Time delay effect on direct output feedback controlled mass damper systems

Investigates the stability of a single degree of freedom (SDOF) system with an optimal direct output feedback controlled mass damper. An active mass damper system can take the form of a hybrid mass damper (HMD) or a fully active mass damper (AMD) depending upon imposed design constraint resulting from space, strength and power limitations. The control effects of the HMD and the AMD are first examined. The continuous-time direct output feedback control algorithm (LQR) is used to find the required control force. In active control, the control force execution time delay can not be avoided or eliminated even with present technology, which can be critical to the performance of the control system. The influence of time delay for a SDOF model with both HMD and AMD systems using continuous-time control gains is then discussed. Explicit formulas and numerical solutions to determine the maximum delay time which causes onset of system instability is obtained.