appropriate assumptions the linearised small perturbation equations are derived for the purposes of stability and control analysis. The mathematical development shows that control is effected not by pilot weight shift, but by centre of gravity shift and that lateral-directional control by this means is weak, and is accompanied by significant instantaneous adverse response.The development of a comprehensive semi-empirical mathematical model of the flexible wing aerodynamics is described. In particular, the modelling attempts to quantify camber and twist dependencies. The performance of the model is shown to compare satisfactorily with measured hang glider wing data obtained in earlier full scale experiments. The mathematical aerodynamic model is then used to estimate the hang glider stability and control derivatives over the speed envelope for substitution into the linearised equations of motion.

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