Semi–active Control of Adaptive Friction Dampers for Structural Vibration Control

Reduction of structural vibrations is of major interest in mechanical engineering for lowering sound emission of vibrating structures, improving accuracy of machines and increasing structure durability. Besides design optimization and passive damping treatments, active structural vibration control can be applied to reduce unwanted vibrations. They become more and more important as lightweight constructions evolve. In this contribution, two semi-active control laws for control of friction dampers are derived and investigated. Purely semi-active control has the advantage to yield intrinsically stable closed-loop systems and low energy consumption compared to active vibration control. In the experimental implementation, the control make use of piezoelectric stack actuators to apply adjustable normal forces between structure and attached friction damper elements. Roughly speaking, the normal forces are controlled accordingly to the measured structural vibrations in order to achieve optimal damping effect. The control algorithms make use of reduced finite-element models of the structural dynamics for the estimation of the not observable relative displacement beneath the normal force actuator based on acceleration measurements. Experimental results of the control algorithms for a beam test structure with an attached friction damper with one adjustable normal force show the effectiveness of the algorithms. The control laws are compared with respect to their effectiveness, need of actuator bandwidth, applicable frequency bandwidth and energy consumption.