• Journal of the Korean Society of Physical Medicine
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• v.11 no.2
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• pp.77-82
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• 2016

PURPOSE: The purpose of this study was to investigate the validity of dynamic balance measurements using a smartphone. METHODS: Thirty subjects were selected out of Y-university students without fractures, operation history, and inflammatory arthritis who had not started regular exercise during the past three months. Their dynamic balance ability was measured by the Biodex Balance System (Biodex Medical Systems, Inc., USA) using smartphones. The smartphone utilized in this study was the Galaxy Note4 LTE (SM-N910K, Samsung, Korea), and the application was the Sensor Kinetics pro (Ver.2.1.2, INNOVENTIONS Inc, US). The dynamic balance ability was measured in triplicate. RESULTS: With eyes closed, a low level of correlation (r>0.30, p<0.05) and low reliability (ICC>0.60) were determined between the roll value of the smartphone gyroscope versus the medial/lateral score of the Biodex Balance System. With eyes closed, a low level of correlation (r>0.30, p<0.05) and low reliability (ICC>0.60) were determined between the total value of the smartphone gyroscope versus the total score of the Biodex Balance System. CONCLUSION: This study indicated that using a smartphone can generate highly limited data regarding balance ability. They are unlikely to replace the existing more expensive devices entirely. However, smartphones may be highly useful in environments in which an expensive device is not available or when dynamic balance ability should be measured immediately or within a few hours.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.20 no.4
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• pp.17-22
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• 2020

Behavior-based authentication technology, which is currently being researched a lot, requires a long extraction of a lot of data to increase the recognition rate of authentication compared to other authentication technologies. This paper uses the touch sensor and the gyroscope embedded in the smartphone in the Android environment to measure five times to the user to use only the minimum data that is essential among the behavior feature data used in the behavior-based authentication study. By requesting, a total of six behavior feature data were collected by touching the five touch screen, and the mean value was calculated from the changes in data during the next touch measurement to measure the cosine similarity between the value and the measured value. After generating the allowable range of cosine similarity by performing, we propose a user behavior based authentication method that compares the cosine similarity value of the authentication attempt data. Through this paper, we succeeded in demonstrating high performance from the first EER of 37.6% to the final EER of 1.9% by adjusting the threshold applied to the cosine similarity authentication range even in a small number of feature data and experimenter environments.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.5
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• pp.63-71
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• 2003

In this paper we dicuss the dither-stripping methods by V-F(voltage to frequency) conversion of the output of angular velocity sensor which is for detecting the dither motion of the ring laser cavity. In this case, it is very important to evaluate the pulse-to-pulse scale factor between the ring lase output pulse and V-F output pulse, and also to compensate the zero offset of the V-F output pulse. In the case of the dither-stripping by the V-F conversion of angular velocity sensor output, there is a big angle uncertainty in the process of compensating the zero offset due to the dither noise for compensating the V-F output. By differential, the phase of the V-F output is changed. So, to compensate it, we change 90deg of the phase of angular velocity sensor output and delay half sampling time of the phase of ring laser output in advance. In this case the pulse-to-pulse scale factor can be evaluated by the standard deviation of each pulse. We can get the good result of the dither-stripping output by this angle differential method.

• Current Research on Agriculture and Life Sciences
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• v.32 no.2
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• pp.79-84
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• 2014

The precision aerial application of agricultural unmanned helicopters has become a new paradigm for small farms with orchards, paddy, and upland fields. The needs of agricultural applications require easy and affordable control systems. Recent developments of MEMS technology based on inertial sensors and high speed DSP have enabled the fabrication of low-cost attitude system. Therefore, this study evaluates inertial MEMS sensors for estimating the attitude of an agricultural unmanned helicopter. The accuracies and errors of gyro and acceleration sensors were verified using a pendulum system. The true motion values were calculated using a theoretical estimation and absolute encoder measurement of the pendulum, and then the sensor output was compared with reference values. When comparing the sensor measurements and true values, the errors were determined to be 4.32~5.72%, 3.53~6.74%, and 3.91~4.16% for the gyro rate and x-, z- accelerations, respectively. Thus, the measurement results confirmed that the inertial sensors are effective for establishing an attitude and heading reference system (AHRES). The sensors would be constructed in gimbals for the estimating and proving attitude measurements in the following paper.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39C no.9
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• pp.811-819
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• 2014

Activity recognition is a key component in identifying the context of a user for providing services based on the application such as medical, entertainment and tactical scenarios. Instead of applying numerous sensor devices, as observed in many previous investigations, we are proposing the use of smartphone with its built-in multimodal sensors as an unobtrusive sensor device for recognition of six physical daily activities. As an improvement to previous works, accelerometer, gyroscope and magnetometer data are fused to recognize activities more reliably. The evaluation indicates that the IBK classifier using window size of 2s with 50% overlapping yields the highest accuracy (i.e., up to 99.33%). To achieve this peak accuracy, simple time-domain and frequency-domain features were extracted from raw sensor data of the smartphone.

• International journal of advanced smart convergence
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• v.10 no.4
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• pp.66-71
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• 2021

In this paper, we sought ways to accept and reject advertisements using the function of a smartphone gyro sensor to enable selective transmission and reception of YouTube advertisements by linking the gyro function of mobile phones. In the case of YouTube advertisements, the skip button is activated after the advertisement is played for a certain period of time (about 5 seconds) before and after the video is played. During the time the advertisement is maintained, it can be used to achieve various goals such as increased website traffic, brand awareness, and sales induction. Since this type of advertisement is not a setting in which the transition takes place immediately, it can be seen as the most suitable setting to strengthen brand awareness. However, due to the nature of the YouTube advertising system, it is often discarded through users' skipping behavior in the process of sharing and reproducing information. Therefore, in this paper, we implemented an optional advertisement transmission system that applies the principle of gyroscope to minimize wasted advertisements and selectively maintain desired advertisements in consideration of the transmission and reception aspects of advertisement broadcasts. It measures rotational repulsive force with directional stability and car wash characteristics, and uses algorithms to identify the slope and angular speed of mobile phones to ensure that advertisements are transmitted and received. Through this, it is expected that advertisement transmission can be performed on the side of an advertisement provider, and selective advertisement reception can be performed on the side of a user.

• Journal of the Korea Institute of Military Science and Technology
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• v.22 no.2
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• pp.189-196
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• 2019

The inertial sensor errors in SDINS(Strapdown Inertial Navigation System) can be compensated by rotating the inertial measurement unit and it is called RINS(Rotational Inertial Navigation System). It is assumed that the error of the inertial sensor in RINS is a static bias. However, the error of the inertial sensor actually developed and produced is not a static bias due to the change of the temperature applied to the sensor and the influence of the earth's gravity acceleration. In this paper, we propose a six-position gyro bias calibration method to evaluate the gyro bias required for RINS and present the test results of applying it to a ring laser gyro inertial navigation system under development.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.31 no.3
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• pp.411-422
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• 2021

The autonomous driving system mounted on the unmanned vehicle recognizes the external environment through several sensors and derives the optimum control value through it. Recently, studies on physical level attacks that maliciously manipulate sensor data by performing signal-injection attacks have been published. signal-injection attacks are performed at the physical level and are difficult to detect at the software level because the sensor measures erroneous data by applying physical manipulations to the surrounding environment. In order to detect a signal-injection attack, it is necessary to verify the dependability of the data measured by the sensor. As so far, various methods have been proposed to attempt physical level attacks against sensors mounted on autonomous driving systems. However, it is still insufficient that methods for defending and detecting the physical level attacks. In this paper, we demonstrate signal-injection attacks targeting MEMS sensors that are widely used in unmanned vehicles, and propose a method to detect the attack. We present a signal-injection detection model to analyze the accuracy of the proposed method, and verify its effectiveness in a laboratory environment.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.876-881
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• 2003

Reliable attitude estimation during the launch and early orbit phase is a critical issue for a satellite. Typically gyroscopes and other sensors are utilized to estimate the attitude during this phase. It is difficult to estimate the attitude quickly and reliably using gyroscopes because it requires a large computational load and accurate sensor measurements. Furthermore, the gyroscope failure may lead to the loss of the satellite. This paper suggests a simple attitude estimation method of a low earth orbit satellite without using gyroscopes, but only using sun sensors and magnetometers in the sun-acquisition mode. Using Kompsat-I telemetry data, we verified that the suggested algorithm provides attitude estimation within 3 degrees on each axis.

• Journal of Advanced Marine Engineering and Technology
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• v.24 no.1
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• pp.119-126
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• 2000

In constructing the positioning system based on a conventional dead-reckoning for a wheeled vehicle with pneumatic tires, the position estimation error is inevitable as changes of the radius of the wheels depend on live load and variable enviroment. Therefore, this paper proposes the positioning system which can estimate the error source i.e. the vehicle parameter errors, such as the right and left wheel radius error, using gyroscope and ultrasonic sensor and correct the parameter to reduce the dead-reckoned position estimation error. The extended Kalman filter was used as a method for the multisensor data fusion. The simulation to verify the effectiveness of the proposed positioning system is performed.