Active Valve Control for Controlled Energy Release in Non-Linear Semi-Active Devices
Semi-active devices are strictly dissipative, low power control devices designed to reduce seismic structural response damage in buildings using the building’s own motion to produce resistive forces. New semi-active resetable devices with independently controlled valves and chambers can sculpt the device and structural hysteresis loops for specific applications. However, some of the most advantageous hysteresis loops and applications are not possible without active valve control to control the release of stored energy, in contrast to current resetable device control laws that rely on a maximum, fixed rate of stored energy release. This study uses proportional/derivative feedback control to closely track a desired, ideal reference force-displacement response curve. It is validated with a unique diamondshaped control law under sinusoidal and seismically induced, random input motions. A spectral analysis is also done to compare the non-linear, actively controlled results to those obtained with an ideal, linear model. The results show tracking to within 3-5% of the desired force-displacement curve, with mean errors below 1%. Valve delay is the main limitation, where the ratio of valve delay to structural period must be 1/10 or smaller to ensure adequate tracking, thus prescribing valve performance as a function of the structural period of the application. The overall results show that active feedback control of energy release, via active control of the valves, can dramatically increase the design space of possible resetable device hysteresis loops that can be obtained, and thus significantly increase their performance envelope and application potential. The results and approach are fully generalisable to a wide range of energy dissipation devices.