Sensitivity analysis of closed-loop control systems on flexible structures

Local-velocity feedback (LVF) and linear-quadratic Gaussain (LQG) control schemes are implemented on passively tuned reaction mass actuators to control the vibrations of a flexible structure. The structure is lightly damped and possesses closely coupled low-frequency resonant modes. Both LVF and LQG controllers successfully eliminate the structure's vibrations. However, if the passive tuning parameters of the actuators are slightly mistuned, implementing LVF control actually results in an unstable system. On the other hand, LQG control proves to be insensitive to large changes in the passive tuning parameters of the actuators. In fact, the system with LQG control is never unstable, no matter what the actuator's passive tuning parameters are.