Helicopter flight control systems

This material gives a basic aerodynamics related to rotor craft systems. This is a basic theory behind the helicopter blades. How the relative wing is affecting during hover, transnational flight, vertical flight. The theory also gives idea about the ground effect on rotor blades at different conditions.

This project report describes all the work carried out in the design, fabrication and testing of a radio frequency controlled, unmanned aerial vehicle, specifically, a quadcopter. It is a “stepping-stone” project which has the conspicuous aim of motivating drone design in Nigeria. Drones have vast application in both military and civilian use. The first officially indigenous drone made in Nigeria, GULMA, was designed only in 2013 by the Nigerian Air Force. Being a stepping stone project, the U.A.V. is designed basically to perform basic drone movements; the take-off and landing, yaw, pitch, roll and hovering, therefore the addition of payloads (camera, GPS, delivery etc.) is neglected. The project is also aimed at showcasing understanding in basic engineering design, flight mechanism, design analysis with SolidWorks project data analysis with MATLAB and printed circuit board configuration for flight control. The flight controller was configured with the Base Flight Configurator and an excellent practice in design by selection was carried out in selecting the radio frequency transmitter and receiver suitable for the drone design. The project was tested indoors and outdoors, the condition for outdoor testing being dry and windless.
Chapter 1 of this report gives a brief introduction, background to study and the statement of the addressed by the project. Chapter 2 reviews similar projects on Unmanned Aerial Vehicles, specifically quadcopters and compares them. It also contains basic components of a quadcopter and states its vast applications. In Chapter 3, the design method and implementation is stated while in Chapter 4, all tests and results are reported. Finally, Chapter 5 gives a compact and well analysed conclusion of the project.
Keywords: [Stepping-stone project, SolidWorks, MATLAB, Base Flight Configurator]

The old flight instruments made by right brothers have only limited flight instruments that to only mechanical devices such as airspeed indicators, oil pressure gauge, fuel tank and single engine. The trend towards modern aircrafts have advanced features such as mentioned in this article all electronic instruments displays radar such as altimeter, attitude indicator, multiple engines displays of all parameters of aircraft. Indexing terms: fight instruments; pfd airspeed indicator; attitude indicator etc; INTRODUCTION Primary Flight Display (PFD) A PFD presents information about primary flight instruments, navigation instruments, and the status of the flight in one integrated display. Some systems include power plant information and other systems information in the same display. A typical primary flight display is shown in Figure 2-1. Primary Flight Instruments Flight instrument presentations on a PFD differ from conventional instrumentation not only in format, but sometimes in location as well. For example, the attitude indicator on the PFD in Figure 2-1 is larger than conventional round-dial presentations of an artificial horizon. Airspeed and altitude indications are presented on vertical tape displays that appear on the left and right sides of the primary flight display. The vertical speed indicator is depicted using conventional analog presentation. Turn coordination is shown using a segmented triangle near the top of the attitude indicator. The rate-of-turn indicator appears as a curved line display at the top of the heading/navigation instrument in the lower half of the PFD. Cross-Checking the Primary Flight Instruments The PFD is not intended to change the fundamental way in which you scan your instruments during attitude instrument flying. The PFD supports the same familiar control and performance, or primary and supporting methods you use with conventional flight instruments. For example, when using the primary and supporting method to maintain level flight, the altimeter is still the primary instrument for pitch, while the attitude indicator is a direct indicator and the vertical speed indicator provides supporting information. However, you need to train your eyes to find and interpret these instruments in their new formats and locations. Common Errors: Altitude Excursions and Fixation Pilots experienced in the use of conventional flight instruments tend to deviate from assigned altitudes during their initial experience with the PFD, while they adjust to the tape display presentation of altitude information. Another common error is the tendency to fixate and correct deviations as small as one to two feet at the expense of significant deviations on other parameters.

This paper presents a flight control approach based on a state-dependent Riccati equation (SDRE)
and its application to autonomous helicopters. For our experiments, we used two different platforms, an
XCell-90 small hobby helicopter and a larger vehicle based on the Yamaha R-Max. The control design uses a
six-degree-of-freedom nonlinear dynamic model that is manipulated into a pseudo-linear form where system
matrices are given explicitly as a function of the current state. A standard Riccati equation is then solved
numerically at each step of a 50 Hz control loop to design the nonlinear state feedback control law on-line.
In addition, the SDRE control is augmented with a nonlinear compensator that addresses issues with the
mismatch between the original nonlinear dynamics and its pseudo-linear transformation.

The paper deals with the control design of a fault-tolerant actuator for fly-by-wire helicopters, capable of compensating both failure effects and jump resonance phenomena. The study, focused on the performance analysis in case of  ervovalve coil faults, points out that a standard reconfiguration based on demand amplification can imply jump resonances. The proposed strategy eliminates the problem by correlating the jump frequency to the system characteristics, and by  inserting a dynamic notch filter in the actuator closed-loop control.

This paper describes a dual-loop control design for a helicopter model using the state-dependent Riccati equation (SDRE) technique. The dual-loop design decouples vehicle dynamics into translational and attitude parts. In the dual-loop design, the outer loop (guidance loop) controller tracks the desired position and velocity of the vehicle and generates desired roll and pitch as inputs for the inner loop controller. The inner loop controller provides the desired attitude tracking. In this paper, both controllers are based on the augmented SDRE approach, which employs means of mitigating effects of vehicle dynamics
approximations in the SDRE design. The dual-loop SDRE performance is compared to the full-state single-loop SDRE design, in which the whole system dynamics is manipulated
into a state-dependent coefficient form.

In this paper, the effectiveness of discrete yaw direction setting in 4 rotor helicopter control was evaluated by simple computer simulation and Parrot AR. Drone 4 rotor helicopter in horizontal plane automatic position fixing control. For 4 rotor system, it is necessary to control the attitude of the drone and the position in the space simultaneously in order to realize stable flight of the system. The attitude control can be realized by the internal acc / gyro sensors with high sampling rate (near 1 kHz), on the contrary, the position control in the outdoor situation is necessary to realize by the external 3D position measurement method with relatively low sampling rate techniques (lower than 100 Hz) such as GPS. The low sampling rate reduces the positional control stability, and it is causing the control problem such applications of inspection work at high height and long distance. Our attempt is to evaluate the effect of adding discrete yaw direction setting while normal 4 rotor helicopter roll and pitch control in horizontal plane movement by a simple computer simulation and model implementation. By adding the discrete yaw direction setting to the target direction, the fixed position movement control performance of the 4 rotor system could increase comparing with without the yaw direction setting of the 4 rotor system. The proposed method would be useful to improve the 4 rotor system control performance under the relatively low sampling rate positional information acquired situation. Keywords— Discrete yaw direction control, degree of freedom of yaw axis, AR. Drone, 4 rotor system, automatic position stop control.

The subject of this thesis is «What are the underlying causes for helicopter accidents in aerial work in Norway». «- can they be explained through culture, structure and supervising authorities – and a combination of these factors?».  Aerial work in Norway have taken its toll in number of fatal accidents, in spite of an increased safety focus.  My theoretical framework is based on organizational theory, both structure and culture. In addition, theories of high reliability and risk exposed organizations, and how these are handled in the aviation network, make out the base of the study. Data collection was done using a triangulation method between a small N design, quantitative inspired survey and a qualitative study. The survey was done among helicopter company managers and CAA-inspectors. The findings gave a deep insight of the inner life of safety management, both in the companies and regulatory offices. Shortcomings were revealed to be of such standard, that efficient risk and safety management are difficult to uphold. 

The results from this study show strong support for my hypothesis, and I concluded that all the factors mentioned in the initial questions, both singularly, and in combination, are providers for inherent causes to the accident rate.

In a dynamic system such as flight control systems, faults caused by sensors, actuators and controllers can bring on unwanted reactions, reduce overall system efficiency and performance or even lead to failure of the overall, therefore it is required to detect such faults as soon as possible to isolate them accurately. During the past three decades a variety of methods have been developed to detect faults in processes and control systems. In this study, a longitudinal model of a fighter aircraft was selected as an example of a flight control system. Using data-driven methods based on multivariate statistical techniques, such as principal component analysis we tried to detect faults in the sensors. In these methods, calculations will be done based on the calculation of Hotelling's T^2 statistic and squared prediction error (SPE) statistic of the observation vector, and comparing with the statistics of the respective areas, as well as threshold levels, normal or abnormal status were detected. Keywords-flight control system, sensor fault, fault detection, longitudinal aircraft dynamic, data-driven method, multivariate statistical method, principle component analysis.

Yazar: Ercan Caner, Sun Savunma Net, 7 Kasım 2017 Kalkış, iniş ve havır safhaları, helikopter uçuşlarında potansiyel riskler içermektedir. Pilotlar riskleri asgari seviyeye indirebilmek maksadıyla, özellikle yüksek yoğunluk irtifası, azami gros ağırlık ile kapalı ve tepe harekâtında her zaman uyanık olmalı ve durumsal farkındalık seviyelerini en üst derecede korumalıdırlar. https://sunsavunma.net/ana-rotor-kuyruk-rotor-turbulanslari-guclu-cokus/

The paper deals with the control design of a fault-tolerant actuator for fly-by-wire helicopters, capable of compensating both failure effects and jump resonance phenomena. The study, focused on the performance analysis in case of servovalve coil faults, points out that a standard reconfiguration based on demand amplification can imply jump resonances. The proposed strategy eliminates the problem by correlating the jump frequency to the system characteristics, and by inserting a dynamic notch filter in the actuator closed-loop control.

In this paper, the effectiveness of new position control strategy-fast speed yaw and roll control switching method instead of the roll control only in Parrot AR Drone 4 rotor helicopter in horizontal plane for automatic fixed position flight was confirmed. General 4 rotor basic flight controller considers only simple floating control and does not concern the position control in the space, the AR Drone was also developed as realizing the floating control only and it is necessary to control the position by the user. Instead of a simple roll control, fast speed switching yaw and roll controls (plus pitch control) could realize stable automatic fixed position control comparing with the simple roll plus pitch controls in the horizontal plane. Proposed method reduced the AR Drone automatic fixed control within S.D. of x and y axis to 31.6% and 54.8% comparing with the normal roll plus pitch controls S.D. of x and y in 3.5 x 5 x 2.4 m room, and it will useful for hobby-class 4 rotor system's the aircraft position control in such a small room condition. Keywords— Fast speed yaw and roll control switching, AR Drone, automatic fixed position control, degree of freedom of spin axis. I. INTRODUCTION In this paper, the effectiveness of new position control strategy-fast speed yaw and roll control switching method instead of the roll control only in Parrot AR Drone 4 rotor helicopter in horizontal plane for automatic fixed position flight was confirmed. In order to apply the 4 rotor system in real difficult wind flow environments (outdoor, tunnel, bridge site inspections and so on), there are large demands to improve a positional movement control performance of the 4 rotor system [1, 2]. The main object of this paper is to show the effectiveness of new position control strategy-(a) fast speed yaw and roll control switching method instead of (b) the roll control only (Fig.1). Automatic fixed position control experiments show that the fast speed yaw and roll control switching + pitch control method realizes a high performance of the fixed position control comparing with the normal roll + pitch control method. By just changing the roll control strategy, the improvement of the fixed position control performance was confirmed.

In this paper we present a method for optimal control of
MIMO non-linear systems based on a combination of a neural
network (NN) feedback controller and a state-dependent Riccati
equation (SDRE) controller. Optimization of the NN is performed within a receding horizon model predictive control
(MPC) framework, subject to dynamic and kinematic constraints. The SDRE controller augments the NN controller by
providing an initial feasible solution and improving stability.
The resulting technique is applied to a 6 degree of freedom
(DoF) model of an autonomous helicopter.

This paper describes a dual-loop control design for a helicopter model using the statedependent Riccati equation (SDRE) technique. The dual-loop design decouples vehicle dynamics into translational and attitude parts. In the dual-loop design, the outer loop (guidance loop) controller tracks the desired position and velocity of the vehicle and generates desired roll and pitch as inputs for the inner loop controller. The inner loop controller provides the desired attitude tracking. In this paper, both controllers are based on the augmented SDRE approach, which employs means of mitigating effects of vehicle dynamics approximations in the SDRE design. The dual-loop SDRE performance is compared to the full-state single-loop SDRE design, in which the whole system dynamics is manipulated into a state-dependent coefficient form.

The twin-rotor, multi-input, multi-output system is a typical lab-scale helicopter system, since it resembles behavior of helicopter systems. This experimental complex aerodynamic test rig needs precise modeling to assure satisfactory control performance. Therefore, this article is intended to provide a gray-box approach for the modeling of the twin-rotor, multi-input, multi-output system. An algorithm is proposed by dividing the system into independent subsystems that can be estimated for an excitation input or a characteristic response. The proposed algorithm uses trust region optimization methods for successive estimations. The iterative optimization methods of Levenberg–Marquardt, gradient descent active set, and interior point are compared with respect to trust region methods. The model is validated with various sets of scenarios: different inputs, different types of motion, and different operating points. Effect of operating point selection on the parameter estimation process ...

The paper addresses problems in developing robust reduced-order multivariable models of aircraft for cases in which strong inter-axis coupling exists. Attentiin is focussed particularly on helicopter modelling and the associated problems of helicopter flight control system design. In that particluar cases a priori information about parameters of the vehicle model, especially parameters associated with certain types of cross-coupling is also limited. System identification techniques and frequency-domain methods in partcicular offer potential benefitsfor helicopter parameter estimation and for external validation of models. Frequency-domain methods also offer an effective approach to model freduction for multi-input multi-output models and for some aspects of control system design. The helicopter case is used to illustrate how frequency-domain toos can be combined to provide and integrated evironment for both model development and control system design.

The need to implement a process of constraints handling into conventional inverse simulation represents an important problem. To achieve this, a modification of the conventional inverse simulation technique which includes predictive capability, is proposed in this paper. After giving details of the development of the predictive inverse simulation algorithm, the paper demonstrates the applicability of the developed methodology on two aggressive helicopter manoeuvres: pop-up and lteral realignment.