Development and testing of a newly proposed continuously variable stiffness/damping device for vibration control

Many variable stiffness and damping devices have been proposed to mitigate the unwanted effects of vibrations. Although the stiffness or damping of these devices may be varied in real-time, many are limited in range and speed. The objective of this study is to propose a new variable stiffness/damping device to improve upon these limitations. The continuously variable amplification device (CVAD) is comprised of a spherical continuously variable transmission (SCVT) augmented with rack-and-pinions and connected in series with a simple stiffness or damping element. The CVAD amplifies linear motion to the stiffness or damping element, and then amplifies the element force back through the system. The resulting CVAD force is increased by a factor equal to the amplification factor squared, relative to the stiffness or damping element alone. The amplification factor is determined by a single controllable parameter that can be adjusted rapidly in real-time. The resulting system is capable of producing a large, continuous, and instantaneous range of stiffness or damping. In the present work, the concept for the CVAD is proposed and equations are presented for the effective stiffness and damping of the CVAD connected in series with both linear and rotational elements. Then, corresponding mathematical models are developed based on the system's dynamics considering the motion of each component. Numerical simulations are performed for the CVAD connected to a linear and rotational stiffness element and subject to a harmonic input. The results indicate that the same wide range of effective stiffness can be achieved using both elements.