Control of suspension bridge flutter instability using pole-placement technique

The closed-loop state feedback control scheme by pole-placement technique, which is widely used in control literature, is applied to control the flutter instability of suspension bridges. When the mean wind speed U at the bridge site increases beyond the critical flutter wind speed, the real part of the dominant pole of the system is forced to a desired negative value by properly designing a state feed back gain matrix to control the flutter instability. The control force, which is expressed as a product of gain matrix and state vector in modal coordinates, is applied in the form of an active torsional moment in the middle of the bridge span. The values of the state variables are estimated by designing a full order observer system. The application of the control scheme for increasing the critical wind speed for flutter of suspension bridges is demonstrated by considering the Vincent Thomas Bridge as the numerical example. The efficiency of the method for controlling the bridge deck flutter is investigated under a set of parametric variations. The results of the numerical study show that the control scheme using pole-placement technique effectively brings down the divergent oscillation of the bridge at wind speeds greater than the critical wind speed for flutter, to almost zero value within few seconds.