Helicopter Model Research Articles

Attitude Control of Small Electric Helicopter by Using Quaternion Feedback

In this study, a nonlinear attitude controller for a small unmanned electric helicopter is designed by using quaternion feedback provided by the backstepping control method. First, a quaternion-based multi-input multi-output(MIMO) nonlinear attitude model of a small helicopter is derived. This nonlinear model consists of three parts, namely, the time derivatives of the quaternion, the Euler equation of rotation, and the flapping dynamics of the main rotor and the stabilizer bar. Next, a nonlinear MIMO controller that calculates the desired torque input by the backstepping control method is designed. The control law is modified to exclude a online computation of time derivatives of sensor output. The controller achieves the asymptotic stability of the origin of the attitude error system, and guarantees that the helicopter could track arbitrary desired attitude. Finally, a simulation and experiment are performed, and the results of this simulation and experiment show the effectiveness of the suggested nonlinear MIMO controller.

1A2-P01 4ローターヘリコプターの飛行制御に関する研究 : シミュレーションによる制御系の基礎性能検証(飛行ロボット・メカトロニクス)

This article proposes a flight trajectory control system for quadrotor helicopters. Quadrotor helicopters have a symmetrical shape with four thrust rotors and have an advantage for control over general helicopters because of the simple structure. Based on a detailed physical model of a quadrotor helicopter, a hierarchal control architecture is proposed to achieve trajectory control for three degree-of-freedom (DOF) of position and the yaw angle (1DOF) using independent four thrust forces. Simulation to evaluate flight trajectory control performance was conducted and the results showed the validity of the proposed method. Future work will be to make an experimental system and to evaluate the proposed control system by experiment.

A Nonlinear Position Controller for Maritime Operations of Rotary-wing UAVs

AbstractThis paper presents a disturbance attenuation controller for horizontal position stabilization for hover and automatic landings of a Rotary-wing Unmanned Aerial Vehicle (RUAV) operating in rough seas. Based on a helicopter model representing aerodynamics during the landing phase, a nonlinear state feedback H∞ controller is designed to achieve rapid horizontal position tracking in a gusty environment. The resultant control variables are further treated in consideration of practical constraints (flapping dynamics, servo dynamics and time lag effect) for implementation purpose. The high-fidelity closed-loop simulation using parameters of the Vario helicopter verifies performance of the proposed position controller. It 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 great performance improvement and can be applied to ship/RUAV landing systems.

EKF Based Attitude Estimation and Stabilization of a Quadrotor UAV Using Vanishing Points in Catadioptric Images

In recent years, Unmanned Air Vehicles (UAVs) have become more and more important. These vehicles are employed in many applications from military operations to civilian tasks. Under situations where global positioning system (GPS) and inertial navigation system (INS) do not function, or as an additional sensor, computer vision can be used. Having 360° view, catadioptric cameras might be very useful as they can be used as measurement units, obstacle avoidance sensors or navigation planners. Although many innovative research has been done about this camera, employment of such cameras in UAVs is very new. In this paper, we present the use of catadioptric systems in UAVs to estimate vehicle attitude using parallel lines that exist on many structures in an urban environment. After explanation of the algorithm, the UAV modeling and control will be presented. In order to increase the estimation and control speed an Extended Kalman Filter (EKF) and multi-threading are used and speeds up to 40 fps are obtained. Various simulations have been done to present the effectiveness of the estimation algorithms as well as the UAV controllers. A custom test stand has been designed to perform successful experiments on the UAV. Finally, we will present the experiments and the results of the estimation and control algorithms on a real model helicopter. EKF based attitude estimation and stabilization using catadioptric images has found to be a reliable alternative to other sensor usage.

Robust MIMO H∞ Integral-Backstepping PID Controller for Hovering Control of Unmanned Model Helicopter

The problem of stabilization of a model helicopter in a hover configuration subject to parametric uncertainty and external disturbances is addressed. Multiinput multioutput (MIMO) proportional-integral-derivative (PID) control law is reformulated into a full-state feedback control law to synthesize the controller by using robust H∞ control theory. In full-state feedback representation, PID control has implicit integral-backstepping structure. Therefore a new parameter, ρ, can be introduced that acts on the derivative of the control signal. The parameters of MIMO PID controller are then obtained with solving the algebraic Riccati equation with selecting the values of ρ and γ. Model helicopter simulation is carried out to verify the performance of the proposed controller to stabilize the uncertain helicopter model and to suppress external disturbances.

Feedback linearization of the nonlinear model of a small-scale helicopter

In order to design a nonlinear controller for small-scale autonomous helicopters, the dynamic characteristics of a model helicopter are investigated, and an integrated nonlinear model of a small-scale helicopter for hovering control is presented. It is proved that the nonlinear system of the small-scale helicopter can be transformed to a linear system using the dynamic feedback linearization technique. Finally, simulations are carried out to validate the nonlinear controller.

Acceleration-Feedback-Enhanced Robust Control of an Unmanned Helicopter

While a few proposed control strategies have shown their acceptable effectiveness, performance improvement on stability and robustness of unmanned helicopters are still imperative and a great challenge due to strong nonlinearities, extensive parameter uncertainties and external disturbances when the flight condition is terrible, such as flight on a windy day. Because acceleration feedback control is advantageous in terms of simple controller structure and easy implementation, we attempt to incorporate it into the tracking control of an unmanned helicopter that is highly nonlinear and underactuated. In this paper, we use a prefilter to formulate a new acceleration feedback control and then use it as a robust enhancement for the H(infinity) algorithm to attenuate uncertainties and external disturbances involved in the tracking control of an unmanned helicopter. We conduct simulations with an unmanned model helicopter and compare the tracking performance of the helicopter with and without acceleration feedback control. The results show that the use of acceleration feedback control does enhance tracking performance greatly compared to the standard H(infinity) control.

Intelligent predictive control of a model helicopter's yaw angle

In this paper the concept of Control Inertia is introduced and based on this concept, unexpectedly inadequate control behaviour of High Control Inertia systems is explained. Fuzzy compensators are then suggested to improve the control behaviour. This work is in the area of non-model-based control. In order to indicate the merit of the proposed technique, a neuro-predictive (NP) control is designed and implemented on a highly non-linear system, a lab helicopter, in a constrained situation. It is observed that the behaviour of the closed loop system under the NP controller either displays considerable function (with a low value of a particular design parameter) or is very slow (with high values of the same design parameter). In total, the control behaviour is very poor in comparison to existing fuzzy controllers, whereas NP is used effectively in the control of some other systems. Considering the concept of Control Inertia, a Sugeno-type fuzzy compensator was added to the control loop to modify the control command. A newly designed neuro-predictive control with fuzzy compensator (NPFC) improves the performance of the closed loop system significantly by the reduction of both overshoot and settling time. Furthermore, it is shown that the disturbance rejection of the NPFC controlled system as well as it parameter robustness is satisfactory. Copyright © 2010 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society

Nonlinear dynamic modeling and control of a small-scale helicopter

A test bench for experimental testing of the attitude control of a small-scale helicopter is constructed. A nonlinear model with 10 states is developed for this experimental setup. The unknown model parameters are estimated using the extended Kalman filter with flight test data of the helicopter operating on the test bench. In this work, it is proved that the nonlinear helicopter dynamic model may be globally feedback linearized using the dynamic feedback linearization technique. In order to satisfy multiple closed-loop performance specifications simultaneously, a controller is proposed by applying the Convex Integrated Design (CID) method to the feedback linearized model. Finally, the controller is tested in simulation demonstrating the closed-loop performance of the proposed controller.

Nonlinear adaptive aggressive control using recurrent neural networks for a small scale helicopter

This paper presents a nonlinear adaptive aggressive controller to provide the small scale helicopter with full authority of a variety of flight conditions. Adaptive backstepping technique is employed to systematically synthesize the proposed controller with the online parameter adaptation rule to the vehicle mass variations and with the recurrent neural network (RNN) approximation to the coupling effect between the force and moment controls. This single and systematic design methodology is shown to achieve the semi-global ultimate boundedness of the closed-loop helicopter dynamics and accommodate the aggressive control of flight maneuvers from hovering to trajectory tracking. The high-fidelity and well-validated nonlinear model of a small scale helicopter incorporating with unmodeled dynamics and measurement uncertainties is adopted in the numerical simulations. The performance and merits of the proposed controller are exemplified by conducting three simulation scenarios including the slalom maneuver described in the ADS33.

Nonlinear adaptive model following control for a 3-DOF tandem-rotor model helicopter

This paper considers two-input, two-output nonlinear adaptive model following control of a 3-DOF (degree-of-freedom) tandem rotor model helicopter. The control performance is studied by real time implementation of the control algorithms in an actual helicopter testbed. Since the decoupling matrix of the model helicopter is singular, the system is not decouplable by static state feedback, and it is challenging to design a feedback control system. Dynamic state feedback is applied. The controller is designed using a nonlinear structure algorithm. Furthermore, a parameter identification scheme is introduced in the closed-loop system to improve the control performance. Three identification methods are discussed.

Modeling, system identification and robust control of a coaxial micro helicopter

In this paper the design process of robust H ∞ - control for a coaxial micro helicopter is presented. The process starts with the development of a nonlinear dynamic model reflecting all the important elements of the helicopter. The corresponding system parameters are identified using measurement data from test benches and real flight, as well as a nonlinear identification tool, the Covariance Matrix Adaptation Evolution Strategy (CMA-ES). The identified and verified model is then used for the design of H ∞ - controllers for attitude and heave control, which are successfully tested in flight on the real system.

Analysis of a Swashplate Mechanism of the Hingeless Rotor Hub with the Flybar in a Model Helicopter, Part II: Dynamics

Swashplate mechanism is the steering control mechanism used in most helicopters. It is a complex multi-loop closed kinematic chain which controls the angles of attack of the main rotor blades. In most new model helicopters, this mechanism is also equipped with the bell-hiller stabilizer bar (flybar), to improve the stability. This paper aimed at the kinematic analysis of one of the latest architectures of the swashplate mechanism, used for hingeless rotor with the flybar. Hence, the position analysis of each module and whole mechanism, based on parallel manipulators concept with more details involved than other works, was presented here. The kinematic model was further developed to obtain Jacobian matrices, velocity and acceleration analysis in detail. Finally, a particular example was conducted and compared with an ADAMS rigid body dynamic model, to verify the analytical model. In many simulated cases, the results matched.

Analysis of a Swashplate Mechanism of the Hingeless Rotor Hub with the Flybar in a Model Helicopter, Part I: Kinematics

Analysis of a Swashplate Mechanism of the Hingeless Rotor Hub with the Flybar in a Model Helicopter, Part I: Kinematics

クォータニオンフィードバックによる小型電動ヘリコプタの姿勢制御(機械力学,計測,自動制御)

In this paper, we design a quaternion-based attitude controller for small electric helicopter. Firstly, we derive a MIMO(Multi-Input Multi-Output) nonlinear attitude model of a small helicopter. In this model, we adopt the quaternion for attitude expression. This model consist of three parts, the dynamics of quaternion, the Euler's equation, and the dynamics of main rotor and stabilizer. Secondly, we design a MIMO controller by using backstepping control method which is one of nonlinear control method. The asymptotic stability of the origin of error system is achieved by this controller. Simulation and experiment results show that the nonlinear controller is more effective than linear controller which was used in previous study.

Modelling a small-size unmanned helicopter using optimal estimation in the frequency domain

In this paper, a semi-decoupled state-space model of a small-size helicopter is developed for hovering conditions in order to simplify the model identification process. An enhanced identification algorithm in frequency domain is proposed and implemented to estimate the parameters in the state-space model using real flight data collected from a SERVOHELI-40 small-size unmanned helicopter. The accuracy of the identified model is verified by simulation in time domain, using a different set of hovering flight data. The results have shown the accuracy of the developed semi-decoupled model and the effectiveness of the proposed optimal estimation algorithm in frequency domain.

Laser-based trajectory tracking H2 control of autonomous rotorcraft

AbstractThis paper proposes a laser-based trajectory tracking control methodology for rotorcraft operation in environments where absolute position measurements are unavailable or unreliable. Laser-based nonlinear kinematics are formulated in three-dimensions space, and a trajectory-dependent error space is defined to express the dynamic model of the vehicle and the laser-based kinematics. A linear parameter varying (LPV) representation with piecewise affine dependence on the parameters is introduced to model the error dynamics over a set of predefined operating regions. The synthesis problem is stated as a continuous-time H2 control problem, solved using linear matrix inequalities (LMIs) and implemented within the scope of gain-scheduling control theory. The effectiveness of the proposed controller is assessed in simulation using the full nonlinear model of a small-scale helicopter.

Prediction of Helicopter H-V Zone and Cueing the Emergency Maneuver After Power Loss

Prediction of Helicopter H-V Zone and Cueing the Emergency Maneuver After Power Loss The paper presents the results of simulation method for prediction of helicopter H-V zone envelope in the case of engine power loss. Depending on the loss rate of available power, the emergency maneuver for flight continuation is calculated, or the autorotation landing is predicted. The realization of an airborne device with in-built calculating procedure and graphic presentation of H-V zone predicted limits can improve safety level of helicopter flight, and can cue the pilot to make proper decision in emergency conditions. The results of emergency maneuver simulation were verified by comparing them with flight tests of Mi-2Plus helicopter for partial power unit failure, and with records of SW-4 helicopter autorotation landing. The operation of measurement-recording module, which consists of GPS receiver, inertial measurement unit and a computer of PC-104 standard, was checked during flight tests of a radio-controlled helicopter model.

A robust guidance and control scheme of an autonomous scale helicopter in presence of wind gusts

This article deals with the problem of robust trajectory tracking for a scale model autonomous helicopter. A large class of uncertainties/disturbance is addressed, namely uncertain parameters and uniform time-varying tridimensional wind gusts occurring in the vicinity of the aircraft. Using an unknown input observer technique, it is shown that disturbances/uncertainties effects on the autonomous helicopter can be accurately reconstructed online. The analysis further extends to the design of a control law whose methodology takes the disturbance estimation procedure into account. Regarding passivity feature of the resulting model, a control law was designed using robust backstepping techniques. The approach proposed here significantly improves the performance of the control and the flight security by counteracting wind gusts in any flight phases. The framework proposed is applied to a non-linear six degree-of-freedom helicopter model. Consequently, a non-linear dynamic model of miniature helicopter is proposed, which focuses on the key effects in the dynamics of a miniature helicopter. Lyapunov stability analysis is then performed to keep the balance between robustness, short response time and large stability domain with a given security margin to guarantee obstacle avoidance during the tracking trajectory process. Simulations results are presented at the end of the article.

Modeling and System Identification of the muFly Micro Helicopter

An accurate mathematical model is indispensable for simulation and control of a micro helicopter. The nonlinear model in this work is based on the rigid body motion where all external forces and moments as well as the dynamics of the different hardware elements are discussed and derived in detail. The important model parameters are estimated, measured or identified in an identification process. While most parameters are identified from test bench measurements, the remaining ones are identified on subsystems using the linear prediction error method on real flight data. The good results allow to use the systems for the attitude and altitude controller design.