基于分岔分析法的直升机地面转弯运动稳定性研究

Research on the stability of helicopter ground steering motion based on bifurcation analysis method

摘要:

重型直升机在地面滑跑时极易由于重心较高、轮距较短等因素发生冲出跑道或倾覆等严重事故。提出运用分岔分析方法进行稳定性研究，在 MATLAB/Simulink 中建立直升机地面滑跑六自由度非线性动力学模型；基于分岔理论并采用数值延拓工具 AUTO，对直升机地面滑跑转弯方向稳定性展开研究，分析前轮转角对直升机地面滑跑转弯方向稳定性的影响，结合直升机轮胎力、偏航角等因素对系统在不稳定状态时出现的Hopf 分岔现象进行分析。结果表明：直升机地面滑跑转弯失稳的本质为轮胎侧向摩擦力无法提供直升机地面滑跑转弯所需向心力。

Abstract:

Due to the lack of rudder, high center of gravity, short wheelbase and other factors, heavy helicopters are prone to accidents that seriously threaten the safety of life and property such as rushing out of the runway or oversteering when taxiing on the ground. In order to obtain the stable parameter area of helicopter taxiing on the ground and improve the stability of helicopter taxiing on the ground, the bifurcation analysis method is proposed to study the stability. In this paper, a six-degree-of-freedom nonlinear dynamic model of helicopter ground taxiing is established in MATLAB/Simulink. The highly nonlinear forces such as tire force and rotor tension are introduced into the model, which can truly simulate the force of the helicopter when it is on the ground taxiing. Based on the bifurcation theory and the numerical continuation tool AUTO, the stability of the helicopter ground steering direction is studied. The single-parameter stability bifurcation analysis with the front wheel angle as the bifurcation parameter is carried out, and the influence of the front wheel angle on the stability of the helicopter ground steering direction is analysed. Combined with the factors such as helicopter tire force and yaw angle, the Hopf bifurcation phenomenon in the unstable state of the system is analysed. The results show that the essence of the helicopter ground steering instability is that the lateral friction of the tire cannot provide the centripetal force required for the helicopter ground steering.