In this paper, we demonstrate an attachable energy-harvester-powered wireless vibration-sensing module for milling-process monitoring. The system consists of an electromagnetic energy harvester, MEMS accelerometer, and wireless module. The harvester consisting of an inductance and magnets utilizes the electromagnetic-induction approach to harvest the mechanical energy from the milling process and subsequently convert the mechanical energy to an electrical energy. Furthermore, through an energy-storage/rectification circuit, the harvested energy is capable of steadily powering both the accelerometer and wireless module. Through integrating the harvester, accelerometer, and wireless module, a self-powered wireless vibration-sensing system is achieved. The test result of the system monitoring the milling process shows the system successfully senses the vibration produced from the milling and subsequently transmits the vibration signals to the terminal computer. Through analyzing the vibration data received by the terminal computer, we establish a criterion for reconstructing the status, condition, and operating-sequence of the milling process. The reconstructed status precisely matches the real status of the milling process. That is, the system is capable of demonstrating a real-time monitoring of the milling process.
In this paper, we demonstrate a non-contact magnetic/piezoelectric-based thermal energy harvester utilizing an optimized thermal-convection mechanism to enhance the heat transfer in the energy harvesting/converting process in order to increase the power output. The harvester consists of a CuBe spring, Gadolinium soft magnet, NdFeB hard magnets, frame, and piezoelectric PZT cantilever beams. According to the configuration, the energy harvesting/converting process under a temperature-difference is cyclic. Thus, the piezoelectric beams continuously oscillate and subsequently produce voltage responses due to the piezoelectric effect. The maximum voltage response of the harvester under a temperaturedifference of 25°C is 16.6 mV with a cycling frequency of 0.58 Hz. In addition, we compare the testing result of the harvester utilizing the new thermal-convection mechanism reported in this paper and using previous thermal-convection mechanism reported elsewhere. According to the comparison, the results show the harvester utilizing the new thermal-convection mechanism has a higher cycling frequency resulting in a higher power output than the previous mechanism.