MEMS PIEZOELECTRIC ACOUSTIC TRANSDUCER

ABSTRACT

This paper presents the fabrication process and measurement results of microelectro-mechanical (MEMS) piezoelectric acoustic transducers. To increase the output sound pressure, a dome-shaped multi-layer diaphragm is designed and fabricated by adjusting the residual stress in the individual layers. Transducers work in either audio or ultrasonic frequency range if diaphragm is designed in different size. In the frequency range from 100 Hz to 7 kHz, the output sound pressure of audio transducers with 3 mm × 3 mm diaphragm is higher than 0.1 Pa. The maximum output reaches 1.1 Pa at 3.8 kHz. For ultrasonic transducers with 1 mm × 1 mm diaphragm, the maximum output is 1.26 Pa at resonant frequency of 54 kHz. All transducers show acceptable linearity over a wide range of input drive voltage.     

A shoe-equipped piezoelectric transducer system based on PVDF film

Many piezoelectric transducers mounted in shoes have been conducted to harvest energy from walking. However, the energy harvested is influenced by some factors, such as the structure of piezoelectric transducer, piezoelectric material and so forth. Taking into account these factors, a wide-band energy harvester-shoe equipped piezoelectric transducer with cantilever beam structure based on polyvinylidene fluoride (PVDF) piezoelectric film is designed and examined in this paper. The piezoelectric transducer makes little difference in the sensation with the device mounted in the shoes when walking. The harvester can provide a maximum output power of 0.48 mW at the load resistance of 300 kΩ. This study demonstrates that it is feasible to scavenge energy from human motion by piezoelectric harvester to power wearable sensors, such as pedometer, respiration and pulse monitoring system and so on.     

Novel Piezoelectric-Based Power Supply for Driving Piezoelectric Actuators Designed for Active Vibration Damping Applications

This paper describes a novel step-up DC-AC piezoelectric-based power supply for driving piezoelectric actuators. Piezoelectric actuators have been demonstrated to be very attractive in applications requiring fast response and high actuation force, such as active damping applications. These actuators are commonly installed in self-powered systems (cars, helicopters, aircrafts, satellites, etc.) with limitation in the battery performance, dimensions and maximum weight. Nevertheless, the required driving electrical AC voltage for these actuators is typically in the range of 100 V to 1000 V, quite far from the 9 to 24 V of common batteries. Thus, the use of heavy, large and EMI-noisy electromagnetic transformers becomes necessary which is a drawback for the compact size required. This paper introduces an alternative system for driving piezoelectric actuators using a novel design of piezoelectric transformer, the Transoner®. The proposed solution allows a reduction in size, weight and magnetic noise generation compared to the classical electromagnetic-based systems. The work represents a completely novel approach to the possibilities of piezoelectric transformers for powering high voltage piezoelectric actuators. The solution offers significant advantages in environments requiring high integration, low weight, and low electromagnetic interferences operated with batteries. A circuit configuration capable of converting a 24 V DC input voltage up to 600 V _pp AC output voltage with frequency and magnitude control is implemented. Experimental results are presented for a standard multilayer piezoelectric actuator driven at 100 V _pp within the range of 10 Hz to 500 Hz.     

Power output estimation and experimental validation for piezoelectric energy harvesting systems

Many modern devices especially for ubiquitous computing or wireless sensor networks need a long life energy source. Batteries or accumulators are often an insufficient solution. Low frequency vibrations can be found in the most technical facilities or even in the human movements. Even while these vibrations are neither wanted nor used in the most times, they enable us to generate electrical energy. Piezoelectric flexural transducers are a promising choice for utilizing the vibrations for energy harvesting. There are two major influences on the amount of generated energy. First there is the frequency behavior of the piezoelectric transducers, for optimal power output the transducer should be driven in resonance. Second, the energy output is highly dependent on the electrical load of the connected application. Both circumstances, working frequency and electrical load, typically are boundary conditions for the development of the generator. Therefore, it is necessary to handpick the type of piezoelectric elements. To meet the requirements of development engineers, a model based design method for energy harvesting systems is needed. As a first step towards such a method, this work proposes a model for the estimations of the power output of piezoelectric flexural transducers. For the validation of this model an experiment is described in detail. The results of the model and the experiments are compared.     

Piezoelectric actuator design for ultrasonically assisted deep hole drilling

From different chipping machining processes it is known that a superposition of the cutting kinematics with additional vibration energy increases material removal rate and tool life. Concerning the deep drilling process in the scope of smallest diameters from 0.9 to 6 mm insights to this so called hybrid processes are still awaited. Preliminary investigations indicated that here is high, so far unused potential. The goal of current research is an increase in effectiveness of the deep hole drilling process by superimposing additional vibration energy in ultrasonic frequency range by means of a piezoelectric transducer and low-frequency vibrations in the range of acoustic frequencies as well. Positive effects can appear in a couple of areas, e.g. achievable surface quality, feeding force, drilling torque, shape and length of chips, feasibility of machining ceramic materials and tool wear. This paper describes mainly the ultrasound conform design of the vibration unit. Furthermore issues of contactless energy transfer into a rotating tool and model based design of piezoelectric transducers will be addressed.     

Energy harvesting using piezoelectric materials

This paper is presented to achieve the objective of energy harvesting from vibrational sources through piezoelectric materials. In this analysis, two piezoelectric buzzers: 35 mm buzzer and 27 mm buzzer were used to carry out the experiment. The experimental set-up includes an electro-dynamic shaker, function generator and a power amplifier. Buzzer of thickness 35 mm gave maximum output at resonant frequency of 23 Hz and 57 g of mechanical stress while buzzer of thickness 27 mm gave maximum output at resonant frequency of 25 Hz and 27 g of weight. The paper also presents some important applications of piezoelectricity in day-to-day life.     

纵振夹心换能器式圆筒型行波超声电机

提出一种纵振夹心换能器式圆筒型行波超声电机,该电机定子组件由定子圆筒和4个纵振夹心换能器组成,变幅杆和圆筒采用一整块硬铝合金加工而成。利用压电陶瓷片的纵向振动在夹心换能器中激励出纵向振动,实现两组换能器在定子圆筒上激励出2个幅值相等、在时间和空间上均相差p/2的弯振模态响应,2个弯振模态响应叠加在定子圆筒上形成弯曲振动行波,定子齿表面质点产生椭圆运动轨迹,进而通过和转子之间的摩擦耦合实现宏观运动输出。运用有限元法设计了定子圆筒和纵振夹心换能器,并实现了频率简并。测量结果表明,样机的最大转速为110 r/min,堵转力矩为0.5 N×m。     

高分辨率钢弦式位移遥测系统研究

本文论述在钢弦式位移传感器及配套遥测系统研究方面取得的一些成果。叙述了系统构成、各部分功能及传感器的设计思路。重点讨论传感器工作膜设计、弹簧设计及激发器研制等关键技术。传感器量程: 0～100mm,输出频率范围: 900～2300Hz,分辨率:优于0.01％FS。针对传感器输出频率范围窄的特点,文中提出用单片机实现固定m的多倍周期测量法。此外,导出了适于所有钢弦式传感器的拟合公式,特点是拟合精度高,能在很大程度上消除初频漂移带来的误差。最后,给出了系统分辨力测试结果。     

Enhanced piezoelectric energy harvester performance using magnetic force and thermal energy

One possible approach of improving the performance of energy harvesters is to use energy harvester with an external magnetic force to create a nonlinear coupling system. In this work, we report experimental results of a single piezoelectric cantilever beam (PCB) with tip mass or conventional piezoelectric energy harvester (CPEH), and the effect of applying an external magnetic force. The output voltage and power at optimal resistance was 7.62 V and 0.62 mW, respectively, at the resonance frequency of approximately 11 Hz of a CPEH. Also, the output voltage and average power at optimal resistance was 8.56 V and 0.44 mW, respectively, at resonance frequency of 7 Hz of a PCB with fixed opposing magnet. Furthermore, the output voltage and average power at optimal resistance was 13.31 V and 1.77 mW, respectively, at resonance frequency of 11 Hz of a PCB with opposing magnet attached at a second cantilever. In addition, comparison between the experimental results of all different configurations showed a reasonable enhancement of performance of energy harvester when an external magnetic force added over the main PCB. Finally, the performance of a multisource energy harvester with magnetic, thermal and mechanical sources is also presented in this study. In this case, it is demonstrated that increase in output voltage with temperature gradient under effect of magnetic force; the results of 2^nd and 3^rd model showed 44% and 99% enhancement of its original output voltage value at 1.2 °C and 2.7 °C temperature difference, respectively.     

“工字形”直线超声电机的结构设计与模态分析

为了提高直线超声电机的输出性能,研制了纵弯复合模态“工字形”直线超声电机,对“工字形”弹性体的几种复合振动模态及其驱动方案进行了分析,确定了振子的工作模态。完成了“工字形”振子的结构设计,利用ANSYS软件对“工字形”压电振子进行了优化设计,确定了定子各结构参数。纵向伸缩振动模态固有频率和弯曲振动模态固有频率分别为33.07kHz和33.08kHz,频率差8Hz。根据优化设计结果,试制了原理样机。对样机的输出性能进行了实验研究。实验结果表明:当驱动频率为31.10 kHz,激励电压峰峰值为250V时,电机动子Vmax为240mm/s;驱动力Fmax为0.5N。     

复合式动能采集器的多自由度宽频带设计优化

提出了一种多自由度宽频带压电 磁电复合式动能采集器,该动能采集器可以在多方向采集动能,有效地工作于较宽的频带,且可以同时以压电和磁电方式收集动能,大大提高了动能采集效率。介绍了复合式动能采集器的结构;分析和优化了采集器的拾振系统,从理论上验证了采集器的多自由度和宽频带的特性;介绍了磁电换能系统。研究结果表明,采集器在不同的工作频率下出现了两个振动峰值,验证了采集器的宽频带动能采集特性。通过实验测试进一步得出,与压电或磁电换能系统各自的输出性能相比,压电 磁电复合式换能系统的总体输出性能有所提高。     

压电参数d33特性测试装置设计

纵向压电应变常数d33是表征压电陶瓷材料机电转换性能的重要参数之一.有别于常规的静态、动静态检测方式,设计了一种基于扫频方法的新型d33参数测试装置.通过检测不同频率信号激励时线路的电流变化,实现压电陶瓷d33参数的检测计算.该装置具有性能参数检测操作方便、检测过程效率高等特点.     

Optimal design and application of a piezoelectric energy harvesting system using multiple piezoelectric modules

To enhance the output power of piezoelectric energy harvesting system up to the watt level, we designed a multi-piezoelectric array (MPA) energy harvesting system that can overcome the limitations of a single-piezoelectric harvesting systems. The MPA energy harvesting system was designed using an impact-type harvester utilizing a hitting stick, as such systems can generate higher output power than vibration-type methods using a cantilever in a single-piezoelectric energy harvesting system. We investigated the effects that various connection and rectification methods had on the output power of a piezoelectric energy harvesting system consisting of four 35?×45?×?0.2 mm³ piezoelectric modules. We found that the output power was highest when each module was rectified before the modules were connected in parallel and that the optimal load resistance was inversely proportional to the number of modules if they were connected in parallel. To obtain watt-level power from the proposed MPA energy harvesting system, we designed a system consisting of 102 piezoelectric modules based on the derived optimized experimental conditions, from which we were able to obtain an output power of 1.99 W at 1800 hpm (hits per minute) and 500 Ω.     

大容性负载双极性高压功率放大器设计

设计了一种适合压电陶瓷驱动器等大容性负载动态应用的双极性高压功率放大器,它基于误差放大式原理,采用高压集成运放(PA89)驱动多组并联功率放大级的电路结构,在实现双极性高电压输出的同时具有很强的电流驱动能力.该放大器驱动等效电容为2.5μF的压电陶瓷驱动器时,能实现单端到地-500～+500V高压输出,电压增益40dB...     

Piezoelectric materials for bistable energy harvester: A comparative study

This paper deals with the potential of various lead-free piezoelectric materials for energy harvesting. The performance of these materials is simulated for unimorph bistable piezoelectric energy harvester. The finite element method considering first-order shear deformation theory is used to model the system. The energy harvesting potential of bistable system (Non-linear) is compared with its linear counterpart. The results depict that the mean power density is almost 100% higher in case of bistable system. K_0.5Na_0.5NbO₃-LiSbO₃ (KNN-LS) family exhibited better performance than the conventional lead-based piezoelectric material lead zirconate titanate (PZT). The mean power density of K_0.5Na_0.5NbO₃-LiSbO₃-CaTiO₃ (2 wt.%) is reported to be 65% higher than PZT.     

压电式振动能量采集电源管理电路分析

压电式振动能量采集的应用十分广泛,在许多能量采集装置中都采用压电元件实现能量转换。分析了振动能量采集装置中压电元件采集的能量输出管理电路,包括标准能量采集电路、DC-DC变换的优化标准能量采集电路、同步电荷提取电路、电感同步开关采集电路和双同步开关采集电路等五种电源管理电路的原理,比较了它们的能量采集输出效率,指出了各种电源管理电路的特点和适用条件。     

尺蠖式压电陶瓷驱动电源设计

为了满足尺蠖式压电陶瓷驱动器的控制需要,设计了相应的驱动电源。DSP是控制器,通过网口接收上位机的控制命令,通过异步总线与FPGA进行数据通信,FPGA操作4路D/A生成4路满足相应时序要求的波形,波形经过精密运放前级放大和由分立元器件搭建的功率放大,输出到尺蠖式压电陶瓷驱动器的电源输入端。测试和试验表明,电源带宽高,纹波小,阶跃响应特性和动态特性良好,能够精确的控制尺蠖式压电陶瓷驱动器微位移定位,可以应用在精密工程技术领域中。     

Designing a piezoelectric energy harvesting system for the superconductor Maglev

In order to convert the lateral vibration of the superconductor Maglev bogie system into usable energy, an energy harvesting system was designed and optimized by applying steel balls for piezoelectric material to effectively convert mechanical energy into electrical energy. Experiments were conducted to investigate the effect of the vibration displacement (0.2, 0.4, 0.6, 0.8, 1.0 mm), vibration frequency (2, 4, 6, 8, 10 Hz) and vibration direction (x-axis and y-axis) for each different size of steel ball (12.7, 15.8, 17.0, or 20.0 mm). The following experimental results were found, first, as the vibration displacement increased, the average power output also increased. The total weight of the balls affected the results at higher vibration displacements. Second, as the vibration frequency increased, larger balls tended to have a jump point in average power output, with a general trend of increasing average power output. Finally, the x-axis direction effect had more distinct differences for individual ball weight dependences due to the mobility factor of the balls, considering calculated total weight and total area percent. After the optimum condition was found, the wireless sensor was connected and the experimental data suggested the possibility of applying piezoelectric materials to exploit the ambient and random vibrations of a superconductor Maglev bogie system.     

Design,fabrication and finite element modeling of a new wagon wheel flextensional transducer

Cymbal and moonie transducers exhibit greatly improved performance characteristics compared to a simple piezoelectric disk. This behavior is mainly due to the amplifying nature of the endcaps employed in these devices. Although these endcaps improve the displacement by amplifying the small lateral displacement associated with the d ₃₁ coefficient to a large axial displacement, this mechanism generates a very high tangential stress in the caps, which leads to a reduction in the efficiency of this transformation. In this paper, we report on a new end cap design, called the wagon wheel flextensional transducer, in which some of the clamping boundary conditions are eased by removing the metal in areas of high stress concentration. In the wagon wheel design, the tangential stresses are further reduced, thereby improving the efficiency of the transformation of the lateral to axial displacement, and consequently increasing the displacement response of the devices. Structural and impedance analyses of the devices were carried out using the commercially available software codes, ABAQUS and ATILA, respectively. Results reported for finite element modeling and experimental characterization suggest that these devices exhibit improved displacement characteristics compared to cymbal devices with similar dimensions.     

Energy harvesting with a cymbal type piezoelectric transducer from low frequency compression

In this paper a piezoelectric energy harvester based on a Cymbal type structure is presented. A piezoelectric disc ?35?mm was confined between two convex steel discs ?35?mm acting as a force amplifier delivering stress to the PZT and protecting the harvester. Optimization was performed and generated voltage and power of the harvester were measured as functions of resistive load and applied force. At 1.19?Hz compression frequency with 24.8?N force a Cymbal type harvester with 250?μm thick steel discs delivered an average power of 0.66?mW. Maximum power densities of 1.37?mW/cm³ and 0.31?mW/cm³ were measured for the piezo element and the whole component, respectively. The measured power levels reported in this article are able to satisfy the demands of some monitoring electronics or extend the battery life of a portable device.