HBM实行快速傅里叶变换，这是谐波平衡法中的一个重要的环节-Harmonic Balance Method is a very useful method in solving rotor dynamics, and fast fourier transform is an important part in it

运用增量谐波平衡法求解二自由度非线性微分方程(Solving nonlinear differential equation with two degrees of freedom by incremental harmonic balance method)