Purpose:The aim of the current study was to investigate the association of accelerometer-measured sleep duration and different intensities of physical activity(PA)with the risk of incident type 2 diabetes in a populat...Purpose:The aim of the current study was to investigate the association of accelerometer-measured sleep duration and different intensities of physical activity(PA)with the risk of incident type 2 diabetes in a population-based prospective cohort study.Methods:Altogether,88,000 participants(mean age=62.2±7.9 years,mean±SD)were included from the UK Biobank.Sleep duration(short:<6 h/day;normal:6-8 h/day;long:>8 h/day)and PA of different intensities were measured using a wrist-won accelerometer over a 7-day period between 2013 and 2015.PA was classified according to the median or World Health Organization-recommendation:total volume of PA(high,low),moderate-to-vigorous PA(MVPA)(recommended,not recommended),and light-intensity PA(high,low).Incidence of type 2diabetes was ascertained using hospital records or death registries.Results:During a median follow-up of 7.0 years,1615 incident type 2 diabetes cases were documented.Compared with normal sleep duration,short(hazard ratio(HR)=1.21,95%confidence interval(95%CI):1.03-1.41)but not long sleep duration(HR=1.01,95%CI:0.89-1.15)was associated with excessive type 2 diabetes risk.This increased risk among short sleepers seems to be protected against by PA.Compared with normal sleepers with high or recommended PA,short sleepers with low volume of PA(HR=1.81,95%CI:1.46-2.25),not recommended(below the World Health Organization-recommended level of)MVPA(HR=1.92,95%CI:1.55-2.36),or low light-intensity PA(HR=1.49,95%CI:1.13-1.90)had a higher risk of type 2 diabetes,while short sleepers with a high volume of PA(HR=1.14,95%CI:0.88-1.49),recommended MVPA(HR=1.02,95%CI:0.71-1.48),or high light-intensity PA(HR=1.14,95%CI:0.92-1.41)did not.Conclusion:Accelerometer-measured short but not long sleep duration was associated with a higher risk of incident type 2 diabetes.A higher level of PA,regardless of intensity,potentially ameliorates this excessive risk.展开更多
The nitrogen-vacancy (NV) center quantum systems have emerged as versatile tools in the field of precision measurement because of their high sensitivity in spin state detection and miniaturization potential as solid-s...The nitrogen-vacancy (NV) center quantum systems have emerged as versatile tools in the field of precision measurement because of their high sensitivity in spin state detection and miniaturization potential as solid-state platforms.In this paper,an acceleration sensing scheme based on NV spin–strain coupling is proposed,which can effectively eliminate the influence of the stray noise field introduced by traditional mechanical schemes.Through the finite element simulation,it is found that the measurement bandwidth of this ensemble NV spin system ranges from 3 kHz to hundreds of kHz with structure√optimization.The required power is at the sub-μW level,corresponding to a noise-limited sensitivity of 6.7×10^(-5) /√Hz.Compared with other types of accelerometers,this micro-sized diamond sensor proposed here has low power consumption,exquisite sensitivity,and integration potential.This research opens a fresh perspective to realize an accelerometer with appealing comprehensive performance applied in biomechanics and inertial measurement fields.展开更多
Purpose: This study focused on maintaining and improving the walking function of late-stage older individuals while longitudinally tracking the effects of regular exercise programs in a day-care service specialized fo...Purpose: This study focused on maintaining and improving the walking function of late-stage older individuals while longitudinally tracking the effects of regular exercise programs in a day-care service specialized for preventive care over 5 years, using detailed gait function measurements with an accelerometer-based system. Methods: Seventy individuals (17 male and 53 female) of a daycare service in Tokyo participated in a weekly exercise program, meeting 1 - 2 times. The average age of the participants at the start of the program was 81.4 years. Gait function, including gait speed, stride length, root mean square (RMS) of acceleration, gait cycle time and its standard deviation, and left-right difference in stance time, was evaluated every 6 months. Results: Gait speed and stride length improved considerably within six months of starting the exercise program, confirming an initial improvement in gait function. This suggests that regular exercise programs can maintain or improve gait function even age groups that predictably have a gradual decline in gait ability due to enhanced age. In the long term, many indicators tended to approach baseline values. However, the exercise program seemingly counteracts age-related changes in gait function and maintains a certain level of function. Conclusions: While a decline in gait ability with aging is inevitable, establishing appropriate exercise habits in late-stage older individuals may contribute to long-term maintenance of gait function.展开更多
Vector accelerometer has attracted much attention for its great application potential in underground seismic signal measurement. We propose and demonstrate a novel vector accelerometer based on the three fiber Bragg g...Vector accelerometer has attracted much attention for its great application potential in underground seismic signal measurement. We propose and demonstrate a novel vector accelerometer based on the three fiber Bragg gratings(FBGs)embedded in a silicone rubber compliant cylinder at 120° distributed uniformly. The accelerometer is capable of detecting the orientation of vibration with a range of 0°–360° and the acceleration through monitoring the central wavelength shifts of three FBGs simultaneously. The experimental results show that the natural frequency of the accelerometer is about 85 Hz, and the sensitivity is 84.21 pm/g in the flat range of 20 Hz–60 Hz. Through experimental calibration, the designed accelerometer can accurately obtain vibration vector information, including vibration orientation and acceleration. In addition, the range of resonant frequency and sensitivity can be expanded by adjusting the hardness of the silicone rubber materials. Due to the characteristics of small size and orientation recognition, the accelerometer can be applied to low-frequency vibration acceleration vector measurement in narrow spaces.展开更多
For the purpose of improving the precision of the inertial guidance system,it is necessary to enhance the accuracy of the accelerometer.Combining the micro-fabrication processes with resonant sensor technology,a high-...For the purpose of improving the precision of the inertial guidance system,it is necessary to enhance the accuracy of the accelerometer.Combining the micro-fabrication processes with resonant sensor technology,a high-resolution inertial-grade novel micro resonant accelerometer is studied.Based on the detecting theory of the resonant sensors,the accelerometer is designed,fabricated,and tested.The accelerometer consists of one proofmass,two micro leverages and two double-ended-tuning-fork (DETF) resonators.The sensing principle of this accelerometer is based on that the natural frequency of the DETF resonator shifts with its axial load which is caused by inertial force.The push-pull configuration of the DETF is for temperature compensation.The two-stage micro leverage mechanisms are employed to amplify the force and increase the sensitivity of the accelerometer.The micro leverage and the resonator are modeled for static analysis and nonlinear modal analysis via theory method and finite element method (FEM),respectively.The geometrical parameters of them are optimized.The amplification factor of the leverage is 102,and the sensitivity of the resonator on theory is about 62 Hz/g.The samples of the accelerometer are fabricated with deep reactive ion etching (DRIE) technology which can get a high-aspect ratio structure for contributing a greater sensing-capacitance.The measuring results of the samples by scanning electron microscopy (SEM) show that the process is feasible,because of the complete structure,the sound combs and micro leverages,and the acceptable errors.The frequency of the resonator and the sensitivity of the accelerometer are tested via printed circuit board (PCB),respectively.The result of the test shows that the frequency of the push-resonator is about 54 530 Hz and the sensitivity of the accelerometer is about 55 Hz/g.The amplification factor of the leverage is calculated more accurately because the coupling of the two stages leverage is considered during derivation of the analysis formula.In addition,the novel differential structure of the accelerometer can greatly improve the sensitivity of the accelerometers.展开更多
This paper reports a piezoelectric nanogenerator(NG) with a thickness of approximately 80 μm for miniaturized self-powered acceleration sensors. To deposit the piezoelectric zinc oxide(ZnO) thin film, a magnetron spu...This paper reports a piezoelectric nanogenerator(NG) with a thickness of approximately 80 μm for miniaturized self-powered acceleration sensors. To deposit the piezoelectric zinc oxide(ZnO) thin film, a magnetron sputtering machine was used. Polymethyl methacrylate(PMMA) and aluminum-doped zinc oxide(AZO) were used as the insulating layer and the top electrode of the NG, respectively. The experimental results show that the ZnO thin films annealed at 150℃ exhibited the highest crystallinity among the prepared films and an optical band gap of 3.24 eV. The NG fabricated with an AZO/PMMA/ZnO/stainless steel configuration exhibited a higher output voltage than the device with an AZO/ZnO/PMMA/stainless steel configuration. In addition, the annealing temperature affected the open-circuit voltage of the NGs;the output voltage reached 3.81 V when the annealing temperature was 150℃. The open-circuit voltage of the prepared self-powered accelerometer increased linearly with acceleration. In addition, the small NG-based accelerometer, which exhibited excellent fatigue resistance, can be used for acceleration measurements of small and lightweight devices.展开更多
In view of the problem that the current single-antenna GPS attitude determination system can only determine the body attitude when the sideslip angle is zero and the multiantenna GPS/SINS integrated navigation system ...In view of the problem that the current single-antenna GPS attitude determination system can only determine the body attitude when the sideslip angle is zero and the multiantenna GPS/SINS integrated navigation system is of large volume, high cost, and complex structure, this approach is presented to determine the attitude based on vector space with single-antenna GPS and accelerometers in the micro inertial measurement unit (MIMU). It can provide real-time and accurate attitude information. Subsequently, the single-antenna GPS/SINS integrated navigation system is designed based on the combination of position, velocity, and attitude. Finally the semi- physical simulations of single-antenna GPS attitude determination system and single-antenna GPS/SINS integrated navigation system are carried out. The simulation results, based on measured data, show that the single-antenna GPS/SINS system can provide more accurate navigation information compared to the GPS/SINS system, based on the combination of position and velocity. Furthermore, the single-antenna GPS/SINS system is characteristic of lower cost and simpler structure. It provides the basis for the application of a single-antenna GPS/SINS integrated navigation system in a micro aerial vehicle (MAV).展开更多
Micro-Opto-Electro-Mechanical Systems(MOEMS)accelerometer is a new type of accelerometer which combines the merits of optical measurement and Micro-Electro-Mechanical Systems(MEMS)to enable high precision,small volume...Micro-Opto-Electro-Mechanical Systems(MOEMS)accelerometer is a new type of accelerometer which combines the merits of optical measurement and Micro-Electro-Mechanical Systems(MEMS)to enable high precision,small volume and anti-electromagnetic disturbance measurement of acceleration.In recent years,with the in-depth research and development of MOEMS accelerometers,the community is flourishing with the possible applications in seismic monitoring,inertial navigation,aerospace and other industrial and military fields.There have been a variety of schemes of MOEMS accelerometers,whereas the performances differ greatly due to different measurement principles and corresponding application requirements.This paper aims to address the pressing issue of the current lack of systematic review of MOEMS accelerometers.According to the optical measurement principle,we divide the MOEMS accelerometers into three categories:the geometric optics based,the wave optics based,and the new optomechanical accelerometers.Regarding the most widely studied category,the wave optics based accelerometers are further divided into four sub-categories,which is based on grating interferometric cavity,Fiber Bragg Grating(FBG),Fabry-Perot cavity,and photonic crystal,respectively.Following a brief introduction to the measurement principles,the typical performances,advantages and disadvantages as well as the potential application scenarios of all kinds of MOEMS accelerometers are discussed on the basis of typical demonstrations.This paper also presents the status and development tendency of MOEMS accelerometers to meet the ever-increasing demand for high-precision acceleration measurement.展开更多
Parkinson’s disease is neurodegenerative in nature and associated with characteristic movement disorders, such as hand tremor. Wireless accelerometer applications may advance the quality of care for Parkinson’s dise...Parkinson’s disease is neurodegenerative in nature and associated with characteristic movement disorders, such as hand tremor. Wireless accelerometer applications may advance the quality of care for Parkinson’s disease patients. The acceleration waveform of the respective hand tremor can be recorded and stored for post-processing and progressive status tracking. A wireless accelerometer configuration for monitoring Parkinson’s disease hand tremor is presented. The proposed configuration is envisioned to be conducted with the assistance of a caregiver. For initial engineering proof of concept simulated Parkinson’s disease tremor is recorded through a wireless accelerometer node and contrasted to a statically positioned and tandem activated wireless accelerometer node. Statistical significance is acquired regarding the quantification of the simulated Parkinson’s disease tremor acceleration waveform and statically positioned acceleration waveform, while demonstrating a considerable degree of accuracy, consistency, and reliability.展开更多
Tremor is a manifestation of a variety of human neurodegenerative diseases, notably Parkinson’s disease (PD) and Essential Tremor (ET), both affecting millions worldwide. PD is primarily caused by a progressive loss ...Tremor is a manifestation of a variety of human neurodegenerative diseases, notably Parkinson’s disease (PD) and Essential Tremor (ET), both affecting millions worldwide. PD is primarily caused by a progressive loss of dopamine neurons in the nigrostriatal system that leads to widespread motor symptoms such as bradykinesia, rigidity, tremor and postural instability. ET typically involves a tremor of the arms, hands or fingers. No definitive test or biomarker is yet available for PD or ET, so the rate of misdiagnosis is relatively high. As tremor is a very common feature at the onset of both diseases, it is crucial to be able to characterize it. This is made possible using acce?lerometers to quantify the tremor amplitude and frequency. In this work we aim to find tasks involving upper limb movements that are suitable to modulate both types of tremor. Four tasks were tested, differing on whether the arms moved together or alternatingly and whether loads were added. Significant differences in tremor measures were found when patients were asked to perform simultaneous rapid arms movements with loads placed on their wrists. These results may allow the design of an efficient fMRI protocol for identifying the cortical circuits responsible for the modulation of tremor.展开更多
A combination of large mass,weak spring and nano-grating is the key for a nano-grating accelerometer to measure nano-G acceleration.A novel compact nano-grating accelerometer integrating a large mass with nano-grating...A combination of large mass,weak spring and nano-grating is the key for a nano-grating accelerometer to measure nano-G acceleration.A novel compact nano-grating accelerometer integrating a large mass with nano-grating is proposed.First,the numbers of diffraction orders are calculated.Then,structure parameters are optimized by finite element analysis to achieve a high sensitivity in an ideal vibration mode.Finally,we design the fabrication method to form such a compact nano-grating accelerometer and successfully fabricate the uniform and well-designed nano-gratings with a period of 847 nm,crater of 451 nm by an FIB/SEM dual beam system.Based on the ANSYS simulation,a nano-grating accelerometer is predicted to work in the first modal and enables the accelerometer to have displacement sensitivity at 197 nm/G with a measurement range of±1 G,corresponding to zeroth diffraction beam optical sensitivity 1%/mG.The nano-gratings fabricated are very close to those designed ones within experimental error to lay the foundation for the sequent fabrication.These results provide a theoretical basis for the design and fabrication of nano-grating accelerometers.展开更多
A triaxial high-g accelerometer of microelectro mechanical systems (MEMS) has a struc- ture of multi-chips combination and will be used in aerospace field, civil and military fields. The ac- celerometer can measure ...A triaxial high-g accelerometer of microelectro mechanical systems (MEMS) has a struc- ture of multi-chips combination and will be used in aerospace field, civil and military fields. The ac- celerometer can measure the acceleration of the carrier. The chips with island-membrane structures on its back surfaces are made by MEMS dry processing. The chip is reasonable and can work well under high impact load; Titanium alloy base is also stronger in high shock environment, these are proved by finite element analysis. Finally, the MEMS combined triaxial high-g accelerometer is vali- dated by high impact calibration experiments in order to get a key performance index, including range, sensitivity and transverse sensitivity and so on. These data can satisfy the need of design but some problems remain, these will be eliminated by improvement of the processing technology and materials.展开更多
A six-axis force sensor with parallel 8/4-4 structure is introduced and its measurement principle is analyzed.Based on condition numbers of Jacobian matrix spectral norm of the sensor,the relationship between the forc...A six-axis force sensor with parallel 8/4-4 structure is introduced and its measurement principle is analyzed.Based on condition numbers of Jacobian matrix spectral norm of the sensor,the relationship between the force and moment isotropy and some structural parameters is deduced.Orthogonal test methods are used to determine the degree of primary and secondary factors that have significant effect on sensor characteristics.Furthermore,the relationship between each performance index and the structural parameters of the sensor is analyzed by the method of the atlas,which lays a foundation for structural optimization design of the force sensor.展开更多
Parkinson’s disease is a growing medical concern as societies, such as the United States of America, become progressively aged. Therapy strategies exist for the amelioration of Parkinson’s disease symptoms, and the ...Parkinson’s disease is a growing medical concern as societies, such as the United States of America, become progressively aged. Therapy strategies exist for the amelioration of Parkinson’s disease symptoms, and the quantification of attributes, such as hand tremor, can provide valuable feedback. Wearable and wireless accelerometer systems for monitoring Parkinson’s disease patients have been progressively advanced over the course of the past half-decade. In particular, wireless accelerometer nodes and smartphones, such as the iPhone, hold promise for optimizing therapy strategy by providing convenient quantified feedback. This perspective review addresses the current advances in wearable and wireless accelerometer systems for monitoring Parkinson’s disease patients and forecasts for the near future.展开更多
Dear Editor,We have read with interest the commentary by McAvoy and Tudor-Locke on our article entitled "Association of accelerometer-derived step volume and intensity with ho spitalizations and mortality in olde...Dear Editor,We have read with interest the commentary by McAvoy and Tudor-Locke on our article entitled "Association of accelerometer-derived step volume and intensity with ho spitalizations and mortality in older adults:A prospective cohort study". The authors expressed some concerns about our methodology used to define accelerometer-derived step intensity and the analytical approach applied in our study.展开更多
The noise of closed loop micro-electromechanical systems(MEMS) capacitive accelerometer is treated as one of the significant performance specifications.Traditional optimization of noise performance often focuses on de...The noise of closed loop micro-electromechanical systems(MEMS) capacitive accelerometer is treated as one of the significant performance specifications.Traditional optimization of noise performance often focuses on designing large capacitive sensitivity accelerometer and applying closed loop structure to shape total noise,but different noise sources in closed loop and their behaviors at low frequencies are seldom carefully studied,especially their behaviors with different electronic parameters.In this work,a thorough noise analysis is established focusing on the four noise sources transfer functions near 0 Hz with simplified electronic parameters in closed loop,and it is found that the total electronic noise equivalent acceleration varies differently at different frequency points,such that the noise spectrum shape at low frequencies can be altered from 1/f noise-like shape to flat spectrum shape.The bias instability changes as a consequence.With appropriate parameters settings,the 670 Hz resonant frequency accelerometer can reach resolution of 2.6 μg/(Hz)1/2 at 2 Hz and 6 μg bias instability,and 1300 Hz accelerometer can achieve 5μg/(Hz)1/2 at 2 Hz and 31 μg bias instability.Both accelerometers have flat spectrum profile from 2 Hz to 15 Hz.展开更多
Parkinson’s disease manifests in movement disorder symptoms, such as hand tremor. There exists an assortment of therapy interventions. In particular deep brain stimulation offers considerable efficacy for the treatme...Parkinson’s disease manifests in movement disorder symptoms, such as hand tremor. There exists an assortment of therapy interventions. In particular deep brain stimulation offers considerable efficacy for the treatment of Parkinson’s disease. However, a considerable challenge is the convergence toward an optimal configuration of tuning parameters. Quantified feedback from a wearable and wireless system consisting of an accelerometer and gyroscope can be enabled through a novel software application on a smartphone. The smartphone with its internal accelerometer and gyroscope can record the quantified attributes of Parkinson’s disease and tremor through mounting the smartphone about the dorsum of the hand. The recorded data can be then wirelessly transmitted as an email attachment to an Internet derived resource for subsequent post-processing. The inertial sensor data can be consolidated into a feature set for machine learning classification. A multilayer perceptron neural network has been successfully applied to attain considerable classification accuracy between deep brain stimulation “On” and “Off” scenarios for a subject with Parkinson’s disease. The findings establish the foundation for the broad objective of applying wearable and wireless systems for the development of closed-loop optimization of deep brain stimulation parameters in the context of cloud computing with machine learning classification.展开更多
The rapid development of MEMS technology has made MEMS accelerometers mature and the application range has been expanded. Many kinds of MEMS accelerometers are researched. According to the working principle of MEMS ac...The rapid development of MEMS technology has made MEMS accelerometers mature and the application range has been expanded. Many kinds of MEMS accelerometers are researched. According to the working principle of MEMS accelerometer, it can be divided into: piezoresistive, piezoelectric, capacitive, tunnel, resonant, electromagnetic, thermocouple, optical, inductive, etc. Due to its outstanding features in terms of size, quality, power consumption and reliability, MEMS sensors are used in military applications and where high environmental resistance is required. MEMS accelerometers are developing rapidly and have good application prospects. In order to make MEMS accelerometers more widely understood, the advantages of MEMS accelerometers are expounded. The research status of MEMS accelerometers is introduced, and MEMS are analyzed. The application of accelerometers in real-world environments, and the development trend of MEMS accelerometers in the future. More scholars will invest in MEMS accelerometer research, pursuing high performance, low power consumption, high precision, multi-function, and interaction. Strong MEMS accelerometers will be ubiquitous in the future.展开更多
With the recent development of digital Micro Electro Mechanical System (MEMS) sensors, the cost of monitoring and detecting seismic events in real time can be greatly reduced. Ability of MEMS accelerograph to record...With the recent development of digital Micro Electro Mechanical System (MEMS) sensors, the cost of monitoring and detecting seismic events in real time can be greatly reduced. Ability of MEMS accelerograph to record a seismic event depends upon the efficiency of triggering algorithm, apart from the sensor's sensitivity. There are several classic triggering algorithms developed to detect seismic events, ranging from basic amplitude threshold to more sophisticated pattern recognition. Algorithms based on STA/LTA are reported to be computationally efficient for real time monitoring. In this paper, we analyzed several STA/LTA algorithms to check their efficiency and suitability using data obtained from the Quake Catcher Network (network of MEMS accelerometer stations). We found that most of the STA/LTA algorithms are suitable for use with MEMS accelerometer data to accurately detect seismic events. However, the efficiency of any particular algorithm is found to be dependent on the parameter set used (i.e., window width of STA, LTA and threshold level).展开更多
基金supported by the National Key R&D Program of China(2021YFC2501500)National Natural Science Foundation of China(82171476)。
文摘Purpose:The aim of the current study was to investigate the association of accelerometer-measured sleep duration and different intensities of physical activity(PA)with the risk of incident type 2 diabetes in a population-based prospective cohort study.Methods:Altogether,88,000 participants(mean age=62.2±7.9 years,mean±SD)were included from the UK Biobank.Sleep duration(short:<6 h/day;normal:6-8 h/day;long:>8 h/day)and PA of different intensities were measured using a wrist-won accelerometer over a 7-day period between 2013 and 2015.PA was classified according to the median or World Health Organization-recommendation:total volume of PA(high,low),moderate-to-vigorous PA(MVPA)(recommended,not recommended),and light-intensity PA(high,low).Incidence of type 2diabetes was ascertained using hospital records or death registries.Results:During a median follow-up of 7.0 years,1615 incident type 2 diabetes cases were documented.Compared with normal sleep duration,short(hazard ratio(HR)=1.21,95%confidence interval(95%CI):1.03-1.41)but not long sleep duration(HR=1.01,95%CI:0.89-1.15)was associated with excessive type 2 diabetes risk.This increased risk among short sleepers seems to be protected against by PA.Compared with normal sleepers with high or recommended PA,short sleepers with low volume of PA(HR=1.81,95%CI:1.46-2.25),not recommended(below the World Health Organization-recommended level of)MVPA(HR=1.92,95%CI:1.55-2.36),or low light-intensity PA(HR=1.49,95%CI:1.13-1.90)had a higher risk of type 2 diabetes,while short sleepers with a high volume of PA(HR=1.14,95%CI:0.88-1.49),recommended MVPA(HR=1.02,95%CI:0.71-1.48),or high light-intensity PA(HR=1.14,95%CI:0.92-1.41)did not.Conclusion:Accelerometer-measured short but not long sleep duration was associated with a higher risk of incident type 2 diabetes.A higher level of PA,regardless of intensity,potentially ameliorates this excessive risk.
基金Project supported by the National Natural Science Foundation of China (Grant No.62071118)the Primary Research & Development Plan of Jiangsu Province (Grant No.BE2021004-3)。
文摘The nitrogen-vacancy (NV) center quantum systems have emerged as versatile tools in the field of precision measurement because of their high sensitivity in spin state detection and miniaturization potential as solid-state platforms.In this paper,an acceleration sensing scheme based on NV spin–strain coupling is proposed,which can effectively eliminate the influence of the stray noise field introduced by traditional mechanical schemes.Through the finite element simulation,it is found that the measurement bandwidth of this ensemble NV spin system ranges from 3 kHz to hundreds of kHz with structure√optimization.The required power is at the sub-μW level,corresponding to a noise-limited sensitivity of 6.7×10^(-5) /√Hz.Compared with other types of accelerometers,this micro-sized diamond sensor proposed here has low power consumption,exquisite sensitivity,and integration potential.This research opens a fresh perspective to realize an accelerometer with appealing comprehensive performance applied in biomechanics and inertial measurement fields.
文摘Purpose: This study focused on maintaining and improving the walking function of late-stage older individuals while longitudinally tracking the effects of regular exercise programs in a day-care service specialized for preventive care over 5 years, using detailed gait function measurements with an accelerometer-based system. Methods: Seventy individuals (17 male and 53 female) of a daycare service in Tokyo participated in a weekly exercise program, meeting 1 - 2 times. The average age of the participants at the start of the program was 81.4 years. Gait function, including gait speed, stride length, root mean square (RMS) of acceleration, gait cycle time and its standard deviation, and left-right difference in stance time, was evaluated every 6 months. Results: Gait speed and stride length improved considerably within six months of starting the exercise program, confirming an initial improvement in gait function. This suggests that regular exercise programs can maintain or improve gait function even age groups that predictably have a gradual decline in gait ability due to enhanced age. In the long term, many indicators tended to approach baseline values. However, the exercise program seemingly counteracts age-related changes in gait function and maintains a certain level of function. Conclusions: While a decline in gait ability with aging is inevitable, establishing appropriate exercise habits in late-stage older individuals may contribute to long-term maintenance of gait function.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 61927812, 61735014, and 62105261)。
文摘Vector accelerometer has attracted much attention for its great application potential in underground seismic signal measurement. We propose and demonstrate a novel vector accelerometer based on the three fiber Bragg gratings(FBGs)embedded in a silicone rubber compliant cylinder at 120° distributed uniformly. The accelerometer is capable of detecting the orientation of vibration with a range of 0°–360° and the acceleration through monitoring the central wavelength shifts of three FBGs simultaneously. The experimental results show that the natural frequency of the accelerometer is about 85 Hz, and the sensitivity is 84.21 pm/g in the flat range of 20 Hz–60 Hz. Through experimental calibration, the designed accelerometer can accurately obtain vibration vector information, including vibration orientation and acceleration. In addition, the range of resonant frequency and sensitivity can be expanded by adjusting the hardness of the silicone rubber materials. Due to the characteristics of small size and orientation recognition, the accelerometer can be applied to low-frequency vibration acceleration vector measurement in narrow spaces.
文摘For the purpose of improving the precision of the inertial guidance system,it is necessary to enhance the accuracy of the accelerometer.Combining the micro-fabrication processes with resonant sensor technology,a high-resolution inertial-grade novel micro resonant accelerometer is studied.Based on the detecting theory of the resonant sensors,the accelerometer is designed,fabricated,and tested.The accelerometer consists of one proofmass,two micro leverages and two double-ended-tuning-fork (DETF) resonators.The sensing principle of this accelerometer is based on that the natural frequency of the DETF resonator shifts with its axial load which is caused by inertial force.The push-pull configuration of the DETF is for temperature compensation.The two-stage micro leverage mechanisms are employed to amplify the force and increase the sensitivity of the accelerometer.The micro leverage and the resonator are modeled for static analysis and nonlinear modal analysis via theory method and finite element method (FEM),respectively.The geometrical parameters of them are optimized.The amplification factor of the leverage is 102,and the sensitivity of the resonator on theory is about 62 Hz/g.The samples of the accelerometer are fabricated with deep reactive ion etching (DRIE) technology which can get a high-aspect ratio structure for contributing a greater sensing-capacitance.The measuring results of the samples by scanning electron microscopy (SEM) show that the process is feasible,because of the complete structure,the sound combs and micro leverages,and the acceptable errors.The frequency of the resonator and the sensitivity of the accelerometer are tested via printed circuit board (PCB),respectively.The result of the test shows that the frequency of the push-resonator is about 54 530 Hz and the sensitivity of the accelerometer is about 55 Hz/g.The amplification factor of the leverage is calculated more accurately because the coupling of the two stages leverage is considered during derivation of the analysis formula.In addition,the novel differential structure of the accelerometer can greatly improve the sensitivity of the accelerometers.
基金supported by the National Natural Science Foundation of China (No. 61671017)Key Project of Excellent Youth Talent Support Program in Colleges and Universities of Anhui Province (No. gxyqZD2018004)+1 种基金Provincial Natural Science Foundation of Anhui Higher Education Institution of China (No. KJ2016A787)Anhui Provincial Natural Science Foundation of China (No. 1508085ME72)
文摘This paper reports a piezoelectric nanogenerator(NG) with a thickness of approximately 80 μm for miniaturized self-powered acceleration sensors. To deposit the piezoelectric zinc oxide(ZnO) thin film, a magnetron sputtering machine was used. Polymethyl methacrylate(PMMA) and aluminum-doped zinc oxide(AZO) were used as the insulating layer and the top electrode of the NG, respectively. The experimental results show that the ZnO thin films annealed at 150℃ exhibited the highest crystallinity among the prepared films and an optical band gap of 3.24 eV. The NG fabricated with an AZO/PMMA/ZnO/stainless steel configuration exhibited a higher output voltage than the device with an AZO/ZnO/PMMA/stainless steel configuration. In addition, the annealing temperature affected the open-circuit voltage of the NGs;the output voltage reached 3.81 V when the annealing temperature was 150℃. The open-circuit voltage of the prepared self-powered accelerometer increased linearly with acceleration. In addition, the small NG-based accelerometer, which exhibited excellent fatigue resistance, can be used for acceleration measurements of small and lightweight devices.
基金the Astronautic Technology Foundation (HTZC0405)
文摘In view of the problem that the current single-antenna GPS attitude determination system can only determine the body attitude when the sideslip angle is zero and the multiantenna GPS/SINS integrated navigation system is of large volume, high cost, and complex structure, this approach is presented to determine the attitude based on vector space with single-antenna GPS and accelerometers in the micro inertial measurement unit (MIMU). It can provide real-time and accurate attitude information. Subsequently, the single-antenna GPS/SINS integrated navigation system is designed based on the combination of position, velocity, and attitude. Finally the semi- physical simulations of single-antenna GPS attitude determination system and single-antenna GPS/SINS integrated navigation system are carried out. The simulation results, based on measured data, show that the single-antenna GPS/SINS system can provide more accurate navigation information compared to the GPS/SINS system, based on the combination of position and velocity. Furthermore, the single-antenna GPS/SINS system is characteristic of lower cost and simpler structure. It provides the basis for the application of a single-antenna GPS/SINS integrated navigation system in a micro aerial vehicle (MAV).
基金supports from National Natural Science Foundation of China(No.62004166)Fundamental Research Funds for the Central Universities(No.31020190QD027)+2 种基金Natural Science Basic Research Program of Shaanxi(Program No.2020JQ-199)China National Postdoctoral Program for Innovative Talents(No.BX20200279)Key Research and Development Program of Shaanxi Province(2020GXLH-Z-027,2020ZDLGY04-08).
文摘Micro-Opto-Electro-Mechanical Systems(MOEMS)accelerometer is a new type of accelerometer which combines the merits of optical measurement and Micro-Electro-Mechanical Systems(MEMS)to enable high precision,small volume and anti-electromagnetic disturbance measurement of acceleration.In recent years,with the in-depth research and development of MOEMS accelerometers,the community is flourishing with the possible applications in seismic monitoring,inertial navigation,aerospace and other industrial and military fields.There have been a variety of schemes of MOEMS accelerometers,whereas the performances differ greatly due to different measurement principles and corresponding application requirements.This paper aims to address the pressing issue of the current lack of systematic review of MOEMS accelerometers.According to the optical measurement principle,we divide the MOEMS accelerometers into three categories:the geometric optics based,the wave optics based,and the new optomechanical accelerometers.Regarding the most widely studied category,the wave optics based accelerometers are further divided into four sub-categories,which is based on grating interferometric cavity,Fiber Bragg Grating(FBG),Fabry-Perot cavity,and photonic crystal,respectively.Following a brief introduction to the measurement principles,the typical performances,advantages and disadvantages as well as the potential application scenarios of all kinds of MOEMS accelerometers are discussed on the basis of typical demonstrations.This paper also presents the status and development tendency of MOEMS accelerometers to meet the ever-increasing demand for high-precision acceleration measurement.
文摘Parkinson’s disease is neurodegenerative in nature and associated with characteristic movement disorders, such as hand tremor. Wireless accelerometer applications may advance the quality of care for Parkinson’s disease patients. The acceleration waveform of the respective hand tremor can be recorded and stored for post-processing and progressive status tracking. A wireless accelerometer configuration for monitoring Parkinson’s disease hand tremor is presented. The proposed configuration is envisioned to be conducted with the assistance of a caregiver. For initial engineering proof of concept simulated Parkinson’s disease tremor is recorded through a wireless accelerometer node and contrasted to a statically positioned and tandem activated wireless accelerometer node. Statistical significance is acquired regarding the quantification of the simulated Parkinson’s disease tremor acceleration waveform and statically positioned acceleration waveform, while demonstrating a considerable degree of accuracy, consistency, and reliability.
文摘Tremor is a manifestation of a variety of human neurodegenerative diseases, notably Parkinson’s disease (PD) and Essential Tremor (ET), both affecting millions worldwide. PD is primarily caused by a progressive loss of dopamine neurons in the nigrostriatal system that leads to widespread motor symptoms such as bradykinesia, rigidity, tremor and postural instability. ET typically involves a tremor of the arms, hands or fingers. No definitive test or biomarker is yet available for PD or ET, so the rate of misdiagnosis is relatively high. As tremor is a very common feature at the onset of both diseases, it is crucial to be able to characterize it. This is made possible using acce?lerometers to quantify the tremor amplitude and frequency. In this work we aim to find tasks involving upper limb movements that are suitable to modulate both types of tremor. Four tasks were tested, differing on whether the arms moved together or alternatingly and whether loads were added. Significant differences in tremor measures were found when patients were asked to perform simultaneous rapid arms movements with loads placed on their wrists. These results may allow the design of an efficient fMRI protocol for identifying the cortical circuits responsible for the modulation of tremor.
基金Supported by the National Natural Science Foundation of China under Grant No 60908016.
文摘A combination of large mass,weak spring and nano-grating is the key for a nano-grating accelerometer to measure nano-G acceleration.A novel compact nano-grating accelerometer integrating a large mass with nano-grating is proposed.First,the numbers of diffraction orders are calculated.Then,structure parameters are optimized by finite element analysis to achieve a high sensitivity in an ideal vibration mode.Finally,we design the fabrication method to form such a compact nano-grating accelerometer and successfully fabricate the uniform and well-designed nano-gratings with a period of 847 nm,crater of 451 nm by an FIB/SEM dual beam system.Based on the ANSYS simulation,a nano-grating accelerometer is predicted to work in the first modal and enables the accelerometer to have displacement sensitivity at 197 nm/G with a measurement range of±1 G,corresponding to zeroth diffraction beam optical sensitivity 1%/mG.The nano-gratings fabricated are very close to those designed ones within experimental error to lay the foundation for the sequent fabrication.These results provide a theoretical basis for the design and fabrication of nano-grating accelerometers.
基金Supported by the National Natural Science Foundation of China(61273346)the National Defense Major Fundamental Research Program of China(20110003)+3 种基金the National Defense Key Fundamental Research Program of China(20132010)Specialized Research Fund for the Doctoral Program of Higher Education(20121101120009)Excellent Young Scholars Research Fund of Beijing Institute of Technology(2012YG0203)the Program for the Fundamental Research of Beijing Institute of Technology(2015CX02034)
文摘A triaxial high-g accelerometer of microelectro mechanical systems (MEMS) has a struc- ture of multi-chips combination and will be used in aerospace field, civil and military fields. The ac- celerometer can measure the acceleration of the carrier. The chips with island-membrane structures on its back surfaces are made by MEMS dry processing. The chip is reasonable and can work well under high impact load; Titanium alloy base is also stronger in high shock environment, these are proved by finite element analysis. Finally, the MEMS combined triaxial high-g accelerometer is vali- dated by high impact calibration experiments in order to get a key performance index, including range, sensitivity and transverse sensitivity and so on. These data can satisfy the need of design but some problems remain, these will be eliminated by improvement of the processing technology and materials.
基金supported by the Open Foundation of Graduate Innovation Base(Laboratory)of Nanjing University of Aeronautics and Astronautics (No.kfjj20170512)the National Natural Science Foundation of China(No. 51175263)
文摘A six-axis force sensor with parallel 8/4-4 structure is introduced and its measurement principle is analyzed.Based on condition numbers of Jacobian matrix spectral norm of the sensor,the relationship between the force and moment isotropy and some structural parameters is deduced.Orthogonal test methods are used to determine the degree of primary and secondary factors that have significant effect on sensor characteristics.Furthermore,the relationship between each performance index and the structural parameters of the sensor is analyzed by the method of the atlas,which lays a foundation for structural optimization design of the force sensor.
文摘Parkinson’s disease is a growing medical concern as societies, such as the United States of America, become progressively aged. Therapy strategies exist for the amelioration of Parkinson’s disease symptoms, and the quantification of attributes, such as hand tremor, can provide valuable feedback. Wearable and wireless accelerometer systems for monitoring Parkinson’s disease patients have been progressively advanced over the course of the past half-decade. In particular, wireless accelerometer nodes and smartphones, such as the iPhone, hold promise for optimizing therapy strategy by providing convenient quantified feedback. This perspective review addresses the current advances in wearable and wireless accelerometer systems for monitoring Parkinson’s disease patients and forecasts for the near future.
基金funded by the University of Castilla-La Mancha (MS2021)
文摘Dear Editor,We have read with interest the commentary by McAvoy and Tudor-Locke on our article entitled "Association of accelerometer-derived step volume and intensity with ho spitalizations and mortality in older adults:A prospective cohort study". The authors expressed some concerns about our methodology used to define accelerometer-derived step intensity and the analytical approach applied in our study.
基金Project(61404122)supported by the National Natural Science Foundation of China
文摘The noise of closed loop micro-electromechanical systems(MEMS) capacitive accelerometer is treated as one of the significant performance specifications.Traditional optimization of noise performance often focuses on designing large capacitive sensitivity accelerometer and applying closed loop structure to shape total noise,but different noise sources in closed loop and their behaviors at low frequencies are seldom carefully studied,especially their behaviors with different electronic parameters.In this work,a thorough noise analysis is established focusing on the four noise sources transfer functions near 0 Hz with simplified electronic parameters in closed loop,and it is found that the total electronic noise equivalent acceleration varies differently at different frequency points,such that the noise spectrum shape at low frequencies can be altered from 1/f noise-like shape to flat spectrum shape.The bias instability changes as a consequence.With appropriate parameters settings,the 670 Hz resonant frequency accelerometer can reach resolution of 2.6 μg/(Hz)1/2 at 2 Hz and 6 μg bias instability,and 1300 Hz accelerometer can achieve 5μg/(Hz)1/2 at 2 Hz and 31 μg bias instability.Both accelerometers have flat spectrum profile from 2 Hz to 15 Hz.
文摘Parkinson’s disease manifests in movement disorder symptoms, such as hand tremor. There exists an assortment of therapy interventions. In particular deep brain stimulation offers considerable efficacy for the treatment of Parkinson’s disease. However, a considerable challenge is the convergence toward an optimal configuration of tuning parameters. Quantified feedback from a wearable and wireless system consisting of an accelerometer and gyroscope can be enabled through a novel software application on a smartphone. The smartphone with its internal accelerometer and gyroscope can record the quantified attributes of Parkinson’s disease and tremor through mounting the smartphone about the dorsum of the hand. The recorded data can be then wirelessly transmitted as an email attachment to an Internet derived resource for subsequent post-processing. The inertial sensor data can be consolidated into a feature set for machine learning classification. A multilayer perceptron neural network has been successfully applied to attain considerable classification accuracy between deep brain stimulation “On” and “Off” scenarios for a subject with Parkinson’s disease. The findings establish the foundation for the broad objective of applying wearable and wireless systems for the development of closed-loop optimization of deep brain stimulation parameters in the context of cloud computing with machine learning classification.
文摘The rapid development of MEMS technology has made MEMS accelerometers mature and the application range has been expanded. Many kinds of MEMS accelerometers are researched. According to the working principle of MEMS accelerometer, it can be divided into: piezoresistive, piezoelectric, capacitive, tunnel, resonant, electromagnetic, thermocouple, optical, inductive, etc. Due to its outstanding features in terms of size, quality, power consumption and reliability, MEMS sensors are used in military applications and where high environmental resistance is required. MEMS accelerometers are developing rapidly and have good application prospects. In order to make MEMS accelerometers more widely understood, the advantages of MEMS accelerometers are expounded. The research status of MEMS accelerometers is introduced, and MEMS are analyzed. The application of accelerometers in real-world environments, and the development trend of MEMS accelerometers in the future. More scholars will invest in MEMS accelerometer research, pursuing high performance, low power consumption, high precision, multi-function, and interaction. Strong MEMS accelerometers will be ubiquitous in the future.
基金IIT Roorkee under the Faculty Initiation Grant No.100556
文摘With the recent development of digital Micro Electro Mechanical System (MEMS) sensors, the cost of monitoring and detecting seismic events in real time can be greatly reduced. Ability of MEMS accelerograph to record a seismic event depends upon the efficiency of triggering algorithm, apart from the sensor's sensitivity. There are several classic triggering algorithms developed to detect seismic events, ranging from basic amplitude threshold to more sophisticated pattern recognition. Algorithms based on STA/LTA are reported to be computationally efficient for real time monitoring. In this paper, we analyzed several STA/LTA algorithms to check their efficiency and suitability using data obtained from the Quake Catcher Network (network of MEMS accelerometer stations). We found that most of the STA/LTA algorithms are suitable for use with MEMS accelerometer data to accurately detect seismic events. However, the efficiency of any particular algorithm is found to be dependent on the parameter set used (i.e., window width of STA, LTA and threshold level).