Dynamic analysis on hub–beam system with transient stiffness variation

To adapt to various environments, many intelligent robots have incorporated components of variable stiffness, which typically vary transiently. In order to design appropriate forms of stiffness variation, it is important to study how such variations can affect the system's dynamic behaviors. This study investigates a hub–beam system with transient variable stiffness under large-scale motion. We consider two forms of transient variable stiffness: a step-like variation and periodic variations. Although the step-like variation is simple, it can induce complex response dynamics, and hence, it is difficult to predict the vibration amplitude. This difficulty, however, can be avoided by considering transient periodic variable stiffness. For this type of variation, resonance-like behaviors are observed, where the amplitude initially increases exponentially with time and becomes stationary after the stiffness stops varying. Such transient nature of stiffness variation can significantly affect resonance behaviors, including resonance amplitudes and the number of resonance regions. Based on these findings, we present a method to design optimal periodic variable stiffness for reducing vibrations. Our results provide insights into the design, utilization, and control of transient variable stiffness systems, particularly for many robots with variable components, where reducing vibrations is important.