“…Nonetheless, when the dynamics of the system are considered, the unconditional stability assumption no longer holds and a limit to the control gain exists. Several techniques have been proposed to increase the stability margin of VF including: the Acceleration Feedback Control (Diaz and Reynolds, 2010), the Inner Control Loop Approach (Díaz et al, 2012a), the Integral Resonant Control (Díaz et al, 2012b), the Virtual Mass Technique (Mao et al, 2020), the adaptive reduction of VF gain (Ahmadi, 2020), or the Independent Modal Space Phase-Lead VF Control (Xue et al, 2022). The SISO VF schemes may perform poorly when the target structure exhibits closely-spaced modes.…”