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Performance of frequency translation in separating a photoplethysmographic signal from an additive motion artifact
(2019-02-01)
Koseeyaporn, Jeerasuda
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Sinchai, Sakkarin
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Wardkein, Paramote
Obtaining red and infrared (IR) photoplethysmographic (PPG) signals by a general method in a commercial pulse oximeter is overlapped with an additive motion artifact (MA) signal routinely. When the red and IR PPG signals are combined with the MA signal, a percentage of oxygen saturation (SpO2) is unreliable. To prevent the overlapping problem, a technique of frequency translation is introduced to shift the PPG frequency components away from the MA frequency components. The introduced approach remodels an LED-driving system by substituting an alternating current (AC) source for a traditional direct current (DC) source in the commercial pulse oximeter. To assess the performance, the SpO2 values computed from the red and IR PPG signals acquired by the presented solution are evaluated when four natural poses of motion occur. Besides, the well-known methods are used to calculate the SpO2 values from the red and IR PPG signals sensed by the conventional LED-emitting system during motion for the efficient comparison. The well-known methods are discrete saturation transform (DST), fast independent component analysis (fICA) and compression of Fourier coefficients (CFC). The resulting SpO2 values show that the technique of frequency translation provides overall mean error lower than the selected schemes for all postures. The overall mean error of the introduced technique is 1.1% while the approaches of DST, fICA and CFC yield the overall mean errors by 2.9%, 15.4% and 8.4%, respectively.
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Influence of Light Intensity on a Motion Artifact Signal in a Photoplethysmographic Signal
(2018-11-27)
Koseeyaporn, Jeerasuda
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Sinchai, Sakkarin
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Tuwanut, Panwit
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Wardkein, Paramote
A photoplethygraphic (PPG) signal acquired from a commercial pulse oximeter is habitually disfigured by a motion artifact (MA) signal while any motion takes place. Inherently, the MA signal can either be additive or multiplicative, By having the MA signal intertwined with the PPG signal, the estimate of the oxygen saturation (SpO2) value is unreliable. The computation of SO02 value is based on proper red and infrared (IR) PPG signals measured by the pulse oximeter. Generally, the frequency components of the red and IR PPG signals as well as the MA signal are in the same range. To overwhelm this problem, the frequency components of the red and IR PPG signals are severed from the frequency band of the MA signal. To implement the separation, a legacy source of driving red and IR LEDs in the pulse oximeter is replaced by two alternating current sources having different frequencies. With this solution, the additive MA signal is no longer involved but the multiplicative MA signal is yet not concluded. In this work, change in light intensity fed to both red and IR LEDs is studied whether the changed light intensity has any impact on the multiplicative MA signal. According to the study, it is found that change in light intensity does not affect the multiplicative MA signal. The multiplicative MA signal still exists since the overall calculated SpO2 values have some error up to 1 %. Besides, change in light intensity does not improve the quality of the estimated SpO2 values while resting.
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Human Identification Technique Based Behavioural Standing Still on Force Plates
(2018-09-11)
Sirisilpa, Pattraporn
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Sinchai, Sakkarin
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Wardkein, Paramote
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Sangpisit, Wipa
This article proposes the human identification technique based behavioural standing still on force plates. Since the body sway that occurs during a quiet stand is caused by the movement of the center of mass and the center of pressure, thus the transfer of weight on the left and right feet of each person has a unique characteristic. This characteristic is then applied to identify individuals. In addition, the signals obtained from eyes open and eyes close condition are studied. The processing results are obtained by MATLAB program. The results of the proposed method show that the behavioural standing still signal in eyes open condition can be applied for human identification. However, the further study and improvement of the proposed principle is needed to acquire better in false rate of identification.
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Distance Measurement Technique Using Phase Difference of Two Reflected Ultrasonic Frequencies
(2018-09-11)
Chongchamsai, Munchuphon
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Sinchai, Sakkarin
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Wardkein, Paramote
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Boonjun, Surapol
This paper proposes a simple method of distance measurement utilizing phase difference of two reflected ultrasonic frequencies. To obtain the phase difference, an alternating signal which contains two sinusoidal signals having different frequencies is fed to an ultrasonic transmitter. When the transmitted signal is reflected and received by the ultrasonic receiver, the received signal is first squared. Then, a time shift property of Fourier transform is applied to the squared signal to acquire the phase difference. The phase difference is converted to a time-of-flight (TOF) value and turned to the distance. To experiment the proposed technique, a DSP TMS620C6713 board is employed to generate the alternating signal as well as to receive the reflected signal, and to process the received signal. In the experiment, two sinusoidal signals having frequencies of 39.85 kHz and 40.6 kHz are used. The results show that the obtained distance by the presented approach has fairly low error only 0.15 centimeters compared to the actual distance.
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Distance Detection Technique Using Enhancing Inverse Perspective Mapping
(2018-09-11)
Wongsaree, Preaw
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Sinchai, Sakkarin
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Wardkein, Paramote
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Koseeyaporn, Jeerasuda
This paper presents a distance determination technique using an image from the single forward camera. Since too dark or too bright of the image and non-linear relation between height of the object and distance from the camera have effect on the performance of the detection process. Therefore, automatic brightness adjustment and inverse perspective mapping (IMP) is applied in the proposed scheme. In addition, region of interest (ROI) determination is used to decrease the processing time. The experimental results confirm that the proposed technique can detect distance of the object in front of the car where the error is 7.96%.
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Frequency Estimation of Short Range Radar Using Adaptive FIR Notch Filter and SAGC for Velocity Detection
(2018-09-11)
Chinakaew, Pannipa
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Sinchai, Sakkarin
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Wardkein, Paramote
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Koseeyaporn, Jeerasuda
This research proposes the velocity detection for short range radar using an adaptive FIR notch filter and a sinusoidal automatic gain control scheme (SAGC). A HB 100 module with amplifying gain of 20 times produces Doppler signal and this signal is fed to a laptop through a sound card with sampling frequency of 8000 Hertz. The signal is processed by the SAGC to amplify the amplitude of the signal to be unity. To detect the frequency of the signal, an algorithm of indirect frequency estimation based on adaptive FIR notch filter is performed. After that, the resulting frequency is converted to velocity. All procedures in this work are processed by MATLAB program. The results of the proposed method have better signal to noise ratio compared with existing method. In addition, the presented work consumes low computational time.
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A Photoplethysmographic Signal Isolated from an Additive Motion Artifact by Frequency Translation
(2018-08-01)
Sinchai, Sakkarin
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Kainan, Pattana
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Wardkein, Paramote
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Koseeyaporn, Jeerasuda
Acquiring a precise percentage of oxygen saturation (SpO2) from a finger-probe pulse oximeter is dependent on both artifact-free red and infrared photoplethysmoghaphic (PPG) signals. Nonetheless, in real-life situations, these PPG signals are corrupted by a motion artifact (MA) signal that is generated from either finger or hand movement. To resolve this MA interference, the cause of the adulteration of PPG signals by the MA signal is examined. The MA signal is found to behave like an additive noise. Additionally, the frequency responses of the MA and PPG signals show that these signals are in the same frequency band. Hence, instead of direct current, a sinusoidal wave alternating current is proposed to drive an LED source in order to shift the PPG frequency band away from the MA frequency band. Experimentally, a commercial finger-probe pulse oximeter is employed. To determine the performance of the presented scheme, the resulting PPG signals are compared with those from employing the old-fashioned LED-driving method. In addition, the accuracy is verified by computing the SpO2 value. The results reveal that the proposed approach successfully retains the fundamental morphologies of the PPG structures when motion occurs. Moreover, the calculated SpO2 values from the proposed technique provide an average error of approximately 1.4%, whereas the conventional method yields a mean error approximately 4.2%.
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Estimating an optimal setpoint to lessen errors in filling weighing system based on Kalman filtering
(2014-01-01)
Sinchai, Sakkarin
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Saechia, Sukkharak
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Limpiti, Tulaya
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Koseeyaporn, Jeerasuda
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Wardkein, Paramote
A weighing system in which a sensor is not mounted to a discharger especially in vertical filling gives rise to an excess of weight added to the given target of weight. In addition, the excess is not constant on account of some factors, such as vibration of the machine, flow of the substance, and cycle time of the system. These factors cause the surplus to oscillate. To overcome this problem, Kalman filtering is performed to predict the optimal setpoint to meet the defined target. To illustrate the performance of the proposed technique, the resulting outcome is compared with that of using the conventional statistical method. The results have shown that the proposed approach has significantly increased the speed and lowered the error. It is pointed out that the proposed algorithm may be preferable to the traditional statistical technique due to its effectiveness and its simple implementation. © 2014 IEEE.

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