Abstract: Unbalanced vibration signal of coaxial dual-rotor system with little rotating speed difference is a composite signal called “beat”, which is composed of uneven vibration of internal and external rotor. Through studying the characteristic of beat, a method of separating two rotors’ unbalanced weight from beat is put forward. The effect between two rotors’ unbalanced vibrations is very weak ,which is proved by experiments and theoretic calculation. Eight effect coefficient method is brought out to deal with whole machine balancing for dual-rotors systems with little rotating speed difference. Balancing experiments successfully are made in two ways, balancing outer rotor singly and balancing two rotors simultaneously. Practice prove that eight effect coefficient method can get high balancing precision, simplify the balancing of this rotors system and has great application prospect.

Key words: Dual-rotor, Signal process, Whole machine balancing