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Design of piezoelectric power generator in tire
Abstract
A novel power generator in the tire which is applied in a wireless Tire Pressure Monitor System (TPMS) was designed. The piezoelectric convertor constructed by bender arrays was merged to the inner surface of a tire to transform the mechanical deformation into the electric power and supply to the sensors of TPMS. A Finite Element Model (FEM) for the convertor was established based on the second piezoelectric function and the piezoelectric convertor with different sizes was analyzed by ANSYS 11.0 in a transient method. Then, a target of 6 cm2 was selected to observe its characteristics, and the effective current is 5 μA. As the wireless sending component needs 10 mA every 30 s, an array with 40 piezoelectric convertors was used in the generator and a power conditioning circuit with a multiple path charge coupling module was also designed. Experiments show that when the frequency of tire rotation is 15 Hz, the average power through the conditioning circuit is 150-350 μW and the instantaneous power can reach 50 mW, which proves that the power generator can work efficiently.
A designing structure which can harvest multi-direction vibration energies was proposed by using the new Rainbow shape piezoelectric energy transferring elements. In order to analysis and test the electricity generation of the piezoelectric energy transferring elements, the finite element analysis and practical tests were performed. The simulation results indicate that the open circuit voltage of Rainbow shape piezoelectric energy transferring elements will be reduced with the increases of the width and thickness of a metal substrate, the width and length of a piezoelectric film and the initial curvature radii of energy transferring elements; and it will be increased with the increase of the length of the metal substrate and shows a maximum with the increase of the thickness of piezoelectric film. The experimental result demonstrates the validity of finite element analysis and emphasizes that the open circuit voltage of energy transferring elements will have a maximum when the thickness of piezoelectric film is 0.25 mm. Furthermore, in the output power tests, the maximal output power of Rainbow shape piezoelectric energy transferring elements is about 7.75 μW. The results of simulation and experiment provide helps for designing, manufacturing and realizing the Rainbow shape piezoelectric energy transferring elements.
Based on hydro-solid coupling theory, the cantilever valve piezoelectric pump was comprehensively analyzed, and its dynamic model was established. After analysis of the interactions between hydro-mass, output pressure, system damp and working frequency, it is concluded that the decrease of chamber height will enhance the working frequency and stabilization. Then the vibrator structure parameters were confirmed through computing the influence law between vibrator structure parameter and amount of deformation. The conclusions show that the best thickness ratio is from 0.45 to 0.55 and the best diameter ratio is 0.8 to 0.9 between piezoelectric ceramic layer and the metal plate layer, respectively. The influence of the output form on the output ability also be considered, the result shows that axial output is in favor of the output ability of the pump.
Based on controlling the orderly changes of the PZT moving mechanism and friction between supporting faces in mechanical way, a kind of inertial piezoelectric actuator was proposed. The relationship between the driving voltage and the driving force and the distance were analyzed, the structure of a new inertial piezoelectric actuator that can realize single dimension reciprocating motion was designed and manufactured. The experimental results show that the simple associated symmetry electrical signal can provide stable stepping movement with the speed of 1 mm/s, high resolution of 20 nm and maximum loading capacity of 1000 g, it is expected that the proposed actuator will be widely applied to precision industry.
Mechanical energy generated by human activity may be converted to electrical energy using piezoelectric film inserts inside a shoe. This electrical energy can be collected in the form of charge accumulated in a storage capacitor. Under this scheme, the storage capacitor needs only to be connected to the load when it has enough energy for the requested operation. This time interval depends on several parameters: piezoelectric type and magnitude of excitation, required energy and voltage, and magnitude of the capacitor. This work analyzes these parameters to find an appropriate choice of storage capacitor and voltage intervals.