Machines with high speed rotation, high power, and lighter weight are the challenge in design of modern rotation machinery. In analysis of coaxial dual rotor system, the problem leads to a multi-degree of freedom system (1multi-DOF). The resulting equation of motion cannot be solved analytically. For multi-DOF system, numerical method has to be implemented. In this study, the equations of motion of co-axial dual rotor system was solved numericallyusing MATLAB programming language. This study compares the result of two methods used: the pseudo-modal method and the direct method, with the aim of getting the most effective method in predicting critical rotational speedby plotting Campbell diagram. It was foundthat the difference in the value of critical speeds between Pseudo Modal and the Direct Method is 0%-9,56% for the first 6 lowest frequencies and 0.09%-3.58% for the first 8 lowest frequencies.

高速旋转、大功率、重量更轻的机器是现代旋转机械设计的挑战。在同轴双转子系统分析中，该问题导致了多自由度系统（1multi-DOF）。由此产生的运动方程无法解析求解。对于多自由度系统，必须采用数值方法。本研究采用MATLAB编程语言对同轴双转子系统的运动方程进行数值求解。本研究比较了拟模态法和直接法两种方法的结果，旨在通过绘制坎贝尔图获得预测临界转速的最有效方法。发现Pseudo Modal与Direct Method的临界速度值相差0%-9，