The cost function of the optimal control problem is a weighted sum of the squared horizontal and vertical components of the helicopter velocity at touchdown . the control ( horizontal and vertical components of the thrust coefficient ) required to minimize the cost function is obtained using nonlinear optimal control theory 其次，定义最优控制问题的性能指标为直升机着陆时的水平和垂直速度的加权平方和为最小，并采用一阶梯度算法得到使性能指标最小的控制规律。
