• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2005.06a
• /
• pp.1883-1886
• /
• 2005

In this paper, a decoupled dual servo (DDS) stage for ultra-precision scanning system with large working range is introduced. In general, dual servo systems consist of a fine stage for short range and a coarse stage for long range. The proposed DDS also consists of a $XY\theta$ fine stage for handling and carrying workpieces and one axis coarse stage. Its coarse stage consists of air bearing guide system and a coreless linear motor with force ripple. The fine has four voice coil motors(VCM) as its actuator. According to a VCM's nature, there are no mechanical connections between coils and magnetic circuits. Moreover, VCM doesn't have force ripples due to imperfections of commutation components of linear motor systems - currents and flux densities. However, due to the VCM's mechanical constraints the working range of the fine is about $25mm^2$. To break that hurdle, the coarse stage with linear motors is used to move the fine about 500mm. Because of the above reasons, the proposed DDS can achieve higher precision scanning than other stages with only one servo. With MATLAB's Sequential Quadratic Programming (SQP), the VCMs are optimally designed for the highest force under conditions and constraints such as thermal dissipations due to its coil, its size, and so on. And for their movements without any frictions, guide systems of the DDS are composed of air bearings. To get precisely their positions, a linear scale with 5nm resolution are used for the coarse stage's motion and three plane mirror laser interferometers with 5nm for the fine's $XY\theta$ motions. With them, on scanning the two stages have same trajectories. The control algorithm is named Parallel method. The embodied ultra-precision scanning system has sub 100nm following error and in-positioning stability.

• The Journal of Korean Academy of Sensory Integration
• /
• v.12 no.1
• /
• pp.25-38
• /
• 2014

Objective : This study was conducted to determine effects of school-based occupational therapy through a systematic review Methods : We systematically reviewed studies published in PubMed and Ovid from 2000 to June 2014 using keyword 'school' or 'children' and 'occupational therapy'. Fourteen studies were selected. The level of evidence, participants, assessment, intervention area, method and effects were analyzed by reviewing full text. Results : The most group and age of participants were normal child with fine motor difficulties and 6~8 years old in selected studies. The most target area of intervention was handwriting, fine motor and visuo-motor integration (68.8%) and the most method was direct treatment (71.4%). The top on the assessment was Beery-Buktenica Test of Visual-Motor Integration (14.9%) and next was Bruininks-Oseretsky Test of Motor Proficiency (11.1%). Effects of school based occupational therapy were founded in the visual motor integration, learning skill, level of participation, fine motor, play and behavioral problem. Conclusion : This systematic review provides evidence concerning the participants, intervention, assessment and effects of school based occupational therapy. It should be used for basic data for the research and practice of school-based occupational therapy.

• Journal of Sensor Science and Technology
• /
• v.24 no.4
• /
• pp.228-231
• /
• 2015

Ultrasonic motors provide high torques and quick responses compared to their magnetic counterparts; therefore, they are widely used in small-scale applications such as mobile phones, microrobots, and auto-focusing modules in digital cameras. To determine the feasibility of lead-free piezoceramics for ultrasonic motor applications, we fabricated a ring-type piezoceramic with a KNN-based lead-free piezoceramic (referred to as CZ5), intended for use in an auto-focusing module of a digital camera. The vibration of the lead-free stator was observed at 45.1 kHz. It is noteworthy that the fully assembled lead-free ultrasonic motor exhibited a revolution speed of 5-7 rpm, even though impedance matching with neighboring components was not considered. This result suggests that the tested KNN-based piezoceramic has great potential for use in ultrasonic motor applications, requiring minimal modifications to existing lead-based systems.

• Proceedings of the KSME Conference
• /
• 2004.04a
• /
• pp.840-845
• /
• 2004

In many applications, piezoelectric motor has been used in the areas where excellent controllability, fine position resolution are required or magnetic field noise should be eliminated. However the piezoelectric motor has two major demerits. One is difficulty in maintaining vibration amplitude constantly with temperature rise and wear, and the other is heat generation induced by dielectric and mechanical loss. In this thesis, piezoelectric motor to overcome these problems is proposed. And proposed piezoelectric motor is operated using momentum exchange between bimorph and rotor. To maximize steady state velocity and static torque of proposed motor, the guideline is established using two bimorph models. Then the guideline is partially proved by comparison between simulation and experiment. There was no heat generation in the few hours of experiments.

• Proceedings of the KIEE Conference
• /
• summer
• /
• pp.1034-1036
• /
• 2004

The most basic form of a direct-drive linear motor is the voice coil motor(VCM). The voice coil motor employs a stationary permanent magnet field assembly in conjunction with a moving coil winding assembly to produce a force proportional to the current applied to the coil. Voice coil motor provide motion capable of extremely fine position sensitivity, limited only by the feedback sensor used to close the control loop. This paper presents dual-servo voice coil motor for improvement of driving range and position resolution. The voice coil motor is a cylindrical shape to improve reliability of a nanoindenter.

• Journal of the Korean Academy of Child and Adolescent Psychiatry
• /
• v.28 no.4
• /
• pp.244-251
• /
• 2017

Objectives: The objective of this study was to investigate the effect of pharmacological treatments for attention-deficit hyperactivity disorder (ADHD) on motor coordination, using the Developmental Coordination Disorder Questionnaire (DCDQ). Methods: The participants were recruited from April 2015 to November 2016 from the Department of Psychiatry of Asan Medical Center and were treated for 3 months with methylphenidate or atomoxetine. The illness severity at baseline and 3 months were scored using the ADHD Rating Scale (ARS), Clinical Global Impression-Severity Scale (CGI-S) and/or Clinical Global Impression-Improvement Scale (CGI-I). A total of 39 children with ADHD (age $8.0{\pm}1.4years$, 36 boys) completed the Advanced Test of Attention (ATA) and their parents completed the DCDQ at baseline and 3 months. The paired t-test, mixed between-within analysis of variance and correlation analysis were used. Results: The CGI-S (p<0.001), ARS (p<0.001), and fine motor/hand writing (p=0.005) on the DCDQ were significantly changed between pre-treatment and post-treatment. When the participants were divided into those who were suspected of having developmental coordination disorder (DCD) (n=23) and those who probably did not (n=16), the control during movement, fine motor/hand writing and general coordination scores on the DCDQ showed the main effects for group (p<0.001, p<0.001 and p<0.001, respectively). The fine motor/hand writing on the DCDQ has a significant main effect for time [F(1,37)=7.31, p=0.010, ${\eta}^2=0.405$] and the interaction effect between group and time was also significant [F(1,37)=4.63, p=0.038, ${\eta}^2=0.111$]. The baseline visual commission error on the ATA is significantly correlated with the changes in the DCDQ total scores (r=0.330, p=0.040). Conclusion: Our results provide preliminary evidence that pharmacological treatment for ADHD improves not only the core symptoms of ADHD, but also the motor coordination. Further studies are needed to confirm the effect of the pharmacological treatment for ADHD on the motor coordination.

• Aerospace Engineering and Technology
• /
• v.3 no.2
• /
• pp.7-10
• /
• 2004

KOMPSAT-2 needs fine accuracy attitude control when it is operated in Science mode. Reaction Wheel is a necessary part of fine controlling the attitude of satellite. The reaction Wheel Assembly(RWA) is a device which provides reaction torque for attitude-control of spacecraft. It consists of an electric motor, a rotating flywheel, motor control device electrics, commutation electronics and associated power converters. This document identifies what activities to be carried out to integrate the RW#1 for ETB tests.

• Proceedings of the KIEE Conference
• /
• 2005.10c
• /
• pp.158-161
• /
• 2005

For low power motor control, there are increasing demands for compactness, cost effective and built in many functions. Hence Intelligent Power Module(IPM) is considered as an important technology in inverter-driven motor applications. Regarding BID-IPM(Built In DC/DC converter, Intelligent Power Module) newly developed to integrate NPT-IGBT, HVIC and Flyback converter in a compact package, this paper discussed design of BID-IPM and presented the experimental results by using signal source board and equivalent load test board.

• Transactions of the Korean Society of Machine Tool Engineers
• /
• v.11 no.1
• /
• pp.17-25
• /
• 2002

This system is composed of fine and coarse apparatus, measurement system and control system. Piezoelectric actuator is designed far fee positioning. We make a study of precision apparatus that is used in the various industrial machine. The study was carried out to develope a precision positioning apparatus, consisting of servo motor and piezoelectric actuator Coarse positioning using lead screw is thrived by servo motor. Control system output a signal from laser interferometer to amplifier of servo motor and piezoelectric actuator after digital signal processing (DSP). Resolution of this apparatus measure with laser interferometer. In this study, design method and control system with ultra precision position apparatus are researched. As the first step, we have estimated for control performance and system stability before an actual apparatus is manufactured by MATLAB with SIMUUNK including various frictions those are composed of pre-design and system modeling.

• The Journal of Korean Academy of Sensory Integration
• /
• v.9 no.1
• /
• pp.21-31
• /
• 2011

Objective : This study investigated the relationships of handwriting legibility and perceptual-motor skills, and handwriting speed and perceptual-motor skills. And identified the predictors that most affect the handwriting of preschool children. Methods : Twenty-three typically developing preschool aged children (mean age: 68.61 months, SD=2.04) were selected through the Korean-Denver Developmental Screening Test-2(K-DDST-2). The children were tested with regard to handwriting legibility, visual perception, visual-motor integration and fine-motor coordination. Results : First, a significant relationship was not found among handwriting legibility, visual perception, visualmotor integration and fine-motor coordination. Second, a significant relationship was found among handwriting speed, visual perception and fine-motor coordination. Third, stepwise multiple regression analyses showed that general visual perception were significant predictors for handwriting speed. Conclusion : Occupational therapists should evaluate children's visual perception levels utilizing a standardized test, and focus on general visual perception in order to improve handwriting skill(speed). Also, occupational therapists are expected to play an important role in the management and treatment of children's handwriting skills.