Helicopter Model Research Articles

Adaptive neural tracking control for uncertain nonlinear systems with input and output constraints using disturbance observer

This paper investigates the tracking control problem for a class of strict-feedback nonlinear uncertain systems in the presence of unknown disturbance, input and output constraints. By using backstepping approach, an adaptive tracking controller is developed on the basis of neural network and disturbance observer. The Nussbaum function is introduced to tackle the problem of the nonlinear term arising from the input saturation, and the barrier Lyapunov function is employed to prevent the outputs from violating the constraints. The disturbance observer is developed to estimate unknown external disturbances. The proposed control scheme can guarantee that all signals of the closed-loop system are bounded by using the Lyapunov analysis method. Finally, the simulation results for three degrees of freedom (3-DOF) model helicopter are given to illustrate the effectiveness of the developed control scheme.

Deterministic learning enhanced neutral network control of unmanned helicopter

In this article, a neural network–based tracking controller is developed for an unmanned helicopter system with guaranteed global stability in the presence of uncertain system dynamics. Due to the coupling and modeling uncertainties of the helicopter systems, neutral networks approximation techniques are employed to compensate the unknown dynamics of each subsystem. In order to extend the semiglobal stability achieved by conventional neural control to global stability, a switching mechanism is also integrated into the control design, such that the resulted neural controller is always valid without any concern on either initial conditions or range of state variables. In addition, deterministic learning is applied to the neutral network learning control, such that the adaptive neutral networks are able to store the learned knowledge that could be reused to construct neutral network controller with improved control performance. Simulation studies are carried out on a helicopter model to illustrate the effectiveness of the proposed control design.

Adaptive Neuro-Fuzzy Black-Box Modeling Based on Instrumental Variable Evolving Algorithm

In this paper, an online identification algorithm for instrumental variable-based evolving neuro-fuzzy modeling applied to dynamic systems in noisy environment is proposed. The adopted methodology is based on neuro-fuzzy inference system with Takagi–Sugeno evolving structure, which employs an adaptive distance norm based on the maximum likelihood criterion with instrumental variable recursive parameter estimation. The application and performance analysis of the proposed algorithm is based on black-box modeling of a 2DOF Helicopter with errors in variables.

On determining the acoustic properties of main helicopter rotor models on an open test bench

The paper presents the results of experimental studies on developing a technique to determine the acoustic properties of models of main helicopter rotors on an open test bench. The method of maximum length sequences is used to choose the optimum arrangement of microphones for an open test bench that would minimize the influence of parasitic echo. The results of processing the data of an acoustic experiment with a model rotor are detailed.

Main helicopter rotor trimming using computational fluid dynamics method in forward flight

In this paper, a computational fluid dynamics trimming method is proposed and compared with wind tunnel experiment and the blade element method. The NASA’s generic ROBIN helicopter model is adopted for transient simulations to obtain the final main rotor trimming conditions. Totally three steps were applied to the computational fluid dynamics method. The first step is associated with no cyclic pitch motion, the second is regarding pure longitudinal cyclic pitch motion and the last is concerning with pure lateral cyclic pitch motion. At the same time, a simple linear equation system between the roll and pitching moment was established to get the final longitudinal and lateral cyclic pitch angles for the main rotor through the above three steps. An overset grid approach was used where the volume around each blade was modeled in an individual overset grid region. The rotor rotation was resolved with three degrees per time-step. Turbulence was modeled with the well-known SST K-omega model with second-order convection. The helicopter was in straight forward flight with an advance ratio of [Formula: see text]. Three sources of stick angles, which are also called rotor trimming angles, were shown and compared with each other. And the corresponding results were also plotted with a type of history plot in the computational fluid dynamics condition. In the simulations, the results became quasi periodic after about 1.5 rotations and four rotor rotations were simulated for each case. The pitch moment coefficient and roll moment coefficient were all trimmed to about zero by the computational fluid dynamics trimming method while moments were not removed thoroughly in the other two source conditions.

Hovering stability of a model helicopter

Purpose The purpose of this paper is to investigate the stability of a small scale six-degree-of-freedom nonlinear helicopter model at translator velocities and angular displacements while it is transiting to hover with different initial conditions. Design/methodology/approach In this study, model predictive controller and linear quadratic regulator are designed and compared within each other for the stabilization of the open loop unstable nonlinear helicopter model. Findings This study shows that the helicopter is able to reach to the desired target with good robustness, low control effort and small steady-state error under disturbances such as parameter uncertainties, mistuned controller. Originality/value The purpose of using model predictive control for three axes of the autopilot is to decrease the control effort and to make the close-loop system insensitive against modeling uncertainties.

A System Identification Strategy for Nonlinear Model of Small-Scale Unmanned Helicopters

A System Identification Strategy for Nonlinear Model of Small-Scale Unmanned Helicopters

Composite model of a research flight simulator for a helicopter with the hingeless main rotor

This paper presents a composite model of a flight simulator. This simulator is intended for carrying out investigative tests of flight dynamics imitation models of a hingeless rotor helicopter. A schematic diagram, composition and operation channels of the flight simulator software are presented. A possibility of applying the control lag is estimated.

Measuring model of helicopter’s hovering stabilization parameters against point objects

Обґрунтовано модель вимірів параметрів стабілізації висіння гелікоптера відносно точкових об’єктів, яка вимагає меншого обсягу обчислень і зберігає високу швидкість і точність стабілізації. Досліджено можливість скорочення векторів стану та вимірювань за рахунок використання розширеного фільтра Калмана та штатних вимірювачів

Robust control of small-scale unmanned helicopter with matched and mismatched disturbances

In this paper, a novel robust control method for small-scale unmanned helicopter with matched and mismatched disturbances is investigated. The control objective is to make the helicopter track the predefined position and yaw angle reference trajectories. First, the helicopter model is linearized with approximate feedback linearization technique. Then, by using the estimation of the mismatched disturbances and their derivatives, the helicopter system is reconstructed to an equivalent system, where the mismatched disturbances are turned into the major matched component and minor mismatched component. These disturbances are suppressed by feedforward technique and H∞ feedback control algorithm. Finally, simulation results demonstrate the effectiveness and robustness of the proposed control strategy for small-scale unmanned helicopter in the presence of both matched and mismatched disturbances. The proposed novel robust control method can attenuate the mismatched disturbances from the state variables of the reconstructed system.

Adaptive backstepping trajectory tracking controller for a miniature helicopter

SummaryAn adaptive backstepping controller is proposed to achieve the asymptotically stable trajectory tracking for a miniature helicopter. The helicopter model is firstly decomposed into a cascaded structure between the position and attitude loops with unmodeled dynamics. The backstepping technique is applied to exploit this cascaded structure and to streamline the controller design procedure. Hyperbolic tangent functions, instead of traditional sign functions, are adopted to complete adaptive algorithms for adjusting the upper bounds of the unmodeled dynamics. Further, the controller introduces an auxiliary dynamic system to ensure the thrust constraint and to obviate singularity during the command attitude extraction. The stability analysis demonstrates that, the asymptotical stability of the auxiliary dynamic system warrants the asymptotically stable tracking of the miniature helicopter system. Simulations verify the theoretical results and analyze the tracking performance. Copyright © 2016 John Wiley & Sons, Ltd.

Helicopter nonlinear aerodynamics modelling using VehicleSim

This work describes a model developed to analyze the aerodynamic loads on a helicopter model on conventional configuration implemented with VehicleSim, a multibody software specialized in modelling mechanical systems composed by rigid bodies. The rotors are articulated and the main rotor implementation takes into account flap, lag and feather degrees of freedom for each of the equispaced blades as well as their dynamic couplings. This article presents an aerodynamic model that allows to simulate hover, climb, descent and forward flight as well as trajectories under the action of several aerodynamics loads. The aerodynamic model has been built up using blade element theory. All the dynamics, aerodynamic forces and control action are embedded in a single code, being this an advantage as the compilation time is greatly reduced. The software used in this work, VehicleSim does not need external connection to other software. This new tool may be used to develop robust control methods. The nonlinear equations of the system which can be very complex, are obtained, in particular, this article presents the equations for flap and lag degrees of freedom in hover flight. The control approach used in here consists of PID controllers (proportional, integral, derivative), which allow to use VehicleSim command exclusively to simulate several helicopter flight conditions. The results obtained are shown to agree with the expected behaviour.

Assessment of Helicopter Model Accuracy Through Inverse Simulation

The paper deals with the assessment of the reliability of simplified rotorcraft models in the evaluation of maneuvering potential using inverse simulation. Inverse solutions obtained for the same maneuver from models of different complexity and fidelity are compared with the objective of identifying the most appropriate model for a consistent evaluation of vehicle handling qualities at the minimum computational cost. A total of nine rotor blade models, three main rotor inflow models, and two fuselage aerodynamic databases are combined for deriving 10 different helicopter simulation models analyzed in five maneuvers. Inverse solutions are obtained by means of an integration method for hurdle-hop, slalom, and lateral repositioning maneuvers. Once the maneuvers are solved for the baseline rotorcraft model, the uncertainty associated with the command law identified by means of simpler models is determined. The quantitative evaluation of model reliability from a set of simulation tests is further analyzed on a pop-up-pop-down maneuver and a 180 deg fast turn for validating the approach. The results show that uncertainty intervals are correctly identified, although with some degree of conservativeness when less demanding maneuvers are dealt with.

Distributed Atmospheric Turbulence Model for Helicopter Flight Simulation and Handling-Quality Analysis

A distributed atmospheric turbulence model is developed for helicopter flight simulation. The impacts of different aerodynamic surfaces on handling qualities with helicopter in turbulence are analyzed. Both helicopter flight dynamic model and turbulence model are validated against the flight test data, which shows that the proposed model improves the accuracy of the simulation of rotor blade element turbulence model on the vertical axis within the interested frequency range for handling-quality analysis. A quantitative index is developed to study the impact of turbulence on helicopter handling qualities by analyzing the effects of different aerodynamic surfaces on helicopter response to turbulence. The results show that the main rotor has the dominant effects on both the heave and roll handling qualities, the airframe has the primary effect on the pitch handling quality, and the tail rotor has an important effect on the yaw handling quality. Furthermore, the impacts of the main rotor in turbulence on the helicopter handling qualities of roll, pitch, and yaw increase with the forward speed at lower speeds but decrease at higher speeds. The increment trend with the forward speed of the airframe’s impacts on the pitch and yaw handling qualities reduces at higher speeds.

Singularity-free backstepping controller for model helicopters

This paper develops a backstepping controller for model helicopters to achieve trajectory tracking without singularity, which occurs in the attitude representation when the roll or pitch reaches ±π2. Based on a simplified model with unmodeled dynamics, backstepping technique is introduced to exploit the controller and hyperbolic tangent functions are utilized to compensate the unmodeled dynamics. Firstly, a position loop controller is designed for the position tracking, where an auxiliary dynamic system with suitable parameters is introduced to warrant the singularity-free requirement for the extracted command attitude. Then, a novel attitude loop controller is proposed to obviate singularity. It is demonstrated that, based on the established criteria for selecting controller parameters and desired trajectories, the proposed controller realizes the singularity-free trajectory tracking of the model helicopter. Simulations confirm the theoretical results.

Review, Design, Optimization and Stability Analysis of Fractional-Order PID Controller

This paper will establish the importance and significance of studying the fractional-order control of nonlinear dynamical systems. The foundation and the sources related to this research scope is going to be set. Then, the paper incorporates a brief overview on how this study is performed and p resent the organization of this study. The present work investigates the effectiveness of the physical-fractional and biological-genetic operators to develop an Optimal Form of Fract ional-order PID Controller (O2Fo-PIDC). The newly developed Fo-PIDC with optimal structure and parameters can, also, imp rove the performances required in the modeling and control of modern manufacturing-industrial process (MIP). The synthesis methodology of the proposed O2Fo-PIDC can be viewed as a mu l ti -level design approach. The hierarchical Multiobject ive genetic algorith m (M GA ), adopted in this work, can be visualized as a comb ination of structural and parametric genes of a controller orchestrated in a h ierarch ical fashion. Then, it is applied to select an optimal structure and knowledge base of the developed fractional controller to satisfy the various design specification contradictories (simplicity, accuracy, stability and robustness). Index Terms—Optimal fractional-order controllers, BIBO stability analysis, Multiobjective genetic algorith m, CE150 Helicopter model.

Wind-tunnel tests of a heavy-class helicopter optimised for drag reduction

ABSTRACTWind-tunnel tests of a heavy-class helicopter model were carried out to evaluate the effectiveness of several components optimised for drag reduction by computational fluid dynamics analysis. The optimised components included different hub-cap configurations, a fairing for blade attachments and the sponsons. Moreover, the effects of vortex generators positioned on the back ramp were investigated. The optimisation effect was evaluated by comparison of the drag measurements carried out for both the original and the optimised helicopter configurations. The comprehensive experimental campaign involved the use of different measurement techniques. Indeed, pressure measurements and stereo particle image velocimetry surveys were performed to achieve a physical insight about the results of load measurements. The test activity confirms the achievement of an overall reduction of about 6% of the original model drag at cruise attitude.

Numerical investigation of the aerodynamic and acoustical properties of a shrouded rotor

The problem of shrouded rotor rotation is numerically solved basing on the Navier–Stokes equations in a noninertial coordinate system. The configuration considered is a model helicopter tail rotor.The calculations are performed using edge-based reconstruction (EBR) schemes on unstructured tetrahedral grids with the variables determined at gridpoints. The numerical results on the aerodynamic forces and the acoustic radiation intensity and direction in the far field are presented and analyzed.

Hybrid controller design and simulation for a small-size autonomous helicopter

Purpose – During flight, a small-size autonomous helicopter will suffer external disturbance that is wind gust. Moreover, the small-size helicopter can carries limited payload or battery. Therefore control system of an autonomous helicopter should be able to eliminate external disturbance and optimize energy consumption. The purpose of this paper is to propose a hybrid controller structure to control a small-size autonomous helicopter capable to eliminate external disturbance and optimize energy consumption. The proposed control strategy comprise of two components, a linear component to stabilize the nominal linear system and a discontinuous component to guarantee the robustness. An integral control is included in the system to eliminate steady state error and tracking reference input. Design/methodology/approach – This research started with derived mathematic model of the small-size helicopter that will be controlled. Based on the obtained mathematic model, then design of a hybrid controller to control the autonomous helicopter. The hybrid controller was designed based on optimal controller and sliding mode controller. The optimal controller as main controller is used to stabilize the nominal linear system and a discontinuous component based on sliding mode controller to guarantee the robustness. Findings – Performance of the proposed controller was tested in simulation. The hybrid controller performance was compared with optimal controller performance. The hybrid controller has better performance compared with optimal controller. Results of the simulation shows that the proposed controller has good performance and robust against external disturbances. The proposed controller has better performance in rise time, settling time and overshoot compared with optimal controller response both for step input response and tracking capability. Originality/value – Hybrid controller to control small-size helicopter has not reported yet. In this research new hybrid controller structure for a small size autonomous helicopter was proposed.

A Scalable Parallel PWTD-Accelerated SIE Solver for Analyzing Transient Scattering From Electrically Large Objects

A scalable parallel plane-wave time-domain (PWTD) algorithm for efficient and accurate analysis of transient scattering from electrically large objects is presented. The algorithm produces scalable communication patterns on very large numbers of processors by leveraging two mechanisms: 1) a hierarchical parallelization strategy to evenly distribute the computation and memory loads at all levels of the PWTD tree among processors and 2) a novel asynchronous communication scheme to reduce the cost and memory requirement of the communications between the processors. The efficiency and accuracy of the algorithm are demonstrated through its applications to the analysis of transient scattering from a perfect electrically conducting (PEC) sphere with a diameter of 70 wavelengths and a PEC square plate with a dimension of 160 wavelengths. Furthermore, the proposed algorithm is used to analyze transient fields scattered from realistic airplane and helicopter models under high frequency excitation.