Tandem Rotor Helicopter Research Articles

The fountain flow signature around a generic tandem-rotor helicopter hovering near the ground

The fountain flow signature around a generic tandem-rotor helicopter hovering near the ground

State estimation based actuator fault detection for tandem rotor helicopter with experimental validation

Timely fault detection is essential to flight safety of tandem rotor helicopter. In this paper, a fault detection method is proposed based on state estimation and the deviation between the measured value and the estimated value. Firstly, a polyhedral linear parameter varying (LPV) model is established to solve the nonlinear coupling problem of the helicopter in different moving directions. Then, to obtain actuator fault information, a robust state observer is developed to generate the residual. Meanwhile, a mixed [Formula: see text] algorithm is designed to calculate observer gain by configuring performance parameters, which makes the residuals both sensitive to actuator faults and robust to external disturbances. Furthermore, a dynamic threshold method is introduced to evaluate the residual signal for actuator fault detection. Finally, based on the 3-dof helicopter platform, the effectiveness of the proposed method is verified through comparative simulation and experimental tests.

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.

Cascaded Model Predictive Control of a Tandem-Rotor Helicopter

This letter considers cascaded model predictive control (MPC) as a computationally lightweight method for controlling a tandem-rotor helicopter. A traditional single MPC structure is split into separate outer and inner-loops. The outer-loop MPC uses an SE2(3) error to linearize the translational dynamics about a reference trajectory. The inner-loop MPC uses the optimal angular velocity sequence of the outer-loop MPC to linearize the rotational dynamics. The outer-loop MPC is run at a slower rate than the inner-loop allowing for longer prediction time and improved performance. Monte-Carlo simulations demonstrate robustness to model uncertainty and environmental disturbances. The proposed control structure is benchmarked against a single MPC algorithm where it shows significant improvements in position and velocity tracking while using significantly less computational resources.

Model Predictive Control of a Tandem-Rotor Helicopter With a Nonuniformly Spaced Prediction Horizon

This paper considers model predictive control of a tandem-rotor helicopter. The error is formulated using the matrix Lie group SE2(3). A reference trajectory to a target is calculated using a quartic guidance law, leveraging the differentially flat properties of the system, and refined using a finite-horizon linear quadratic regulator. The nonlinear system is linearized about the reference trajectory enabling the formulation of a quadratic program with control input, attitude keep-in zone, and attitude error constraints. A non-uniformly spaced prediction horizon is leveraged to capture the multi-timescale dynamics while keeping the problem size tractable. Monte-Carlo simulations demonstrate robustness of the proposed control structure to initial conditions, model uncertainty, and environmental disturbances.

Feedback-linearization based robust relatively optimal trajectory tracking controller for 3-DOF helicopter

This paper proposes a feedback linearization-based robust trajectory tracking controller for the elevation and pitch axes of three degrees of freedom (3-DOF) helicopter. The 3-DOF helicopter is a benchmark system that operates on the same principle of operation as that of a tandem-rotor helicopter. Accurate control of this laboratory set up in the presence of external disturbances is a sophisticated problem as it is easily affected by external disturbances due to its low weight. Hence, to ensure efficient trajectory tracking performance in the presence of uncertainties and disturbances a nonlinear disturbance observer is integrated with a feedback linearization (FL) based relatively optimal trajectory tracking controller (ROTTC). Feedback linearization of the nonlinear model results in a decoupled linear error dynamics for each axis, which is used for the design of the ROTTC. The stability of the 3-DOF helicopter in the presence of estimation error and parameter uncertainties is analyzed using the Lyapunov method. A comparison study with an FL-based robust linear quadratic regulator (RLQR) method illustrates the superiority of the proposed method in terms of tracking error and disturbance estimation. The efficacy of the proposed controller to accommodate external disturbances is demonstrated with real-time implementation on the 3-DOF helicopter with a strong wind disturbance as well as an impulse disturbance.

A Laboratory Prototype Tandem Helicopter With Two Degrees of Freedom

Unmanned aircraft have had a great impact on society, their applications in various fields are increasing day by day, so it becomes necessary to propose, develop or validate new designs and concepts that help minimize operating errors or improve the safety of aircraft. One way to understand the operating principle of these unmanned aircraft is through laboratory prototypes or test benches; these prototypes allow experimentation and testing in controlled environments to minimize errors in their operation. This article presents a novel configuration for a laboratory prototype of a tandem-rotor helicopter with two degrees of freedom (DOF), and the dynamic modeling, control, signal filtering, and implementation of the control and filtering system using a microcontroller and a low-cost prototype made with easily accessible materials. This is to promote education, research, and technological development in this area of engineering.

Outwash flow measurement around the subscale tandem rotor in ground effect

Numerous issues are yet to be discovered about the small tandem rotor aerodynamics in the vicinity of ground. In this paper, a multipurpose test rig has been used to test outwash patterns of a sub-scale model of a generic tandem rotor helicopter in ground effect using two total-static rakes at different positions ahead and aft of the rotor(s). The results showed that in tandem rotor, the change in the rakes distance from the rotors has mild influence on the outwash flow velocity. The interaction between rotor wakes and formation of the fountain flow impressed the outwash of the rotors and changed their behavior in comparison with a single rotor. For the elevation higher than z/2R = 0.8, the outwash averaged velocity of the rotors due to flow recirculation was negative. As the rotor elevation decreased, outwash accelerated by moving away from the rotor within the measurement area. Comparing the results of present study with the experiments for the CH-47D helicopter indicated that the overlap between the rotors was caused the outwash velocity be more than non-overlapping rotors. Tuft flow visualizations showed the evidences of a fountain flow between the rotors and that, in the vicinity of tandem rotors, the resultant outwash velocity was inward due to formation of the fountain flow and the consequent suction.

Variance constrained trajectory tracking for tandem-rotor helicopters

PurposeThis paper aims to present novel results for trajectory tracking of tandem-rotor helicopters via variance-constrained controllers.Design/methodology/approachRegarding these purposes, linearized tandem-rotor helicopter models are benefitted.FindingsVariance-constrained controllers are very beneficial for trajectory tracking of tandem-rotor helicopters while there exists variance bounds on outputs of interest.Practical implicationsVariance-constrained controllers can be used for cheaper tandem-rotor helicopter operations with high trajectory tracking quality.Originality/valueApplying variance-constrained control strategy for tandem-rotor helicopters during trajectory tracking. This also causes less fuel consumption and green environment, and good trajectory tracking quality.

B22 交差反転式4発ロータヘリコプタのモデリング(M-OS10-2 自律知能無人ビークルの運動と制御II,M-OS10 自律知能無人ビークルの運動と制御,「海を越え,国を越え,世代を超えて!」)

In this paper, we propose the intermeshing quadrotor helicopter which has feature of the tandem rotor helicopter and the intermeshing helicopter. Kinematic and aerodynamic characteristics of this helicopter have not yet been well known because such a helicopter does not exist so far. Therefore, we aim at conducting motion analysis of the helicopter. First, equation of motion of the helicopter is derived using multi-body dynamics. Next, we construct the system which enables that the helicopter fly manually. Finally, flight experiment was carried out to collect flight data needed for parameter identification of the model.

Trajectory linearization based output tracking control of an unmanned tandem helicopter with variance constraints

An output tracking control problem for an unmanned tandem rotor helicopter with variance constraints is investigated in this paper. A modified Trajectory Linearization Control (TLC) is proposed to stabilize a nonlinear continuous-time flight dynamics system of the tandem helicopter. The tracking controller structure of TLC is designed by using two-time-scale nonlinear dynamic inversion. The base control law of the translational and attitude loops is designed in a pseudo-inversion feedforward controller to deal with nonlinear features of the plant and a proportional integral controller to stabilize the linear slowly time-variant error system resulted from the nonlinear flight system. Furthermore, a feasible TLC strategy is designed to meet a performance index set including steady trajectory tracking error variance and desired Parallel D-spectrum (PD-) eigenvalues to achieve good flight quality. The Variance-constrained Trajectory Linearization Control (VCTLC) is designed to realize the desired steady tracking precision and agile capability. Flight simulation results show the VCTLC method is feasible and effective in attitude and altitude tracking.

Tandem Helicopter Trim and Flight Characteristics in the Icing Condition

This paper describes an established flight dynamic model with two rotor-icing models that are capable of studying CH-47B tandem rotor helicopter trim and flight characteristics in a rime icing condition. First, considering the ice-shedding phenomenon and the local temperature variation on the rotor blade, an engineering rotor-icing model is developed based on the empirical two-dimensional airfoil icing tunnel data. Second, using the principle of computational fluid dynamics, a theoretical rotor-icing model is set up for comparison with the engineering rotor-icing model. As verification, the results of two rotor-icing models are shown to have acceptable agreement. Analysis was made on the effects of icing on trims, stability, and some flying qualities of tandem rotor helicopters in terms of forward velocity, icing time, atmospheric temperature, liquid water content, and median volumetric diameter. The degradation of flying qualities of tandem rotor helicopters in hovering due to icing is studied mainly with respect to the following aspects: attitude quickness, interaxis coupling, and vertical axis control power. Finally, conclusions of all the work are summarized at the end of this paper.

Studies of trims, stability, controllability, and some flying qualities of a tandem rotor helicopter

Two mathematical models for determining the trims of a tandem rotor helicopter were constructed separately using two technologies (momentum theory and vortex theory). A computational method for the stability and control derivatives was proposed based on the linear perturbation theory and the five-point central difference algorithm. The stability roots of a CH-47B tandem rotor helicopter in the uncoupled mode were calculated. As a verification, the calculated, referenced, and test data of comparable trims and stability roots were shown to have acceptable agreement. Analysis presented included stability and controllability features of the tandem rotor helicopter, based on the momentum theory model. According to ADS-33E-PRF, the flying qualities of the tandem rotor helicopter in hovering were studied mainly with respect to four aspects: bandwidth, attitude quickness, interaxis coupling, and disturbance of the lateral gust. Indications of all the work are summarized at the end of this article.

NONLINEAR CONTROL FOR A TANDEM ROTOR HELICOPTER

In this paper a Lyapunov control algorithm for a tandem rotor helicopter is obtained using backstepping techniques. A simple model dynamics for a behavior of a helicopter close to hover is obtained. Some simulation results are presented to illustrate the performance of such controller.

Combining expert system and analytical redundancy concepts for fault-tolerant flight control

A technique for rule-based fault-tolerant flight control is presented. The objective is to define methods for designing control systems capable of accommodating a wide range of aircraft failures, including sensor, control, and structural failures. A software architecture that integrates quantitative analytical redundancy techniques and heuristic expert system concepts for the purpose of in-flight, real-time fault tolerance is described. The resultant controller uses a rule-based expert system approach to transform the problem of failure accommodation task scheduling and selection into a problem of search. Control system performance under sensor and control failures using linear discrete-time deterministic simulations of a tandem-rotor helicopter's dynamics is demonstrated. It is found that the rule-based control technique enhances existing redundancy management systems, providing smooth integration of symbolic and numeric computation, a search-based decision-making mechanism, straightforward system organization and debugging, an incremental growth capability, and inherent parallelism for computational speed.

Flight test of a digital controller used in a helicopter autoland system

This paper describes the flight test evaluation of an advanced digital helicopter flight control system. The controller was designed using an optimal control design procedure for a fully coupled lateral and longitudinal vehicle model. Explicit integrals of the guidance error were included to produce a Type 1 characteristic. Gain scheduling was used to account for changes in the vehicle dynamics. The digital controller was exercised by combining it with state estimators, a trajectory generator and a closed-loop guidance algorithm to form a helicopter autoland system. A CH-47 tandem rotor helicopter was equipped with sensors, on-board digital flight computers and electro-hydraulic actuators. The system was exercised by automatically flying straight-in descending decelerating trajectories typical of VFR manual landing approaches. A description of the test-ground facilities, the flight hardware and software, and the velocity and position tracking performance is included.

Digital flight control design for a tandem-rotor helicopter

Methods and results in the continuing development of a digital flight control system (DFCS) for a CH-47B helicopter are presented. The helicopter is the research vehicle for the NASA VTOL Approach and Landing Technology (VALT) Program, and it equipped with comprehensive equipment for the investigation of navigation, guidance, and control requirements for future VTOL aircraft. Two control modes (attitude-command and velocity-command) are implemented, and each mode provides ‘Type 1’ response to guidance commands. DFCS design is based upon optimal estimation and control methods, which are found to provide flexible and efficient means for defining practical digital control systems.

Some Technical Aspects of Boeing Helicopters

I will describe in this paper some features of current Boeing-Vertol production helicopters that I have selected as those which strike me personally as being of particular engineering interest. But first just to provide some perspective on the subject I would like to summarise the background of the present Vertol Division of The Boeing Company. The Company was formed in 1944 as the Piasecki Aircraft Corporation and its first product was the HRP Tandem Rotor Helicopter, which first flew in 1945. This was followed by the HUP in 1948, the H-21 in 1952 and the H-16 in 1953. In 1956 the Company was renamed Vertol and the next aircraft to fly was the Model 107 Prototype in 1958. In 1960 Vertol was acquired by Boeing and became the Vertol Division. The currently manufactured models about which I am going to talk, are the 107 series (now mostly in production as the US Marine Corps Model CH-46, Sea Knight) and the 114 series (in service with the US Army as the CH-47, Chinook) of helicopters.

RESULTS OF SOME WIND TUNNEL AND FLIGHT STUDIES WITH HELICOPTERS AT NASA

Wind-tunnel tests and analytical studies which indicate power requirements of tandem-rotor helicopters in forward flight

The Development and Flight Testing of Helicopters

SummaryThe successful development of a helicopter and its introduction into service may be influenced by several factors but a well co-ordinated development programme is by far the most important. A practical and realistic balance between representative ground tests and the subsequent flight proving is essential if the project is to be completed within a reasonable budget and time scale. The two parts of this paper cover these phases and aim to show how they are related in a particular development programme. The use of major fully representative ground rigs is discussed in relation to pre-flight functioning and fatigue life assessment; this is followed by the initial flight trials and finally the structural and performance clearance of the helicopter over its full design envelope. Although the tests and techniques described are generally applicable, the examples quoted relate to the Bristol Type 192, tandem rotor helicopter. The opinions expressed are personal and do not necessarily represent those of the Bristol Aircraft Limited.