Structural Vibration Control Performance of Semi-active Cam-Lever Friction Devices Under Varying Friction Surfaces

Incorporating damping devices into building structures enhances their safety and serviceability when faced with natural hazards such as earthquakes and strong winds. Depending on their working principle, there are three main categories in which damping devices can be classified: passive, semi-active, and active systems. Passive devices employ natural mechanisms to dissipate energy, whereas active devices enhance their dissipation capabilities using external power. In contrast, semi-active devices integrate both principles, enabling them to reliably dissipate energy akin to passive devices and adapt like active systems, all while consuming less power. Recent trends have shown additional popularity for variable-friction dampers as semi-active devices due to their adaptability with only a variable clamping force. Hence, utilizing a cam (i.e., a surface with a variable radius) to exert a variable normal force, a novel friction damper has been created. The cam is attached to both a lever and a slider-crank mechanism, transforming rotational movement into the linear movement of an actuator. The proposed mechanism offers a mechanical advantage to comfortably adjust the position of the levers and vary the normal force. Previous prototypes were used to improve the mechanism’s behavior and guarantee the efficient application of a normal force. The performance of the proposed devices is evaluated by increasing the number of friction plates beyond the original two plates, with the ultimate goal of determining the scalability of force produced by the system. The latest prototype also examines factors such as manufacturing materials and stiffness of components. The experimental evaluation of the proposed device occurs at a small scale, utilizing aluminum and additive manufacturing of components, and an Arduino microcontroller to adjust the positions of the levers. To characterize the device, the test specimen is exposed to simulated harmonic and earthquake motions through a cyber-physical testing setup to evaluate its performance in a realistic structural control scenario. The results indicate the device can have additional normal forces applied to the friction surface to increase the passive capabilities of the device if the actuation system malfunctions. Overall, this research promotes the use of modern technology in structural engineering to improve system efficiency, reduce costs, and enhance safety and reliability in civil infrastructure.