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Previous work on active vibration control of floors has focused on direct velocity feedback (DVF) control laws with a saturation nonlinearity that aimed to ensure the actuators were not overdriven and to level off the response in the case of unstable behaviour. This paper presents a novel response-dependent velocity feedback (RDVF) control law as a possible improvement to DVF control laws. A maximum voltage to the actuator amplifier is set and a variable gain proportional to the reciprocal of the maximum of the absolute value of a sampled signal in a fixed block of data is derived. A switching off rule is introduced to switch off the actuator once the vibration mitigation function has been achieved, thus preventing the onset of limit cycles. Sensor and actuator dynamics are introduced and a simplified model of a laboratory structure for analytical studies is derived, based on its first mode of vibration. Analytical and experimental studies of active vibration control with DVF and RDVF velocity feedback control schemes are presented for harmonic, impulsive and human walking excitations. The reduction in response observed using RDVF technique is comparable with optimum reductions using DVF without requiring a specific gain to be set.

This paper looks at AVC studies in three different office floor case studies in past field trials. Some of the estimated modal properties for each of these floors from experimental modal analysis (EMA) tests are shown as well as some selected mode shapes of fundamental modes of vibration. These reflect the variability in their dynamic characteristics by virtue of their different designs and thus the potential for their 'liveliness' under human induced excitation. An overview of some of the controller schemes pursued in the various field trials are mentioned as well as a brief insight being provided into some challenges encountered in their designs and the physical siting of the collocated sensor and actuator pairs used in the field trials. The measure for the vibration mitigation performances in this work is in the form of uncontrolled and controlled point accelerance FRFs which show attenuations in the target modes of vibration between 13-18 dB. These tests also show the variability in vibration mitigation performances between the various controllers.

This study presents the results of vibration suppression of a walkway bridge structure with a single actuator and sensor pair by using a proportional-integral (PI) controller and observer-based poleplacement controllers. From the results of experimental modal analysis (EMA), reduced order models of the walkway are identified. These are used for the design of a PI controller as well as for state estimation procedures that are necessary for development of reduced-order observer controllers. The respective orders of the latter are dependent on the number of plant modes used for their designs. They are formulated from plant and observer feedback gains that are obtained from specification of desired floor closed-loop eigenvalues and observer eigenvalues. There are numerous solutions possible with the observer-based controller design procedures whereas the PI controller defaults to a particular solution. There is also the flexibility for isolation and control of target vibration modes with the observer-based controllers for higher controller orders from a purely single-input single-output controller scheme as demonstrated in the analytical and experimental studies presented. Further, in this work, a design space of potential feedback gains is specified, where only a single plant mode has been used for the observer-based controller design process, and a multi-objective genetic algorithm optimisation scheme is used to search for an optimal solution within some pre-defined constraint conditions. The best solution here is regarded as one that offers the greatest vibration mitigation performance amongst the solutions identified.

Active vibration control (AVC) of human-induced vibrations in structures with proof-mass actuators has been subject to much research in recent years. This has predominantly focussed on footbridges and floors and there is some evidence that this research is paving the way for commercial installations of AVC where traditional vibration control measures are not appropriate. However, the design of an AVC system is a complex task because of the influence of actuator dynamics, the contributions from higher frequency modes of vibration and the effect of low and high pass filters that are required to make the control algorithm implementable. This puts the AVC design process beyond the abilities of the vast majority of civil design engineers, even at a scheming stage to approximate what sort of reductions could be achieved by such a system. This paper considers a generalised system and investigates what sort of performance can be achieved in theory by a perfect AVC system, then considers the added complexity of actuator dynamics to demonstrate how this degrades the performance from optimal.