Acceleration-based active vibration control of a footbridge using grey-box model identification

Abstract

An active vibration control scheme for a footbridge based on grey-box model identification is proposed to reduce pedestrian-induced vibrations. The Carbon Fibre Reinforced Plastic (CFRP) stress ribbon bridge with a span of 13m was built at the Technische Universitat Berlin. Its lightness and flexibility result in high vibration sensitivity. The feasibility of the new control approach is demonstrated in simulations using an experimentally validated linear state-space model of the real footbridge. The active forces to control the first three vertical modes are generated by three pairs of pneumatic muscle actuators (PMA) that are installed in the footbridge's handrail. The motion of the bridge is sensed by two accelerometers placed below the bridge deck. To design the control system, a linear grey-box state-space model is determined with the reference forces of the exact I/O-linearization controlled PMAs as inputs and the two vertical accelerations as outputs. Based on the identified model, an observer estimates the vertical modal velocities. After statically decoupling the first three modes by an input transformation, each of these modes is controlled by a delayed velocity feedback to bring modal velocity and control force in phase. Gain and delay of the controllers have been chosen by means of the root locus method.