Academic literature on the topic 'Phugoid oscillation'

Phugoid mode is a lowly damped, low-frequency oscillatory motion representing vertical translation usually related to kinetic and potential energy interchange. MIL-F-8785C standard has ruled out qualitative specification requirements on measurement of flying and handling qualities of piloted aircraft. For phugoid mode, these requirements lie in the value of its damping ratio. Small aircraft is sensitive to atmospheric conditions and poor phugoid mode performance is observed in many unmanned aircraft. This paper discusses the effect of airspeed and altitude to phugoid mode of small, unmanned blended wing-body (BWB) aircraft named Baseline-II E-2. Baseline-II is a low subsonic, remotely-piloted UAV used to study the behaviour of a BWB-type aircraft. The case presented here is an E-2 version in which a specifically-designed canard is incorporated as its longitudinal control surface. Five Category B flight cases (airspeeds) per altitude-case, and three altitude cases (low, medium and high) are studied. Model-N dynamic model is introduced here to become the basis of flight simulation. The model is compared to models derived by other authors and approximation equations. The mean of simulating phugoid behaviour is using state-space representation of the aircraft using Matlab SIMULINK. The computations show that Baseline-II E-2 undamped natural frequency of phugoid mode is inversely-proportional to airspeed and reduces as altitude increases. These have adverse effect on its damping ratio that increases near parabolically when the aircraft flies faster, and reduces when it climbs up. The cause of these trends is looked into in detail and issues concerning Baseline-II E-2’s unsatisfactory and unstable phugoid mode oscillation at low speed are addressed.

Transient response of an aircraft in longitudinal motion has two modes of oscillatory motion short period mode and phugoid modes and failure to achieve satisfactory level would mean poor flying and handling qualities leading to unnecessary pilot workload. This study proposes a stability augmentation system (SAS) in longitudinal flying modes for steady and level flight at all airspeeds and altitudes within Baseline-II E-2 BWBs operational flight envelope (OFE). The main controlling component of this stability augmentation system is a set of canard, a control surface located in front of the wing. It must be able to compensate Baseline-II E-2 BWB poor transient responses damping ratios so that good flying quality can be achieved. Observation from the transient responses of the unaugmented system signify high-frequency short-period oscillations with almost constant low damping ratio at an altitude, and low-frequency phugoid oscillation with varying damping ratio depending on airspeed. A conclusive behaviour of natural frequencies and damping ratios against dynamic pressure leads to the understanding on how dynamic pressure influences the flying qualities. Derivation of dynamic equations in terms of dynamic pressures enables one to design and device a feedback system to compensate poor flying qualities of the original unaugmented aircraft with conclusive relationship between important parameters and dynamic pressure are put in the overall dynamic equation. Two feedback gain systems, pitch attitude and pitch rate gains are scheduled based on dynamic pressure values and are combined into the aircraft longitudinal SAS. The proposed SAS has proven to be the suitable candidate for Baseline-II E-2 BWB as it is able to ensure Level 1 flying qualities, longitudinally.

In this study, a guidance scheme for an aerodynamically controlled hypersonic boost-glide class of flight vehicle is proposed. In this work, optimum glide dynamic pressure corresponding to maximum L/ D throughout the flight is calculated and a mid-course guidance law formulation to track the dynamic pressure while suppressing phugoid oscillations is proposed for real-time flight trajectory shaping. Efficacy of the proposed guidance scheme has been demonstrated through simulation studies. Robustness analysis on the proposed guidance algorithm is carried out using Monte Carlo technique. Lastly, a pattern search algorithm-based offline generated maximum L/ D optimal trajectory existing in literature, which meets minimum dynamic pressure, maximum airframe skin temperature, as well as other in-flight and terminal constraints is used as reference trajectory to evaluate the performance of the proposed guidance scheme.

AbstractFor the entry guidance problem of hypersonic gliding vehicles (HGVs), an analytical predictor–corrector guidance method based on feedback control of bank angle is proposed. First, the relative functions between the velocity, bank angle and range-to-go are deduced, and then, the analytical relation is introduced into the predictor–corrector algorithm, which is used to replace the traditional method to predict the range-to-go via numerical integration. To eliminate the phugoid trajectory oscillation, a method for adding the aerodynamic load feedback into the control loop of the bank angle is proposed. According to the quasi-equilibrium gliding condition, the function of the quasi-equilibrium glide load along with the velocity variation is derived. For each guidance period, the deviation between the real-time load and the quasi-equilibrium gliding load is revised to obtain a smooth reentry trajectory. The simulation results indicate that the guidance algorithm can adapt to the mission requirements of different downranges, and it also has the ability to guide the vehicle to carry out a large range of lateral maneuvers. The feedback control law of the bank angle effectively eliminates the phugoid trajectory oscillation and guides the vehicle to complete a smooth reentry flight. The Monte Carlo test indicated that the guidance precision and robustness are good.

Mission of Unmanned Aerial Vehicle (UAV) “Elang Avionik” is surveillance and aerial photographs. Therefore the flight of UAV must be stable and controlable, and first step activity is dynamic modelling and stability analisys. The problems of UAV system is disturbance, noise of sensor, MIMO and uncertainty dynamic model. For good result using the multivariable robust control, with some step research that is: (1)modeling and stability analysis, (2) design and implementation of PID control system, (3) flight dynamic parameter identification, (4) design and implementation of hardware in the loop simulation, (5) design and implementation of multivariable robust control, (6) test and evaluation of system. Simulation result show that the eigen value in longitudinal is: phugoid mode = –0,061293±0,40526i and non-oscillation mode = –6,1121±4,9253. In lateral directional is:dutch roll mode = –0,91089±5,7994i, spiral mode= –0,036563, and roll subsidence mode = –12,7181. Location of poles system on the left of imaginary axis, the means that the character of system is dynamic stable. But settling time to steady state condition is very long and improved by control system design.
 Key word: State space, Longitudinal, Lateral, Stable static, Stable dynamic

Baigiamajame magistro darbe nagrinėjamas koncepcinio ultralengvojo lėktuvo „Kiras“ skrydžio stabilumas. Išilginio stabilumo charakteringi parametrai skaičiuoti rankiniu būdu bei Athenos sūkurių tinklelio principu veikiančia AVL stabilumo analizės programa. Šoninio judesio spiralės režimo tikrosios reikšmės, Fugoido, trumpojo periodo bei „olandiško žingsnio“ svyravimų tikrosios reikšmės įvertintos AVL. Darbas taip pat apima svyravimų dekremento, periodo T 1/2, laiko t 1/2, svyravimų ciklinio dažnio wn, ciklų skaičiaus N 1/2 ir kt. analizę esant skirtingam lėktuvo judesiui. Ankstyvoje projektavimo stadijoje buvo rastas ultralengvojo lėktuvo spiralinis nestabilumas. Ši klaida ištaisyta priartėjimo metodu keičiant uodegos geometriją ir sparno skersinį V kampą. Skaičiavimais bei kompiuteriniu skrydžio judesio modeliavimu įvertinus rezultatus buvo sukurta nauja kilio geometrija. Galiausiai pateikiamos baigiamojo darbo išvados ir siūlymai. Darbo apimtis – 54 p. teksto be priedų (67 p. su pried.), 9 iliustr., 10 lent., 12 bibliografinių šaltinių. Atskirai pridedami darbo priedai.<br>Stability analysis of conceptual design ultralight aircraft “Kiras” is presented in this master’s thesis. Longitudinal stability is evaluated by manual counting and Athena vortex – lattice based AVL program. Lateral derivatives, such as eigenvalues of spiral mode, “dutch roll“, Phugoid and short period oscillations were estimated by AVL . Thesis involves analysis of damping ratio, period T 1/2, time t 1/2, ocsillation circular frequency wn, number of cycles N 1/2 of distinct aircraft motions. The range of eigenvalues for specified run cases were automatically generated by AVL eigenmode meniu. At early phase of ultralight aircraft design, spiral instability was found. This problem fixed by approach method by correction of tail geometry and wing dihedral. According to the counting results and computerized motion analysis of an airplane, the corrected geometry of vertical tail is offered. Finally, the conclusions were made. Thesis consist of: 54 p. text without appendixes (67 p. with), 9 pictures, 10 tables, 12 bibliographical notes. Appendixes included.