Triangular Cantilever Research Articles

Optimization of cantilever piezoelectric harvester to triangular shape with material reduction using finite element analysis

The paper studies the piezoelectric output performance of a piezoelectric harvester with four piezoceramic layers, assessing if the piezoelectric material can be reduced. The shape optimization regards cantilevers with trapezoidal or triangular longitudinal sections, maintaining comparable electric response with the original rectangular structure. The piezoelectric material is subjected to maximum mechanical stress in the fixed constrained area, decreasing gradually down to null stress towards the free tip. It is worthwhile to study if the material reduction would result in an increased effectiveness in terms of voltage output per unit volume of piezoelectric material. The simulations conducted in COMSOL Multiphysics employ Structural Mechanics – Piezoelectric Devices module, in a Multiphysics approach through Piezoelectric Effect, coupling Solid Mechanics with Electrostatics. It was found that the electric response increases per unit volume of piezoelectric material in triangular configuration with material reduction. A comparable voltage output is obtained after reducing the amount of piezoceramic material towards the free tip, while using an inertial mass of the same value. Hence, the piezoelectric material is used more effectively in the case of triangular cantilever with material cutdown than the traditional rectangular shaped cantilever. The paper also addresses shape optimization while maintaining the same mechanical stress, studying the response when increasing the tip mass for the purpose. All the structures render an even more significantly increased power output for matching optimum load resistor.

Multi‐Length Engineering of (K, Na)NbO3 Films for Lead‐Free Piezoelectric Acoustic Sensors with High Sensitivity

AbstractWith increasing concerns about noise pollution, the pursuit of highly dependable piezoelectric acoustic sensors for real‐time noise monitoring has come to the forefront of scientific research. Lead‐based perovskite piezoelectric films, exemplified by lead zirconate titanate Pb(Zr,Ti)O3 (PZT), surpass traditional piezoelectric materials such as ZnO and AlN in their piezoelectric properties, promising substantial advancements in next‐generation acoustic sensor technologies. However, the toxic nature of lead in PZT materials poses formidable environmental and human health risks. In an unprecedented breakthrough, it presents the pioneering development of an environmentally benign lead‐free piezoelectric Micro‐Electro‐Mechanical System (MEMS) acoustic sensor based on potassium sodium niobate (K,Na)NbO3 (KNN) film. High‐quality <001> textured 3 µm‐thick KNN film is successfully integrated into commercially used Si substrate, rendering exceptional piezoelectricity (transverse piezoelectric coefficients e31* of ≈8.5 C m−2) with satisfactory thermal stability. The atomic‐scale Z‐contrast imaging and piezoresponse force microscopy characterizations reveal that the outstanding piezoresponse originates from the local coexistence of multiple phases and the enhancement of extrinsic piezoelectric contributions from in‐plane polarization anisotropy. Finite element simulation is employed to design the triangular cantilever structure and annular diaphragm structure, each corresponding to different operating bandwidths. The resultant MEMS acoustic sensors stand out with outstanding acoustic performance (the high sensitivity and expansive receiving field of view), which are attributed to the microstructural engineering at multi‐length scales for the excellent piezoelectric properties of KNN film. These features enable sensitive acoustic monitoring in various environments, including large‐scale power grids and urban traffic.

Application of piezoelectric self powered wireless sensor in CCAL vibration environment monitoring

With the growth of the economy and social progress, people's requirements for mechanical equipment are becoming higher and higher, and the complexity of mechanical equipment is also increasing. To improve the safety and reliability of mechanical equipment, the establishment of Wireless Sensor Network (WSN) with the function of monitoring and self energy supply in vibration environment is an effective way to solve this problem. This study presents a piezoelectric self-powered wireless sensor monitoring system with a piezoelectric self-powered circuit model, and utilizes the FFT algorithm to reduce power consumption and achieve a sleep-wake-sleep cycle intermittent periodic operation mechanism for low-power devices. The results show that the charging speed of the PISS structure is 2.4 %, 65.8 %, and 80 % faster than the standard, SISS, and SCE structures, respectively. Compared with the triangular cantilever, the output voltage and output power of the rectangular cantilever have increased by 59.5 % and 80.9 %, respectively. When the acceleration is 1 g, the output power and output voltage are 0.5 mW and 6 V, respectively. When the acceleration is 2 g, the output power and output voltage are 2.2 mW and 12 V, respectively. The above results indicate that the piezoelectric self-powered wireless sensor monitoring system in this study has a certain reference value in the field of self-powered wireless sensors.

Electronic Stethoscope Based on Triangular Cantilever Piezoelectric Bimorph MEMS Transducers

Cardiac auscultation is an orthodox method to prevent and diagnose cardiovascular diseases. Traditional stethoscopes cannot offer a highly reliable diagnosis, and electronic stethoscopes suffer from low signal-to-noise ratio (SNR) and high cost. This paper reports an electronic stethoscope based on piezoelectric bimorph MEMS transducers for cardiac sound monitoring. The stethoscope prototype, measuring 37 <inline-formula> <tex-math notation="LaTeX">$\times 28\times12$ </tex-math></inline-formula> mm³, contains a preamplifier, holders and polydimethylsiloxane (PDMS) packaging. The transducer is designed using a lumped element model, fabricated by MEMS process, packaged, and assembled for final use. A triangular cantilever is chosen as a basic element for the transducer, with analytical analysis showing high sensitivity per unit area as a figure of merit (FoM). Performance parameters such as sensitivity and noise are experimentally characterized and consistent with simulation results. Owing to the outstanding receiving performance of the aluminum nitride (AlN) material and bimorph triangular cantilever structure of the transducer, compared with the commercial electronic stethoscopes, the proposed stethoscope demonstrates real-time phonocardiogram (PCG) with higher SNR. With its small size, high performance and low cost, the stethoscope is developed for portable and wearable cardiac sound monitoring. [2022-0007]

The invention relates to a small logistics handling trolley based on omni-directional wheel movement

Through the research and analysis of the existing gantry crane and cantilever crane to unload and transport goods, at the same time the application of the characteristics of triangular stability, a combination of the advantages of the three; A triangular omnidirectional cantilever crane is designed and developed by using electric push rod instead of rope lifting and the most basic triangular body.

Research and Development of a Wireless Self-Powered Sensing Device Based on Bridge Vibration Energy Collection.

Traditional bridge monitoring has found it difficult to meet the current diversified needs, and frequent replacement of sensor batteries is neither economical nor environmentally friendly. This paper presents a wireless acceleration sensor with low power consumption and high sensitivity through integrated circuit design, data acquisition and wireless communication design, package design, etc. The accuracy of the sensor in data collection was verified through calibration and performance comparison tests. The ability of triangular piezoelectric cantilever beam (PCB) was tested through design and physical manufacture. Finally, the self-powered performance of the sensor was tested by connecting the sensor and the triangular PCB through a circuit, which verifies the feasibility of using the PCB to collect bridge vibration energy and convert it into electrical energy to supply power for sensor, and also explore the green energy collection and application.

On the PZT/Si unimorph cantilever design for the signal-to-noise ratio enhancement of piezoelectric MEMS microphone

This study presents the design, fabrication, and testing of a novel piezoelectric micro-electro-mechanical-systems microphone with the partially removed lead zirconate titanate (PZT) unimorph structure for signal-to-noise ratio (SNR) enhancement. To demonstrate the feasibility of the presented concept, the unimorph cantilever array with the patterned (triangular shape) PZT film on top of a rectangular Si layer is simulated, fabricated, and tested. In comparison, the rectangular and triangular unimorph cantilever arrays with fully covered PZT film are also investigated. The proposed and reference cantilever arrays have the same foot print for fair comparison. Simulations show the proposed design has the highest output electrical energy which indicates the proposed design could successfully enhance the SNR. Moreover, acoustic measurements in the standard anechoic box show the proposed Si cantilever with patterned PZT film design could significantlyimprove the SNR. As compared to the reference microphone with triangular PZT/Si unimorph cantilever, the proposed design shows a 9.8 dB enhancement in SNR. Finally, the influences of initial structure deflections (due to the thin film residual stresses) on the low frequency responses for proposed and reference microphone designs are also investigated.

Design and Construction of a Low-Force Stylus Probe for On-machine Tool Cutting Edge Measurement

A new on-machine profiler employing a cantilever beam was proposed and developed to measure the sharp micro-cutting edges of precision cutting tools with low measuring force of 0.1 mN. The proposed profiler consists of a probe unit and a positioning unit. The probe unit employs a stylus mounted on the free end of a hollow triangular cantilever beam and a laser displacement sensor to detect the deflection of the cantilever beam. The positioning unit consists of two single-axis DC servo motor stages for precise positioning of the probe unit. The cantilever is designed with the assistance of the finite element method. In order to demonstrate the feasibility of the proposed measurement system, experiments are conducted and the measurement result for a micro-cutting edge is compared with that by a commercial profiler. Furthermore, a method to compensate for the measurement error caused by the lateral displacement of the cantilever beam is proposed. The compensated measurement results show good agreement within ± 2 μm with those obtained by the commercial profiler.

Design and analysis of high-frequency fiber Bragg grating vibration sensor

The fiber Bragg grating vibration sensor has received a lot of attention due to its unique performance. However, the natural frequency of the sensor limits its development and application. This paper presents an acceleration sensor with an isosceles triangular cantilever and mass block structure, which has high natural frequency and high sensitivity. The optical fiber sensing system consists of two fiber gratings. One section of the fiber grating is pasted on the cantilever and serves as an accelerometer; the other is used as a reference grating. The first-order natural frequency of the accelerometer is 8356 Hz, and its sensitivity is 0.46 pm g−1. A vibration test confirms the reliability of the sensor, and the resonant frequency of the sensor is 8193 Hz. The principle of light intensity demodulation is adopted in the sensor system and its sensitivity is 45.82 mV g−1 with a linearity of 0.997. The sensor has the advantages of high frequency and sensitivity, and thus can be applied to the rail transit bearing systems

Analysis of Coupled Dynamic and Voltage Models of Piezoelectric Cantilever Energy Harvester using Differential Transformation Method

In this work, differential transformation method with after treatment technique is applied to develop analytical models for the prediction of the behavior and output voltage of cantilever piezoelectric energy harvesters. The analytical results are in a good agreement with the experimental results in literature. The first mode of vibration has the lowest resonant frequency, and typically provides the most deflection and therefore electrical energy. The output voltage increases with the length of the beam but increase in the thickness of the beam decreases the output voltage. The results depict that the shape of the cantilever energy harvester plays an important role in improving the harvester’s efficiency. It is established that under the same loading, material and geometrical conditions, triangular cantilever beams are more efficient than rectangular ones. From the results, it is also established that that among all the cantilever beams with uniform thickness, the triangular cantilever, can lead to highest resonance frequency. Therefore, in order to obtain more wideband piezoelectric energy harvester, the geometrical and material designs of piezoelectric resonant cantilevers must be properly analyzed.

Vibration analysis of transverse galloping of different bluff bodies

The purpose of this research is to identify the best Blunt Body (BB) configuration for a piezoelectric wind energy harvesting system. The bluff body configurations studied are square, trapezoid, cone, cylinder, and aerofoil which are experimented on the rectangular and triangular cantilever beam. The increase in displacement and vibration velocity with respect to incident wind velocity is reported experimentally. Experimental findings suggest square BB and triangular cantilever are best suited for transverse galloping. A comprehensive study of galloping of the cantilever beams on its various regions with respect to the wind velocity is done. An overall increase of 27% displacement is reported in the triangular cantilever beam when compared to the rectangular cantilever beam. Cut–in speed for the above configurations is also studied and results are plotted. Results prove Trapezoidal BB and aerofoil BB has the least and highest cut-in speed respectively.

Fertilizer monitoring using micromachined cantilever

Abstract. In this study, we will create a grid of micro electro-mechanical (MEMS) sensors, which will measure the contents of soil, especially urea. This will inform the farmers about the condition of soil in real time, and thus allowing them to know how much fertilizer they need to add. MEMS sensor is placed in the soil to measure the soil content by chemical reaction with the fertilizers; its accuracy can be improved if these sensors are placed on multiple points, i.e., they are placed in a grid. In the present study, we designed micro-cantilever based gas detectors, to detect ammonia present in the fertilizers. Several designs were proposed to find the best fit for this purpose. Numerical studies have been carried out on the proposed designs, to evaluate the displacement sensitivity and the voltage developed in the piezoelectric layer, and the triangular cantilever was found to be the most sensitive cantilever for that purpose.

Design and analysis of a hollow triangular piezoelectric cantilever beam harvester for vibration energy collection

The vibration of transportation infrastructure is random and of low frequency. The vibration energy can be collected and converted into electric energy by installing the piezoelectric cantilever beam (PCB) harvesters on the transportation infrastructure. The resonance frequency and the resonance number of the PCB harvesters within the low frequency range play critical roles. This paper presents an analysis of four types of PCB harvesters designed according to the characteristics mentioned above to evaluate the influence of three different shapes (rectangle, trapezoid and triangle) on the power generation capacity of the piezoelectric cantilever beams. The results show that the triangular PCB harvesters are more suitable for the low-frequency vibration environment of transportation infrastructure, and they usually have higher voltage outputs. In order to widen the resonant frequency of the triangular cantilever to better adapt to the random vibration environment of the transportation infrastructure, the performance of a hollow triangular piezoelectric cantilever beam (HTPCB) was also assessed. Through modeling and analysis, the resonant frequency of the HTPCB has a broader low frequency range. In practical applications, deployment of the HTPCB harvesters on transportation infrastructures such as pavements and bridges can collect more energy in the random and low-frequency vibration environment of the transportation infrastructures.

One novel type of miniaturization FBG rotation angle sensor with high measurement precision and temperature self-compensation

In order to achieve rotation angle measurement, one novel type of miniaturization fiber Bragg grating (FBG) rotation angle sensor with high measurement precision and temperature self-compensation is proposed and studied in this paper. The FBG rotation angle sensor mainly contains two core sensitivity elements (FBG1 and FBG2), triangular cantilever beam, and rotation angle transfer element. In theory, the proposed sensor can achieve temperature self-compensation by complementation of the two core sensitivity elements (FBG1 and FBG2), and it has a boundless angel measurement range with 2π rad period duo to the function of the rotation angle transfer element. Based on introducing the joint working processes, the theory calculation model of the FBG rotation angel sensor is established, and the calibration experiment on one prototype is also carried out to obtain its measurement performance. After experimental data analyses, the measurement precision of the FBG rotation angle sensor prototype is 0.2 ° with excellent linearity, and the temperature sensitivities of FBG1 and FBG2 are 10 pm/℃ and 10.1 pm/℃, correspondingly. All these experimental results confirm that the FBG rotation angle sensor can achieve large-range angle measurement with high precision and temperature self-compensation.

A Novel MEMS Device for Scanning Profile Measurement with Three Cantilever Displacement Sensors

A novel Micro Electro Mechanical System (MEMS) measurement device for straightness measurement with a three point method has been proposed. This device integrates three cantilever displacement sensors with a narrow pitch on a silicon chip. The authors determine appropriates shape, dimensions of the cantilever, and a fabrication process. According to simulation results, a triangular cantilever with altitude 12 mm long, base 4mm long, and 0.25 mm thickness was adopted to realize the target measuring range of 100 μm. Near the end of each cantilever, a square frustum probe 250 μm high which was fabricated by anisotropic wet etching was placed. Near the base of cantilevers, four piezo resistance gauges were formed; two are active gauges for measuring stress arise from a displacement at the probe and the others are dummy gauges for temperature compensation. Wiring and contact terminals were fabricated on the base substrate and the total size of the device is 20 mm × 32 mm. The fabrication process of this device was designed and result of a trial production was reported.

Numerical Study of Hydrodynamic Forces for AFM Operations in Liquid.

For advanced atomic force microscopy (AFM) investigation of chemical surface modifications or very soft organic sample surfaces, the AFM probe tip needs to be operated in a liquid environment because any attractive or repulsive forces influenced by the measurement environment could obscure molecular forces. Due to fluid properties, the mechanical behavior of the AFM cantilever is influenced by the hydrodynamic drag force due to viscous friction with the liquid. This study provides a numerical model based on computational fluid dynamics (CFD) and investigates the hydrodynamic drag forces for different cantilever geometries and varying fluid conditions for Peakforce Tapping (PFT) in liquids. The developed model was verified by comparing the predicted values with published results of other researchers and the findings confirmed that drag force dependence on tip speed is essentially linear in nature. We observed that triangular cantilever geometry provides significant lower drag forces than rectangular geometry and that short cantilever offers reduced flow resistance. The influence of different liquids such as ultrapure water or an ethanol-water mixture as well as a temperature induced variation of the drag force could be demonstrated. The acting forces are lowest in ultrapure water, whereas with increasing ethanol concentrations the drag forces increase.

Fan-structure wind energy harvester using circular array of polyvinylidene fluoride cantilevers

A fan-structure piezoelectric energy harvester was proposed and tested in order to collect wind energy. Polyvinylidene fluoride was chosen due to its flexibility and longevity when compared to lead zirconate titanate. The impact-induced piezoelectric energy harvester consists of a stator and a rotor and a circular array of four cantilevers, utilize the rotor blades’ periodic impact on the free end of the cantilevers to generate oscillatory motion of cantilevers. A circular array of polyvinylidene fluoride cantilevers was fixed around the rotor in order to increase output power, save space at the same time. Static and transient characteristics of different cantilevers were investigated using finite element method and the result showed that polyvinylidene fluoride triangular cantilever performs the best in output voltage and power. Under the condition of optimal impedance and optimal overlap distance, a sum AC output power of four cantilevers without connection to each other approach to 0.75 mW was measured at the wind speed of 7 m/s when the blade number of rotor is 7 or 9. Two branches 0.27 mW DC output power was obtained when each two cantilevers in parallel connection in the case of full-wave rectification of each cantilever at the wind speed of 7 m/s.

Design of the lower chassis of a monorail personal rapid transit (MPRT) car using the evolutionary structural optimization (ESO) method

The Evolutionary Structural Optimization (ESO) procedure was applied to the design of the lower chassis of a monorail personal rapid transit (MPRT) car. As part of the early-stage development effort, ESO was used to identify a good topology of the lower chassis structure, which is effective in material usage, with lowly-stressed material removed. The procedure started with building a three-dimensional finite element model of the topology that occupies the design envelop, and lowly stressed elements were removed step by step during the ESO procedure. Multiple load cases concerning acceleration, deceleration, left turn, and right turn were analyzed separately, and a simple procedure dealing with multiple load cases was adopted. After 14 calculation increments, 80 % of the initial material was removed. The resulting topology reveals a reasonable frame structure with rounded outer corners, triangular cantilever supports, and Michell style beam structures, suitable as a starting reference for the structure design of a MPRT.

真直形状測定用 3 点法マルチカンチレバー変位計の高感度化モデルの検討

In this study, we developed a multi cantilever device for straightness measurement using the three point method. This device has three triangular cantilever works as displacement sensors. When the displacement is given at the probe placed at the end of the cantilever, stress arises in the cantilever. Displacement is measured by detecting the stress change using two piezo resistances at the root of the cantilever. This paper presents the results of sensitivity evaluation of improved device models. To improve the sensitivity, we considered the shape to make stress concentration in the strain detecting section of the device, and examined the effects by the finite element method. As a result, it was confirmed that transverse notches on both sides at the root of the cantilever and a rectangular hole between the piezo resisances are effective for sensitivity improvement and crosstalk reduction. Furthermore, we also simulate models of changing thickness of each part and models of changing position of piezo resistance.

Lead-Free (K,Na)NbO&lt;sub&gt;3&lt;/sub&gt; Impact-Induced-Oscillation Microenergy Harvester

We developed microenergy harvesters using impact-induced oscillation to scavenge electrical power from low frequency (<200 Hz) and random environmental vibrations. The microharvesters comprised a (K,Na)NbO3/Si composite cantilever and a cylindrical cavity to guide a metal ball to perpendicularly strike the cantilever. Through ball impact, oscillation of the cantilever was induced, generating electrical power at ambient vibration frequencies from 20 to 150 Hz. The contact time of ball impact was identified as a key parameter for power enhancement and was effectively tuned by adjusting the impact position on the triangular cantilever. The experimental output power when the impact position was at the base of the cantilever was 34.6 nW. This value is tenfold higher than that from conventional devices in which the ball strikes the tip of the cantilever. [2015-0063]