1g Acceleration Research Articles

Tapered substrate thickness to enhance the performance of a piezoelectric energy harvester

In this paper, the improvement of the performance of a piezoelectric (PZ) cantilever beam using a non-uniform substrate thickness is presented. This reduces the resonant frequency, improves the stress distribution and generates more output voltage and power. Both analytical and finite-element method analyses were performed to investigate the effect of a tapered substrate thickness on a PZ cantilever beam. A tapered substrate thickness was used in rectangular and trapezoidal cantilever structures. All of the designed cantilever structures had the same fabrication area, and their performance was evaluated and compared using an excitation acceleration of 1g (9.8 m/s2). The tapered-down trapezoidal cantilever achieved a minimum resonant frequency of 62.41 Hz, which was 48.83% less than the resonant frequency of the uniform rectangular cantilever beam. The output peak voltage and average power of the proposed tapered-down trapezoidal cantilever beam were 12.36 V and 21 μW, respectively, which were improved by 44 and 74.48%, respectively, compared with those of the uniform rectangular cantilever structure.

Magnetic coupled ultra-low frequency piezoelectric energy harvester for self-powered sensors

Harvesting human motion energy to power various sensors has attracted more and more attention of researchers. Aiming to harvest the ultra-low frequency vibration energy generated by human motion, this paper proposes a magnetic coupled scheme which consists of two flextensional transducers with two endmost magnets, a center magnet, and a tube. Through magnetic coupling effect, the ultra-low frequency vibration energy is amplified and effectively harvested, and the output voltage amplitude at 5Hz reaches 22V under the initial distance of 48mm and the acceleration of 1g. The output voltage amplitude of the harvester is related to the initial distance and excitation acceleration which are theoretically analyzed in this paper.

Contact and Non-Contact Dual-Piezoelectric Energy Harvesting System Driven by Cantilever Vibration

In this study, a dual-piezoelectric energy harvesting system with contact and non-contact characteristics was driven by a cantilever beam. The harvester performance of the multipoint energy harvesting system driven by cantilever-beam vibration was designed, detailed analysis and optimization strategies were developed, and its application in the security field was successfully demonstrated. Herein, we provide theoretical guidance for the design of the dual-piezoelectric energy harvesting. We designed and fabricated a prototype of the dual-piezoelectric energy harvesting. A test system was designed and constructed. The relationships among the distance and frequency of the two piezoelectric acquisition mechanisms and the open-circuit voltage were investigated. Additionally, the effects of different loads on the output power were examined. The peak power reached 10.12 mW under a gravitational acceleration of 1g. The analysis indicated that the dual-piezoelectric energy harvest device has a higher energy harvest efficiency than the single-piezoelectric energy harvest device. Owing to the multipoint harvest strategy, even if a generator suddenly deteriorates or fails, the entire system can maintain a certain power output, which is more commercially feasible. The results of this study indicate that the output of the piezoelectric energy harvesting is stable and reliable and that the output energy satisfies the requirements for a safety warning device.

A Vibration Energy Harvester With Targeted Frequency-Tuning Capability

One of the major challenges for vibration energy harvesters is to match their resonant frequency with ambient vibration frequency. The main limitation of the existing frequency-tuning techniques is the uncontrollable tuning process, i.e., the incapability of tuning the frequency to a desired value. In this article, we report a tunable electromagnetic vibration energy harvester capable of being tuned to a specific target frequency. The device adjusts the resonant frequency by changing the effective length of two polyimide springs through a set of smart tuning structures with scales. A maximum frequency tuning range of 58 Hz (46 Hz-104 Hz, 126% relative tuning range) is realized with the proposed device. At a sinusoidal acceleration of 1g, an output peak-to-peak voltage of 263.4 mV and an output power of 143.6 μW are obtained at the frequency of 56 Hz.

Daily 30-min exposure to artificial gravity during 60\xa0days of bed rest does not maintain aerobic exercise capacity but mitigates some deteriorations of muscle function: results from the AGBRESA RCT

PurposeSpaceflight impairs physical capacity. Here we assessed the protective effect of artificial gravity (AG) on aerobic exercise capacity and muscle function during bed rest, a spaceflight analogue.Methods24 participants (33 ± 9 years, 175 ± 9 cm, 74 ± 10 kg, 8 women) were randomly allocated to one of three groups: continuous AG (cAG), intermittent AG (iAG) or control (CTRL). All participants were subjected to 60 days of six-degree head-down tilt bed rest, and subjects of the intervention groups completed 30 min of centrifugation per day: cAG continuously and iAG for 6 × 5 min, with an acceleration of 1g at the center of mass. Physical capacity was assessed before and after bed rest via maximal voluntary contractions, cycling spiroergometry, and countermovement jumps.ResultsAG had no significant effect on aerobic exercise capacity, flexor muscle function and isometric knee extension strength or rate of force development (RFD). However, AG mitigated the effects of bed rest on jumping power (group * time interaction of the rmANOVA p < 0.001; iAG − 25%, cAG − 26%, CTRL − 33%), plantar flexion strength (group * time p = 0.003; iAG − 35%, cAG − 31%, CTRL − 48%) and plantar flexion RFD (group * time p = 0.020; iAG − 28%, cAG − 12%, CTRL − 40%). Women showed more pronounced losses than men in jumping power (p < 0.001) and knee extension strength (p = 0.010).ConclusionThe AG protocols were not suitable to maintain aerobic exercise capacity, probably due to the very low cardiorespiratory demand of this intervention. However, they mitigated some losses in muscle function, potentially due to the low-intensity muscle contractions during centrifugation used to avoid presyncope.

Adaptability of a jump movement pattern to a non-constant force field elicited via centrifugation.

Humans are accustomed to Earth’s constant gravitational acceleration of 1g. Here we assessed if complex movements such as jumps can be adapted to different acceleration levels in a non-constant force field elicited through centrifugation. Kinematics, kinetics and muscle activity of 14 male subjects (age 27±5years, body mass 77±6kg, height 181±7cm) were recorded during repetitive hopping in a short-arm human centrifuge for five different acceleration levels (0.5g, 0.75g, 1g, 1.25g, 1.5g). These data were compared to those recorded during normal hops on the ground, and hops in a previously validated sledge jump system. Increasing acceleration from 0.5g to 1.5g resulted in increased peak ground reaction forces (+80%, p<0.001), rate of force development (+100%, p<0.001) and muscle activity (+30 to +140%, depending on phase, side and muscle). However, most of the recorded parameters did not attain the level observed for jumps on the ground or in the jump system. For instance, peak forces during centrifugation with 1g amounted to 60% of the peak forces during jumps on the ground, ground contact time was prolonged by 90%, and knee joint excursions were reduced by 50%. We conclude that in principle, a quick adaptation to acceleration levels other than the normal constant gravitational acceleration of 1g is possible, even in the presence of a non-constant force field and Coriolis forces. However, centrifugation introduced additional constraints compared to a constant force field without rotation, resulting in lower peak forces and changes in kinematics. These changes can be interpreted as a movement strategy aimed at reducing lower limb deflections caused by Coriolis forces.

Microgravity Environments: The Physical Exercise in The Space

The human body has a great capacity for adaptation, even in the case of significant changes in environmental conditions; like prolonged microgravity. The force of gravity on the earth produces an acceleration of 1g (g is the symbol that indicates the acceleration due to gravity). The term microgravity indicates a reduced force of gravity and is therefore used to describe conditions in which the force of gravity is less than that on the earth’s surface (less than one g). For example, the gravity force of the moon is only 17% of that of the earth, or 0.17g. The term microgravity is often used to describe conditions in space, because the body may not always be in conditions of weightlessness, i.e. at 0g.

Design of a spiral-shaped piezoelectric energy harvester for powering pacemakers

In this paper, a spiral-shaped piezoelectric cantilever structure is proposed to harvest the energy from the vibration of a heartbeat. The proposed cantilever structure is 14 μm thin and has outer dimensions of 6 mm × 6 mm. The spiral structure reduces the stiffness of the cantilever beam, which reduces the resonant frequency. A proof mass is introduced in the spiral structure to reduce further the resonant frequency of the cantilever beam. Due to its biocompatible nature, zinc oxide (ZnO) is used as the piezoelectric material for the design. The proposed structure has a resonant frequency of 30·6 Hz, which is suitable for harvesting energy from the human heartbeat. The resonant frequency of the proposed 3-turn spiral cantilever beam is 33·18% lower than that of the 2·5-turn spiral cantilever beam and 54·93% lower than that of the 2-turn spiral. The proposed harvester generates a peak output open-circuit voltage of 4 V and a peak output power of 5·3 μW at a resonant frequency of 30·6 Hz for a sinusoidal acceleration of 1g (1g = 9·8 m/s2).

A Low-Frequency Three-Dimensional Hybrid Energy Harvester

This paper reports a new design of a three-dimensional vibration energy harvester with high energy output and low working frequency. In a three-dimensional vibrating environment, this electromagnet harvesting structure will have voltage outputs from any directions under a low driving frequency. The volume is about 30mm*30mm*27mm. For an excitation acceleration of 1g, the peak voltage and power output of the electromagnetic part under the vertical vibration can reach to 1.3 V and 0.31mW/cm3, respectively. When the excitation comes from horizontal direction, the peak voltage and power output of electromagnetic part can reach to 361 mV and 0.88mW at 30 Hz. The maximum output of triboelectric part under the vertical vibration can reach to 20V and 17.32μW/cm2 at the excitation frequency of 35 Hz.

A Multiple Vibration Modes Separation Technique Based on 3*5 Element Energy Harvester Array: Frequency, Bandwidth Adjustment, and Electrical Characterization

A neat 3*5 element energy harvester array exploiting multiple vibration modes separation technique, has been designed, fabricated, and characterized. A considerable wideband of 15.6 Hz at simulation and 13 Hz at experiment has been gained in a very low frequency range (below 50 Hz), with the acceleration of 1g. Experimental results show that the adjusted harvester could generate the output power of about 2.1 mW at an 8 Hz resonant frequency with the optimum load resistance 350 $\text{k}\Omega $ . Meanwhile, the half-power (1.05 mW) bandwidth could reach up to 15.3 Hz. These results enable the designed device to improve viability for power supply of low power micro electron devices in some special low frequency vibration environment, such as large engineering applications, bridge monitoring, and wildlife monitoring.

Fiber optic mechanical vibration sensor

A novel cantilever-type fiber Bragg grating (FBG) mechanical vibration sensor has been proposed with an excellent sensitivity through the use of the mechanical axial property of a suspended optical fiber with two fixed ends, enhancing the sensitivity and the resonant frequency. The experimental results show a resolution of 0.006g (where g represents the gravitational acceleration of 1g= 9.81 m/s2), a resonant frequency of 227.3 Hz and a working bandwidth range of 10-210 Hz. The linearity and relative sensitivity errors are 1.9 % and ±4.4 %, respectively.

Unsymmetrical, interdigital vibration energy harvester: Bandwidth adjustment based on mode separation technique

Vibration-based piezoelectric energy harvesting technique is a promising way for power supply of smart and mobile wireless sensor networks. The novel structures of harvester with low frequency, wide bandwidth and large output power have drawn great attention. In this paper, vibration energy harvester with unsymmetrical, interdigital pick-up structure and voltage synchronous management circuit have been designed, fabricated, and characterized. The working bandwidths of 11.2Hz at simulation and 12.3Hz at experiment have been gained for the designed structure based on mode separation technique in a low vibrational frequency range (below 25Hz) with the acceleration of 1g. Experimental results show that the proposed harvester can generate the output power of about 151.3μW (5.91 times of our previous work), which can maintain the normal work of given electronic devices (containing 18 light emitting diodes) by using a matched voltage synchronous management circuit. These results make it a promising candidate for power supply of low power micro electron devices in some special low frequency vibration environment, such as large engineering, bridge monitoring, wildlife monitoring, etc.

Design and analysis of a MEMS-based bifurcate-shape piezoelectric energy harvester

This paper presents a novel piezoelectric energy harvester, which is a MEMS-based device. This piezoelectric energy harvester uses a bifurcate-shape. The derivation of the mathematical modeling is based on the Euler-Bernoulli beam theory, and the main mechanical and electrical parameters of this energy harvester are analyzed and simulated. The experiment result shows that the maximum output voltage can achieve 3.3V under an acceleration of 1g at 292.11Hz of frequency, and the output power can be up to 0.155mW under the load of 0.4MΩ. The power density is calculated as 496.79μWmm−3. Besides that, it is demonstrated efficiently at output power and voltage and adaptively in practical vibration circumstance. This energy harvester could be used for low-power electronic devices.

A non-linear 3D printed electromagnetic vibration energy harvester

This paper describes a novel electromagnetic energy harvester that exploits the low flexural modulus of ABS and comprises of a nonlinear mechanism to enhance the generated power and bandwidth. The device is printed using desktop additive manufacturing techniques (3D printing) that use thermoplastics. It has a ‘V’ spring topology and exhibits a softening spring non-linearity introduced through the magnetic arrangement, which introduces a monostable potential well. A model is presented and measurements correspond favourably. The produced prototype generates a peak power of approximately 2.5mW at a frame acceleration of 1g and has a power bandwidth of approximately 1.2→1.5Hz and 3.5→3.9Hz during up and down sweeps respectively. The device has a power density of 0.4mW/cm3 at a frame acceleration of 1g and a density of 0.04mW/cm3 from a generated power of 25μW at 0.1g.

Development of a Broadband Triboelectric Energy Harvester With SU-8 Micropillars

This paper describes a broadband energy harvester working on the principle of contact electrification or triboelectric charging. Design and fabrication of the device have been discussed. The device uses contact and separation mechanism using a cantilever to generate triboelectric charges. This mechanism introduces nonlinearity in the cantilever, which results in broadband behavior of triboelectric energy harvester. The device uses SU-8 micropillar arrays to enhance the triboelectric charging. A study is conducted to study the effect of the micropillar sizes on the power output of devices. The devices were tested at different acceleration levels. The peak power output achieved is 0.91 μW at an acceleration of 1g. The amplitude limiter based design of the energy harvester enables broadening of operating bandwidth as the acceleration level increases. A maximum operating bandwidth of 22.05 Hz was observed at 1.4g increasing from an operating bandwidth of 9.43 Hz at 0.4g.

Vibration-based energy harvesting with stacked piezoelectrets

Vibration-based energy harvesters with multi-layer piezoelectrets (ferroelectrets) are presented. Using a simple setup with nine layers and a seismic mass of 8 g, it is possible to generate a power up to 1.3 µW at 140 Hz with an input acceleration of 1g. With better coupling between seismic mass and piezoelectret, and thus reduced damping, the power output of a single-layer system is increased to 5 µW at 700 Hz. Simulations indicate that for such improved setups with 10-layer stacks, utilizing seismic masses of 80 g, power levels of 0.1 to 1 mW can be expected below 100 Hz.

A thermal accelerometer directly integrated on organic substrate

A thermal accelerometer was developed and evaluated. The presented device was fabricated directly on an organic substrate, which ensures a high level of thermal isolation, while also facilitating direct electrical communication to the macroworld. The role of the seismic mass was utilized by a fluid (water), which was confined in a tank adjusted on the sensor surface. Acceleration quantification is achieved by the monitoring of the cooling effect on the heating element. A sensor signal of 32mV for an acceleration of 1g was obtained.

航空機用加速度計の製作

An accelerometer for use on aeroplanes was designed and constructed at the Oosaka Branch of the Central Meteorological Observatory to investigate the turbulence or gustiness.1. A direct reading accelerometer-is a simple instrument, having two pendulums each supported by a piano-wire. The instrument is put in a small box. This is used for a preliminary investigation of the period of vibration of aeroplanes caused by gusts.2 An accelerometer with an air damper.-Tbe constants of this instrument are as follows: proper period T0=0.17sec, damping ratio υ=5.4, geometrical magnification V=3.41, statical deviation for the acceleration of 1g=26.7mm, coefficient of friction r=0.4mm_??_0.1mm.The record is obtained automatically with a smoked paper. A steel flat spring is used to give resistive force for an oscillating part having a mass of lead. The writing pen is made of a thin steel wire stuck on the end of the oscillating part, The air-damper consists of a piston with several small holes through which the air escapes.