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Abstract In an active vibration isolation system using velocity feedback, the phase-lead due to high pass filter and the phase-lag due to time delay limit the controller gain. This paper extends and applies a simple frequency range selector to increase the critical control gain. The selector uses the isolated mass's acceleration, velocity and displacement and is tuned by two knobs. Our proposed approach has simple static switching law, suppresses both low and high frequency control and does not add additional phase-lead or phase-lag. A simple expression of the effective gain is presented to give insight into the influence of two tuning knobs. Numerical simulations and a simple experiment are performed to illustrate the controller's effectiveness under harmonic and random disturbances.

This paper presents the theoretical upper bound of the harvested power, which is amplified by a generalized electrical damping switching controller in a linear time invariant system. The upper bound is found by maximizing a single-variable function with respect to the switching time. The upper bound shows the possibility of raising the power-frequency curve over the optimal passive curves reported in literature. The optimal switching time of the upper bound shows the mechanics that determine the optimality. The upper bound solution is not only a good benchmark to evaluate but also a clear guide to design any other practical controllers. To demonstrate these two benefits, four examples in literature were revisited: the Single DOF electromagnetic and piezoelectric energy harvesters, the Dual-mass vibration energy harvester and the quarter car hybrid electromagnetic suspension. A demonstration controller is proposed in all examples. The upper bound is used to evaluate the demonstration controller. The optimal switching time is used to explain the reason of a good or bad controller.

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