• Journal of the Institute of Convergence Signal Processing
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• v.22 no.3
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• pp.128-133
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• 2021

Recently Recently, the incidence of spinal diseases due to poor posture among students and office workers is increasing, and various studies have been conducted to help maintain correct posture. In previous studies, a membrane sensor or a pressure sensor was placed on the seat cushion to see the weight bias, or a sensor that restrained the user was attached to measure the position change. In our previous study, we developed a sensor device which can be easily attached to the body with an adhesive gel sheet and that measures and outputs the user's posture and body position in real time, but it has a limitation in the accuracy of the sensor value. In this study, a study was conducted to improve the performance of the position conversion sensor device and quantitatively evaluate the accuracy of the angle conversion measurement value, and a high accuracy with 2.53% of error rate was confirmed. In future research, it is considered that additional research targeting actual users is needed by diversifying posture correction training contents with multimedia elements added.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.1325-1328
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• 2007

When we visualize the sound field radiated from a spherical sound source, spherical acoustic holography is proper among acoustic holography methods. However, there are measurement errors due to sensor position mismatch, sensor mismatch, directivity of sensor, and background noise. These errors are amplified if one predicts the pressures close to the sources: backward prediction. The goal of this paper is to quantitatively examine the effects of the error due to sensor position mismatch on acoustic pressure estimation. This paper deals with the cases of which the measurement deviations are distributed irregularly on the hologram plane. In such cases, one can assume that the measurement is a sample of many measurement events, and the cause of the measurement error is white noise on the hologram plane. Then the bias and random error are derived mathematically. In the results, it is found that the random error is important in the backward prediction. The relationship between the random error amplification ratio and the measurement parameters is derived quantitatively in terms of their energies.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.1140-1141
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• 2017

Depth of SWASH(Small Waterplane Area Single Hull) vessel which is an input value of its control system is measured by ultrasonic sensor. Distance to the its center of gravity can be simply calculated through ultrasonic sensor attached to the front of the vessel from the known values. However, it is to be calibrated with respect to its position for the accurate depth because it has geometric relation between the measurement value of ultrasonic sensor and the depth. In this research, depth calibration method of SWASH vessel using its position and ultrasonic sensor is introduced.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.11
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• pp.1907-1912
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• 2016

In fact, in order to obtain good performances and low torque ripple, a high-resolution sensor is needed, which is costly and usually needs a special construction for the machine. So researchers are becoming aware of their cost and are exploring the possibility of cost reduction. Information of rotor position is necessary to drive Linear Switched Reluctance Motor(LSRM). Therefore, linear optical encoder is used to detect a mover position. Normally, since the price of encoder, which is used for linear motor is relatively higher than the one used for rotory motor and the cost of additional equipment increases with the length of motor. This is not always appropriate, considering economical efficiency in case of using the linear optical encoder. As a results, LSRM has a great part for the total cost. Therefore, in this paper, we propose LSRM position detecting modeling with reflective type photo-sensor. Additionally, we have investigated the possibility of the reduced position sensor for LSRM drives with advanced control technique. To certify the overall characteristics of the proposed method, a simulation using PSIM software has been carried out and the informative results are displayed.

• Journal of Sensor Science and Technology
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• v.28 no.6
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• pp.414-419
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• 2019

An ultrasonic based magnetostrictive position sensor (MPS) provides an indication of real target position. It determines the real target position by multiplying the propagation speed of ultrasonic wave and the time-of-flight between the receiving signals; one is the initial signal by an excitation current and the other is the reflection signal by the ultrasonic wave. The propagation speed of the ultrasonic wave depends on the temperature of the waveguide. Hence, the change of the propagation speed in various environments is a critical factor in terms of the positioning accuracy in the MPS. This means that the influence of the changes in the waveguide temperature needs to be compensated. In this paper, we presents a novel way to improve the positioning accuracy of MPSs using temperature compensation for waveguide. The proposed method used the inherent measurement blind area for the structure of the MPS, which can simultaneously measure the position of the moving target and the temperature of the waveguide without any additional devices. The average positional error was approximately -23.9 mm and -1.9 mm before and after compensation, respectively. It was confirmed that the positioning accuracy was improved by approximately 93%.

• Journal of Power System Engineering
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• v.20 no.3
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• pp.22-28
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• 2016

Energy consumption rapidly increases with industrial development. therefore an interest in the efficiency of various power converters is increasing. Especially, the field of high-efficiency small motors widely distributed for industrial and family use is considered a very important field in terms of efficient energy usage, and accordingly, in the field of small electric equipment, the use of BLDC that allows high-efficiency drive in an inductor gradually increases. However, for the BLDC drive, information on the position of the rotor is essential. Both methods using a magnetic encoder and an optical encoder to detect the information on the position of the rotor obtain the information by three position sensitive devices, and if any one of these position sensitive devices fails to function, no positional information can be obtained, so there is a limitation in implementing a position sensor with high reliability. In the paper, proposes a new type of encoder that can obtain the positional information on the position of the rotor using a single position sensor in order to overcome the issues that it has to use numerous signal flows and that the reliability is reduced for the acquisition of positional information generated by using multiple position detectors. The encoder in the proposed method replaced the function of generating positional information from multiple sensors with the shape of the encoder plate and the capture function of MICOM. In order to verify the validity of the position detection technique by the proposed encoder, a prototype was produced, and an experiment using the capture function of DSP was conducted through this.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2010.05a
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• pp.1095-1096
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• 2010

• Journal of the Korean Institute of Intelligent Systems
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• v.15 no.1
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• pp.75-80
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• 2005

In this paper, a 3-dimensional analysis of magnetic road and a position sensing system for an autonomous vehicle system is described. Especially, a new position sensing system, end of the important component of an autonomous vehicle, is proposed. In a magnet based autonomous vehicle system, to sense the vehicle position, the sensor measures the field of magnetic road. The field depends on the sensor position of the vehicle on the magnetic road. As the rotation between the magnetic field and the sensor position is highly complex, it is difficult that the relation is stored in memory. Thus, a neural network is used to learn the mapping from th field to the position. The autonomous vehicle system with the proposed position sensing system is tested in experimental setup.

• IEMEK Journal of Embedded Systems and Applications
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• v.9 no.3
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• pp.151-156
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• 2014

In this paper, we propose a position estimation method of an entertainment robot in a performance stage. A position information is needed to produce contents of an entertainment robot performance. First, the performance stage is realized by a CD (cadmium sulfide) sensor matrix with a constant distance. Then the proposed position estimation uses ON/OFF information of a CD sensor in a performance stage. We confirmed that the position of the robot is detected with an maximum 4cm in position evaluation experiments. The robot was traveling to the final target position in the walking experiment with 75cm and 120cm path plan. Ultimately, the effectiveness of the proposed estimation is assessed by experimental results of a robot in performance stage. Also, in the proposed system installed by a robot performance contents, there is no necessity to mount a position estimation device on a robot; therefore an advantage of our system is that an entertainment robot commercialized by robot vendor can be utilized in our performance stage directly.

• Current Optics and Photonics
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• v.5 no.4
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• pp.362-369
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• 2021

Absolute position sensors are widely used in machine tools and precision measuring instruments because measurement errors are not accumulated, and position measurements can be performed without initialization. The laser speckle-based absolute position sensor, in particular, has advantages in terms of simple system configuration and high measurement accuracy. Unlike traditional absolute position sensors, it does not require an expensive physical length scale; instead, it uses a laser speckle image database to measure a moving surface position. However, there is a problem that a huge database is required to store information in all positions on the surface. Conversely, reducing the size of the database also decreases the accuracy of position measurements. Therefore, in this paper, we propose a new method to measure the surface position with high precision while reducing the size of the database. We use image stitching and approximation methods to reduce database size and speed up measurements. The absolute position error of the proposed method was about 0.27 ± 0.18 ㎛, and the average measurement time was 25 ms.