In order to solve the limited life problem of typical battery power supply, a self-powered method that is based on the environmental energy harvesting has emerged as an amazing power supply approach. The Tribo-electric-Nano-generator (TENG) has been widely studied because of its high efficiency, low fabrication cost, and high output voltage. However, low output power conversion efficiency has restricted its practical application because of its own extremely high output impedance. In order to match the high output impedance of TENG and increase the output power, this paper presents an adaptable interface conditioning circuit, which is composed of an impedance matching circuit, a synchronous rectifier bridge, a control circuit, and an energy storage device. In the impedance matching circuit, the energy loss of coupling inductance could be reduced by using the bi-directional switch to increase the frequency, and impedance matching circuit can be used to increase the output efficiency of TENG. Experimental results show that, in about 3.6 s, the storing capacitor voltage was basically stable at 5.5 V by using the proposed adapted interface conditioning circuit in this paper. The charging efficiency has increased by 50%.

Engine health monitoring is very important to maintain the life of engines, and the power supply to sensor nodes is a key issue that needs to be solved. The piezoelectric vibration energy harvester has attracted much attention due to its obvious advantages in configuration, electromechanical conversion efficiency, and output power. However, the narrow bandwidth has restricted its practical application. A self-powered engine health monitoring system was proposed in this paper, and an L-shaped wideband piezoelectric energy harvester was designed and implemented. The L-shaped beam-mass structure and the piezoelectric bimorph cantilever beam structure was combined to form the wideband piezoelectric energy harvester configuration, which realized effective output at both resonance points. The theoretical model and finite element simulation analysis of the wideband piezoelectric energy harvester were proposed and the parameters were optimized based on that to meet the requirement of the vibration frequency of the engine. The experimental results show that the proposed energy harvester can be applied into the automobile engine health monitoring system. Engine signal analysis results also demonstrate that the proposed system can be used for engine health monitoring.

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As one of the core devices for an electro-optic analog-to-digital converter (ADC), the Mach-Zehnder (MZ) modulator plays an important role, and the output stability of the MZ modulator has a decisive influence on the conversion accuracy of the ADC. This paper proposed a pilot tone-based method to stabilize the bias point of the modulator. This method could obtain the corresponding control voltage of the MZ modulator by adding a KHz-level dither tone to the bias end of the modulator and calculating the ratio of the first and second harmonic components. The experimental results showed that the output optical power of the modulator was stable at 3.2 dB when the bias point of the modulator was set at the orthogonal point. Moreover, the fluctuation range was not more than 0.15 dB, the first harmonic of the output signal was stable at 50.5 dB, and the fluctuation range was not more than 0.6 dB. The proposed bias controller based on the field programmable gate array (FPGA) and digital signal processing (DSP) can stabilize the modulator bias point at the orthogonal point and with a relatively high locking accuracy.