Based on the research results of conventional rigid support nonlinear energy harvesters, in this paper we conceive a kind of structure with an elastic support external magnet with the intent to keep the system in the state of bistable oscillation, even under low-intensity excitation conditions. It has been proved that elastic support systems have better power output performance than rigid support systems when excited at low-intensity vibrations. In addition, elastic support nonlinear energy harvesters do not need real-time adjustment of the magnet interval towards the variable-intensity random excitation source, consequently achieving maximum power output and sufficient electromechanical energy conversion of the system.

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A two-dimensional Duffing oscillator which can produce stochastic resonance (SR) is studied in this paper. We introduce its SR mechanism and present a generalized parameter-adjusted SR (GPASR) model of this oscillator for the necessity of parameter adjustments. The Kramers rate is chosen as the theoretical basis to establish a judgmental function for judging the occurrence of SR in this model; and to analyze and summarize the parameter-adjusted rules under unmatched signal amplitude, frequency, and/or noise-intensity. Furthermore, we propose the weak-signal detection approach based on this GPASR model. Finally, we employ two practical examples to demonstrate the feasibility of the proposed approach in practical engineering application.

This paper deduces a unified mathematical model of open-circuit fault of six-phase induction machine, and purposes a fault-tolerence sensorless strategy based on the sliding mode observer(SMO) to estimate the rotor flux and rotor speed. In the proposed control scheme, the sliding mode observer is improved to achieve the rotor speed and rotor flux identification under healthy and arbitrary open circuit faults. The stability of the observer is proved by the Lyapunov function. The quasi proportional resonance (QPR) controller is introduced in the harmonic plane to suppress the harmonic current after the fault. The simulation and experiment results show that the proposed sensorless fault-tolerant control strategy based on sliding mode observer can accurately and effectively identify the rotor speed and rotor flux of the machine under normal and fault conditions.

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