Realization Of Negative Stiffness And Optimization Design Of Novel Dynamic Vibration Absorbers

In the field of vibration control,dynamic vibration absorber(DVA)is a common and efficient device to suppress vibration.The traditional dynamic vibration absorber has poor control effect on low frequency vibration,while negative stiffness device and amplifying mechanism have great advantages in this respect.In this thesis,theoretical design of a negative stiffness device is studied,and the negative stiffness device and amplifier mechanism are applied into the DVA.In order to improve the performance of the DVA,the work fulfilled in this thesis is as follow:(1)A hydraulic linear negative stiffness device is designed.The stiffness formula of the device is obtained through the static analysis of the device.It is proved that the presented device can provide linear negative stiffness in the case of a small displacement of the system vibration.(2)A dynamic vibration absorber containing a negative stiffness device is studied,in which the negative stiffness device and the main system are subjected to displacement excitation simultaneously.The parameters are optimized by sequential quadratic programming algorithm,and the control effect of the model under harmonic excitation and random excitation is studied.(3)A magnifying mechanism and a negative stiffness device are introduced into the Voigt type DVA.According to the fixed-point theory and the characteristics of negative stiffness,the optimal parameters of the model are studied.Compared with a variety of existing dynamic vibration absorbers,it is found that the model can effectively suppress vibration under harmonic excitation and random excitation.(4)A magnifying mechanism and a grounded stiffness element are introduced into the grounded type dynamic vibration absorber,and the optimal parameters of the model are studied based on the fixed-point theory.It is found that with the change of the mass ratio of the system and the magnification ratio,the grounded stiffness element may have three cases: negative stiffness,zero stiffness and positive stiffness.Compared with some existing DVAs,it is found that the grounded linear spring element of the model has good control performance under three cases.Theoretically,the best control performance is obtained when the grounded stiffness element is appropriate positive stiffness.(5)A semi-active dynamic vibration absorber with negative stiffness is proposed,which can track the change of excitation frequency by the short-time Fourier transform(STFT)and change the negative stiffness of the system accordingly.Compared with some existing models under harmonic excitation and non-stationary excitation,it is shown that the model has better control performance in low-frequency region.