Helicopter Maneuvers Research Articles

Investigation of Energy-Maneuverability Methods for Helicopter Performance Assessments

Energy-maneuverability diagrams are an important tool that operational pilots use to understand helicopter maneuver performance through excess available power across a wide range of conditions. These representations are based upon a number of assumptions that have not been rigorously investigated for helicopter applications. The present work reports the results of an investigation into the theory and application of helicopter maneuverability through simulation and flight test. The computational portion of the work focused on a systematic investigation into some of the key simplifying assumptions that are commonly applied in the creation of energy-maneuverability diagrams using two rotor wake aerodynamic modeling methods. The flight test portion of the work provided important operational context for understanding the practical application of the simulation results. The study illustrated that the fundamental assumption employed in estimating maneuver power requirements for energy-maneuverability representations appears to be reasonable in conditions of the greatest practical relevance; however, another key assumption that is invoked to convert excess power into climb performance would likely lead to overestimating the vehicle capability in important operational conditions. Additionally, the flight test data demonstrated that, at high angles of bank, energy-maneuverability results should be considered for trending information rather than for detailed climb performance values.

An Improved Feedforward-Robust Algorithm for Active Vibration Control of Helicopter Maneuver Flight

To solve the problem of secondary path mutation and external disturbance abrupt changes during helicopter maneuver flight, the previous research proposed a hybrid active vibration control law. To improve the engineering applicability, the original algorithm is ameliorated to the least mean square-input-output-based robust (LMS-IOBR) algorithm. The system model within the target frequency band can be identified through the input-output data to avoid constructing complex state observers. In addition, the output form of the feedback controller is constructed by an autoregressive moving average model with extra input, which is beneficial to improve operational efficiency. Numerical simulations demonstrate that compared with the original algorithm, controller real-time computation can be reduced by 52% with control effects guaranteed at the same time. Furthermore, to verify the effectiveness and adaptability of LMS-IOBR, multi-input multioutput vibration control experiments are carried out on a specially developed simple platform for simulating helicopter maneuver states. Comparative tests in various typical states are performed between the LMS-IOBR and the multichannel least mean square algorithm. Under the complex circumstances of simulating continuous subduction uplift, the peak response of closed-loop system attenuates by 80% and 70%, and the vibration of two points is reduced to 15% and 20%, respectively, within 3 s. The experimental results demonstrate that the proposed LMS-IOBR algorithm shows stronger transient adaptability and robustness against external disturbance excitation and secondary channel mutation in helicopter maneuver flight.

Vibroacoustic Helicopter Impact on Elevated Helipad

Abstract A helicopter landing and taking off on an elevated helipad is a source of noise that affects the environment and causes vibrations of the landing pad or the building infrastructure. Vibrations are also excited by the air stream flowing through the main rotor and transferred to the landing pad by contact of the helicopter chassis. Vibrations are transferred to the building through the structure of the helipad. Depending on the damping properties of the structure and the vibro-isolating elements used, vibrations can be felt in rooms used by people and also transmitted to devices located in the building. The subject of the study described in this paper is the vibroacoustic effects of an EC-135 helicopter on an elevated landing pad during landing, standstill with the propulsion system engaged and take-off. Measurements of vibrations and noise were made at points located both on the landing pad and in the building. The paper presents selected results of measurements in various phases of flight and helicopter manoeuvres. The frequency analyses of the fragment of the measurement data for the flight phase, in which the highest levels of impact were recorded, were also performed and included. The results are presented as graphs and annotated.

Helicopter Rotor Ground Effect and Frigate Interaction Investigated by Particle Image Velocimetry

Helicopter maneuvers on frigates develop an essential role during military operations. However, the complex flow generated by the frigate bluff-body shapes and the interaction with the helicopter downwash during the recovery process must be studied in detail. In addition, the ground effect can also affect helicopter performance during the maneuver. This study aims to use particle image velocimetry in wind tunnel to analyze the airflow generated by a 1:100-scaled helicopter rotor of the Sea King SH-3 navy helicopter isolated and with the presence of a full and a partial ground to consider the ground effect at different heights. Once the rotor has been studied, experimental tests were carried out of the rotor working next to a frigate model during the recovery maneuver. The measured velocity indicates that the flow asymmetry below the rotor can increase with the proximity to a partial ground distance up to 1.39 times. During the study of the rotor for the frigate landing approach, the downwash asymmetry is also important and changes abruptly the tendency during the last phase of the maneuver. It can lead to dangerous instabilities and problems for the helicopter pilot during the hovering over ships.

Portable Biosensors for Psychophysiological Stress Monitoring of a Helicopter Crew.

This study aims to analyze the psychophysiological stress response of a helicopter crew using portable biosensors, and to analyze the psychophysiological stress response differences of experienced and non-experienced crew members. We analyzed 27 participants (33.89 ± 5.93 years) divided into two different flight maneuvers: a crane rescue maneuver: 15 participants (three control and 12 military) and a low-altitude maneuver: 12 participants (five control and seven military). Anxiety, rating of perceived exertion, subjective perception of stress, heart rate, blood oxygen saturation, skin temperature, blood lactate, cortical arousal, autonomic modulation, leg and hand strength, leg flexibility, spirometry, urine, and short-term memory were analyzed before and after both helicopter flight maneuvers. The maneuvers produced a significant increase in stress and effort perception, state of anxiety, and sympathetic modulation, as well as a significant decrease in heart rate, blood oxygen saturation, leg and inspiratory muscle strength, and urine proteins. The use of biosensors showed how a crane rescue and low-altitude helicopter maneuvers produced an anticipatory anxiety response, showing an increased sympathetic autonomic modulation prior to the maneuvers, which was maintained during the maneuvers in both experienced and non-experienced participants. The crane rescue maneuver produced a higher maximal heart rate and decreased pulmonary capacity and strength than the low-altitude maneuver. The psychophysiological stress response was higher in the experienced than in non-experienced participants, but both presented an anticipatory stress response before the maneuver.

Investigations of the vortex ring state on a helicopter main rotor using the URANS solver

PurposeThis paper aims to present the novel methodology of computational simulation of a helicopter flight, developed especially to investigate the vortex ring state (VRS) – a dangerous phenomenon that may occur in helicopter vertical or steep descent. Therefore, the methodology has to enable modelling of fast manoeuvres of a helicopter such as the entrance in and safe escape from the VRS. The additional purpose of the paper is to discuss the results of conducted simulations of such manoeuvres.Design/methodology/approachThe developed methodology joins several methods of computational fluid dynamics and flight dynamic. The approach consists of calculation of aerodynamic forces acting on rotorcraft, by solution of the unsteady Reynold-averaged Navier–Stokes (URANS) equations using the finite volume method. In parallel, the equations of motion of the helicopter and the fluid–structure-interaction equations are solved. To reduce computational costs, the flow effects caused by rotating blades are modelled using a simplified approach based on the virtual blade model.FindingsThe developed methodology of computational simulation of fast manoeuvres of a helicopter may be a valuable and reliable tool, useful when investigating the VRS. The presented results of conducted simulations of helicopter manoeuvres qualitatively comply with both the results of known experimental studies and flight tests.Research limitations/implicationsThe continuation of the presented research will primarily include quantitative validation of the developed methodology, with respect to well-documented flight tests of real helicopters.Practical implicationsThe VRS is a very dangerous phenomenon that usually causes a sudden decrease of rotor thrust, an increase of the descent rate, deterioration of manoeuvrability and deficit of power. Because of this, it is difficult and risky to test the VRS during the real flight tests. Therefore, the reliable computer simulations performed using the developed methodology can significantly contribute to increase helicopter flight safety.Originality/valueThe paper presents the innovative and original methodology for simulating fast helicopter manoeuvres, distinguished by the original approach to flight control as well as the fact that the aerodynamic forces acting on the rotorcraft are calculated during the simulation based on the solution of URANS equations.

Modelling of Helicopter Main Rotor Aerodynamic Loads in Manoeuvres

Abstract The article discusses the method of modelling of the helicopter main rotor aerodynamic loads during steady state flight and manoeuvres. The ability to determine these loads was created by taking into account the motion of each blade relative to the hinges and was a result of the applied method of aerodynamic loads calculating. The first part of the work discusses the basic relationships that were used to build the mathematical model of helicopter flight. The focus was also on the method of calculating of the aerodynamic forces generated by the rotor blades. The results of simulations dedicated to the “jump to hover” manoeuvre were discussed, showing the possibilities of analysing aerodynamic loads occurring in unsteady flights. The main rotor is considered separately in an “autonomous” way and treated as a source of averaged forces and moments transferred to the hub. The motion of individual blades is neglected, and their aerodynamic characteristics are radically simplified. The motion of individual blades is neglected, and their aerodynamic characteristics are radically simplified. This can lead to significant errors when attempting to model dynamic helicopter manoeuvres. The more complex model of helicopter dynamics is discussed.

A Comparison of Helicopter Main Rotor Features Due to Stiffness of Rotor Blade-Hub Connection

Abstract The paper presents results of simulation calculations concerning an influence of stiffness of blade-hub connection on rotor loads and blades deflections in hover, level flight and pull up maneuver. The three versions of rotor are considered with articulated, elastic and stiff connections of blades and hub. The blades with the same distributions of stiffness, mass and the same aerodynamic characteristics are applied for all rotor cases. The rotor loads are calculated applying Runge-Kutta method to solve the equations of motion of deformable blades. According to the Galerkin method, the parameters of blades motion are treated as combination of considered blade bending and torsion eigen modes. The results of calculations indicate for possibility to generate the greater rotor control moments and to improve helicopter maneuverability in the case of applying the non-changed blade of articulated rotor combined with elastic rotor hub.

A turboshaft engine NMPC scheme for helicopter autorotation recovery maneuver

Fast response for turboshaft engine plays an important role in shaping sound helicopter maneuver ability during some typical violent maneuvers like autorotation power recovery. An engine NMPC (nonlinear model predictive control), integrated with flight predictive information, is proposed to obtains better engine response speed and reduces the rotor transient droop during autorotation power recovery. The on-board nonlinear predictive model consists of two parts: one is “load” model – a main rotor torque model, the other is a turboshaft engine model. A suitable objective function is specified for the NMPC algorithm, being related to the deviation between the torque provided by the power turbine and that demanded by helicopter. The smaller torque deviation when its clutch being connected is, the less main rotor speed droop is. Finally, comparison simulations with a popular H2/H∞ robust control are demonstrated. It shows that by using the NMPC control law proposed here, the main rotor speed droop is only 0.36% with respect to reference speed, whereas it is 2.3% when using the robust control. Moreover, the designed control law is able to shorten the stable time a lot during the process, as the stable time is about 5 s when employing the new scheme, while it is about 20 s for the robust control.

A general method for closed-loop inverse simulation of helicopter maneuver flight

Maneuverability is a key factor to determine whether a helicopter could finish certain flight missions successfully or not. Inverse simulation is commonly used to calculate the pilot controls of a helicopter to complete a certain kind of maneuver flight and to assess its maneuverability. A general method for inverse simulation of maneuver flight for helicopters with the flight control system online is developed in this paper. A general mathematical describing function is established to provide mathematical descriptions of different kinds of maneuvers. A comprehensive control solver based on the optimal linear quadratic regulator theory is developed to calculate the pilot controls of different maneuvers. The coupling problem between pilot controls and flight control system outputs is well solved by taking the flight control system model into the control solver. Inverse simulation of three different kinds of maneuvers with different agility requirements defined in the ADS-33E-PRF is implemented based on the developed method for a UH-60 helicopter. The results show that the method developed in this paper can solve the closed-loop inverse simulation problem of helicopter maneuver flight with high reliability as well as efficiency.

Inverse Simulation of a Full-Scale Helicopter Using Finite Difference Technique

Inverse simulation is a computational method that determines the control inputs required for a dynamic system to achieve a desired output. In case of helicopter dynamics, inverse simulation is used to obtain the pilot control inputs required for the helicopter to accomplish a desired maneuver. Complex configuration of helicopter makes its model inversion is significantly more difficult than fixed wing aircrafts. In this paper, a general method, used to define any helicopter maneuver in earth axes system, is introduced. An algorithm, for solving the helicopter inverse simulation problem at a given maneuver by using the differentiation approach, is presented. This method is based on converting the model nonlinear differential equations to algebraic difference equations which can be solved at each time step by an iterative scheme. The accuracy of this technique is improved by increasing the order of the finite difference scheme and decreasing the time step. The verification of the inverse simulation results is achieved by supplying the resultant control inputs to the direct simulation code and the helicopter flies in the desired maneuver.

미래전에서 헬기전력 주도의 기동전 연구

The United States Army has a vicrory which is has a Gulf War and Iraq War. What is the a victory reason about Gulf War and Iraq War? I thought about that a case study solve to a victory of Gulf War and Iraq War. That is a with a armored unit, a mechanized unit and rotary wing unit maneuver warfare. So I can begin a study on Future Maneuver Warfare and a Application to Rotary Wing Maneuver Warfare. A maneuver warfare is the maneuver has a decisive war to the victory or`` fail. That is not fight with the enemy``s equipment and personnel. But has a advantage of maneuver to decisive battle situation about the enemy direction. The maneuver has a decisive strike which is has a advantage area than the enemy has a advantage area. Also the maneuver could has a deep battle area. The reason has a about ``psychological or mental paralysis achievement``. Therefore maneuver warfare is very important. Also the scientific technique and weapon system is developed to the precision guided missle. And rotary wing weapon system``s speed and ability is better than any weapon system before. So rotary wing have been to the rotary wing revolution in 1980``s. The rotary wing can over front line to the enemy rear area than armored and mechanized unit. In the Middle East War, Gulf War and Iraq War the rotary wing weapons have to victory which is the maneuver go to rear in Iraq. Now the precision guided missle``s development and the urbanization is limited armored unit and mechanized unit to the maneuver. Therefore in the future war the rotary wing weapon which is will cary out important role and function than armored unit and mechanized unit. Also Helicopter maneuver could will be the multidimensional high speed maneuver warfare with armored and mechanized unit in the future war.

Simulation of helicopter boundary maneuvers of obstacle avoidance with predicted control funcion

Simulation of helicopter boundary maneuvers of obstacle avoidance with predicted control funcion

State-Space Rotor Aeroelastic Modeling for Real-Time Helicopter Flight Simulation

This paper introduces a new approach for the identification of linear state-space models of dynamical systems of arbitrary complexity. The identification procedure is described and applied for modeling aeroelastic response of helicopter main rotors. With the aim of developing a tool that might be conveniently applied for real-time simulations of helicopter flight dynamics, the state-space model considered is a reduced-order description of loads transmitted to the airframe due to hub motion and blade pitch controls. In order to validate the proposed approach, loads from the state-space, reduced-order model are compared with those predicted by the complete full-state, nonlinear rotor model for prescribed helicopter maneuvers.

Helicopter Maneuver Flight Simulation and Control Law Design

This paper presents a solution to helicopter maneuver flight simulation according to ADS33 flying qualities requirement standard. Associated with aerodynamics and control law design methodology, the proposed scheme achieved satisfactory control performance by analyzing helicopter attitude and control parameter variation law at certain operating condition. To level flight acceleration, method based on force and moment balance is analyzed. To pirouette maneuver, a segment linear approximated trajectory is developed for attitude and velocity stability. All objective function is based on minimizing position error and attitude error. For a single rotor four bladed model helicopter in pirouette maneuver, experimental results certified its efficiency.

Robust Nonlinear Controls of Model-Scale Helicopters Under Lateral and Vertical Wind Gusts

A helicopter maneuvers naturally in an environment where the execution of the task can easily be affected by atmospheric turbulence, which leads to variations of its model parameters. This paper discusses the nature of the disturbances acting on the helicopter and proposes an approach to counter the effects. The disturbance consists of vertical and lateral wind gusts. A 7-degrees-of-freedom (DOF) nonlinear Lagrangian model with unknown disturbances is used. The model presents quite interesting control challenges due to nonlinearities, aerodynamic forces, under actuation, and its non-minimum phase dynamics. Two approaches of robust control are compared via simulations with a Tiny CP3 helicopter model: an approximate feedback linearization and an active disturbance rejection control using the approximate feedback linearization procedure. Several simulations show that adding an observer can compensate the effect of disturbances. The proposed controller has been tested in a real-time application to control the yaw angular displacement of a Tiny CP3 mini-helicopter mounted on an experiment platform.

A TMO‐based flight program of an unmanned helicopter

– The purpose of this paper is to introduce a new danger‐aware Operational Flight Program (OFP) for the unmanned helicopter's auto‐navigation based on the well‐known time‐triggered message‐triggered object (TMO) model., – In this design with the TMO, the danger‐awareness means two things. First, an unmanned helicopter maneuvers on safe altitudes to avoid buildings or mountains when navigating to the target position. It is assumed that minimum safe altitudes are given on evenly spaced grids and on the center points of every four adjacent grids. A three‐dimensional (3D) path‐finding algorithm using this safe‐altitude information is proposed. Second, a helicopter automatically avoids a zone with very high temperature caused by a fire., – Since the auto‐flight control system requires componentized real‐time processing of sensors and controllers, the TMO model that has periodic and sporadic threads as members, has been used in designing the OFP. It has been found that using the TMO scheme is a way to construct a very flexible, well‐componentized and timeliness‐guaranteed OFP., – As the RTOS, RT‐eCos has been used. It was developed a few years ago based on the eCos3.0 to support the real‐time thread model of the TMO scheme. To verify this navigation system, a hardware‐in‐the‐loop simulation (HILS) system also has been developed., – Designing an OFP by using the real‐time object model TMO and the proposed 3D safe path finding algorithm is a whole new effective deadline‐based approach. And the developed OFP can be used intensively in the phase of disaster response and recovery.

Finding Optimal Controls for Helicopter Maneuvers Using the Direct Multiple-Shooting Method

The purpose of this paper deals with direct multiple-shooting method (DMS) to resolve helicopter maneuver problems of helicopters. The maneuver problem is transformed into nonlinear problems and solved DMS technique. The DMS method is easy in handling constraints and it has large convergence radius compared to other strategies. When parameterized with piecewise constant controls, the problems become most effectively tractable because the search direction is easily estimated by solving the structured Karush-Kuhn-Tucker (KKT) system. However, generally the computation of function, gradients and Hessian matrices has considerably time-consuming for complex system such as helicopter. This study focused on the approximation of the KKT system using the matrix exponential and its integrals. The propose method is validated by solving optimal control problems for the linear system where the KKT system is exactly expressed with the matrix exponential and its integrals. The trajectory tracking problem of various maneuvers like bob up, sidestep near hovering flight speed and hurdle hop, slalom, transient turn, acceleration and deceleration are analyzed to investigate the effects of algorithmic details. The results show the matrix exponential approach to compute gradients and the Hessian matrix is most efficient among the implemented methods when combined with the mixed time integration method for the system dynamics. The analyses with the proposed method show good convergence and capability of tracking the prescribed trajectory. Therefore, it can be used to solve critical areas of helicopter flight dynamic problems.

Investigation of helicopter maneuverability by the power balance method

The algorithms for calculating available overloads and maneuvers are presented. Nesterov’s loop maneuver is analyzed.

Numerical simulation of helicopter maneuverability in aerobatics research

A method for calculating available overloads and for subsequent evaluation of helicopter maneuverability is proposed taking into account specific operational conditions.