A system for monitoring heart pulse, respiration and posture in bed.
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A non-invasive system has been developed to monitor cardiac vibrations, respiration and posture of inbed hospitalized patients and elderly people who need constant care. These physiological variables are recorded by four 2 x 28 cm piezoelectric film acceleration sensors, eight 2 x 2 cm small pressure sensors and a 5 x 100 cm long pressure sensor. The piezoelectric sensors, attached to the chest over the heart during bed sleep or rest, detect the movements produced by the heartbeat and respiration. The eight small pressure sensors are attached at various positions on the upper and lower body. A longer pressure sensor, to detect the patient leaving the bed, is attached to the side of the bed. These sensor outputs are digitized at a sampling rate of 200 Hz using a 12-bit A/D converter and stored on a personal computer. The computer detects cardiac vibrations and respiration from upper chest movements and posture from the pressures recorded by small and long pressure sensors.Keywords:
Heart beat
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The results of the development of a remote vibration amplitude and frequency (vibrating acceleration) and also object rotation speed meter are presented. The range of measured parameters are: rotation speeds of 180 to 80000 RPM, vibration frequency of 3 Hz to 10 kHz, and vibration amplitudes up to 5 mm. The device operates in a 5 mm wave band.
Tachometer
Frequency band
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A non-invasive system has been developed to monitor cardiac vibrations, respiration and posture of inbed hospitalized patients and elderly people who need constant care. These physiological variables are recorded by four 2 x 28 cm piezoelectric film acceleration sensors, eight 2 x 2 cm small pressure sensors and a 5 x 100 cm long pressure sensor. The piezoelectric sensors, attached to the chest over the heart during bed sleep or rest, detect the movements produced by the heartbeat and respiration. The eight small pressure sensors are attached at various positions on the upper and lower body. A longer pressure sensor, to detect the patient leaving the bed, is attached to the side of the bed. These sensor outputs are digitized at a sampling rate of 200 Hz using a 12-bit A/D converter and stored on a personal computer. The computer detects cardiac vibrations and respiration from upper chest movements and posture from the pressures recorded by small and long pressure sensors.
Heart beat
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A piezoelectric tripod shaker and a seek-acceleration simulator system developed to evaluate the dynamic characteristics of a head assembly in a hard disk drive and to investigate the effects of vibration during the seek period are discussed. This shaker has three orthogonally placed piezoelectric devices that use flexible mechanisms to avoid interference from each other's vibration. The shaker has a displacement of 4 mu m, a frequency range of 10 kHz, and a mode isolation of over 20 dB. Experimental results of a head assembly, with a standard mini slider shaken in various directions, show that the sway mode (f3 mode) of the lateral (Y-shake) acceleration is dominant. The flying-height fluctuation is obtained during the seed period by using the seek-acceleration simulator system.< >
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Seismocardiography (SCG) is a non-invasive measurement of the vibrations of the chest caused by the heartbeat. SCG signals can be measured using a miniature accelerometer attached to the chest, and are thus well-suited for unobtrusive and long-term patient monitoring. Additionally, SCG contains information relating to both cardiovascular and respiratory systems. In this work, algorithms were developed for extracting three respiration-dependent features of the SCG signal: intensity modulation, timing interval changes within each heartbeat, and timing interval changes between successive heartbeats. Simultaneously with a reference respiration belt, SCG signals were measured from 20 healthy subjects and a respiration rate was estimated using each of the three SCG features and the reference signal. The agreement between each of the three accelerometer-derived respiration rate measurements was computed with respect to the respiration rate derived from the reference respiration belt. The respiration rate obtained from the intensity modulation in the SCG signal was found to be in closest agreement with the respiration rate obtained from the reference respiration belt: the bias was found to be 0.06 breaths per minute with a 95% confidence interval of -0.99 to 1.11 breaths per minute. The limits of agreement between the respiration rates estimated using SCG (intensity modulation) and the reference were within the clinically relevant ranges given in existing literature, demonstrating that SCG could be used for both cardiovascular and respiratory monitoring. Furthermore, phases of each of the three SCG parameters were investigated at four instances of a respiration cycle-start inspiration, peak inspiration, start expiration, and peak expiration-and during breath hold (apnea). The phases of the three SCG parameters observed during the respiration cycle were congruent with existing literature and physiologically expected trends.
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Low frequency vibration occurs especially in ground transportation, either as a cause in adjacent environment or within the vehicle itself. The piezoelectric accelerometers commonly used for vibration measurement are not suitable, hence other sensors capable of measuring accelerations down to sub-hertz region have to be used. Based on some previous experience with MEMS acceleration sensors a three-axial MEMS accelerometer was interfaced to a data acquisition unit. The digitised data were processed by scripts by Matlab ® with the aim to discriminate between low frequency translatory acceleration and vibration acceleration. Some preliminary results of this endeavour are presented.
Vibrator (electronic)
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In this paper we have implemented a Polyvinylidene fluoride (PVDF) based energy harvester system using a speaker based vibration set-up. The vibration energy of the cantilever is harvested using commercially available piezoelectric sensor and the acceleration is measured by an accelerometer. Theoretical analysis of vibration as well as experimental validation has been carried out. The energy harvester is capable of extracting sufficient energy at low environmental vibration within the frequency range of 23 Hz to 35 Hz. With application of 465 mN, the cantilever deflects around 2 mm and the output of piezo sensor is 4.32 V pp while the accelerometer output is 2.88 V pp . It is observed that for a limited range of frequency the low cost speaker has a linear behaviour. The maximum power is achieved as 782 μW with load resistance of 3.3 kΩ using the current set-up and it can be utilised for energy harvesting within the specific range of frequencies.
Polyvinylidene fluoride
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This work presents a convenient and non-contact acoustic sensing approach for measuring ground vibration. This approach, which uses an instantaneous dynamic tire pressure sensor (DTPS), possesses the capability to replace the accelerometer or directional microphone currently being used for inspecting pavement conditions. By measuring dynamic pressure changes inside the tire, ground vibration can be amplified and isolated from environmental noise. In this work, verifications of the DTPS concept of sensing inside the tire have been carried out. In addition, comparisons between a DTPS, ground-mounted accelerometer, and directional microphone are made. A data analysis algorithm has been developed and optimized to reconstruct ground acceleration from DTPS data. Numerical and experimental studies of this DTPS reveal a strong potential for measuring ground vibration caused by a moving vehicle. A calibration of transfer function between dynamic tire pressure change and ground acceleration may be needed for different tire system or for more accurate application.
Pressure measurement
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The main premise originally assumed as the cause for noise was the vibration caused by the barrel and projectile. This vibration was studied and removed. It is apparent that multiple sinusoidal vibrations are present. In a given object, a vibrational mode is induced with a frequency that depends on the object's physical dimensions and on the velocity of the propagating wave through the material or medium of that object. However, the rails could be considered as being positioned on a uniform and soft base which supports the rails from breech to muzzle. Any barrel fiber frequency mode would not be apparent in the accelerometer trace, nor would the rail effects. The projectile provides a filtering medium which would favor only the modes that it could uphold. The projectile has the greatest influence on this data, as was apparent in the frequency analysis. It is sufficient to run a low-pass filter on the data up to the fundamental mode of the projectile.< >
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High-frequency steel and concrete floors are often used to support sensitive equipment to minimize vibration response to walking. Equipment vibration tolerance limits are sometimes expressed as waveform peak acceleration, and are more often expressed as narrowband spectral acceleration, or one-third octave spectral velocity. Current methods predict the waveform peak response after a footstep. However, postprocessing beyond what is practical for typical design office usage is often required to predict responses directly comparable to spectral tolerance limits. Also, current methods are not calibrated to provide a specific level of conservatism. This paper presents new methods for predicting the waveform peak acceleration, narrowband spectral acceleration maximum magnitude, and one-third octave spectral velocity maximum magnitude. A total of 89 walking vibration tests were performed on five high-frequency floor bays. The measurements are used to assess the precision of the proposed methods and to calibrate the prediction methods to provide a specific probability that the actual response will exceed the predicted response. The measurements are compared to predictions by the proposed method and five established methods.
Narrowband
Shock response spectrum
Spectral shape analysis
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Micro-fabricated piezoelectric vibration energy harvesters with resonance frequencies of 31–232 Hz are characterized and deployed for testing on ambient vibration sources in the machine room of a large building. A survey of 23 ambient vibration sources in the machine room is presented. A model is developed which uses a discretization method to accept measured arbitrary acceleration data as an input and gives harvester response as output. The modeled and measured output from the energy harvesters is compared for both vibrometer and ambient vibration sources. The energy harvesters produced up to 43 nW rms g −2 on a laboratory vibrometer and 10 nW g −2 on ambient vibration sources typically in large buildings.
Ambient vibration
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