Preventing stroke saturation of inertial actuators used for active vibration control of floor structures

Abstract

Active vibration control techniques using inertial-mass actuators have gained some level of acceptance in civil structures. Recent research indicates the effectiveness of this technique in mitigation of human-induced excitation in pedestrian structures such as floors and footbridges. However, there are some drawbacks associated with the use of inertial-mass actuators which needs to be dealt with. One of the main disadvantages of using inertial actuators is their stroke saturation non-linearity. When the stroke saturation phenomenon happens, excessive movement of inertial mass along the stroke hits the ends of actuator and can destabilize the system or even damage the actuator. This paper presents a novel velocity feedback control strategy to robustly prevent stroke saturation of inertial actuator. Two inner loops are added into a direct velocity feedback (DVF) control loop. First inner loop is a proportional-derivative (PD) controller based on the measured displacement of inertial mass. The second inner loop is implemented as a DVF gain modifier based on the actuator mass displacement over-range. This adaptively reduces the DVF gain, by an amount proportional to the over-range by displacement ratio, when inertial mass displacement is predicted to exceed the certain limit. Theoretical and experimental study of the control strategy is examined on a laboratory scale floor structure using an inertial-mass actuator. Both the results demonstrate the effectiveness of the proposed control strategy. The displacement of actuator's mass is kept within the stroke limits while satisfactory control performance is maintained.