Helicopter Model Research Articles

Disturbance Rejection for Nonlinear Uncertain Systems With Output Measurement Errors: Application to a Helicopter Model

As a virtual sensor, disturbance observer provides an alternative approach to reconstruct lumped disturbances (including external disturbances and system uncertainties) based upon system states/outputs measured by physical sensors. Not surprisingly, measurement errors bring adverse effects on the control performance and even the stability of the closed-loop system. Toward this end, this paper investigates the problem of disturbance observer-based control for a class of disturbed uncertain nonlinear systems in the presence of unknown output measurement errors. Instead of inheriting from the estimation-error-driven structure of Luenberger-type observer, the proposed disturbance observer only explicitly uses the control input. It has been proved that the proposed method endows the closed-loop system with strong robustness against output measurement errors and system uncertainties. With rigorous analysis under the semiglobal stability criterion, the guideline of gain choice based upon the proposed structure is provided. To better demonstrate feature and validity of the proposed method, numerical simulation and comparative experiments of a helicopter model are implemented.

Autonomous Trajectory Tracking Control for a Large-Scale Unmanned Helicopter under Airflow Influence

In this paper, a complete nonlinear dynamic unmanned helicopter model considering wind disturbance is proposed to achieve realistic simulations and teasing out the effect of wind on the control system. The wind velocity vector which is horizontal as seen in the inertial frame can be obtained by subtracting the airspeed measured by atmospheric data computer from the inertial speed measured by GPS. The design of the controller fully considers the existence of wind, and the wind disturbance is suppressed by the method of hierarchical control combined with the integral sliding mode control (SMC). The stability proof is given. Hardware in the loop (HIL) tool is employed as a practical engineering solution, and it is an essential step in validating the new algorithm before moving to real flight experiments.

Effect of the Simultaneous Variation in Blade Root Chord Length and Blade Taper on Maneuvering Manned Helicopter Control Effort

In this article, the influence of simultaneous variation in blade root chord length and blade taper on the flight control effort of maneuvering helicopter is researched. For this intention, helicopter models which are complex, control-oriented, physics-based models and capturing the main-physics and essential-dynamics are benefited. The influence of simultaneous variation in the blade root chord length and blade taper (i.e., in both chordwise and lengthwise directions dependently) on the control effort of a maneuvering manned helicopter and also on the closed-loop responses are worked. Comparisons in terms of the control effort and peak-values with and without variations in the blade root chord and blade taper changes are followed. For helicopter control variance-constrained controllers (i.e. output variance-constrained controllers) are useful.

Robust adaptive control for unmatched systems with guaranteed parameter estimation convergence

SummaryThis paper provides a modified model reference adaptive control (MRAC) scheme to achieve better transient control performance for systems with unknown unmatched dynamics, where an adaptive law with guaranteed convergence is introduced. We first revisit the standard MRAC system and analyze the tracking error bound by using L2‐norm and Cauchy‐Schwartz inequality. Based on this analysis, we suggest a feasible way to compensate the undesired transient dynamics induced by the gradient descent–based adaptive laws subject to sluggish convergence or even parameter drift. Then, a modified adaptive law with an alternative leakage term containing the parameter estimation error is developed. With this adaptive law, the convergence of both the estimation error and tracking error can be proved simultaneously. This enhanced convergence property can contribute to deriving smoother control signal and improved control response. Moreover, this paper provides a simple and numerically feasible approach to online verify the well‐known persistent excitation condition by testing the positive definiteness of an introduced auxiliary matrix. Comparative simulations based on a benchmark 3‐DOF helicopter model are given to validate the effectiveness of the proposed MRAC approach and show the improved performance over several other MRAC schemes.

Nonlinear Modeling and Flight Validation of a Small-Scale Compound Helicopter

The compound configuration is a good option for helicopters to break through speed limitation and improve maneuverability. However, the compound configuration applied on the small-scale helicopter has not been investigated in detail. In this study, an 11-state nonlinear dynamics model of a small-scale compound helicopter was established with the help of first physical principles and linear modification method. The ducted fan, free-rotate wing and horizontal stabilizer were considered in the compound configurations. To validate the accuracy of the model, high-quality flight data were obtained in hover and forward flights from 15 m/s to 32 m/s. Results show that the overall responses of the developed nonlinear model matched the hover data. In forward flight, it was proved that the nonlinear model has high accuracy in agreement with trim results and time-domain simulations. The wing model works well below 27 m/s. Furthermore, the effectiveness of the elevator and aileron in high speed was also verified in the simulation of a coordinated turn.

Performance improvements of helicopter basic fuselage model by passive vortex generators

Wind-tunnel tests of a heavy-class helicopter model were carried out to evaluate the effectiveness of a passive flow control system in alleviating fuselage parasite drag. An array of counter-rotating vortex generators was installed to reduce/remove the flow separation occurring on the rear-loading ramp responsible for the high-pressure drag. Novel technical solutions for the VGs’ design and location were selected compared to the previous work. A geometrically scaled 1:7 basic fuselage of a heavy-class helicopter was investigated with and without a passive flow control system using various measurement techniques. In particular, pressure measurements and stereo particle image velocimetry surveys were performed to obtain physical insights into load measurements. This paper reports promising results from wind-tunnel experiments, including the observation of significant drag reduction for a wide range of fuselage angles of attack and side slip angles without a negative impact on other aerodynamic characteristics.

Multi‐objective optimal motion control of a laboratory helicopter based on parallel simple cell mapping method

AbstractThis paper presents a study of multi‐objective optimal design of nonlinear control systems and has validated the control design with a twin rotor model helicopter. The gains of the porportional integral differential (PID) control are designed in the framework of multi‐objective opitmization. Eight design paramaters are optimized to minimize six time‐domain objective objective functions. The study of multi‐objective optimal design of feedback control with such a number of design paramaters and objective functions is rare in the literature. The Pareto optimal solutions are obtained by the proposed parallel simple cell mapping method consisting of a robust Pareto set recovery algorithm and a rolling subdivision technique. The proposed parallel simple cell mapping algorithm has two features: the number of cells in the invariant set grows linearly with the rolling subdivisions, and the Pareto set is insensitive to the inital set of seed cells. The current control design is compared with the classical LQE control for linear systems, and is also experimentally validated. The current design provides improved control performance as compares with the LQR control, and is applicable to complex nonlinear systems.

Finite Time Terminal Synergetic Controller for Nonlinear Helicopter Model

In this paper, an almost new control approach called terminal synergetic control which works based on user defined manifold is applied to a nonlinear helicopter model. Stability analysis is convestigated using Lyapunov stability theory. Synergetic controller is applied to this nonlinear fifth-order helicopter model to control height and angle. Simulation results showed that it has faster and smoother response in tracking reference inputs in comparison to sliding mode control, intelligent autopilot controller and feedback linearization method.

Mathematical Modelling, Simulation and Application of Full Flight Helicopter Simulator

In Aviation, Flight simulators are highly technological devices which are especially used to create the highly-accurate and zero-risk training environment for orientation, emergency, refresher, combat readiness & maintenance / testing pilot training. Full Flight Simulators are the simulators including a cockpit exactly like the real cockpit, visual system which is very close adapting the outside world images, a main simulation software which simulates the aerodynamic flight performance and the disruptive effects of helicopter. In this study, mathematical modelling of AS-532 Cougar helicopter by using Newton-Euler equation. Matlab-Simulink is used for demonstration of simulation results. Comparison of real simulator values and simulation results are enclosed.

Helicopter routing model with non-deterministic failure rate for evacuation of multiple oil platforms

Transportation between offshore oil platforms and land facilities is an important subject within emergency logistics. Although for these facilities helicopters have been considered as the most appropriate transportation vehicles due to their speed, reliability and accessibility, they also involve risks which can lead to fatalities. Within this context, the present work is focused on the development of a helicopter routing model that integrates non-deterministic failure rate as function of the helicopter’s cumulative traveled distance/time. Due to the complexity of the transportation task we also developed a Bayesian approach to generate instances for accurate testing and an evolutionary meta-heuristic to provide suitable solutions for large instances. As findings, the proposed routing model determined that reliable transportation decreases as failure rate increases. As consequences, the time-to-failure and the length of reliable flights decrease. This can lead to require more routes and helicopters to serve a set of facilities. The advances of the present work can be extended to other industries and logistic fields where reliable route planning is required in the presence of failure risks associated to the vehicles used for transportation (i.e., maritime and port logistics, risk and security management, transportation systems design and strategic sourcing and procurement).

The roles of emerging multinational companies’ technology-driven FDIs in their learning processes for innovation

Purpose The purpose of this paper is to contextually theorise the different patterns of emerging multinational companies’ (EMNCs’) learning processes for innovation and the different influences of their technology-driven FDIs (TFDIs) on the processes. Design/methodology/approach A comparative case study method and process tracing technique are employed to investigate how and why firms’ learning processes for innovation took place, how and why the TFDIs emerged and influenced the firms’ learning processes in different ways. Findings The paper identifies two different patterns of learning process for innovation (Glider model vs Helicopter model) and two different roles of the case firms’ TFDIs (accelerator vs starter) in the different contexts of their learning processes. It is found that the capability building of the domestic wind energy industry has an important influence on the case of EMNCs’ learning processes and thus on the roles of their TFDIs. Research limitations/implications The limitation of the paper lies in its small number of cases in a specific industry of a specific country. The two contextually identified learning models and roles of TFDIs may not be applied to other industries or other countries. Future research should investigate more cases in broader sectoral and geographic scope to test the models and also to identify new models. Practical implications For EMNCs, who wants to use the Helicopter model to rapidly gain production and innovation capability, cross-cultural management and integration management are crucial to practitioners. For emerging countries with ambitions to explore the global knowledge and technology pool, besides of the EMNC’s capability building, the capability building in the domestic industries should not be overlooked by policy makers. Originality/value The paper develops a dynamic and contextual analytical framework which helps to answer the important questions about how and under what context a TFDI emerges and influences firm’s learning process for innovation. It theorises the EMNCs’ learning process and TFDIs in the context of the development of the domestic industry. It strengthens the explanatory power of the learning-based view and adds new knowledge to the current FSA/CSA discourse in the international business literature.

Neural network-based adaptive fault tolerant tracking control for unmanned autonomous helicopters with prescribed performance

In this paper, the issue of prescribed performance-based fault tolerant control is investigated for the medium-scale unmanned autonomous helicopter with external disturbance, system uncertainty and actuator fault. The altitude and attitude combination unmanned autonomous helicopter model is established. An error transformation function is proposed to guarantee that the tracking error satisfies the prescribed performance. The parameter adaptation method is adopted to handle the external unknown disturbance and the radial basis function neural networks are employed to approximate the interaction functions including the system uncertainty. The auxiliary system is introduced to weaken the effect of actuator fault, which can effectively avoid the singularity. Based on the backstepping control technology, an adaptive neural fault tolerant control scheme is developed to ensure the boundness of all closed-loop system signals and the specified tracking error performance. Simulation studies on the medium-scale unmanned autonomous helicopter are performed to demonstrate the efficiency of the designed control strategy.

A simulation investigation of helicopter ground resonance phenomenon

PurposeThe purpose of this paper is to present a simulation method applied for investigation of helicopter ground resonance phenomenon.Design/methodology/approachThe considered physical model of helicopter standing on ground with rotating rotor consists of fuselage and main transmission gear treated as stiff bodies connected by elastic elements. The fuselage is supported on landing gear modeled by spring-damper units. The main rotor blades are treated as set of elastic axes with lumped masses distributed along blade radius. Due to Galerkin method, parameters of blades motion are assumed as a combination of bending and torsion eigen modes. A Runge–Kutta method is applied to solve equations of motions of rotor blades and helicopter fuselage.FindingsThe presented simulation method may be applied in preliminary stage of helicopter design to avoid ground resonance by proper selection of landing gear units and blade damper characteristics.Practical implicationsGround resonance may occur in form of violently increasing mutual oscillations of helicopter fuselage and lead-lag motion of rotor blades. According to changes of stiffness and damping characteristics, simulations show stable behavior or arising oscillations of helicopter. The effects of different blade balance or defect of blade damper are predicted.Originality/valueThe simulation method may help to determine the envelope of safe operation of helicopter in phase of take-off or landing. The effects of additional disturbances as results of blades pitch control as swashplate deflection are introduced.

TS Fuzzy Model-Based Controller Design for a Class of Nonlinear Systems Including Nonsmooth Functions

This paper proposes a novel robust controller design for a class of nonlinear systems including hard nonlinearity functions. The proposed approach is based on Takagi–Sugeno (TS) fuzzy modeling, nonquadratic Lyapunov function, and nonparallel distributed compensation scheme. In this paper, a novel TS modeling of the nonlinear dynamics with signum functions is proposed. This model can exactly represent the original nonlinear system with hard nonlinearity while the discontinuous signum functions are not approximated. Based on the bounded-input-bounded-output stability scheme and ${L_{1}}$ performance criterion, new robust controller design conditions in terms of linear matrix inequalities are derived. Three practical case studies, electric power steering system, a helicopter model and servo-mechanical system, are presented to demonstrate the importance of such class of nonlinear systems comprising signum function. Furthermore, to show the superiorities of the proposed approach, it is applied to these systems; and, the experimental real-time hardware-in-the-loop results are compared with the published literature with the same topic.

SOFTWARE-HARDWARE COMPLEX OF QUALIFICATION EVALUATION OF MI-171 HELICOPTER SIMULATOR

Urgency of the research. Flight safety is an actual practical issue which solving influences the future of Ukraine as a transport state. As a consequence of technical progress aviation technology is becoming more and more sophisticated and reliable. However, the intensity of the impact on a person caused by various adverse factors, including information overloads, is constantly increasing. Statistics show that up to 80% of accidents and disasters occur due to pilot errors. The reason for about 35 % of these errors is lack of professional training, and about 40% of the errors are caused by inexperience of the crew. Target setting. The cost of aircraft, crew training and the "price" of error increase simultaneously. Cost of professional training of helicopter crews on complex flight simulators is an order of magnitude lower than on real helicopters. Therefore, today the focus of increasing the safety of flights is to improve the level of flight training and flight experience via the use of flight simulators with a high level of information adequacy to a real helicopter. Actual scientific researches and issues analysis. In order to ensure the possibility of the trained crew to obtain the appropriate official documents stating their professional training level, the simulator must be certified according to national and international requirements, i.e. the adequacy of its handling qualities to the appropriate qualities of a simulated helicopter must be guaranteed. Uninvestigated parts of general matters defining. The equipment allows simulating the conduct of the helicopter in all flight modes, including critical ones: control failure, landing in the mode of main lift rotor autorotation, etc., developing practical recommendations for the flight crew, as well as to train the flight crew to find ways out of emergencies. Receiving information about the flight mode, the parameters of the onboard systems, the external environment, etc., the crew envision the information flight model. The information model of the simulator should be as similar as possible to the information model of the real helicopter. Consequently, the basic components of the simulator are the imitation systems providing the influence of the information creating the adequate picture of the flight on sense organs of the crew, including eyesight – a visualization system, flight control equipment, etc.; hearing – a system of aviation noise simulation; vestibular apparatus – a motion generation system; tactile channel – a system for loading control levers. The research objective. The listed systems form the informational model of the simulator, which should be coordinated with the movement of the helicopter. A mathematical model of the helicopter movement dynamics and the models of the mentioned systems provide this coordination. To provide the operation of the complex flight simulator, nonlinear mathematical models of helicopter dynamics based on the modified discrete vortex method have been developed. The models describe the flow of the volumetric design of the propeller apparatus and allow simulating a real-time flight in different modes, including "post-stall" condition. The statement of basic materials. The principles and approaches to the qualification evaluation of complex flight helicopter simulators in accordance with the requirements of the EU (CS-FSTD (H)) and IKAO (Doc 9625) are analyzed. The performance capabilities of a complex full-flight Mi-171 helicopter simulator created by SPA "AVIA" are described. The necessity of certification of flight simulators in compliance with international standards is substantiated. The analysis of the validation procedure is performed. The structure and functioning of the software complex designed to automate validation tests are described. Conclusions. An algorithm for obtaining a conclusion on the test result for one of the tests is presented.

Robust Control based on ADRC and DOBC for Small-Scale Helicopter

Abstract This paper introduces and compares two robust control techniques estimating disturbances for small-scale unmanned helicopters: adaptive disturbance rejection control (ADRC) and disturbance observer based control (DOBC). The six-degree-of-freedom dynamics model of the unmanned helicopter includes modeling errors and uncertainties that degrade control performance. Furthermore, the external disturbance and complex internal coupling seriously affect the control stability of the small unmanned aerial vehicle (UAV), but this is difficult to be considered in advance for controller design. For this reason, ADRC and DOBC are designed using a minimum nominal model to compensate for internal uncertainties and external disturbances. Simulation results based on slalom maneuvers show that the proposed controller successfully compensates for disturbance and provides excellent performance compared to the case of using only the PID controller. Other than to unmanned helicopters, it is applicable to most dynamic systems that can be approximated as a double integrator system.

Design and Application of a Database-Driven PID Controller based on Sparse Modeling

This paper considers a group method of data handling based PID (GMDH-PID) controller using LASSO that is one of the sparse modeling methods. A database-driven PID (DD-PID) controller is one of the effective nonlinear PID controller design methods. However, some electrical control units in industrial systems cannot implement its algorithm because the DD-PID control scheme requires a large amount of memory capacity and high-performance processor. In this paper, a GMDH-PID controller that approximately expresses the behavior of the DD-PID controller by combinations of simple nonlinear functions is proposed to solve the above problem. The proposed method employs LASSO as a coefficient calculation method of the GMDH in which some coefficients can be calculated as zero in order to avoid the influence of the multicollinearity. The usefulness of the proposed method is evaluated by an experimental result of a helicopter model.

Influence on Aerodynamic Performance of a Compound Helicopter by Wing Incidence Angle

This paper investigates the influence on aerodynamic performance of a winged compound helicopter due to change of the lift share ratio between a rotor and a wing through a numerical simulation. The lift share ratio is defined by the wing incidence angle. A compound helicopter model is constructed with the UH-60A helicopter rotor and the fuselage configuration, which is based on the JAXA scaled down model. The fuselage model combines the body with a rectangular wing of an aspect ratio of 10. Flight condition at a cruising speed corresponding to an advance ratio of 0.703 is simulated, where the rotor speed is reduced to 75% RPM. Numerical simulation results show that the aerodynamic performance degrades significantly by rotor/wing aerodynamic interaction, where a decreasing wing lift relates to a rotor thrust increase. To minimize the aerodynamic drag caused by the rotor/wing interaction, it is found that the wing should be installed at an incidence angle of the highest lift to drag ratio, and the wing area should be adjusted to satisfy the optimal rotor/wing lift ratio.

Modeling the unstable DelftaCopter vertical take-off and landing tailsitter unmanned air vehicle in hover and forward flight from flight test data

The DelftaCopter is a tilt-body tailsitter unmanned air vehicle which combines a large swashplate controlled helicopter rotor with a biplane delta-wing. Previous research has shown that the large moment of inertia of the wing and fuselage significantly interacts with the dynamics of the rotor. While this rigid rotor cylinder dynamics model has allowed initial flight testing, part of the dynamics remains unexplained. In particular, higher frequency dynamics and the forward flight dynamics were not modeled. In this work, the cylinder dynamics model is compared with the tip-path plane model, which includes the steady-state flapping dynamics of the blades. The model is then extended to include the wing and elevon dynamics during forward flight. Flight test data consisting of excitations with a large frequency content are used to identify the model parameters using grey-box modeling. Since the DelftaCopter is unstable, flight tests can only be performed while at least a rate feedback controller is active. To reduce the influence of this active controller on the identification of the dynamics, one axis is identified at a time while white noise is introduced on all other axes. The tip-path plane model is shown to be much more accurate in reproducing the high-frequency attitude dynamics of the DelftaCopter. The significant rotor–wing interaction is shown to differ greatly from what is seen in traditional helicopter models. Finally, an Linear-Quadratic Regulator (LQR) controller based on the tip-path plane model is derived and tested to validate its applicability. Modeling the attitude dynamics of the unstable DelftaCopter from flight test data has been shown to be possible even in the presence of the unavoidable baseline controller.

Trim investigation for coaxial rigid rotor helicopters using an improved aerodynamic interference model

The coaxial rigid rotor helicopter has been proposed as a future high-performance rotorcraft concept. However, the aerodynamic interference of this helicopter is complicated because it couples with the unique flapping feature of the rigid rotor, which further alters the trim characteristics of coaxial rigid rotor helicopters. Thus, a multi-point vortex ring element (MVRE) model is developed to simulate the aerodynamic interference between rotors. The method for establishing this MVRE model is illustrated, and a wind tunnel experimental dataset is used to assess its precision hover and forward flight states. Next, a flight dynamics model of the coaxial rigid rotor helicopter is built based on the MVRE aerodynamic interference model and the flapping feature of the rigid rotor. The influence of the rotor wake on the fuselage and the horizontal and vertical tails can also be calculated using this model. The trim characteristics of this helicopter are evaluated with flight test data for speeds ranging from 0 m/s to 80 m/s, and the results confirm that this model can reflect the trim characteristics with satisfactory precision. In addition, the calculation process demonstrates that the MVRE model provides a much faster computing rate. Considering the aerodynamic interference and rigid rotor characteristics, the trim results of the coaxial rigid rotor helicopter present unique features: aerodynamic interference in the coaxial rotor system not only increases the collective pitch and the collective differential but also adds a negative gradient under the forward speed in the longitudinal cyclic pitch in the low-speed forward flight range. Moreover, the rotor wake effect on the other parts of the helicopter is distinct from the corresponding effects on conventional helicopters in terms of the trim characteristics.