Helicopter Model Research Articles

Fault‐tolerant attitude tracking control of tandem rotor helicopter considering internal actuator saturation and external wind gust

SummaryTandem rotor helicopter is configured with two main rotors distributed along the longitudinal direction and without anti‐torque tail rotor. Therefore, the control strategy of tandem rotor helicopter can be quite different from that of traditional helicopter systems. In this article, a fault‐tolerant attitude tracking controller is presented for tandem rotor helicopter, with considerations of external wind disturbance and internal actuator problem. First, attitude control oriented dynamic model of the tandem rotor helicopter is constructed, in which both actuator fault and saturation are involved. Base on statistical characteristics of practical wind condition as well as aerodynamic properties of the helicopter rotors, a detailed wind load model is further established. Then, a fault‐tolerant attitude tracking controller is proposed for the tandem rotor helicopter system by incorporating nonsingular terminal sliding mode control with an adaptive super twisting algorithm, which allows a simultaneous regulation of the three angular motions via two propeller rotors. Finally, based on Quanser's 3‐dof helicopter system, comparative simulation tests are performed to demonstrate the effectiveness as well as advantages of the proposed fault‐tolerant controller design.

Small unmanned helicopter modeling method based on a hybrid kernel function PSO-LSSVM

Small unmanned helicopter modeling method based on a hybrid kernel function PSO-LSSVM

Flight data-driven intelligent prediction for fuselage vibration of helicopter

PurposeHelicopter fuselage vibration prediction is important to keep a safety and comfortable flight process. The helicopter vibration mechanism model is difficult to meet of demand for accurate vibration prediction. Thus, the purpose of this paper is to develop an intelligent algorithm for accurate helicopter fuselage vibration analysis.Design/methodology/approachIn this research, a novel weighted variational mode decomposition (VMD)- extreme gradient boosting (xgboost) helicopter fuselage vibration prediction model is proposed. The vibration data is decomposed and reconstructed by the signal clustering results. The vibration response is predicted by xgboost algorithm based on the reconstructed data. The information transfer order between the controllable flight data and flight attitude are analyzed.FindingsThe mean absolute percentage error (MAPE), root mean square error (RMSE) and mean absolute error (MAE) of the proposed weighted VMD-xgboost model are decreased by 6.8%, 31.5% and 32.8% compared with xgboost model. The established weighted VMD-xgboost model has the highest prediction accuracy with the lowest mean MAPE, RMSE and MAE of 4.54%, 0.0162, and 0.0131, respectively. The attitude of horizontal tail and cycle pitch are the key factors to vibration.Originality/valueA novel weighted VMD-xgboost intelligent prediction methods is proposed. The prediction effect of xgboost model is highly improved by using the signal-weighted reconstruction technique. In addition, the data set used is collected from actual helicopter flight process.

Stealth performance evaluation of helicopter against airborne early warning radar considering trimming control

Airborne pulse Doppler radar is a key threat to the military helicopter, and assessing the stealth performance of helicopter against airborne early warning radar is helpful to the helicopter’s stealth design and operational planning. In this paper, the Shooting and Bouncing Ray (SBR) and Uniform Theory of Diffraction (UTD) based high-frequency algorithms are used to calculate the Radar Cross Section (RCS) of helicopter, and the radar range equations are used to evaluate the stealth performance. In order to account for the effects of rotor flapping motions during actual flight, the aerodynamics model of whole helicopter is established and the attitudes and controls of helicopter at different flight states are trimmed and input into the RCS calculation module. The effects of helicopter flight speed, flying direction and operational environment on radar stealth performance are studied in focus. It is demonstrated by the results that the trimming control does have a great influence of more than 5 dB on the RCS of helicopter, and the introduction of the trim calculation brings the helicopter’s returns calculation closer to the reality. Variations in flight speed lead to the changes in the stealth performance of helicopter against Early Warning Aircraft (EWA), and the helicopter flight speed can be planned according to the operational requirements to minimize exposure distance or exposure time. Variations in flying direction mainly affect the detection properties of helicopter returns, and flying in the same direction with EWA usually gives the helicopter better low-observability than flying head-on. Variations in operational environment mainly affect the radar detection performance and the sensitivity of the detection performance to external factors; the same amount of change in some external factor causes a different amount of change in the helicopter’s detectability in different environments.

Numerical Analysis of Glauert Inflow Formula for Single-Rotor Helicopter in Steady-Level Flight below Stall-Flutter Limit

This article addresses the numerical computation problem of induced inflow ratio based on the helicopter momentum theory in forward flight. The Glauert inflow formula (equation) is a nonlinear equation usually solved by the Newton–Raphson method in a relatively small number of iterations. However, many high-order convergence multipoint iterative methods have been developed over the last decade. The study examines several selected methods in terms of finding ones that provide a solution in only one iteration with acceptable accuracy. Furthermore, the influence of initial guesses on the accuracy of the obtained solutions has been investigated. In this regard, the practical range of parameters of the Glauert inflow equation for helicopters in forward flight is roughly determined by simplified modeling of a power and stall-flutter limitation. For these purposes, a basic low-fidelity longitudinal trim model of a single-rotor helicopter in steady-level flight is modified and numerically solved by a symbolic transformation of a system of 20+ nonlinear equations into a single nonlinear equation.

Sliding-mode observer–based active fault-tolerance control for a two-degree-of-freedom helicopter system with sensor faults

In this paper, an active fault-tolerance controller is proposed for a two-degree-of-freedom (2-DOF) helicopter model with different types of sensor faults. The proposed controller is designed by combining an interval type-2 fuzzy logic control approach with a sliding-mode control technique. In addition, the controller is compensated by a sliding-mode observer used to estimate faults in real-time. For the proposed control scheme, the overall stability of the closed-loop system is proven using the Lyapunov stability theory. Finally, numerical simulations and experiments verify that the proposed scheme achieves superior control performance in the case of sensor failure.

On shift selection for Krylov subspace based model order reduction

Mechanical systems are often modeled with the multibody system method or the finite element method and numerically described with systems of differential equations. Increasing demands on detail and the resulting high complexity of these systems make the use of model order reduction inevitable. Frequently, moment matching based on Krylov subspaces is used for the reduction. There, the transfer functions of the full system and of the reduced system are matched at distinct frequency shifts. The selection of these shifts, however, is not trivial. In this contribution we suggest an algorithm that evaluates an increasing number of shifts iteratively until a reduced model that approximates the full model in a subspace with very low approximation error is found. Thereafter, the projection matrix that spans this subspace is decomposed with singular value decomposition and only most important directions are retained. In this way, small reduced models with good approximation properties that do not exceed a predefined error bound can be found or low-error models for a given reduced order can be generated. The evaluation of more shifts than necessary and further reduction by means of singular value decomposition is the novelty of this contribution. In this paper, this novel approach is extensively studied and, furthermore, applied to the numerical example of an industrial helicopter model.

Use of the WASPAS Method to Select Suitable Helicopters for Aerial Activity Carried Out by the Military Police of the State of Rio de Janeiro

Using a multi-criteria decision support method (WASPAS) to analyze and rank alternatives, this article proposes a method to assist in the selection of helicopter models that are the most suitable for police air activity in the State of Rio de Janeiro. A robust technical basis for defining the essential requirements of an aircraft is established, and solutions that can ensure the effective and safe execution of missions are indicated. Helicopter models were evaluated by considering predefined criteria, and the weights of these criteria were attributed using a questionnaire that was administered to pilots and aerostatic operators of Public Air Units (UAP) in several states of the federation. As a result of the evaluation of the 15 helicopter models used by police services in the State of Rio de Janeiro, the modeling with the WASPAS method ranked the Sikorsky UH-60 (Black Hawk) model in first place, the Leonardo AW 139 model in second place, and the Bell 412 model in third place. Based on the available data, we suggest that a comparative study integrating the Entropy and CRITIC methods be conducted to measure the weights of the criteria associated with the application of other multi-criteria techniques, such as COMET, MACAB, SPOTIS, VIKOR, SAPEVO, and PROMETHEE.

Aerodynamic Interaction between a Rotor and a Wing on Compound Helicopter in Forward Flights

This paper investigates the influence on aerodynamic performance of the rotor/winged-body configuration due to change of advance ratio and the lift share ratio between a rotor and a wing through numerical simulations. A computational model of compound helicopter is constructed with a main rotor of UH-60A helicopter and a winged-body configuration where the fuselage is designed by JAXA and the wing is rectangular. Flight conditions at various cruising speed corresponding to an advance ratio of 0.1 to 0.7 is simulated. As a result, the flow around the wing is deflected in a direction of decreasing angle of attack. This trend becomes stronger as the advance ratio decreases. The lift share of the rotor increases between 0.05 and 0.08 at the advance ratio of 0.1 to 0.7. The total effective drag coefficient increases due to the aerodynamic interaction, the increase of the rotor effective drag coefficient is greater than that of the winged-body. The drag coefficient of the wing of the winged-body becomes negative at the advance ratio of 0.1 and 0.15. The rotor effective drag coefficient and the winged-body drag coefficient increase significantly at high advance ratio. Therefore, the total effective lift-to-drag ratio decreases as the advance ratio increases, and it decreases by 18% at the advance ratio of 0.7. In addition, the advance ratio of the maximum total lift-drag ratio is smaller than that designed without aerodynamic interaction between the rotor and wing-body.

Robust Control Based on a Time-varying UDE for an Under-actuated 3-DOF Helicopter

The UDE (uncertainty and disturbance estimator) based control approach has received increasing attention in recent years due to its simplicity and effectiveness to attenuate the influence of uncertainties and disturbances. Despite this fact, the trade-off issue of its steady-state performance and transient performance has not been addressed explicitly. A novel time-varying UDE (TV-UDE) is proposed to resolve the trade-off issue in this paper. The main idea behind the design is to use a differential equation with a time-varying parameter, rather than a transfer function, to represent the underlying filtering relationship. By changing the UDE gain smoothly, the performance limitations of a fixed-gain UDE are avoided. Moreover, the TV-UDE is reduced to a classic UDE when its parameter value is finally frozen. Two design specifications are provided to guide the design of the time-varying parameter. We then apply this design to the angular trajectory tracking problem of a 3-DOF helicopter model, and reveal the four time-scales property of the closed-loop dynamics. The advantages of the proposed approach are shown by simulation comparisons.

OPTIMAL ALLOCATION OF FLEET OF HELICOPTERS AND AIRPORTS TO TRANSPORT PASSENGERS IN OFFSHORE MARITIME UNITS

The choice and distribution of the optimal fleet mix of helicopters to service the offshore air operation is an important logistical problem that has a potential to reduce costs considered in the oil and gas industry. The variability of helicopter models and sizes, as well as the possible operational restrictions of airport bases and airspace, requires that adequate numerical techniques of Operational Research are applied. In this context, this work develops a model to determine the trajectories and distances traveled between airport bases and offshore maritime units and vice-versa, through an airspace modeled by a directed graph. Also develop a helicopter performance model to obtain the estimated payload and flight times for each specified mission and last but not least an integer linear programming model to allocate an optimal fleet and airport mix for passenger transport through the use of different helicopter sizes. The model was applied to offshore units operating in the Santos basin due to their strategic importance in the oil and gas industry. The results obtained included a map of preferred regions for two different helicopter sizes (large and medium), the weekly flight tables showing the allocation of helicopters and airport for different demand scenarios, additionally the impact of fuel prices on different airport bases and the concentration of movements on air routes are also evaluated in order to complement the analysis.

Stealthy replay attack detection of 3-DOF helicopter benchmark system using dynamic watermarking approach

Cyber security for unmanned systems has drawn tremendous research attention in recent years owing to its priority in ensuring system performance and safety. This paper presents a dynamic watermarking-based active detection approach for unmanned helicopter system under stealthy replay attacks. First, the dynamic model of the 3-DOF helicopter and the replay attack model are constructed, respectively. Statistical analysis is conducted using Kalman filter residuals to interpret the concealment of stealthy replay attacks for a system under intrusion. Then, as traditional chi-square detector is unable to detect stealthy replay attacks, an active detector by incorporating dynamic watermarking with the chi-square detector is explored. Finally, by conducting simulations of the detection procedures under different test scenarios comparatively using traditional chi-square detector and the proposed approach, the effectiveness and merits of the watermarking approach is verified sufficiently. The watermarking-based approach is promising in comprehensive detections against stealthy replay attacks for enhancing system security.

Analysis of the influence of wave parameters on helicopter floating characteristics

Foreign countries have accumulated rich experience in the research of helicopter floating characteristics. From the model test in the 1950s to the current numerical simulation and extrapolation evaluation, its technical maturity is significantly higher than that in domestic related fields. In order to fully study the influence of wave parameters on helicopter floating characteristics, sort out and refine the model test methods suitable for the study of helicopter floating characteristics, this paper takes a helicopter model as the research object, and carries out the research on the helicopter model test technology with emergency buoys, focusing on the influence range of wave parameters and wave direction on helicopter test results. The results show that the motion response of the helicopter under regular wave conditions presents typical periodic changes. When the helicopter encounters the influence of transverse wave, the rolling amplitude decreases with the increase of wavelength, and the acceleration amplitude of the nose and in the aircraft first increases and then decreases with the increase of wavelength; Under other wave direction conditions, the rolling angle, the acceleration amplitude of the nose and in the machine first increase and then decrease with the increase of the wavelength.

Co-design Optimization of a Novel Multi-identity Drone Helicopter (MICOPTER).

Delivery drones have always faced challenges when it comes to reliably deliver packages. This paper introduces a novel concept of a hybrid drone called “MICOPTER” to alleviate this issue. Being able to fly in three modes of aircraft, helicopter, and gyrocopter, the proposed model of the multi-identity helicopter comprises a 2DOF tilting mechanism of rotors and a folding wing system leading to better performance and controllability. To scrutinize the idea, MICOPTER is compared to other types of Unmanned Aerial Vehicles (UAVs) in terms of different performance parameters. The performance goal of the MICOPTER is the realization of a predetermined standard delivery drone mission based on Amazon Prime Air. According to the relevant literature, the corresponding conceptual design equations are formulated and the traditional matching diagram method is utilized to attain the initial design point. Afterward, a multidisciplinary-feasible design matrix is provided as well as multi-objective optimization to strive for optimal feasible configurations while maximizing cruise velocity and range. Furthermore, the configuration and performance of some of the feasible design points on the final Pareto frontier are compared with the traditional design. Finally, by simulating a typical flight profile and using robust non-linear backstepping control, the controllability of the proposed configuration is investigated. The controller performance is assessed considering its stability and tracking 8-shape trajectory. Results indicate the MICOPTER capabilities as a novel configuration in both terms of design performance and controllability.

Modeling and Robust Tracking Decoupling Control of a Coaxial Unmanned Helicopter Based on the Improved Alternating Direction Method of Multipliers.

In this paper, a robust tracking control strategy based on the dynamic feedback linearization method is proposed for the nonlinear and highly coupled dynamic characteristics of coaxial unmanned helicopter. The mathematical model of the coaxial unmanned helicopter is determined by fault analysis. Then the high-order state system is dynamically feedback linearized by extending the state variables, and the dynamic characteristics of the zeros are analyzed according to the expected tracking characteristics of the inner loop. The pole placement of the subsystem realizes robust monitoring of height and position commands by designing robust compensators. On this basis, an outer loop proportional derivative controller is designed for the horizontal positioning subsystem to realize position tracking. Loop tracking simulation ensures the good separation characteristics of feedback linearization method, and trajectory tracking simulation under fault conditions ensures the control ability and durability of the designed controller.

Aerodynamic Modeling and Performance Analysis of Variable-Speed Coaxial Helicopter

In this paper, the variable-speed coaxial helicopter is modelled by the blade element method, non-uniform inflow method and empirical function method, and the aerodynamic performance analysis method is proposed. To ensure the accuracy of this method, a flight test of the verification aircraft has been performed, and the rotor speed and required power under different forward flight speeds have been obtained. By comparing the experimental results with the calculation results, it is ascertained that the rotor speed trim error of this method is less than 6%, and the required power calculation error is less than 5%, which demonstrates the accuracy of this method. Finally, when the rotor diameter, hovering collective pitch and hovering rotor speed are equal, the required power of variable-speed coaxial helicopter and variable collective-pitch coaxial helicopter is compared through this method. The comparison results show that the variable-speed coaxial helicopter has low required power when it is less than the forward flight speed corresponding to the hovering rotor speed. When the forward speed is higher than that corresponding to the hovering rotor speed, the variable-pitch coaxial helicopter has lower required power.

Simulation study on fire extinguishing system of ultra-fine powder extinguishing agent in helicopter engine compartment

The design of the engine compartment fire extinguishing system determines the release, flow and dispersion characteristics of the ultra-fine powder extinguishing agent (UPEA), which affects its effectiveness. The simulation of the UPEA fire extinguishing system in the engine compartment of a helicopter model was carried out, and the results of the study showed that, the maximum mass flow of UPEA particles at the nozzle of the fire extinguishing system pipe was 5.2 kg/s, and the injection time was 0.31s. At the same inlet air temperature in the engine compartment, the smaller the inlet air flow, the longer the engine compartment UPEA concentration maintenance time. At the same inlet flow, the higher the inlet air temperature, the shorter the duration of UPEA concentration in the engine compartment. The duration of the lowest extinguishing agent concentration was 0.70s at an inlet air temperature of 121°C and an inlet air flow of 0.423kg/s. Under different inlet air flow and temperature conditions, the UPEA concentration at all 12 monitor points in the engine compartment was maintained for more than 0.5s, meeting the design requirements. The research results have guiding significance for fire extinguishing system design of certain helicopters.

A Fault Detection Method Based on Embedded Feature Extraction and SVM Classification for UAV Motors

In this study, a lightweight method has been proposed for the early detection of faults in UAV motors. To test our method, balance, magnet, propeller, and bearing failure have been created in 820KV UAV motors. UAVs can have single or multi motors. Therefore, helicopter, duocopter, tricopter, and quadcopter models have been created. Sounds have been collected by installing healthy and faulty motors on these models. Sound datasets consisting of five classes have been obtained for four cases (helicopter, duocopter, tricopter, and quadcopter models). Feature extraction has been performed on the collected sound signals using Mel-frequency Cepstral Coefficients (MFCC) method. Support Vector Machines (SVM) are used to perform fault classification on selected features. In the proposed method, 100% accuracy has been computed for helicopter and duocopter models. In the tricopter and quadcopter models, 99.06% and 90.53% accuracy have been calculated, respectively. Since the proposed method is based on sound, it can detect many types of faults. In addition, since our method is lightweight, it is in an architecture that can work in real-time in embedded systems.

Sampled-Data Based Fault-Tolerant Control Design for Uncertain CE151 Helicopter System with Random Delays: Takagi-Sugeno Fuzzy Approach

This study inspects the issue of robust reliable sampled data control (SDC) for a class of Takagi-Sugeno (TS) fuzzy CE151 Helicopter systems with time-varying delays and linear fractional uncertainties. Specifically, both the variation range and the distribution probability of the time delay are considered in the control input. The essential aspect of the suggested results in this study is that the time variable delay in the control input is dependent not only on the bound but also on the distribution probability of the time delay. The prime intent of this study is to enhance a state feedback reliable sampled-data controller. By constructing an appropriate Lyapunov-Krasovskii functional (LKF) and employing a linear matrix inequalities (LMIs) approach, a new set of delay-dependent necessary conditions is obtained to ensure the asymptotic stabilisation of a TS fuzzy CE151 Helicopter system with a prescribed mixed H∞ and passivity (MH∞P) performance index. The acquired results are expressed as LMIs, which are easily addressed using standard optimization algorithms. In addition, an exemplary scenario based on the CE151 helicopter model is presented to demonstrate the less conservative nature of the obtained results as well as the application of the recommended unique design approaches.

A fuzzy adaptive controller design for integrated guidance and control of a nonlinear model helicopter

A fuzzy adaptive controller design for integrated guidance and control of a nonlinear model helicopter