为了分析真实状态下直升机在沙尘环境中的下降参数对沙盲的影响。本文以Z-3直升机为研究对象，首先采用考虑地面效应影响的自由尾迹方法计算旋翼气动力，分部件建立直升机的动力学模型，并选取合适的特征点进行配平和小扰动线化。然后基于轨迹跟踪串级控制系统和模型切换方法得到直升机下降过程的操纵量和状态量，在此基础上对下降过程的流场进行离散，结合沙场计算方法得到下降过程沙场，并获取沙场对驾驶员的视觉影响。基于上述过程采用Kriging代理模型方法建立直升机下降参数与真实下降状态下沙盲影响的映射关系模型，并采用遗传算法对此模型进行沙盲抑制效果的下降参数优化。结果表明：本文方法可以有效模拟真实直升机飞行过程的操纵和状态，得到真实的直升机起降过程流场和沙盲情况；近地面切向气流容易引起起沙，但沙盲现象需综合考虑流场情况；对Z-3直升机，较快的垂直下降速度可以减少起沙量，但也会导致沙粒的扬起和留存；直升机下降过程以斜下降或空间曲线的方式下降沙盲抑制效果更好，经过优化，直升机以垂直下降、斜下降和两种曲线下降时沙尘浓度相比于垂直基准下降的沙浓度分别下降13.41%、17.52%、16.45%和3.44%。
In order to analyze the influence of the descent parameters of the helicopter in the dust environment on the sand blindness in the real state. In this paper, the Z-3 helicopter is taken as the research object. Firstly, the free wake method considering the influence of ground effect is used to calculate the rotor aerodynamic force. The dynamic model of the helicopter is established by components, and the appropriate feature points are selected for trim and small disturbance linearization. Then, based on the trajectory tracking cascade control system and the model switching method, the control quantity and state quantity of the helicopter descent process are obtained. On this basis, the flow field of the descent process is discretized, and the sand field of the descent process is obtained by combining the sand field calculation method, and the visual influence of the sand field on the driver is obtained. Based on the above process, the Kriging surrogate model method is used to establish the mapping relationship model between the helicopter descent parameters and the brownout effect in the real descent state, and the genetic algorithm is used to optimize the descent parameters of the brownout suppression effect of this model. The results show that the proposed method can effectively simulate the control and state of the real helicopter flight process, and obtain the real flow field and brownout situation of the helicopter take-off and landing process. The tangential airflow near the ground is easy to cause sand, but the sand blindness phenomenon needs to consider the flow field. For the Z-3 helicopter, the faster vertical descent speed can reduce the amount of sand, but also lead to the uplift and retention of sand; in the process of helicopter descent, the effect of sand blindness suppression is better in the way of oblique descent or spatial curve. After optimization, the sand concentration of vertical descent, oblique de-scent and two kinds of curve descent is reduced by 13.41 %, 17.52 %, 16.45 % and 3.44 % respectively compared with the sand concentration of vertical benchmark descent.
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