• Journal of Sensor Science and Technology
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• v.23 no.6
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• pp.362-367
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• 2014

In this study, a postural change detection sensor module (PCDSM) was developed to detect postural changes in activities of daily living (ADL) and falls. The PCDSM consists of eight mercury sensors that measure angle variations in $360^{\circ}$ rotation and $90^{\circ}$ tilting. From the preliminary study, the output characteristics of the PCDSM were confirmed with the angle variations of rotational motion and a tilting table. Three experiments were conducted to test rotational motion, postural changes, and falling and lying. The results confirmed that the PCDSM could effectively detect postural changes, movement patterns, and falls or non-falls.

• ETRI Journal
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• v.40 no.4
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• pp.522-530
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• 2018

In this study, we developed a robotic walker that actively controls its speed and direction of movement according to the user's gait intention. Sensor fusion between a low-cost light detection and ranging (LiDAR) sensor and inertia measurement units (IMUs) helps determine the user's gait intention. The LiDAR determines the walking direction by detecting both knees, and the IMUs attached on each foot obtain the angular rate of the gait. The user's gait intention is given as the directional angle and the speed of movement. The two motors in the robotic walker are controlled with these two variables, which represent the user's gait intention. The estimated direction angle is verified by comparison with a Kinect sensor that detects the centroid trajectory of both the user's feet. We validated the robotic walker with an experiment by controlling it using the estimated gait intention.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2005.04a
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• pp.235-239
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• 2005

In this research, we investigated the frequency characteristic of low-velocity impact induced damage signals on graphite/epoxy composite laminates using high-speed fiber Bragg grating(FBG) sensor system. Appling the FBG sensors to damage assessment, we need to study the response of FBG sensors as the damage signals of the different incident angles because FBG shows different directional sensitivity. In order to discriminate an impact induced damage signal from that of undamaged case, drop impacts with different energies were applied to the composite panel with different incident angle to the FBG sensor. Finally, detected impact signals were compared using frequency distributions of wavelet detail components in order to find distinctive signal characteristics of composites delamination.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.35 no.8
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• pp.735-740
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• 2007

Star sensor provides highly accurate attitude information by imaging the stars in the dark space. The sensor output is disabled when the sensor avoidance of the Sunlight or the Earth's albedo is not satisfied. This paper studies the Sun and Earth avoidance characteristics of the star sensors according to the mounting direction. Then the paper proposes a systematic way of determining the star sensors mounting direction for typical remote sensing missions

• Smart Media Journal
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• v.8 no.4
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• pp.53-57
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• 2019

In this paper, we propose a flex sensor-based data glove to track the movements of human fingers for virtual reality education. By putting flex sensors and utilizing an accelerometer, this data glove allows people to enjoy applications for virtual reality (VR) or augmented reality (AR). With the maximum and minimum values of the flex sensor at each finger joint, it determines an angle corresponding to the bending value of the flex sensor. It tracks the movements of fingers and hand gestures with respect to the angle values at finger joints. In order to prove the effectiveness of the proposed data glove, we implemented a VR classroom application.

• Journal of the Institute of Convergence Signal Processing
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• v.12 no.4
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• pp.348-354
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• 2011

Mobile robots performed various missions in various environments. In order to move to target precisely, the mobile robots need a precise position sensing system In this paper, a new high precision docking sensor is proposed. Proposed docking sensor consists of linear CCD(charge coupled device) sensor and ultrasonic sensors. The docking sensor system can measure lateral position(X), longitudinal position(Y) and angle(${\theta}$) between the sensor and flat target with simple mark. Two ultrasonic sensors measure two distances which can be converted to longitudinal position and angle. Linear CCD sensor measures lateral position using center mark of the target. To verify performance of the sensor, the sensor is applied to an omnidirectional mobile robot. Several experimental results show highly precise performance of the sensor. Repeatability of the docking sensor is less than 1mm and $0.2^{\circ}$. Proposed docking sensor can be applied for precise docking of mobile robot.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.11
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• pp.2289-2294
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• 2009

In this paper, we proposed a fuzzy controller for racing of a line trace vehicle. Sensor values are computed by statuses of line detecting sensors attached to the line trace vehicle and these sensor values are used for fuzzy inference rules of steering angle control to decide steering angle as output. The decided steering angle is also used for fuzzy inference rules of motor speed control to decide motor speed as output. We experimented and analyzed two proposed methods - one is fuzzy control of steering angle only and the other is fuzzy control of both steering angle and motor speed. In the experiment, we verified that the second proposed method was more efficient in racing speed.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.29 no.10
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• pp.73-82
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• 2015

This paper proposes an ripple reduction algorithm and analyzes the effects of offset and scale errors generated by voltage sensor while measuring grid voltage in grid-tied single-phase inverters. Generally, the grid-connected inverter needs to detect the phase angle information by measuring grid voltage for synchronization, so that the single-phase inverter can be accurately driven based on estimated phase angle information. However, offset and scale errors are inevitably generated owing to the non-linear characteristics of voltage sensor and these errors affect that the phase angle includes 1st harmonic component under using SRF-PLL(Synchronous Reference Frame - Phase Locked Loop) system for detecting grid phase angle. Also, the performance of the overall system is degraded from the distorted phase angle including the specific harmonic component. As a result, in this paper, offset and scale error due to the voltage sensor in single-phase grid connected inverter under SRF-PLL is analyzed in detail and proportional resonant controller is used to reduce the ripples caused by the offset error. Especially, the integrator output of PI(Proportional Integral) controller in SRF-PLL is selected as an input signal of the proportional resonant controller. Simulation and experiment are performed to verify the effectiveness of the proposed algorithm.

• Journal of Institute of Control, Robotics and Systems
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• v.15 no.11
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• pp.1102-1107
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• 2009

An ultrasonic sensor has been widely used as a range sensor for its low cost and capability of detecting some obstacles, such as glasses and black surfaces, which are not well detected by a laser scanner and an IR sensor. Although low-cost sensors are preferred for practical service robots, they suffer from the inaccurate and insufficient range information. This paper proposes a novel approach to obstacle avoidance using low-cost anisotropic ultrasonic sensors with wide beam angle. In this paper, obstacles can be detected by the proposed sensor configuration which consists of one transmitter and three receivers. Because even wide obstacles are represented by a point, which corresponds to the intersection of range data from each receiver of the anisotropic sensor, a robot cannot avoid wide obstacles successfully. This paper exploits the probabilistic mapping technique to avoid collision with various types of obstacles. The experimental results show that the proposed method can robustly avoid obstacles in most indoor environments.

• Aerospace Engineering and Technology
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• v.11 no.2
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• pp.39-48
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• 2012

In case a measurement output of gyro sensor is an accumulated angle counts, it is usually provided as a binary bit counter which is allowed to roll-over at its maximum or minimum value. And it is a well known fact that the roll-over behavior restricts the measurement range of the processed sensor output below the actual measurable range of sensor hardware itself. In this study, a conventional sensor data processing method for a gyro with an accumulated angle output is introduced. And also, an improved method which can extend the processed output range over the conventional one is proposed. It is also derived that the increased range depends on the variation speed of a input signal. Finally, the derived equations and the performance of the proposed algorithm are verified using a computer simulation.