Optimum design of dynamic absorber for pattern formation phenomena generated in contact rotating systems (3rd report, in the case of a multi-degree-of-freedom system)

Pattern formation phenomena often occur in contact rotating systems. In a previous report, a countermeasure employing a dynamic absorber was suggested and optimized for a single-DOF system. When a similar design is applied to a multi-DOF system, some additional difficulties arise. Due to different natural modes, multiple dynamic absorbers are required. As a result, the calculation effort increases significantly due to the dramatic increase in the number of design parameters when all of the absorbers are designed simultaneously. Additionally, as the modes are somewhat interdependent, it is difficult to design appropriate dynamic absorbers for a multi-DOF. In order to overcome these difficulties, a systematic mode-by-mode design approach is proposed. Meanwhile, a criterion clarifying the relativity of unstable vibration modes before and after adding the dynamic absorbers is derived by using the stability analysis developed in earlier studies. The effectiveness of the proposed method is then verified with results calculated numerically from an example 5-DOF system.