In active control applications to civil engineering structures, large control forces are required, but the generation of such forces may render the active control implementation impractical. To overcome this drawback, the actuator force can be supplied by the flow of compressed air: it applies a force to the jet supporting structure thanks to the principle of Momentum Preservation (Conservation). The air is stored in a tank and it flows towards a semi-rigid pipe to the final actuator-jets, simply realized as nozzles. The flow through each nozzle is controlled by an on-off electro-valve, and the system response is monitored by accelerometers. The main achievement is that the resulting control system is indipendent of external energy supply, enough energy having been stored, as compressed air, in a tank. In this way the reliability of the control system is not affected by the availability of external electric power, that in case of earthquake can easily be interrupted. While many studies have been made on pulse-control methods, only a few have investigated the implementation of such nonlinear control schemes. The focus of this work is on the experimental investigation of some of the numerous practical issues one meets in the development of actuators based on mass-ejection techniques. A single degree of freedom system, i.e. a simple vertical cantiliver with a lumped mass at the top, is tested on a shaking-table under different excitation time-histories, and the efficiency of the controller is evaluated.
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