A study is conducted on the feasibility of helicopter ground and air resonanceby using actively controlled tabs mounted at the trailing edge of an aerofoil. A method isdeveloped to obtain the optimal feedback control ...A study is conducted on the feasibility of helicopter ground and air resonanceby using actively controlled tabs mounted at the trailing edge of an aerofoil. A method isdeveloped to obtain the optimal feedback control law through constructing a referencemodel according to requirements of stability levels in the modal space. The effects of rotorspeed and length and location of tabs on the control law are analyzed, and it is found possible that a controller can be designed into constant feedback gain against rotor speed andto feed back only to the dominant system states to eliminate the unstable range of rotorspeed.展开更多
Rotor Head Vibration Absorber (RHVA) is a new kind of vibration reduc-tion device for helicoper, which provides some advantages in applications. The mechan-ical model for analysing and designing such kind of device is...Rotor Head Vibration Absorber (RHVA) is a new kind of vibration reduc-tion device for helicoper, which provides some advantages in applications. The mechan-ical model for analysing and designing such kind of device is presented, two analyticalmethods (in frequency domain and time domain) and its adaptabihty are studied. At thesame time the charactenstics of RHVA are analysed. The deduced rotor receptancesproved by model test are presented. At last the effectiveness of mechanical model andanalytical methods presented in this paper and of RHVA are illustrated in the calculation example.展开更多
The 2-dimensional equivalent model used in helicopter ground resonance analysis is convenient for its simplicity and clarity. The equivalent body mass, the stiffness and the damping are derived from the modal charaCte...The 2-dimensional equivalent model used in helicopter ground resonance analysis is convenient for its simplicity and clarity. The equivalent body mass, the stiffness and the damping are derived from the modal charaCteristics. In this paper, a 3-dimensional space model is constructed to analyse the ground resonance.There is little difference between the calculated results of the 2-dimensional equivalent model and those of the 3-dimensional space model. Hence, the 2-dimensional model is verified for the practical application. Generally, the linear lead-lag damping of the equivalent rotor blade at the modal frequency is derived from the lead-lag damper characteristics by a procedure of iteration. The transformation of the imaginary part of the complex modulus of the viscoelastic damper into a linear velocity damping is complicated in analysis. A method to use the complex modulus directly in the ground resonance analysis is derived and verified.展开更多
文摘A study is conducted on the feasibility of helicopter ground and air resonanceby using actively controlled tabs mounted at the trailing edge of an aerofoil. A method isdeveloped to obtain the optimal feedback control law through constructing a referencemodel according to requirements of stability levels in the modal space. The effects of rotorspeed and length and location of tabs on the control law are analyzed, and it is found possible that a controller can be designed into constant feedback gain against rotor speed andto feed back only to the dominant system states to eliminate the unstable range of rotorspeed.
文摘Rotor Head Vibration Absorber (RHVA) is a new kind of vibration reduc-tion device for helicoper, which provides some advantages in applications. The mechan-ical model for analysing and designing such kind of device is presented, two analyticalmethods (in frequency domain and time domain) and its adaptabihty are studied. At thesame time the charactenstics of RHVA are analysed. The deduced rotor receptancesproved by model test are presented. At last the effectiveness of mechanical model andanalytical methods presented in this paper and of RHVA are illustrated in the calculation example.
文摘The 2-dimensional equivalent model used in helicopter ground resonance analysis is convenient for its simplicity and clarity. The equivalent body mass, the stiffness and the damping are derived from the modal charaCteristics. In this paper, a 3-dimensional space model is constructed to analyse the ground resonance.There is little difference between the calculated results of the 2-dimensional equivalent model and those of the 3-dimensional space model. Hence, the 2-dimensional model is verified for the practical application. Generally, the linear lead-lag damping of the equivalent rotor blade at the modal frequency is derived from the lead-lag damper characteristics by a procedure of iteration. The transformation of the imaginary part of the complex modulus of the viscoelastic damper into a linear velocity damping is complicated in analysis. A method to use the complex modulus directly in the ground resonance analysis is derived and verified.
