Spelling suggestions: "subject:"helicopters - eontrol systems"" "subject:"helicopters - 7control systems""
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A multidisciplinary design approach to size stopped rotor/wing configurations using reaction drive and circulation controlTai, Jimmy C. M. 08 1900 (has links)
No description available.
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Stability and control characteristics of model helicoptersVisagie, Jonathan Gerhardus 12 1900 (has links)
Thesis (MScEng)--University of Stellenbosch, 2004. / ENGLISH ABSTRACT: A need exists for the development of an unmanned rotorcraft capable
of autonomous flight, as would be required for the survey of high
voltage electricity supply lines. A program was initiated at the
University of Stellenbosch in December 2002 in order to develop such
an aircraft.
The first goal of this thesis was the development of software that could
calculate the stability and control derivatives of a model helicopter.
These derivatives could then be used in the formulation of an
appropriate helicopter control strategy. The second goal of the thesis
was an investigation of the stability and control characteristics of model
helicopters.
The trim settings of the helicopter were required in the calculation of
the stability and control derivatives. A computer program was
developed to determine the trim settings of a helicopter in forward
flight. Another program was developed to calculate the stability and
control derivatives, using the results of the trim analysis.
The trim analysis was based on the assumption of negligible coupling
between the longitudinal and lateral modes of motion. The method
proposed by Bramwell (1976) was used to perform the trim analysis.
The stability and control derivatives were calculated by obtaining the
trim settings from the trim analysis. These derivatives were then used
to solve the roots of the characteristic equations of the longitudinal and
lateral modes of motion. The stability of the helicopters were
investigated firstly by examining the stability derivatives and secondly
through root-loci analyses.
The most important results were the following:
• The root-loci analyses indicated that a helicopter without a
horizontal stabiliser suffered from instability of the phugoid
mode. It was also found that the short-period motion of these
helicopters was heavily damped. Fitting a horizontal stabiliser to
these helicopters caused the phugoid motion to become stable
even at low speeds. This was achieved at the cost of a reduction
in short-period motion damping.
• The periods of the lateral and longitudinal motions were smaller
than those found on full-scale helicopters. This was attributed to
the small mass and inertia properties of the model helicopters. An increase in speed is generally accompanied by an increase in
the stability of the helicopters. This could be attributed to the
effective operation of the tail surfaces at higher speeds.
• The axial climbing speed of a helicopter is influenced by the rotor
speed. A low rotor speed allows higher climbing velocities at a
given power setting. This was due to lower induced power losses
at low rotor speed, assuming that no blade stall occurs.
• The rotor speed does not influence the incremental amount of
power (M:,) required to achieve a certain climbing velocity, due
to the fact that the profile power losses are constant for a certain
rotor speed.
• The simplified horseshoe-vortex theory can be used to analyse
the downwash angle at the horizontal stabiliser if the helicopter
is in high-speed forward flight. / AFRIKAANSE OPSOMMING: Daar is tans 'n vraag na die ontwikkeling van onbemande rotor-vlerk
vliegtuie wat die vermoë beskik om hulself te beheer. Hierdie tipe
vliegtuie sal gebruik word om byvoorbeeld hoë-spannings elektrisiteitverskaffingsdrade
na te gaan. 'n Program is in Desember 2002 by die
Universiteit van Stellenbosch begin om sulke vliegtuie te ontwikkel.
Die eerste doel van hierdie tesis was om sagteware te ontwikkel wat
die stabiliteit- en beheerafgeleides van 'n model helikopter kon
bereken. Hierdie afgeleides kan dan gebruik word om 'n gepaste
helikopter beheerstrategie saam te stel. Die tweede doel van die tesis
was om die stabiliteit- en beheerseienskappe van model helikopters te
ondersoek.
Die berekening van die stabiliteit- en beheerafgeleides van die
helikopter berus op die beheerinsette benodig om die helikopter in
ewewig te hou (trim). 'n Rekenaarprogram is ontwikkelom hierdie
beheerinsette vir 'n helikopter in voorwaartse vlug te bereken. 'n Ander
program is ontwikkelom die stabiliteit- en beheerafgeleides te bereken
met behulp van die ewewig beheerinsette.
Die analise van die helikopter in ewewig berus op die aanname dat die
grootte van die koppeling tussen die longitudinale en laterale
beweginsmodusse weglaatbaar klein is. Die beheerinsette van die
helikopter in ewewig tydens voorwaartse vlug is bereken deur van
Bramwell (1976) se metode te gebruik. Die stabiliteit- en
beheerafgeleides is bereken deur van hierdie beheerinsette gebruik te
maak. Die afgeleides is gebruik om die wortels van die karakteristieke
vergelykings van die longitudinale en laterale bewegingsmodusse te
bereken. Die stabiliteit van die helikopters is eerstens beoordeel deur
die stabiliteitsafgeleides te ondersoek en tweedens deur middel van 'n
wortel-lokus analise.
Die belangrikste resultate is as volg:
• Die wortel-lokus analise toon dat 'n helikopter sonder 'n
horisontale stabiliseerder phugoid-onstabiliteit (Iangperiode
onstabiliteit) het. Die kort-periode beweging van hierdie
helikopters het verder groot hoveelhede demping aangetoon. Die
phugoid-beweging kon selfs teen lae snelhede gestabiliseer word
deur 'n horisontale stabiliseerder aan te heg. Hierdie stabiliteit is
egter bereik ten koste van die demping van die kort-periode
beweging wat verminder is. • Die periodes van die longitudinale en laterale bewegings is
kleiner gewees as vir volskaal helikopters. Dit kan toegeskryf
word aan die klein massa en inersie van die model helikopters.
• Die stabiliteit van die helikopter is in die algemeen verbeter soos
die snelheid verhoog. Dit kan toegeskryf word aan die beter
werking van die stert teen die verhoogde snelhede.
• Die klimtempo van die helikopter word beïnvloed deur die
hoofrotor snelheid. 'n Lae hoofrotor snelheid laat 'n hoër
klimptempo toe teen 'n spesifieke drywinginset. Dit is as gevolg
van die laer geïndusseerde drywingsverliese teen die laer
hoofrotor snelheid. Daar word aanvaar dat die lugvloei oor die
lem nie staak nie.
• Die hoofrotor snelheid beïnvloed nie die inkrimentele drywing
(M,,) wat benodig word om 'n sekere klimtempo te bereik nie. Dit
is as gevolg van die konstante drywings verliese teen 'n sekere
hoofrotor snelheid.
• Die vereenvoudigde perdeskoenwerwel teorie kan gebruik word
om die afspoel hoek by die horisontale stabiliseerder te bereken
indien die helikopter in hoë-spoed voorwaartse vlug is.
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Development of a rotary-wing test bed for autonomous flightGroenewald, Stephanus 03 1900 (has links)
Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2006. / This project developed a low-cost avionics system for a miniature helicopter to be used for
research in the field of autonomous flight (UAVs).
Previous work was done on a small, electrically powered helicopter with some success, but the
overall conclusion was that the vehicle was underpowered. A new vehicle, the Miniature Aircraft
X−Cell, was chosen for its ability to lift a larger payload, and previous work done with it by a
number of other institutions.
An expandable architecture was designed to allow sensors and actuators to be arbitrarily added to
the system, based on the CAN standard. A CAN sensor node was developed that could digitize
12 channels at up to 16 bit resolution and do basic filtering of the data. Onboard computing was
provided by a PC/104 based computer running Linux, with additional hardware added to
interface with the CAN bus and assist with timing.
A simulation environment for the helicopter was evaluated and shown to provide a good test bed
for the control of the helicopter. Finally, the avionics was used during piloted test-flights to
measure data and judge the performance of both the modified helicopter and the electronics itself.
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Helicopter stability during aggressive maneuversUnknown Date (has links)
The dissertation investigates helicopter trim and stability during level bank-angle and diving bank-angle turns. The level turn is moderate in that sufficient power is available to maintain level maneuver, and the diving turn is severe where the power deficit is overcome by the kinetic energy of descent. The investigation basically represents design conditions where the peak loading goes well beyond the steady thrust limit and the rotor experiences appreciable stall. The major objectives are: 1) to assess the sensitivity of the trim and stability predictions to the approximations in modeling stall, 2) to correlate the trim predictions with the UH-60A flight test data, and 3) to demonstrate the feasibility of routinely using the exact fast-Floquet periodic eigenvector method for mode identification in the stability analysis. The UH-60A modeling and analysis are performed using the comprehensive code RCAS (Army's Rotorcraft Comprehensive Analysis System). The trim and damping predictions are based on quasisteady stall, ONERA-Edlin vi (Equations Differentielles Lineaires) and Leishman-Beddoes dynamic stall models. From the correlation with the test data, the strengths and weaknesses of the trim predictions are presented. / by Ranjith Mohah. / Thesis (Ph.D.)--Florida Atlantic University, 2012. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2012. Mode of access: World Wide Web.
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Linear time invariant models for integrated flight and rotor controlOlcer, Fahri Ersel 08 July 2011 (has links)
Formulation of linear time invariant (LTI) models of a nonlinear system about a periodic equilibrium using the harmonic domain representation of LTI model states has been studied in the literature. This thesis presents an alternative method and a computationally efficient scheme for implementation of the developed method for extraction of linear time invariant (LTI) models from a helicopter nonlinear model in forward flight. The fidelity of the extracted LTI models is evaluated using response comparisons between the extracted LTI models and the nonlinear model in both time and frequency domains. Moreover, the fidelity of stability properties is studied through the eigenvalue and eigenvector comparisons between LTI and LTP models by making use of the Floquet Transition Matrix. For time domain evaluations, individual blade control (IBC) and On-Blade Control (OBC) inputs that have been tried in the literature for vibration and noise control studies are used. For frequency domain evaluations, frequency sweep inputs are used to obtain frequency responses of fixed system hub loads to a single blade IBC input. The evaluation results demonstrate the fidelity of the extracted LTI models, and thus, establish the validity of the LTI model extraction process for use in integrated flight and rotor control studies.
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Design of a DDP controller for autonomous autorotative landing of RW UAV following engine failureMatlala, Puseletso January 2016 (has links)
A dissertation submitted to the Faculty of Engineering and the Built Environment,
University of the Witwatersrand, Johannesburg, in partial fulfilment of the requirements
for the degree of Master of Science in Engineering.
Johannesburg, April 2016 / A Rotary Wing Unmanned Aerial Vehicle (RW UAV) as a platform and its payload
consisting of sophisticated sensors would be costly items. Hence, a RW UAV in the
500 kg class designed to fulfil a number of missions would represent a considerable
capital outlay for any customer. Therefore, in the event of an engine failure, a means
should be provided to get the craft safely back on the ground without incurring
damage or causing danger to the surrounding area. The aim of the study was
to design a controller for autorotative landing of a RW UAV in the event of engine
failure. In order to design a controller for autorotative landing, an acceleration model
was used obtained from a study by Stanford University. FLTSIM helicopter flight
simulation package yielded necessary RW UAV response data for the autorotation
regimes. The response data was utilized in identifying the unknown parameters
in the acceleration model. A Differential Dynamic Programming (DDP) control
algorithm was designed to compute the main and tail rotor collective pitch and the
longitudinal and lateral cyclic pitch control inputs to safely land the craft. The
results obtained were compared to the FLTSIM flight simulation response data.
It was noted that the mathematical model could not accurately model the pitch
dynamics. The main rotor dynamics were modelled satisfactorily and which are
important in autorotation because without power from the engine, the energy in
main rotor is critical in a successful execution of an autorotative landing. Stanford
University designed a controller for RC helicopter, XCell Tempest, which was deemed
successful. However, the DDP controller was designed for autonomous autorotative
landing of RW UAV weighing 560 kg, following engine failure. The DDP controller
has the ability to control the RW UAV in an autorotation landing but the study
should be taken further to improve certain aspects such as the pitch dynamics and
which can possibly be achieved through online parameter estimation. / MT 2017
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Development of a Low-Cost, Low-Weight Flight Control System for an Electrically Powered Model HelicopterCarstens, Nicol 03 1900 (has links)
Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2005. / This project started a new research area in rotary-wing °ight control in the Computer and
Control group at the University of Stellenbosch. Initial attempts to build a quad-rotor
vehicle exposed di±culties which motivated changing to a standard model helicopter as
a test vehicle. A JR Voyager E electrically powered model helicopter was instrumented
with low-cost, low-weight sensors and a data communication RF link.
The total cost of the sensor, communication and microcontroller hardware used is
approximately US$ 1000 and the added onboard hardware weighs less than 0:4 kg. The
sensors used to control the helicopter include a non-di®erential u-Blox GPS receiver,
Analog Devices ADXRS150 rate gyroscopes, Analog Devices ADXL202 accelerometers, a
Polaroid ultrasonic range sensor and a Honeywell HMC2003 magnetometer.
Successful yaw, height and longitudinal position control was demonstrated. Signi¯cant
further work is proposed, based on the literature study performed and the insights and
achievements of the ¯rst rotary-wing unmanned aerial vehicle project in the group.
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Full state control of a Fury X-Cell unmanned helicopterVan Schalkwyk, Carlo 03 1900 (has links)
Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2009. / This thesis describes the successful development of an autopilot for an unmanned
radio controlled helicopter. It presents a non-linear helicopter model. An adaptive
linearised model is derived and used to design a controller. The adaptive full
state controller is tested in various ways, including two aerobatic manoeuvres. A
number of analyses are performed on the controller, including its robustness to parameter
changes, noisy estimates, wind and processing power. The controller is
compared with a non-adaptive counterpart, which leads to the conception, design
and analysis of a much improved control structure. Practical flight test results are
presented and analysed.
In some instances available literature was reworked and re-derived to produce
a genericmodel-controller package that can easily be adapted for helicopters of any
make, model and size.
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The nonlinear modelling and model predictive control of a miniature helicopter UAV01 August 2012 (has links)
M.Ing. / Linear control system theory is well developed and has lead to a number of control system types with well-defined design methods that can be applied to any linear system. Unfortunately, no system in nature is truly linear. As a result, such non-linear systems must be represented by a linear model that is accurate over some region of the operating states of the system. The success of linear control theory in commercial applications is testament to the fact that some types of systems can be adequately represented by a linear model. However, systems with time-varying dynamics or non-linearities such as input or operating state saturation cannot always be adequately controlled by linear control systems. For that reason, non-linear control techniques must be investigated. This project aims to investigate Non-linear Model Predictive Control theory and practical implementation in the context of developing an autopilot for an Unmanned Aerial Vehicle based on a miniature helicopter. A non-linear model of the dynamics of an X-Cell Spectra G radio-controlled helicopter was developed based on the existing literature. A number of experiments were performed to determine the parameters of this model. Significant future work exists in designing additional ground experiments since certain parameters are difficult to measure safely in the laboratory. Additional work to improve the accuracy of the model at high airspeeds, as well as incorporating a more accurate yaw dynamics model, is also required. Following this, a Non-linear Model Predictive Control autopilot was simulated using MATLAB®. The simulation tested the effects of control system parameters such as control horizon and sampling period, as well as the sensor noise susceptibility and its ability to handle wind as a random disturbance. The results determined adequate control system parameters for level flight as well as landing the helicopter under ideal conditions. Simulations in which sensor noise and wind were added showed that the control system is significantly affected by sensor noise and that it cannot hover in the presence of wind. A real-time implementation was not achieved during this work; however, several directions for future research have been discussed.
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Modeling and control of helicopters carrying suspended loadsAdams, Christopher James 05 July 2012 (has links)
Helicopters are often used to transport supplies and equipment. When a heavy load is carried via suspension cables below a helicopter, the load oscillates in response to helicopter motion and disturbance forces, such as wind. This oscillation is dangerous and adversely affects control of the helicopter, especially when carrying large or heavy loads. By adding input shaping to the helicopter's flight controller, the suspended load oscillation caused by helicopter motion is greatly reduced. A significant benefit of this approach is that it does not require measurement of the load position. This thesis contains derivations and analysis of simple planar helicopter-load dynamic models, and these models are verified using experimental data from model-scale, radio-controlled helicopters. The effectiveness of input shaping at eliminating suspended load oscillation is then demonstrated on this experimental hardware. In addition, the design of an attitude command, near-hover flight controller that combines input shaping and a common flight control architecture is illustrated using dynamic models of a Sikorsky S-61 helicopter, and simulation results are shown for example lateral and longitudinal repositioning movements. Results show that applying input shaping to simulated pilot commands greatly improves performance when carrying a suspended load.
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