| The main method of power supply for low-power micro-nano devices such as micro-sensors have been currently batteries.Conventional chemical batteries were limited for use in the field or in areas not easily accessible to humans due to their large size,low power capacity,unsuitability for integrated installation and the need for regular replacement,at the same time,it was expensive to maintain and its waste easily caused pollution to the environment.There is therefore an urgent need for new power supply systems to meet the power requirements of such microelectromechanical systems.For this reason,the harvesting of non-electrical energy from the environment and its conversion into electrical energy for use has been now a more reliable solution.Currently,there has been no relatively well documented methodology for designing piezoelectric vibration energy harvesting devices for specific vibration environments,nor have been there an indicator theory for the construction of vibration energy capture devices for multiparameter assessment.This “gap” in guidance was urgent and necessary to enable the rapid and targeted design of energy harvesters for many typical,stable and uncomplicated engineering scenarios.A scientifically sound and complete methodology for considering the design of energy harvesters was provided in this thesis,and ultimately to provided a feasible and rapid technical route for the design of self-extracting energy systems for common engineering problems.Some preliminary inferences from the principles and uses computer simulations were formed to assist in verification,on the basis of which the inferences were confirmed to explore the laws and further improve the summary,while has formed a series of design guidance conclusions,which are eventually applied to specific engineering problems to prove and test the guidance effect.The advantages and disadvantages of all vibration energy harvesting methods,including electromagnetic,electrostatic and piezoelectric were compared.And the vibration energy harvesting method of piezoelectric material with the highest universality and feasibility was selected as the design target.The theoretical basis of piezoelectric energy harvesting was studied,including the basic concept of piezoelectric effect,the piezoelectric equation,piezoelectric materials and their performance parameters,etc.The electromechanical conversion characteristics,spectral characteristics and performance advantages of the piezoelectric cantilever beam harvester were also analysed theoretically.A vibration energy harvester of a bimorph piezoelectric cantilever beam based on the PZT-5H piezoelectric ceramic was proposed in the thesis.The corresponding inferences were verified by simulation and theoretical validation using COMSOL’s finite element analysis.The finite element method was used to complete modal analysis,static structural analysis,study of the relationship between intrinsic frequency and geometry or mass block weight,comparison of the output performance of rectangular piezoelectric cantilever beams with other shapes of equal strength,analysis of the electrical damping characteristics of piezoelectric cantilever beams and exploration of the differences in frequency characteristics and output characteristics between different clamping and fixation methods.The simulation study has resulted in corresponding research results and a design basis.In order to further validate the results of this paper,the above design guidelines for energy harvesters were applied to practical engineering problems and the results were tested.The design of a resonant energy harvester based on the 0.1g 135 Hz vibration source parameters of the motor unit bearing housing was completed,and the electrical harmonic response of the simulated model under these conditions was 6V and 0.5m W output power.Meanwhile,the LTC3588-1 power management chip was used to design and build the vibration energy harvesting interface circuit;the 2.4G wireless communication module supporting Mist Mesh & BLE protocol and the SI7021 contact digital temperature and humidity sensor were used to build the wireless sensing module.The final product has been a wireless sensing microsystem based on a vibration-based self-extracting power supply with harvester,power circuit module and load module.The designed temperature sensing module for motor bearings based on a vibration energy conversion power supply was tested experimentally on a motor set.In a 135 Hz 0.1g vibration environment,the device was able to output an output voltage of a maximum of 6V and a mean of 5.7V and charge a 0.047 F supercapacitor to 5V in 24 minutes with an average charging power of 0.42 m W.The harvested electrical energy was used to supply the load with a stable 3.3V output via the power supply circuit,successfully enabling the 23.5μW wireless temperature and humidity sensing modules to perform the task of measuring and transmitting the temperature of the bearing of motor. |
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