Tiltrotor aircraft have three flight modes： helicopter mode, airplane mode, and transition mode. A tiltrotor has characteristics of highly nonlinear, time-varying flight dynamics and inertial/-control couplings in it...Tiltrotor aircraft have three flight modes： helicopter mode, airplane mode, and transition mode. A tiltrotor has characteristics of highly nonlinear, time-varying flight dynamics and inertial/-control couplings in its transition mode. It can transit from the helicopter mode to the airplane mode by tilting its nacelles, and an effective controller is crucial to accomplish tilting transition missions. Longitudinal dynamic characteristics of the tiltrotor are described by a nonlinear Lagrangeform model, which takes into account inertial/control couplings and aerodynamic interferences.Reference commands for airspeed velocity and attitude in the transition mode are calculated dynamically by visiting a command library which is founded in advance by analyzing the flight envelope of the tiltrotor. A Time-Varying Linear（TVL） model is obtained using a Taylorexpansion based online linearization technique from the nonlinear model. Subsequently, based on an optimal control concept, an online optimization based control method with input constraints considered is proposed. To validate the proposed control method, three typical tilting transition missions are simulated using the nonlinear model of XV-15 tiltrotor aircraft. Simulation results show that the controller can be used to control the tiltrotor throughout its operating envelop which includes a transition flight, and can also deal with vertical gust disturbances.展开更多
The existing full-span models of the tiltrotor aircraft adopted the rigid blade model without considering the coupling relationship among the elastic blade, wing and fuselage. To overcome the limitations of the existi...The existing full-span models of the tiltrotor aircraft adopted the rigid blade model without considering the coupling relationship among the elastic blade, wing and fuselage. To overcome the limitations of the existing full-span models and improve the precision of aeroelastic analysis of tiltrotor aircraft in forward flight, the aeroelastic stability analysis model of full-span tiltrotor aircraft in forward flight has been presented in this paper by considering the coupling among elastic blade, wing, fuselage and various components. The analytical model is validated by comparing with the calculation results and experimental data in the existing references. The influence of some structural parameters, such as the fuselage degrees of freedom, relative displacement between the hub center and the gravity center, and nacelle length, on the system stability is also investigated. The results show that the fuselage degrees of freedom decrease the critical stability velocity of tiltrotor aircraft, and the variation of the structural parameters has great influence on the system stability,and the instability form of system can change between the anti-symmetric and symmetric wing motions of vertical and chordwise bending.展开更多
An analytical model for aeroelastic stability of the wing/pylon/rotor coupled system with elastic bending-twist coupling wing for tiltrotor aircraft in forward flight has been established in this paper. The investigat...An analytical model for aeroelastic stability of the wing/pylon/rotor coupled system with elastic bending-twist coupling wing for tiltrotor aircraft in forward flight has been established in this paper. The investigation is focused on the effectiveness of the wing elastic bending-twist couplings provided by composite wing beam on the aeroelastic stability for the wing/pylon/rotor coupled system. By introducing the different wing elastic bending-twist couplings into the Boeing’s test model, the aeroelastic stability of the Boeing’s test model with different wing elastic bending-twist couplings has been analyzed. The numerical re-sults indicate that the negative wing beamwise bending-twist elastic coupling (the wing upward beamwise bending engenders the nose-down torsion of the wing section) can saliently enhance the stability of the wing beamwise bending modal. The posi-tive wing chordwise bending-twist elastic coupling (the wing forward chordwise bending engenders the nose-down torsion of the wing section) has a great benefit for increasing the stability of the wing chordwise bending modal.展开更多
基金supported by the National Natural Science Foundation of China (No. 11502008)
文摘Tiltrotor aircraft have three flight modes： helicopter mode, airplane mode, and transition mode. A tiltrotor has characteristics of highly nonlinear, time-varying flight dynamics and inertial/-control couplings in its transition mode. It can transit from the helicopter mode to the airplane mode by tilting its nacelles, and an effective controller is crucial to accomplish tilting transition missions. Longitudinal dynamic characteristics of the tiltrotor are described by a nonlinear Lagrangeform model, which takes into account inertial/control couplings and aerodynamic interferences.Reference commands for airspeed velocity and attitude in the transition mode are calculated dynamically by visiting a command library which is founded in advance by analyzing the flight envelope of the tiltrotor. A Time-Varying Linear（TVL） model is obtained using a Taylorexpansion based online linearization technique from the nonlinear model. Subsequently, based on an optimal control concept, an online optimization based control method with input constraints considered is proposed. To validate the proposed control method, three typical tilting transition missions are simulated using the nonlinear model of XV-15 tiltrotor aircraft. Simulation results show that the controller can be used to control the tiltrotor throughout its operating envelop which includes a transition flight, and can also deal with vertical gust disturbances.
基金supported by the National Natural Science Foundation of China (No. 11572150)
文摘The existing full-span models of the tiltrotor aircraft adopted the rigid blade model without considering the coupling relationship among the elastic blade, wing and fuselage. To overcome the limitations of the existing full-span models and improve the precision of aeroelastic analysis of tiltrotor aircraft in forward flight, the aeroelastic stability analysis model of full-span tiltrotor aircraft in forward flight has been presented in this paper by considering the coupling among elastic blade, wing, fuselage and various components. The analytical model is validated by comparing with the calculation results and experimental data in the existing references. The influence of some structural parameters, such as the fuselage degrees of freedom, relative displacement between the hub center and the gravity center, and nacelle length, on the system stability is also investigated. The results show that the fuselage degrees of freedom decrease the critical stability velocity of tiltrotor aircraft, and the variation of the structural parameters has great influence on the system stability,and the instability form of system can change between the anti-symmetric and symmetric wing motions of vertical and chordwise bending.
文摘An analytical model for aeroelastic stability of the wing/pylon/rotor coupled system with elastic bending-twist coupling wing for tiltrotor aircraft in forward flight has been established in this paper. The investigation is focused on the effectiveness of the wing elastic bending-twist couplings provided by composite wing beam on the aeroelastic stability for the wing/pylon/rotor coupled system. By introducing the different wing elastic bending-twist couplings into the Boeing’s test model, the aeroelastic stability of the Boeing’s test model with different wing elastic bending-twist couplings has been analyzed. The numerical re-sults indicate that the negative wing beamwise bending-twist elastic coupling (the wing upward beamwise bending engenders the nose-down torsion of the wing section) can saliently enhance the stability of the wing beamwise bending modal. The posi-tive wing chordwise bending-twist elastic coupling (the wing forward chordwise bending engenders the nose-down torsion of the wing section) has a great benefit for increasing the stability of the wing chordwise bending modal.
