• Journal of the Korean Society of Industry Convergence
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• v.19 no.2
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• pp.81-87
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• 2016

This paper presents a new approach to control of stable motion of single wheel driving robot system of a pitch that is controlled by an in-wheel motor and a roll that is controlled by a reaction wheel. This robot doesn'thave any actuator for a yaw axis control, which makes the derivation of the dynamics relatively simple. The Lagrange equations was applied to derive the dynamic equations of the one wheel driving robot to implement the dynamic speed control of the mobile robot. To achieve the real time speed control of the unicycle robot, the sliding mode control and optical regulator are utilized to prove the reliability while maintaining the desired speed tracking performance. In the roll controller, the sigmoid-function based robust controller has been adopted to reduce the vibration by the situation function. The optimal controller has been implemented for the pitch control to drive the unicycle robot to follow the desired velocity trajectory in real time using the state variables of pitch angle, angular velocity, angle and angular velocity of the driving wheel. The control performance of the control systems from a single dynamic model has been illustrated by the real experiments.

• Journal of Biomedical Engineering Research
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• v.37 no.1
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• pp.15-20
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• 2016

Essential tremor is a neurological disorder with a tremor of the arms and hands. It is well known that essential tremor is characterized by the postural tremor and the action tremor. There has been no report on the quantitative difference in the characteristics of two tremor types. The purpose of this study was to investigate the possible difference in tremor characteristics of postural and action tremors. Seventeen patients with essential tremor ($68.9{\pm}7.9years$, 7 men, 10 women) participated in this study. Patients performed the tasks of postural maintenance (arms outstretched) and daily actions (spiral drawing). Three-axes (pitch, roll and yaw) gyro sensors were attached on index finger, back of hand and forearm, from which the segment and the joint angular velocities were calculated. Outcome measure was the tremor amplitude defined as the root-mean-square mean of the vector-sum angular velocity at segments and joints. Two-way ANOVA showed that task and joint had main factor on the tremor amplitude (p < 0.05). Post-hoc analysis revealed that tremor amplitude at the metacarpo-phalangeal joint was not affected by task (p > 0.05). However, tremor amplitude at the wrist joint differed among the tasks (p < 0.05), and it was greater in the action tasks than in postural task. Tremor was greater at finger segments than at hand and forearm and it increased in action tasks. The results of this study would be helpful for the understanding and task-specific treatments of the essential tremor.

• Journal of IKEEE
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• v.26 no.4
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• pp.602-613
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• 2022

This paper proposes an algorithm for correcting indirect situations resulting from the wheelchair moving the stairs with wheel-type caterpillar and seat position variable. For analyzing the Yawing movement model, the change of Yaw value was estimated using Roll, Pitch, and Yaw in the driving environment, and it was used as a control variable and the information of the wheel drive controller. The verification confirmed the correction of about 10° of Yawing movement within about 7 seconds. It was confirmed that the angular velocity was reduced by 47.5% in seat position change.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 1995.04a
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• pp.65-92
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• 1995

The final aim of our research project is a study on assessment of automatic steering system of ships in open seas. In order to achieve this aim we need to know the characteristics of each component of the system and also to know the characteristics of disturbance to ship dynamcis. In this paper we provide calculation method of irregular disturbance to ships in autopilot navigation in open seas and also show calculation examples about two kinds of ship ore carrier and fishing boat. The disturbance consists of irregular wave and random wind, The disturbance is calculated as equivalent yaw angular velocity. Each spectrum and time history of disturbance are reasonably evaluated. Further investigation concerning to performance index of autopilot system and energy loss related to automatic course keeping will be dealt with in another paper,

• Journal of the Korean Institute of Navigation
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• v.19 no.2
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• pp.1-12
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• 1995

The final aim of our research project is a study on assessment of automatic steering system of ships in open seas. In order to achieve this aim, we need to know the characteristics of each component of the system, and also to know the characteristics of disturbance to ship dynamics. In this paper, we provide calculation method of irregular disturbance to ships in autopilot navigation in open seas, and also show calculation examples about two kinds of ship, ore carrier and fishing boat. The disturbance consists of irregular wave and random wind. The disturbance is calculated as equivalent yaw angular velocity. Each spectrum and time history of disturbance are reasonably evaluated. Further investigation concerning to performance index of autopilot system and energy loss related to automatic course keeping, will be dealt with in another paper.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.34 no.2
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• pp.165-173
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• 1998

When an automatic course-keeping is concerned, as is quite popular in modem navigation, the closed-loop steering system consists of autopilot device, power unit (or telemotor unit), steering gear, magnetic or gyro compass and ship dynamics. In order to estimate automatic steering system of ships in open seas. we need to know the characteristics of each component of the system, and also to know the characteristics of disturbance to ship dynamics. In this paper, I provide calculation method of imposing irregular disturbance to autopilot navigation system of the ship in open seas, and also show calculation examples about fishing boat. The disturbance consists of the irregular wave and the fluctuating component of wind. Finally, The disturbances are calculated in terms of equivalent yaw angular velocity. Each spectrum and time history of disturbance are reasonably evaluated.

• Journal of the Institute of Electronics and Information Engineers
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• v.53 no.7
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• pp.95-102
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• 2016

Geomagnetic sensors are widely utilized for sensing heading direction of quadrotors. However, measurement from a geomagnetic sensor is easily corrupted by environmental magnetic field interference and roll/pitch directional motion. In this paper, a measurement method of a quadrotor heading direction is proposed for application to yaw attitude control. In order to eliminate roll/pitch directional motion effect, the geomagnetic sensor data is compensated using the roll/pitch angles measured for stabilization control. In addition, yaw-directional angular velocity data from a gyroscope sensor is fused with the geomagnetic sensor data using a complementary filter which is a simple and intuitive sensor fusion method. The proposed method is applied to experiments, and the results are presented to prove validity and effectiveness of the proposed method.

• Journal of Ocean Engineering and Technology
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• v.31 no.2
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• pp.177-182
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• 2017

This paper describes an unscented Kalman filter approach to estimate the bias in magnetic field measurements. A microelectromechanical systems attitude heading reference system (MEMS AHRS) was used to measure the magnetic field, together with the acceleration and angular rate. A magnetic field is usually used for yaw detection, while the acceleration serves to detect the roll and pitch. Magnetic field measurements are vulnerable to distortion due to hard-iron effect and soft-iron effect. The bias in the measurement accounts for the hard-iron effect, and this paper focuses on an approach to estimate this bias. The proposed method is compared with other methods through experiments that implement the navigation of an underwater robot using an AHRS and Doppler velocity log. The results verify that the compensation of the bias by the proposed method improves the navigation performance more than or comparable to the compensation by other methods.

• Journal of the Society of Naval Architects of Korea
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• v.59 no.3
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• pp.173-182
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• 2022

The present study suggests a procedure of establishing a ship dynamics modeling by regression of free-running model test results. The hydrodynamic force and moment of the whole model ship is derived from the low-pass filtered acceleration in the turning circle and zigzag maneuver tests. Force and moment of the propeller and rudder are separated from that of the whole ship to acquire the hull force and moment terms, based on the principles of the component model. The low-pass filter frequency is verified in prior to dynamics modeling, to find the threshold frequency of 2.5 Hz. The dynamics modeling of the hull is compared with the component modeling by captive model tests. Because of strong correlation between sway velocity, yaw angular velocity, and heel angle, each maneuvering coefficient is not able to be validated, but the whole modeling shows good agreement with the captive model tests.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.15 no.1 s.94
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• pp.20-28
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• 2005

This paper addresses uncertainty issues encountered recently in measuring head vibration using the conventional 6-axis or 9-axis bite-bar model. Those conventional bite-bar models are shown to present insufficient information to evaluate a generalized motion of head vibration. In order to overcome such limit, a new theoretical measurement model that consists of four 3-axis linear accelerometers is suggested. It is shown to enable the measurement of three angular acceleration components and six second-order angular velocity-dependent terms. Those nine angular motion-related ones, in addition to the three linear acceleration terms at the origin, are found to make it possible to evaluate the generalized head vibration for a given position. To examine the feasibility of the proposed method, a newly designed 12-axis bite-bar was developed. Detailed experimental results obtained from the developed 12-axis bite-bar are demonstrated in this paper. They illustrate that the popular 6-axis bite-bar model yield about $4.0\%$ relative measurement uncertainty for the pitch component of head vibration, $14\%$ and $10\%$ relative measurement uncertainty for the roll and yaw components of head vibration, respectively. Furthermore, this paper proposes other uncertainty factors to be considered in the future.