Aeromechanical stability analysis of a hybrid heavy lift multirotor vehicle in hover
01 Nov 1985-Journal of Aircraft (American Institute of Aeronautics and Astronautics Inc. (AIAA))-Vol. 22, Iss: 11, pp 965-972
TL;DR: In this paper, nonlinear equations of motion capable of modeling the dynamics of a coupled multi-rotor/support-frame vehicle system have been developed using these equations, an aeromechanical stability analysis was performed in order to identify potential instabilities for this type of vehicle.
Abstract: Hybrid heavy lift airship (HHLA) is a proposed candidate vehicle aimed at providing heavy lift capability at low cost. This vehicle consists of a buoyant envelope attached to a supporting structure to which four rotor systems are attached. Nonlinear equations of motion capable of modeling the dynamics of this coupled multirotor/support-frame vehicle system have been developed. Using these equations, an aeromechanical stability analysis was performed in order to identify potential instabilities for this type of vehicle. The coupling between various blade, supporting structure, and rigid body modes is identified. Furthermore, the effects of changes in buoyancy ratio (buoyant lift/total weight) on the dynamic characteristics of the vehicle were studied.
Citations
More filters
01 Jan 1990
TL;DR: In this article, the authors present an assessment of the state of the art in rotary-wing aeroelasticity as applied to conventional helicopters as well as other VTOL vehicles such as tilting prop-rotors, the X-wing and a hybrid heavy lift vehicle.
Abstract: This survey presents an assessment of the state of the art in rotary-wing aeroelasticity as applied to conventional helicopters as well as other VTOL vehicles such as tilting prop-rotors, the X-wing and a hybrid heavy lift vehicle. The objective is to enable the reader to develop an awareness of what has been accomplished, what remains to be done, and where to find more comprehensive treatments of the various topics discussed. The main topics discussed are: (1) structural modeling; (2) unsteady aerodynamic modeling; (3) formulation of the equations of motion and their solutions; (4) illustrative results for isolated blades in hover and forward flight; (5) illustrative results for coupled rotor/fuselage problems; (6) active control of aeromechanical and aeroelastic problems; (7) active controls for vibration reduction; (8) structural optimization with aeroelastic constraints; (9) gust response analysis of rotors; and (10) aeroelastic problems in special VTOL vehicles. These topics are reviewed with different levels of detail and some useful observation on potentially rewarding areas of future research are made.
42 citations
TL;DR: In this paper, the authors explore the concepts of hybrid airship designs that have been proposed in the recent past, and highlight the current state-of-the-art in this field.
21 citations
TL;DR: In this paper, the authors presented the results of an analytical study aimed at predicting the aeromechanical stability of a helicopter in ground resonance, with the inclusions of aerodynamic forces.
Abstract: This paper presents the results of an analytical study aimed at predicting the aeromechanical stability of a helicopter in ground resonance, with the inclusions of aerodynamic forces. The theoretical results are found to be in good agreement with the experimental results, available in the literature, indicating that the coupled rotor/fuselage system can be represented by a reasonably simple mathmatical model.
21 citations
01 Oct 1988
TL;DR: Theoretical and experimental developments in the aeroelastic and aeromechanical stability of helicopters and tilt-rotor aircraft are addressed in this paper. But the authors focus on the development of dynamic inflow, an unsteady aerodynamic theory for low frequency aero-elastic stability applications.
Abstract: Theoretical and experimental developments in the aeroelastic and aeromechanical stability of helicopters and tilt-rotor aircraft are addressed. Included are the underlying nonlinear structural mechanics of slender rotating beams, necessary for accurate modeling of elastic cantilever rotor blades, and the development of dynamic inflow, an unsteady aerodynamic theory for low frequency aeroelastic stability applications. Analytical treatment of isolated rotor stability in hover and forward flight, coupled rotor-fuselage stability are considered. Results of parametric investigations of system behavior are presented, and correlations between theoretical results and experimental data from small- and large-scale wind tunnel and flight testing are discussed.
18 citations
References
More filters
01 Jan 1983
TL;DR: In this paper, the state of the art in the formulation and solution of rotary-wing aeroelastic stability and response problems is reviewed in detail, including the approximations used in the structural, inertia and aerodynamic operators.
Abstract: The state of the art in the formulation and solution of rotary-wing aeroelastic stability and response problems is reviewed in detail. The approximations used in the structural, inertia and aerodynamic operators are discussed. The important role of geometric nonlinearities, due to moderate deflections, and aerodynamic stall in the aeroelastic stability and response problem are identified. It is also shown that geometric nonlinearities are of primary importance in aeroelastic stability calculations, and have a more limited, though important, role in response calculations. Next, formulation of coupled rotor/fuselage problems is described, for both air and ground resonance type problems. Both topics, the isolated blade problem and the coupled rotor/fuselage problem, are treated for both hover and forward flight. Solution of aeroelastic stability and response problems proceeds in two stages. First, the spatial dependence is eliminated by using Galerkin's method, or by using the finite element method. Next the nonlinear, or linear, ordinary differential equation with periodic coefficients have to be solved for stability or response. Efficient numerical methods for accomplishing these objectives are presented in a comprehensive manner. The paper contains a number of illustrative numerical results which are intended to clarify various aspects of the modeling process and serve as representative results for both aeroelastic stability and response calculations for a variety of blade and rotor configurations.
74 citations
TL;DR: In this paper, the basic aerodynamic and dynamic properties of an example heavy-lift airship (HLA) configuration are analyzed using a nonlinear, multibody, 6-degrees-of-freedom digital simulation.
Abstract: The basic aerodynamic and dynamic properties of an example heavy-lift airship (HLA) configuration are analyzed using a nonlinear, multibody, 6-degrees-of-freedom digital simulation. The slung-payload model is described, and a preliminary analysis of the coupled vehicle-payload dynamics is presented. Trim calculations show the importance of control mixing selection and suggest performance deficiencies in crosswind stationkeeping for the unloaded example HLA. Numerically linearized dynamics of the unloaded vehicle exhibit a divergent yaw mode and an oscillatory pitch mode whose stability characteristic is sensitive to flight speed. An analysis of the vehicle-payload dynamics shows significant coupling of the payload dynamics with those of the basic HLA. It is shown that significant improvement in the vehicle's dynamic behavior can be achieved with the incorporation of a simple flight controller having proportional, rate, and integral-error feedbacks.
22 citations
TL;DR: In this paper, the authors presented the results of an analytical study aimed at predicting the aeromechanical stability of a helicopter in ground resonance, with the inclusions of aerodynamic forces.
Abstract: This paper presents the results of an analytical study aimed at predicting the aeromechanical stability of a helicopter in ground resonance, with the inclusions of aerodynamic forces. The theoretical results are found to be in good agreement with the experimental results, available in the literature, indicating that the coupled rotor/fuselage system can be represented by a reasonably simple mathmatical model.
21 citations
01 Jul 1981
TL;DR: The feasibility of using components from four small helicopters and an airship envelope as the basis for a quad-rotor research aircraft was studied.
Abstract: The feasibility of using components from four small helicopters and an airship envelope as the basis for a quad-rotor research aircraft was studied. Preliminary investigations included a review of candidate hardware and various combinations of rotor craft/airship configurations. A selected vehicle was analyzed to assess its structural and performance characteristics.
4 citations
01 Jan 1984
TL;DR: In this article, nonlinear equations of motion capable of modelling the dynamics of a coupled multi-rotor/support frame/vehicle system have been developed, using these equations the aeroelastic and aeromechanical stability analysis is performed aimed at identifying potential instabilities which could occur for this type of vehicle.
Abstract: Hybrid Heavy Lift Airship (HHLA) is a proposed candidate vehicle aimed at providing heavy lift capability at low cost. This vehicle consists of a buoyant envelope attached to a supporting structure to which four rotor systems, taken from existing helicopters are attached. Nonlinear equations of motion capable of modelling the dynamics of this coupled multi-rotor/support frame/vehicle system have been developed. Using these equations of motion the aeroelastic and aeromechanical stability analysis is performed aimed at identifying potential instabilities which could occur for this type of vehicle. The coupling between various blade, supporting structure and rigid body modes is identified. Furthermore, the effects of changes in buoyancy ratio (Buoyant lift/total weight) on the dynamic characteristics of the vehicle are studied. The dynamic effects found are of considerable importance for the design of such vehicles. The analytical model developed is also useful for studying the aeromechanical stability of single rotor and tandem rotor coupled rotor/fuselage systems.
2 citations