Helicopter Model Research Articles

Assessment of an unstructured mesh approach for CFD predictions of the NH90 fuselage rotor

The five year long GOAHEAD project generated a unique and extended experimental database for CFD validation. It is one of the few experimental investigations where a full model helicopter configuration with flexible rotating blades was considered. In this work, an unstructured mesh approach was adopted in order to demonstrate the potential that existing state-of-the-art, general purpose unstructured flow solvers could offer in simulating complex flow phenomena of helicopter aerodynamics. The entire NH90 helicopter model surface and the rotating blades were discretized with triangular elements. A hybrid-type field mesh was generated, where the near wall flow region was represented by triangular base prismatic element layers and the rest of the flow domain was represented by tetrahedral elements. The rotating blades were considered rigid and enclosed in a circular disc which rotated relative to the helicopter fuselage. Time accurate computations were carried out until time periodicity was achieved only then the computed solutions were in reasonable agreement with the measurements.

A Study on the Control Methods Based on 3-DOF Helicopter Model

The 3 degree of freedom (3-DOF) helicopter system is a typical higher-order times, instability, multi-variable, nonlinear and strong coupling control system. This paper presents the analysis of the mathematical model and the basic principle of PID control and fuzzy PID control, which are based on 3-DOF helicopter systems. In allusion to balance control of 3-DOF helicopter system, PID controller and fuzzy PID controller are designed respectively to control the model. The MATLAB simulation results demonstrate the control effects of both controllers achieve the requirements in this system, and fuzzy self-tuning PID shows more advantages.

A Detailed Nonlinear Dynamic Model of a 3-DOF Laboratory Helicopter for Control Design

AbstractThis work investigates the model of a 3-DOF laboratory helicopter, which constitutes a highly nonlinear system. For this model, advanced control concepts are developed and applied. In the beginning, the equations of motion are derived from a physical modeling approach. The modeling procedure yields highly nonlinear differential equations, from which linear state space systems are derived for arbitrary operating points. The major part of this work consists of the development of different linear and non-linear control architectures. At first, a classic state vector feedback controller with integration of the control error is implemented. Based on the system parameters of the linearized model, a gain scheduling approach is developed using one of the degrees of freedom as scheduling parameter. The gain scheduling application uses both discrete operating points as well as one possible continuous scheduling through interpolation. Additionally, a flatness-based feedforward controller architecture is added for transient set point changes using linear and nonlinear inverse dynamics. The control performance is validated in its dynamical and steady-state behavior. Finally, the previously derived approaches are tested on the actual helicopter.

Singular perturbation control strategy for a three-time-scale autonomous helicopter on a platform

A three-time-scale singular perturbation control law is designed for a nonlinear helicopter model in vertical flight. The proposed control law is based on time-scale decomposition, and is able to achieve the desired altitude by selecting a desired angular velocity, and the associated collective pitch angle of the blades. Numerical results for the singular perturbation control strategy, along with comparison results with the literature, are also presented for the studied nonlinear highly coupled helicopter model.

Predictive inverse simulation of helicopters in aggressive manoeuvring flight

AbstractA conventional inverse simulation does not accommodate control constraints; hence for aggressive manoeuvring flight conditions, where control inputs are close to the limits, these algorithms lose some of their applicability. A modification of the conventional inverse simulation technique that accommodates the onset of physical limits or constraints is proposed in this paper. In this way a process of constraints handling is incorporated into the inverse simulation algorithm. Therefore, the aim of this paper is to demonstrate that conventional inverse simulation can be improved in terms of the realism of the results by applying a predictive capability for applications involving manoeuvring flight. The paper gives details of the development of the predictive inverse simulation algorithm and helicopter model used and, by presenting examples of results calculated for pop-up and lateral realignment manoeuvres demonstrates that a ‘receding horizon’ predictive approach offers improvements in the realism of inverse simulation results.

Closed-form feedback controllers for set-point and trajectory tracking for the nonlinear model of quadrotor helicopters

The paper considers basic control problems in the nonlinear model of a quadrotor-type helicopter. Simple and robust output-based stabilizing controllers are presented for the attitude and the attitude/altitude subsystems. Closed-form feedback controllers have been established for solving the set-point and the trajectory tracking control problems in the considered model that accounts for the nonlinear couplings between attitude and position. The concept of flatness is applied for motion planning for the autonomous quadrotor aerial vehicle.

2A1-H09 同軸二重反転式無人ヘリコプタの運動モデルの導出と運動解析(飛行ロボット・メカトロニクス(1))

In this paper, we derive a mathematical model of a co-axial rotor unmanned helicopter, and we analyze the motion of the helicopter by using the derived model. First, we derive equations of motion of the helicopter by using velocity transformation method which is one of the multi-body dynamics modeling techniques. Forces and moments generated by the rotor are derived based on the aerodynamics of the rotor. Then, we verify the model by comparing the flight experiment data with model output. Finally, the motion analysis using the model is conducted to establish the behavior of the helicopter.

Robust fault isolation observers for non-square systems - a parametric approach

In this article, a linear matrix inequality (LMI)-based design for robust fault isolation observers (FIOs) for linear systems with arbitrary fault detectability indices is presented. A parametric design is used to achieve stable fault isolation in square systems as well as non-square systems. Based on this design, the influence of arbitrary disturbances is attenuated by a proper optimization of the observer gain matrices. The applicability of the proposed design is verified in simulations of a helicopter model.

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.

Control and Identification of Helicopter

A number of student laboratory tasks on control of a small electrical helicopter are presented. The equipment includes three testbeds for detail study of three angular velocities and angle control. Theory of a helicopter modelling and identification approach are supplied. The full system has been implemented.

Non-linear position control for hover and automatic landing of unmanned aerial vehicles

This study presents a disturbance attenuation controller for horizontal position stabilisation for hover and automatic landings of a rotary-wing unmanned aerial vehicle (RUAV) operating close to the landing deck in rough seas. Based on a helicopter model representing aerodynamics during the landing phase, a non-linear state feedback ℋ∞ controller is designed to achieve rapid horizontal position tracking in a gusty environment. Practical constraints including flapping dynamics, servo dynamics and time lag effect are considered. A high-fidelity closed-loop simulation using parameters of the Vario XLC gas-turbine helicopter verifies performance of the proposed horizontal position controller. The proposed controller not only increases the disturbance attenuation capability of the RUAV, but also enables rapid position response when gusts occur. Comparative studies show that the ℋ∞ controller exhibits performance improvement and can be applied to ship/RUAV landing systems.

705 3自由度モデルヘリコプタに対するサンプル値モデルにもとづく制御系の一設計方法(制御1)

705 3自由度モデルヘリコプタに対するサンプル値モデルにもとづく制御系の一設計方法(制御1)

CIFER®를 이용한 무인 헬리콥터의 동특성 분석 (II) - 주파수 응답 해석 -

The aerial application using an unmanned helicopter has been already utilized and an attitude controller would be developed to enhance the operational convenience and safety of the operator. For a preliminary study of designing flight controller, a state space model for an RC helicopter would be identified. Frequency sweep flight tests were performed and time history data were acquired in the previous study. In this study, frequency response of the flight test data of a small unmanned helicopter was analyzed by using the CIFER software. The time history flight data consisted of three replications each for collective pitch, aileron, elevator and rudder sweep inputs. A total of 36 frequency responses were obtained for the four control stick inputs and nine outputs including linear velocities and accelerations and angular velocities in 3-axis. The results showed coherence values higher than 0.6 for every primary control inputs and corresponding on-axis outputs for the frequency range from 0.07 to 4 Hz. Also the analysis of conditioned frequency response showed its effectiveness in evaluating cross coupling effects. Based on the results, the dynamic characteristics of the model helicopter can further be analyzed in terms of transfer functions and the undamped natural frequency and damping ratio of each critical mode.

Application of Results of Experimental Identification in Control of Laboratory Helicopter Model

This article deals with experimental identification and control of laboratory helicopter model CE 150 manufactured by company Humusoft. Structure of the identified system was approximated by linear black-box models. Discrete Input/Output Auto-Regressive Moving Average model with eXternal input (ARMAX) and its state space equivalent were used. Parameters of the models were estimated by regression techniques using System Identification Toolbox for Matlab. Acquired models were validated using simulations, residual analysis and real-time control. Input/output data necessary for identification were obtained by measurements from laboratory model and were processed using Real-Time Toolbox for Matlab. Based on acquired mathematical models input/output and state space controllers were designed (input/output pole placement with integration, state space pole placement with integration and observer). Designed controllers were implemented in Matlab environment using the Real Time Toolbox and their performance was verified by real-time control of the helicopter model.

A Dynamic Model for a Single Helicopter in the Low Airspace with Telegraph Poles and Electrical Wire

In this paper, we propose a dynamic model for a single helicopter in the low airspace with telegraph poles and electrical wire. The numerical results show that the proposed model can qualitatively describe the helicopter's velocity, safe distances, and safe sphere when it runs across the obstacle consisting of telegraph poles and electrical wire.

Helicopter Type and Accident Severity in Helicopter Emergency Medical Services Missions

Whereas accident rates and fatal accident rates for Helicopter Emergency Medical Services (HEMS) were investigated sufficiently, resulting consequences for the occupants remain largely unknown. The present study aimed to classify HEMS accidents in Germany to prognosticate accident severity with regard to the helicopter model used. German HEMS accidents (1 Sept. 1970-31 Dec. 2009) were gathered as previously reported. Accidents were categorized in relation to the most severe injury, i.e., (1) no; (2) slight; (3) severe; and (4) fatal injuries. Only helicopter models with at least five accidents were analyzed to retrieve representative data. Prognostication was estimated by the relative percentage of each injury type compared to the total number of accidents. The model BO105 was most often involved in accidents (38 of 99), followed by BK117 and UH-1D. OfN = 99 accidents analyzed, N = 63 were without any injuries (63.6%), N = 8 resulted in minor injuries of the occupants (8.1%), and N = 9 in major injuries (9.1%). Additionally, N = 19 fatal accidents (19.2%) were registered. EC135 and BK1 17 had the highest incidence of uninjured occupants (100% vs. 88.2%) and the lowest percentage of fatal injuries (0% vs. 5.9%; all P > 0.05). Most fatal accidents occurred with the models UH-1D, Bell 212, and Bell 412. Use of the helicopter models EC135 and BK117 resulted in a high percentage of uninjured occupants. In contrast, the fatality rate was highest for the models Bell UH-I D, Bell 222, and Bell 412. Data from the present study allow for estimating accident risk in HEMS missions and prognosticating resulting fatalities, respectively.

Modeling and Simulation of Helicopter Cabin Electromagnetic Environment

Electromagnetic environment (EME) in helicopter cabin is one of the most important indexes for electromagnetic compatibility (EMC) on airborne platform. The simulation results were not accurate enough because of the difficulties in accurately modeling and the large computation. Due to the inaccuracy of the former modeling method which used the typical geometric, the professional software ICEMCFD/AI*Environment (AIE) was employed to restore the helicopter’s original model, based on the obtain of the accurate helicopter model, the Multi-layer Fast Multipole Method (MLFMM) and Combined Field Integral Equation (CFIE) were employed to analyze the variation of the electric field in the helicopter cabin versus the frequency and other factors with a VHF antenna mounted on the helicopter. Both accuracy and computing speed were concerned, the results have some guidance significance to the EMC preliminary design on airborne platform.

Explicit non-linear model predictive control for autonomous helicopters

Trajectory tracking is a basic function required for autonomous helicopters, but it also poses challenges to control design due to the complexity of helicopter dynamics. This article introduces an explicit model predictive control (MPC) to solve this problem, which inherits the advantages of non-linear MPC but eliminates time-consuming online optimization. The explicit solution to the non-linear MPC problem is derived using Taylor expansion and exploiting the helicopter model. With the explicit MPC solution, the control signals can be calculated instantaneously to respond to the fast dynamics of helicopters and suppress disturbances immediately. On the other hand, the online optimization process can be removed from the MPC framework, which can accelerate the software development and simplify onboard hardware. Due to these advantages of the proposed method, the overall control framework has a low complexity and high reliability, and it is easy to deploy on small-scale helicopters. The proposed explicit non-linear MPC has been successfully validated in simulations and in actual flight tests using a Trex-250 small-scale helicopter.

Neuroevolutionary reinforcement learning for generalized control of simulated helicopters.

This article presents an extended case study in the application of neuroevolution to generalized simulated helicopter hovering, an important challenge problem for reinforcement learning. While neuroevolution is well suited to coping with the domain’s complex transition dynamics and high-dimensional state and action spaces, the need to explore efficiently and learn on-line poses unusual challenges. We propose and evaluate several methods for three increasingly challenging variations of the task, including the method that won first place in the 2008 Reinforcement Learning Competition. The results demonstrate that (1) neuroevolution can be effective for complex on-line reinforcement learning tasks such as generalized helicopter hovering, (2) neuroevolution excels at finding effective helicopter hovering policies but not at learning helicopter models, (3) due to the difficulty of learning reliable models, model-based approaches to helicopter hovering are feasible only when domain expertise is available to aid the design of a suitable model representation and (4) recent advances in efficient resampling can enable neuroevolution to tackle more aggressively generalized reinforcement learning tasks.

Improved digital tracking controller design for pilot-scale unmanned helicopter

In this paper, methods for improved design of digital tracking controller for a pilot-scale unmanned helicopter are considered. By discretizing the linearized helicopter model, the linear quadratic with integral (LQI) capability is investigated and applied in order to develop an efficient tracking system including a state-feedback plus integral action. The helicopter velocities are used to formulate a prescribed position reference tracking trajectory. When both process and measurement noises are present, a Kalman filter (KF) is combined with the LQI to form a linear quadratic Gaussian with integral (LQGI) tracking system. Simulation studies illuminate both the capability of the controller design and the accuracy of the estimator. Next, H 2, H ∞ and mixed H 2 / H ∞ controls are designed and the results between methods are produced and compared.