Research On Active Piezoelectric Energy Supply System For Wireless Sensor Networks

In recent years, wireless sensor networks show broad application prospects in thefields of military defense, disaster prediction, traffic management, health care,environmental science and daily life. The piezoelectric energy supply system canachieve self-power of sensor nodes, improve the performance and service life, andmeet the needs of wireless sensor networks.In order to solve two problems of the narrow band and the low efficiency existedin the traditional piezoelectric energy supply system, this paper presented an adaptiveactive piezoelectric energy supply system. Through the real-time adjustment of theoptimal control voltage, the system can satisfy the resonance requirements within abroad frequency range to achieve impedance matching. Then it can improve the energyharvesting power and drive wireless sensor network node to work normally.Firstly, based on piezoelectric principles and mechanics, the mass-piezo-spring-damper physical model of the piezoelectric energy supply system was built and theelectrical equivalent model was derived. The passive, semi-active, and activepiezoelectric energy supply system was analyzed. The simulation circuit wasestablished. At the same time, the advantages and disadvantages of three differentenergy harvesting systems were studied in detail.Secondly, an adaptive active piezoelectric energy supply technique was proposed.The mathematical expression of the optimal control voltage was derived. It can makethe system work in the resonant state to improve mechanical energy of piezoelectricdevice and reduce the damping cycle. Simultaneously, an adaptive control algorithmwas proposed to achieve the optimal control voltage. The feasibility of the optimalcontrol voltage and the adaptive control algorithm was verified in Matlab.And then, the active piezoelectric energy supply circuit which adopts theMSP430F169microcontroller was built. It mainly consists of a full-bridge rectifier, DC-DC converter, an energy storage unit and a control unit. In the work process ofpower circuit it can collect the output power and the frequency of exciting force, andadjust the amplitude and phase of the optimal voltage to output the maximum outputpower. At the same time, the specific working principle and implementation processwere analyzed in detail.Finally, the double-crystal piezoelectric ceramic was selected and a hardwareplatform was set up to debug the wireless sensor network node. The systemperformance was tested. Experimental results show that the output power of the activepiezoelectric energy supply system is three times as much as the standard energysupply system in the non-resonant frequency. The active piezoelectric energy supplysystem can improve the output in the wideband, and drive the wireless sensor networknodes work normally.