基于混合遗传算法的直升机前推/后拉配平

针对直升机配平模型为多元且初始值难以确定的非线性方程组,以及全局最优解不唯一等问题,发展了一种基于遗传算法/拟牛顿法的高效混合迭代算法。介绍了直升机各个模块动力学方程。其中在旋翼建模中,考虑实际飞行环境下桨叶的运动和操纵特性,以动态入流和叶素法为理论基础,建立了具有配平特性的旋翼气动力模型。基于直升机飞行仿真动力学模型,详细推导了前推/后拉的配平变量和约束方程。通过构造目标函数,将全机配平问题转化为优化问题。通过计算UH-60A直升机在前推/后拉的配平解,并与飞行测试数据进行比较验证。结果表明,前推配平结果与飞行数据有偏差,后拉配平结果与飞行数据吻合。旋翼非定常气动特性是引起总距和脚蹬配平计算误差的主要原因。建立的配平算法适用于直升机不同稳定飞行条件下的仿真。

Push-forward/pull-backward trim for helicopter based on hybrid genetic algorithm

To solve the problems that helicopter trim model has multivariate nonlinear equations,it is difficult to determine its initial value and the global optimal solution is non-unique,an efficient hybrid iteration algorithm is presented in this paper,which combines the genetic algorithm and the quasi-Newton method.The dynamic equations of the different modules of the helicopter are introduced.In modeling the rotor,considering characteristics of the motion and control of the rotor in the actual flight environment,an aerodynamic model of rotor based on dynamic inflow and the blade element theory with the rotor trim is established.The trim control vector and the constraint equations for push-forward/pull-backward are deduced in detail based on helicopter flight dynamic model.Since the objective function is constructed,trim problems are transformed into optimal computation.UH-60A helicopter in the push-forward/pull-backward flight is trimmed,and the trim results are compared with flight test data.It is shown that the pull-backward results agree well with flight data,and there is the discrepancy between the push-forward results and flight data.The primary contribution to the discrepancy of the trim of collective and pedal comes from inaccurate prediction of the unsteady aerodynamic characteristics of the rotor.It is a universal method that can be applied to helicopter trim simulation of different stable flight conditions.