基于直升机地面共振要求的起落架刚度及阻尼优化设计

为给出满足直升机地面共振稳定性要求的起落架刚度及阻尼的优化设计方法，首先构造机体无阻尼时其非稳区的模态阻尼比函数，据此给出机体模态非稳区临界转速的计算方法，结合与旋翼摆振后退型模态共振转速下机体模态阻尼比的计算方法，给出了满足地面共振稳定性的机体固有频率及阻尼要求。然后，根据支持在起落架上的机体自由运动模型，建立机体模态频率及阻尼与起落架刚度及阻尼的关系，从而给出满足直升机地面共振稳定性的起落架刚度及阻尼要求。最后，基于上述稳定性要求，在满足着陆缓冲性能要求的起落架刚度及阻尼范围内，以减小起落架需用阻尼且增大机体最小模态阻尼比为优化目标提出了对其刚度及阻尼进行优化设计的方法，并通过对某型直升机4种不同重量重心状态下的起落架刚度及阻尼进行优化验证了该方法的可行性。

Optimal design for landing gear stiffness and damping based on helicopter ground resonance requirements

To meet the requirement of helicopter ground resonance stability, an optimal design method for landing gear stiffness and damping is proposed. First, a modal damping ratio function in the instable area for the fuselage without damping was constructed. The requirements of fuselage natural frequency and damping for meeting ground resonance stability were given by combining the calculation method of the instable area critical rotate speed with the calculation method of damping ratio at the resonance rotate speed of the fuselage mode. Then, based on the freedom motion model for the fuselage on the landing gear, the relation between landing gear stiffness and damping with fuselage mode frequency and damping was established, and the requirements of landing gear stiffness and damping for meeting ground resonance stability were given. Finally, based on the stability requirements, an optimal design method of landing gear stiffness and damping is proposed to reduce the required damping of landing gear and increase the minimum damping ratio of fuselage mode within the range determined by the buffering property requirements. This method was validated by optimizing the landing gear stiffness and damping of a type of helicopter at 4 states with different weights and gravity centers.