The sensors are located at the mid-span of the cable, and the actuator is installed at the lower support of the cable with the cable anchorage.In the analysis, the x-axis is set along the cable chord, taking the lower end of the cable as the origin. The lower end of the cable is fixed to an actuator that gives the time-varying motion in the cable axial direction (see Figure 2). The cable vibration is measured by an optical tracking sensor attached to the mid-span cable. A controller synthesizes a feedback control signal from the cable response through the signal conditioner and according to the design control algorithm. The feedback control signal drives a piezo-mechanical actuator that can give support motion in the cable axial direction. The actuator motion in the cable axial direction is precisely measured using a gap sensor. The support motion should be, however, very small.