Rotorcraft control response using linearised and non-linear flight dynamic models with different inflow models

2017 ◽  
Vol 121 (1238) ◽  
pp. 553-575 ◽  
Author(s):  
T. Sakthivel ◽  
C. Venkatesan
Keyword(s):  
Dynamic Model ◽  
Dynamic Models ◽  
Model Identification ◽  
Flight Test ◽  
Step Size ◽  
Response Characteristics ◽  
Wide Range ◽  
Non Linear ◽  
Steady Level ◽  
Control Response

ABSTRACTThe aim of the present study is to develop a relatively simple flight dynamic model which should have the ability to analyse trim, stability and response characteristics of a rotorcraft under various manoeuvring conditions. This study further addresses the influence of numerical aspects of perturbation step size in linearised model identification and integration timestep on non-linear model response. In addition, the effects of inflow models on the non-linear response are analysed. A new updated Drees inflow model is proposed in this study and the applicability of this model in rotorcraft flight dynamics is studied. It is noted that the updated Drees inflow model predicts the control response characteristics fairly close to control response characteristics obtained using dynamic inflow for a wide range of flight conditions such as hover, forward flight and recovery from steady level turn. A comparison is shown between flight test data, the control response obtained from the simple flight dynamic model, and the response obtained using a more detailed aeroelastic and flight dynamic model.

Research on roll stability of articulated engineering vehicles based on dynamic lateral transfer load

2020 ◽  
Vol 234 (9) ◽  
pp. 2364-2376
Author(s):  
Xiangyang Xu ◽  
Xing Ai ◽  
Renxiang Chen ◽  
Guosong Jiang ◽  
Xia Hua
Keyword(s):  
Numerical Method ◽  
Dynamic Model ◽  
Load Transfer ◽  
Slope Angle ◽  
Variable Step Size ◽  
Vehicle Speed ◽  
Step Size ◽  
Computational Stability ◽  
Non Linear ◽  
On The Road

A 16-degree-of-freedom non-linear roll dynamic model is developed for an articulated engineering vehicle considering non-linear road excitations and non-linear characteristics of vehicle structures. In addition, a variable step-size numerical method is proposed to solve the non-linear dynamic model. The proposed numerical method can improve the calculation accuracy and the computational stability. Through the proposed dynamic model, an equation is derived considering time-varying tire load characteristics to reflect the roll stability of an articulated engineering vehicle. Using the proposed roll stability equation, the driving stability can be effectively evaluated for an articulated engineering vehicle with different system parameters. The analysis results show that the roll stability decreases significantly with the increase in vehicle speed, centroid height of engineering vehicle, or lateral slope angle. The influence of vehicle speed and lateral slope angle on roll stability is greater than that of the centroid height of engineering vehicle. When steering on the road with a lateral slope angle, the roll angle and the lateral load transfer ratio curves fluctuate with time. As the lateral slope angle increases, the fluctuation is stronger. Overall, the proposed model can accurately evaluate the roll stability of a driving articulated engineering vehicle and accurately determine the unstable tilting of an articulated engineering vehicle.

Nonlinear Dynamic Model of a Two-Stage Pressure Relief Valve for Designers

2001 ◽  
Vol 124 (1) ◽  
pp. 62-66 ◽  
Author(s):  
Pei-Sun Zung ◽  
Ming-Hwei Perng
Keyword(s):  
Dynamic Model ◽  
Nonlinear Dynamic ◽  
Dynamic Models ◽  
Operating Conditions ◽  
Model Parameters ◽  
Nonlinear Dynamic Model ◽  
Relief Valve ◽  
Two Stage ◽  
Pressure Relief ◽  
Wide Range

This paper presents a handy nonlinear dynamic model for the design of a two stage pilot pressure relief servo-valve. Previous surveys indicate that the performance of existing control valves has been limited by the lack of an accurate dynamic model. However, most of the existing dynamic models of pressure relief valves are developed for the selection of a suitable valve for a hydraulic system, and assume model parameters which are not directly controllable during the manufacturing process. As a result, such models are less useful for a manufacturer eager to improve the performance of a pressure valve. In contrast, model parameters in the present approach have been limited to dimensions measurable from the blue prints of the valve such that a specific design can be evaluated by simulation before actually manufacturing the valve. Moreover, the resultant model shows excellent agreement with experiments in a wide range of operating conditions.

Non-Linear Vibration of Thick Dielectric Membrane Disks With Radial Loads

2020 ◽  
Author(s):  
Christopher G. Cooley ◽  
Robert L. Lowe
Keyword(s):  
Frequency Response ◽  
Applied Voltage ◽  
Large Amplitude ◽  
Equation Of Motion ◽  
Membrane Thickness ◽  
Linear Vibration ◽  
Response Characteristics ◽  
Wide Range ◽  
Non Linear ◽  
Large Stretch

Abstract This study analyzes the large-amplitude, non-linear vibration of dielectric elastomer membrane disks with applied voltages through their thickness and mechanical loads applied radially around their outer circumferential surface. The material is modeled as an isotropic ideal dielectric, with the large-stretch mechanical stiffening captured using the Gent hyperelastic constitutive model. The fully non-linear equation of motion for the coupled electromechanical system is derived using Hamilton’s principle. The disk comes to a steady equilibrium where the compressive stresses due to the applied voltage balance the tensile stresses from the applied radial loads. The equilibria are calculated numerically for a wide range of radial loads, applied voltages, and limiting stretches. It is possible for the disk to have two stable steady equilibria at given radial load and applied voltage, which gives rise to an instability where extreme stretches occur for infinitesimal changes in applied voltage. The equation of motion is determined for small vibrations of the system about equilibrium. Unlike for thin membrane disks, the vibrating mass of thick membrane disks depends on the steady equilibrium stretch. The natural frequency for membrane disks meaningfully decreases with increasing thickness due to the inertia associated with dynamic changes in the membrane thickness. The amount of axial inertia depends on the ratio of the nominal disk thickness to its radius and the steady equilibrium stretch. Large amplitude vibrations are numerically investigated for a wide range of system parameters. The frequency response characteristics of circular membranes due to sinusoidal voltage fluctuations are analyzed about small and large equilibrium stretches. Whereas axial inertia meaningfully alters the frequency response about small equilibrium stretches, it has negligible effects on the frequency response about large equilibrium stretches.

An Unmanned Helicopter Model Identification Method Based on the Immune Particle Swarm Optimization Algorithm

2013 ◽  
Vol 347-350 ◽  
pp. 3890-3893 ◽  
Author(s):  
Ting Ting Yang ◽  
Ai Jun Li
Keyword(s):  
Particle Swarm Optimization ◽  
Dynamic Model ◽  
Model Identification ◽  
Particle Swarm ◽  
Flight Test ◽  
Pso Algorithm ◽  
Model Parameters ◽  
Unmanned Helicopter ◽  
Swarm Optimization ◽  
Identification Method

An unmanned helicopter dynamic model identification method based on immune particle swarm optimization (PSO) algorithm is approved in this paper. In order to improve the search efficiency of PSO and avoid the premature convergence, the PSO algorithm is combined with the immune algorithm. The unmanned helicopter model parameters are coded as particle, the error of flight test and math simulation model is objective function, and the dynamic model of unmanned helicopter is identified. The simulation result shows that the method has high identification precision and can realistically reflect the dynamic characteristics.

scholarly journals Dynamic model of nuclear power plant steam turbine

2015 ◽  
Vol 25 (1) ◽  
pp. 65-86 ◽  
Author(s):  
Karol Kulkowski ◽  
Anna Kobylarz ◽  
Michał Grochowski ◽  
Kazimierz Duzinkiewicz
Keyword(s):  
Power Plant ◽  
Nuclear Power Plant ◽  
Steam Turbine ◽  
Dynamic Model ◽  
Nuclear Power ◽  
Dynamic Models ◽  
Operating Conditions ◽  
Internal Variables ◽  
Wide Range ◽  
Optimal Process Control

Abstract The paper presents the dynamic multivariable model of Nuclear Power Plant steam turbine. Nature of the processes occurring in a steam turbine causes a task of modeling it very difficult, especially when this model is intended to be used for on-line optimal process control (model based) over wide range of operating conditions caused by changing power demand. Particular property of developed model is that it enables calculations evaluated directly from the input to the output, including pressure drop at the stages. As the input, model takes opening degree of valve and steam properties: mass flow and pressure. Moreover, it allows access to many internal variables (besides input and output) describing processes within the turbine. The model is compared with the static steam turbine model and then verified by using archive data gained from researches within previous Polish Nuclear Power Programme. Presented case study concerns the WWER-440 steam turbine that was supposed to be used in Żarnowiec. Simulation carried out shows compliance of the static and dynamic models with the benchmark data, in a steady state conditions. Dynamic model also shows good behavior over the transient conditions.

Frequency Response Analysis for Dynamic Model Identification and Control of a Ducted Fan Aerial Vehicle in Hover

2013 ◽  
Vol 332 ◽  
pp. 56-61 ◽  
Author(s):  
Meysam Effati ◽  
Afshin Banazadeh
Keyword(s):  
Frequency Response ◽  
Dynamic Model ◽  
Transfer Functions ◽  
Complex Dynamics ◽  
Model Identification ◽  
Response Analysis ◽  
Ducted Fan ◽  
Power Spectral ◽  
Modern Engineering ◽  
Non Linear

System Identification is a key technology for the development and integration of modern engineering systems including unconventional flying vehicles. These systems are highly parametric with complex dynamics and nonlinearities. Ducted fans are special class of these vehicles that can take off vertically, hover and cruise at very low speed. In this paper, an exact equivalent linear system is found from the non-linear dynamic model of a ducted fan by use of frequency response identification. Here, power spectral density analysis is performed, using CIFER software, to evaluate the input-output responses in hover and to derive the transfer functions based on the coherence criterion. Then, PID controllers are designed by utilizing the identified transfer functions and the performance characteristics of the controllers are evaluated in fully non-linear simulation of the system.

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