Helicopter Model Research Articles

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.

Experimental Verification of Lead-Lag Compensators on a Twin Rotor System

Abstract Twin rotor system is a laboratory setup resembling a simplified helicopter model that moves along both horizontal and vertical axes. The literature on control of twin rotor systems reflects a good amount of research on designing PID controllers and their extensions considering several aspects, as well as onsome nonlinear controllers. However, there is almost no previous work on design of lag-lead type compensators for twin rotor systems. In this study, by considering this open research problem, lag and lead type compensators are designed and then experimentally verified on the twin rotor system. Specifically, first, lag and lag-lag compensators are designed to obtain a reduced steady state error as compared with proportional controllers. Secondly, lead compensation is discussed to obtain a reduced overshoot. Finally, lag-lead compensators are designed to make use of their favorable properties. All compensators are applied to the twin rotor system in our laboratory. From experimental studies, it was observed that steady state error was reduced when a lag compensator was used in conjunction with a lead compensator.

A Study on Torsional Vibration Suppression Method for an Integrated Helicopter / Engine System

Abstract In order to solve the problem of torsional vibration instability of control unit in helicopter/engine system during maneuver flight, this paper has conducted the research on the integrated torsional vibration suppression of helicopter/engine system. Firstly, an integrated helicopter/engine model combined with torsional vibration is established based on the UH-60 helicopter model. Then the torsional vibration filter that is composed of a notch filter and a low-pass filter is applied to speed control loop of the engine to suppress the torsional vibration of power turbine speed. It is shown that the integrated helicopter/engine model combined with torsional vibration can simulate the torsional vibration characteristics under variable rotor speed, and both the low-order and high-order amplitudes of torsional vibration can be effectively eliminated below 0.04 % at constant rotor speed through utilizing the torsional vibration filter. Meanwhile, when the helicopter operates under variable rotor speed, the fundamental frequency of torsional vibration varies from 1.30 Hz to 2.30 Hz. However, all torsional vibration amplitudes within this frequency range can be damped less than 0.05 % through the notch filter whose bandwidth is 2.3 Hz, which proves the remarkable effect of torsional vibration suppression.

An Analysis Model of Helicopter and UAV in Overhead Powerline Inspection

With the development of unmanned aerial vehicle technology, unmanned aerial vehicles have been widely used in inspection of overhead power lines. Compared to traditional helicopters, unmanned aerial vehicles represent advantages of low cost and flexibility that unmanned aerial vehicles can cross complex terrain and security, more important pilots generally take no life risk during tasks. However, unmanned aerial vehicles are significantly limited by inefficiency, flying range and departure spot. Thus energy companies are seeking for a scheme that makes unmanned aerial vehicles and helicopter coordinate in inspection of overhead power lines. This paper presents a mathematic model to assess the performances of unmanned aerial vehicles and helicopter in inspection of overhead power lines in order to provide reference in seeking aerial vehicles coordination scheme.

Experimental Research on the Helicopter Sliding Stability after Ditching

As the application of the helicopter increases rapidly, more and more attention is paid to the safety. Thus the survivability and crashworthiness has been an important assessment items for the helicopter design and flight certification. In this paper, a newly designed ditching experiment with a helicopter model scaled 1:8 was conducted to attain the dynamic response of loads and especially the posture. Parameters such as weight, bladder pressure, lateral wind and ditching velocity were set in different groups to investigate the effect on the sliding stability. Based on the result, comparison and analysis was carried out and some conclusions were given. Meanwhile, the method and process of the experiment was presented in detail and proved an effective and available reference for the helicopter flight certification.

Propeller control strategy for coaxial compound helicopters

The coaxial compound configuration has been proposed as a concept for future high-performance rotorcraft. The co-axial rotor system does not require an anti-torque device, and a propeller provides axial thrust. A well-designed control strategy for the propeller is necessary to improve the performance and the flight dynamics characteristics. A flight dynamics model of coaxial compound helicopter is developed to analyze these influences. The performance and the flight dynamics characteristics in different propeller strategies were first investigated. The results show that there is an improvement in the performance in high-speed flight when the propeller provides more propulsive forces. It also illustrates that a reasonable allocation of the rotor and the propeller in providing thrust can further reduce the power consumption in the mid speed range. In other words, the propeller control strategy can be an effective method to improve the cruise-efficiency. The flight dynamics analysis in this paper includes trim and handling qualities. The trim results prove that the propeller strategy can affect the collective pitch, longitudinal cyclic pitch, and the pitch attitude. If the control strategy is designed only to decrease the required power, it will result in a discontinuity in the trim characteristics. Handling qualities are investigated based on the ADS-33E-PRF requirement. The result demonstrates that the bandwidth and phase delay results and eigenvalue results in various speed at different propeller strategies are all satisfied. However, some propeller control strategies lead to severe inter-axis coupling in high-speed flight. Based on these results, this paper proposes the propeller control strategy for the coaxial compound helicopter. This strategy ensures good trim characteristics and handling qualities, which satisfy the related requirements, and improves the flight range or the performance in high-speed flight.

Constrained control of helicopter vibration to reduce motion blur

PurposeThe purpose of this paper is to examine the success of constrained control on reducing motion blur which occurs as a result of helicopter vibration.Design/methodology/approachConstrained controllers are designed to reduce the motion blur on images taken by helicopter. Helicopter vibrations under tight and soft constrained controllers are modeled and added to images to show the performance of controllers on reducing blur.FindingsThe blur caused by vibration can be reduced via constrained control of helicopter.Research limitations/implicationsThe motion of camera is modeled and assumed same as the motion of helicopter. In model of exposing image, image noise is neglected, and blur is considered as the only distorting effect on image.Practical implicationsTighter constrained controllers can be implemented to take higher quality images by helicopters.Social implicationsRecently, aerial vehicles are widely used for aerial photography. Images taken by helicopters mostly suffer from motion blur. Reducing motion blur can provide users to take higher quality images by helicopters.Originality/valueHelicopter control is performed to reduce motion blur on image for the first time. A control-oriented and physic-based model of helicopter is benefited. Helicopter vibration which causes motion blur is modeled as blur kernel to see the effect of helicopter vibration on taken images. Tight and soft constrained controllers are designed and compared to denote their performance in reducing motion blur. It is proved that images taken by helicopter can be prevented from motion blur by controlling helicopter tightly.

MAKING OF HELICOPTER MODELS WITH POLYGONAL MODELING TECHNIQUES IN MABUR MOTOR GAME WITH 3D BLENDER

Currently 3D modeling has been many developed and widely applied to various fields of industry, one of the modelling techniques is a polygonal modelling technique that can be applied to games with 3D graphics. Games that are currently considered as some entertainment media can only be used as entertainment media to train agility and concentration by making it an interactive game with good visuals. The manufacture of 3D helicopter model aims to produce helicopter models that can be applied to the game Motor Mabur. From the test results of Motor Mabur game that is uploaded on the game site itch.io got the number of views 84, download 30, rating 4, collections 1, comment 10, impressions 110 and ctr 0.91 %.

Multi-Helicopter Search and Rescue Route Planning Based on Strategy Optimization Algorithm

This paper attempts to develop an efficient route planning algorithm to guide the operations of the multi-helicopter search and rescue in emergency. Route planning model of multi-helicopter cooperative search and rescue activity was established first, based on preference ordering of search and rescue objectives, as well as behavioral model of rescue helicopter and on-board detector. Given the route planning model, a multi-helicopter search and rescue route planning general algorithm was developed. The operation mechanism of ant colony algorithm was improved by introducing cooperative modes and the pheromone updating mechanism into existing methods. Furthermore, two cooperative search and rescue modes were studied: one is Overall Cooperative Search and Rescue Mode (OCSARM), in which many ants search and rescue the same region all together; the other is Blocking Cooperative Search and Rescue Mode (BCSARM), which partitions the region into small blocks and appoints helicopter with corresponding performance capabilities. Simulated experiments were developed to test the operability of proposed multi-helicopter search and rescue route planning algorithm. The comparison with existing algorithm shows that the algorithm proposed in this paper reduces computational complexity and evidently enhances algorithm efficiency. Results also indicate that this algorithm not only has the capability of comparing efficiency of two search and rescue modes in different mission requirements but also helps select search and rescue modes before rescue operation.

Helicopter interior noise reduction using compounded periodic struts

This paper characterizes the performance of a novel compounded gearbox periodic strut on controlling the noise in a helicopter cabin through modelling, simulation and experimental research. The strut exhibits low transmissibility in the specified frequency ranges, called “stop bands”. Based on a certain helicopter model, a dynamic acoustic-structure coupled system is first built by using the finite element method and the transfer matrix method. Subsequently, according to the gear mesh vibration transmission path, analyses of the vibration and noise reduction characteristics are conducted. Compared with the plain strut, attenuations of both vibration and noise in excess of 60 dB are obtained in the simulations. On a specially designed helicopter platform, experimental research is conducted simultaneously on the two aspects of fuselage vibration and cabin noise. The effectiveness of the novel strut used for helicopter cabin broadband noise reduction is demonstrated by the agreement between the simulation and experimentation results, where the attenuations of measured fuselage vibration and cabin noise exceed the levels of 40 dB and 30 dB, respectively, in the frequency range from 300 to 2000 Hz.

Performance analysis of variable speed tail rotors with Gurney flaps

Gurney Flaps (GFs) are used for improving the performance of variable speed tail rotors. A validated analytical helicopter model able to predict the main and tail rotor power is utilized. The fixed height GF has substantially small influence on the tail rotor power in hover and low to medium speed forward flight, and can obtain significant power reduction in high speed flight. This ability can be enhanced by decreasing the tail rotor speed. With the deployment of GF, the collective pitch of the tail rotor decreases, and the maximum tail rotor thrust increases. The GF can compensate the reduction of the maximum thrust by the decrease in the tail rotor speed. The GF with a height of 5% of the chord length can almost remedy 50% of the thrust reduction introduced by decreasing 10% of the tail rotor speed. With the increase of GF height, the maximum thrust generated by the tail rotor increases. The GF with larger height can cause the increase in the tail rotor power in hover and low to medium speed flight. The retractable GF can obtain more power savings than the fixed height GF. However, the benefit is substantially small even in high speed flight. Considering the side effects introduced by the active GF, the fixed height GF may be more preferable. The mechanism for the retractable GF to generate more tail rotor thrust is to increase the lift in advancing side due to the higher dynamic pressure.

An unmanned helicopter control with partial small body force compensation: Experimental results

SUMMARYA generally accepted helicopter model used for control includes the effect of Small Body Forces (SBF) which couple the vehicle's rotational subsystem inputs to its translational dynamics. SBF result from tail rotor thrust and lateral forces due to main rotor flapping. It is well-known that SBF lead to a theoretically challenging stabilization problem for the tracking error dynamics. Hence, much of the existing work has neglected SBF in order to simplify control design. We design a controller that directly compensates the influence of the tail rotor component of the SBF. The design is validated in simulation and flight tests.

Deep Convolutional Identifier for Dynamic Modeling and Adaptive Control of Unmanned Helicopter.

Helicopters are complex high-order and time-varying nonlinear systems, strongly coupling with aerodynamic forces, engine dynamics, and other phenomena. Therefore, it is a great challenge to investigate system identification for dynamic modeling and adaptive control for helicopters. In this paper, we address the system identification problem as dynamic regression and propose to represent the uncertainties and the hidden states in the system dynamic model with a deep convolutional neural network. Particularly, the parameters of the network are directly learned from the real flight data of aerobatic helicopter. Since the deep convolutional model has a good performance for describing the dynamic behavior of the hidden states and uncertainties in the flight process, the proposed identifier manifests strong robustness and high accuracy, even for untrained aerobatic maneuvers. The effectiveness of the proposed method is verified by various experiments with the real-world flight data from the Stanford Autonomous Helicopter Project. Consequently, an adaptive flight control scheme including a deep convolutional identifier and a backstepping-based controller is presented. The stability of the flight control scheme is rigorously proved by the Lyapunov theory. It reveals that the tracking errors for both the position and attitude of unmanned helicopter asymptotic converge to a small neighborhood of the origin.

Modelling and hovering control for a coaxial unmanned helicopter using sliding mode

PurposeTo facilitate the nonlinear controller design, dynamic model of a novel coaxial unmanned helicopter (UH) is established and its coupling analysis is presented.Design/methodology/approachThe chattering-free sliding mode controller (SMC) with unidirectional auxiliary surfaces (UASs) is designed and implemented for the coaxial ducted fan UH.FindingsThe coupling analysis based on the established model show severe coupling between channels. For coaxial UH’s special model structure, UAS-SMC controller is proposed to reduce the coupling characteristics between channels of the UH by setting controllers’ output calculation sequence.Originality/valueThe flight control law and control logic are successfully tested in numerical simulation and hardware in the loop (HIL) simulation. The results show best hovering performances without chattering problem, even under the bounded internal dynamics and external disturbances.

Measurement of Pressure Field on Stationary Rotary Wing Model for Further Computation of Chaff Cloud Bloom

This article describes the current situation in the area of electronic warfare. Aircraft protection can be greatly utilised not only in military but also in civilian applications. Active radar signal jamming methods are costly and therefore, aircraft protection using Chaff jamming increases efficiency, application variability and makes aircraft protection affordable. The article describes Chaff and the initial set of measurements designed for measuring aerodynamic pressure around a stationary helicopter model. This data lays foundations for the direction of further development, which is introduced at the end of the article.

Actuator Line Method Simulations for the Analysis of Wind Turbine Wakes Acting on Helicopters

In the present study the actuator line method is used to simulate the wake of a wind turbine and ways to characterize its impact on the flight of a helicopter model through the wake are evaluated. The helicopter within the simulation setup is represented by a dynamic actuator line which was implemented into the flow solver FLOWer. In order to evaluate the loads on the helicopter the thrust force distribution is compared in different areas of the wake. For further improvement of the actuator line implementation different methods to evaluate the angle of attack are compared. This was examined as the angle of attack is a highly important parameter for the actuator line and helps to optimise the accuracy and performance of the actuator line method. As there is no experimental data available and the model of the helicopter comes with distinct simplifications the loads are compared to values without the wake of the wind turbine, thus in free flight.

Wake Characterization of a Free-Flying Model Helicopter in Ground Effect

Measurements of the flow field around a free-flying model helicopter in ground effect for both quasi-steady and unsteady maneuvering flights were performed using stereoscopic particle image velocimetry (PIV). The wake features for hover and forward flight at low advance ratios were characterized and changing flow patterns like recirculation and ground flow were observed to be in good agreement with existing wind tunnel data. Parameters describing both general flow patterns and single blade tip vortices were extracted and showed significant dependence on the forward flight velocity. Landing approaches were performed and large vortical structures were observed close to the rotor disk, which contained high amounts of vorticity due to entrained blade tip vortices. The structures developing for unsteady landing approaches contained distinctly higher velocities and momentum fluxes than expected from quasi-steady conditions at the same advance ratios. For a vertical takeoff maneuver with a rapid increase of collective pitch, the bundling of blade tip vortices into a starting vortex with circulation values up to 6 times higher than for a single blade tip was observed. These results show the significance of experimental data on free-flying helicopters in unsteady maneuvering flight because the resulting flow fields cannot be predicted using steady-state experiments or simulations.

Crack Propagation Analysis of Fiber-Reinforced Composite Hollow Transmission Shaft

The main purpose of this research was to investigate crack propagation resistance of shaft. Hollow transmission composite shafts were produced and their crack behavior was investigated. Glass fiber-reinforced polyester polymer composite material is used for the hollow transmission shaft of Hidasie H260 helicopter model of Dejen Aviation Engineering Complex, DAEC. The elastic engineering constants of composite transmission shaft are determined using the Classic Laminate Theory, CLT. Linear Elastic Fracture Mechanics, LEFM was used to analyze its crack propagation by taking a through-thickness central crack. The stress at the crack tip is analyzed and it was found that the glass fiber-reinforced polyester polymer composite transmission shaft has good resistance to crack propagation. FEA method was used to crack propagation analyses. The model of shaft is generated using Finite Element Method. Due to the symmetry of the problem, only a quarter part of it is modeled and analyzed. The crack-tip region was meshed using quarter point (singular) 8-node quadrilateral elements to get accurate results and the analysis used a fit of the nodal displacements in the vicinity of the crack tip. The maximum stress is at the crack tip since there is a stress concentration at sharp edges.

Analysis of the loads acting on the rotor of a helicopter model close to an obstacle in moderate windy conditions

The present paper describes an experimental investigation of the loads acting on a rotor when it interacts with a simplified cuboid obstacle, representing a low-rise building, in moderate windy conditions. Measurements of forces and moments acting on the rotor were carried out by means of a six-component balance in order to assess the rotor performance for several helicopter positions with respect to the obstacle. Wind tunnel tests have been carried out at an advance ratio of μ=0.05 and compared with the corresponding wind-off tests. The investigation showed that ground effect on the obstacle is generally mitigated in windy conditions and that severe detrimental effects are encountered when the helicopter enters the obstacle wake, especially when the helicopter interacts with its lateral vortex structures.

Dynamic analysis of an SDOF helicopter model featuring skid landing gear and an MR damper by considering the rotor lift factor and a Bingham number

The present study addresses the performance of a skid landing gear (SLG) system of a rotorcraft impacting the ground at a vertical sink rate of up to 4.5 ms−1. The impact attitude is assumed to be level as per chapter 527 of the Airworthiness Manual of Transport Canada Civil Aviation and part 27 of the Federal Aviation Regulations of the US Federal Aviation Administration. A single degree of freedom helicopter model is investigated under different values of rotor lift factor, L. In this study, three SLG versions are evaluated: (a) standalone conventional SLG; (b) SLG equipped with a passive viscous damper; and (c) SLG incorporated a magnetorheological energy absorber (MREA). The non-dimensional solutions of the helicopter models show that the two former SLG systems suffer adaptability issues with variations in the impact velocity and the rotor lift factor. Therefore, the alternative successful choice is to employ the MREA. Two different optimum Bingham numbers for compression and rebound strokes are defined. A new chart, called the optimum Bingham number versus rotor lift factor ‘’, is introduced in this study to correlate the optimum Bingham numbers to the variation in the rotor lift factor and to provide more accessibility from the perspective of control design. The chart shows that the optimum Bingham number for the compression stroke is inversely linearly proportional to the increase in the rotor lift factor. This alleviates the impact force on the system and reduces the amount of magnetorheological yield force that would be generated. On the contrary, the optimum Bingham number for the rebound stroke is found to be directly linearly proportional to the rotor lift factor. This ensures controllable attenuation of the restoring force of the linear spring element. This idea can be exploited to generate charts for different landing attitudes and sink rates. In this article, the response of the helicopter equipped with the conventional undamped, damped, and MREA based SLG are numerically simulated using three sets of Bingham numbers. Namely, an underestimated, optimum, and overestimated Bingham number for every stroke. The simulation results depict that the only feasible solution is when the MREA generates the optimum damping force corresponding to the optimum Bingham numbers. Under this circumstance, the MREA utilizes the available energy absorption stroke to attain a soft landing. Furthermore, in the rebound stroke, the optimum damping force resettles the helicopter to its equilibrium position and prevents oscillations after the end of the rebound stroke.