Semi-Active Control by a Cantilever-type Dynamic Absorber

从理论上分析了一种固有频率可控的阻尼式动力吸振器的减振效果。在此基础上，设计了一个自调谐系统，以保持反共振。控制算法分为粗整定和精整定两个阶段。在粗调中，通过检测激励频率，利用计算机存储的数据库，对减振器臂长的固有频率进行了粗调。在精确调谐中，控制减振器的臂长，使减振器与主体之间的振动相位滞后为90 °，并将该系统应用于由四根弹簧支撑的梁和刚体。在刚体的情况下，必须设置吸振器，使臂的方向垂直于节线。然后，必须控制臂的固有频率和方向。在实验中，振动降低了约15分贝，当激励频率缓慢变化且吸振器能够无延迟地跟踪时，系统保持反共振。然而，当跟踪具有延迟时，系统脱离反共振并且振动增加。通过增加阻尼，可以避免振动的增加。该系统也被应用到管道噪声。

The vibration reduction by a cantilever-type dynamic absorber whose natural frequency can be controlled was theoretically analyzed. Then, an auto-tuning system to keep the antiresonance was made. The control algorithm has two stages, rough tuning and precise tuning. In the rough tuning, the exciting frequency is detected and the natural frequency of the arm length of absorber is tuned due to the data base stored in computer. In the precise tuning, the arm length of absorber is controlled such that the phase lag of the vibration between the absorber and the main body to be 90 decree.This system was applied to a beam and a rigid body which was supported by four sprines. In the case of rigid body, the absorber must be set such that the direction of the arm is normal to the nodal line. Then, both the natural frequency and the direction of the arm must be controlled. In the experiment, the vibration was reduced by about 15 decibel.When the exciting frequency shifts slowly and the absorber can track it without delay, the system keeps the antiresonance. However, when the tracking has a delay, the system goes apart from the antiresonance and the vibration increases. By increasing the damping, the increase of vibration can be avoided. This system was also applied to a duct noise.