• Clinical and Experimental Pediatrics
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• 제49권10호
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• pp.1019-1025
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• 2006

Motor delay, when present, is usually the first concern brought by the parents of children with developmental delay. Cerebral palsy that is the most common motor delay, is a nonspecific, descriptive term pertaining to disordered motor function that is evident in early infancy and is characterized by changes in muscle tone, muscle weakness, involuntary movements, ataxia, or a combination of these abnormalities. A wide range of causative disorders and risk factors have been identified for cerebral palsy, and broadly classified into 5 groups; perinatal brain injury, brain injury related to prematurity, developmental abnormalities, prenatal risk factors, and postnatal brain injury. Delay in attaining developmental milestones is the most distinctive presenting complaint in children with cerebral palsy. A detailed history and thorough physical and neurologic examinations are crucial in the diagnostic process. The clinician should be cautious about diagnostic pronouncement unless the findings are unequivocal. Several serial examinations and history review are necessary. All children with cerebral palsy should undergo a neuroimaging study, preferably MRI, because an abnormality is documented on head MRI(89%) and CT(77%). The high incidence rates for mental retardation, epilepsy, ophthalmologic defects, speech and language disorders and hearing impairment make it imperative that all children with cerebral palsy be screened for mental retardation, ophthalmologic and hearing impairments, and speech and language disorders; nutrition, growth, and swallowing also should be closely monitored.

• 제어로봇시스템학회논문지
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• 제9권8호
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• pp.632-639
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• 2003

This paper proposes a simple compensation scheme for the time delay caused by measurement, calculation and selection of voltage vector in Direct Torque Control (DTC) of an induction motor. In general scheme, it is difficult to know the exact delay time, furthermore the delay time can be varied by program routines for calculation and processing of measured data. In this proposed scheme, by applying voltage vector at the beginning of next sampling period, a fixed delay time is achieved and its compensation becomes much simpler. Furthermore, with the simple compensation algorithm, an improved performance can be achieved by shortening sampling period. Experimental results prove the feasibility of the proposed scheme in induction motor control.

• Journal of Electrical Engineering and Technology
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• 제12권6호
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• pp.2289-2297
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• 2017

Applying a periodic load torque to an AC motor generates a ripple, which is synchronized to the frequency of the periodic load torque, at the speed of the motor. Consequently, numerous studies have focused on reducing the speed ripple caused by the load torque. However, it is difficult to reduce the speed ripple when there is a time delay in acquiring speed information, such as that from a sensorless control. Therefore, we propose a speed control method for reducing speed ripples caused by a periodic load torque when there is a time delay in acquiring the speed information. The proposed method is verified by conducting simulations using the Simulink program from MATLAB, and by applying the method to an actual motor in which speed ripples occur due to a periodic load torque that is synchronized with the speed of the motor.

• 아동학회지
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• 제29권3호
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• pp.339-356
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• 2008

Participants in this study on preschool children's ability to delay gratification were 132 4- to 5 year-old children and their mothers from 6 daycare centers. Mothers completed questionnaires reporting their parenting style, their child's ability to delay gratification, and child's temperament. Children participated in the real and hypothetical settings of the delay of gratification experiment. Data was analyzed by t-test, F-test, correlation and discrimination analysis. Results were that (1) 43% of preschoolers passed the delay of gratification experiment. (2) Older children were more able to delay gratification than younger children. (3) Children's rewards choices in the real setting correlated with their rewards choices in the hypothetical situation of delay of gratification. (4) Children's ability to delay gratification was influenced by their motor intelligence.

• 한국전문물리치료학회지
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• 제4권1호
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• pp.48-62
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• 1997

Several studies have evaluated the effects of types of relative frequency and delay interval of knowledge of results(KR) on motor skill learning independently. The purpose of this study was to determine more effective types of KR relative frequency and KR delay interval for motor learning. Forty-six healthy subjects (15 female, 31 male) with no previous experience with this experiment participated. The subjects ranged in age from 20 to 29 years (mean=23.9, SD=0.474). All subjects were assigned to one of four groups: a high-instant group, a high-delay group, a low-instant group, and a low-delay group. During the acquisition phase, subjects practiced movements to a target (400 mm) with either a high (83%) or low (33%) KR relative frequency, and with either an instantaneous or delayed (after 8s) KR. Four groups were evaluated on retention (after 3min and 24hr) and transfer (450 mm) tests. The major findings were as follows: (1) there were no between-group differences in acquisition and short-term retention (p>0.05, (2) a low (33%) KR relative frequency during practice was as effective for learning as measured by both long-tenn retention and transfer tests, compared with high (83%) KR practice conditions (p<0.05), (3) delayed (8s) KR enhanced learning as measured by both long-term retention and transfer tests, compared with instantaneous KR practice conditions (p<0.05), and (4) there were no interactions between KR relative frequency and KR delay interval during acquisition, retention, and transfer phases. The results suggest that relatively less frequent and delayed KR are more effective types for motor learning than more frequent and instantaneous KR.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2001년도 춘계학술대회 논문집
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• pp.555-559
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• 2001

Feed and spindle motor currents are used toi monitor the cutting process practically. The sensitivity of spindle drive system is lower than that of feed drive system, but the cutting torque is represented well by the spindle motor current. During multi-axis cutting, it is difficult to calculate the resultant cutting force using feed motor currents, because each feed force is reflected by each axis feed motor current with different time delay. It is also difficult to compensate the frictional torque using the feed motor current, because the magnitude of the frictional torque is dependent of the feedrate, table position, and cutting direction. On the other hand, cutting torque can be estimated well using spindle motor current which is independent of the cutting direction.

• 제어로봇시스템학회논문지
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• 제9권12호
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• pp.1001-1008
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• 2003

A time-delay compensation method for vector control system is proposed that can compensate for voltage and current distortions resulting from a time delay in the overall system due to the low pass filter, hysteresis control inverter, microprocessor program computation time, and so on. The proposed scheme estimates the time delay using the difference between the Q-axis stator current command and the time-delayed actual Q-axis stator current in a synchronous reference frame, then compensates the time delay in the voltage and current using the angular displacement of a DQ transformation. Accordingly, the proposed scheme can accurately compensate for the time delay related to the overall system, thereby significantly improving the performance of the vector control system, as verified by simulation and experiment.

• Journal of Electrical Engineering and Technology
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• 제11권1호
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• pp.241-246
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• 2016

This paper presents a method that can improve the performance of permanent magnet synchronous motor current control by minimizing the measured current phase delay caused by the Low Pass Filter(LPF) used to cut off the noises that flowed in when feedback currents are measured. Although existing methods that change the Cutoff Frequency of the LPF can minimize phase delays during high speed rotations, their noise cutoff effects are much lower and this may lead to the decline of control performance. Therefore, in this study, an algorithm that can compensate current phase delays through relatively simple calculations from the synchronous motor d-q axis coordinate transformation matrix and the inverse transformation matrix is proposed and the validity of the proposed method is verified by comparing the waveform of the calculated current with the waveform of actual currents through simulations and experiments.

• 대한의용생체공학회:의공학회지
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• 제29권1호
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• pp.8-16
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• 2008

The aim of this study was to evaluate the motor recovery in 4 chronic hemiparetic patients with Fugl-Meyer (FM) and EMG characteristics before and after the training program. The training was performed at 1hr/day, 5days/week during 6 weeks in 4 chronic stroke patients. Electromyographic activities of the affected hand were recorded during isometric wrist flexion/ extension movements. In all patients, FM was significantly improved after the 6-week training. Onset/offset delay of muscle contraction significantly decreased in the affected wrist after the training. The co-contraction ratio of flexor/extensor muscles decreased significantly. Also, onset/offset delay of muscle contraction and co-contraction ratio correlates significantly with upper limb motor impairment and motor recovery. This EMG technique allows an objective evaluation of changes in muscle activity in post-stroke patients, providing easily measurable, quantitative indices of muscle characteristics.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년 영문 학술대회
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• pp.301-306
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• 2008

A pyrogen igniter was designed to satisfy the required condition of kick motor system for the space launch vehicle. We analyzed the ignition characteristics and performed the combustion tests to verify the internal ballistic performance. In the design process, the arc-image test was carried out to find the sufficient heat flux as varying the initial pressure from 10 to 700kPa. The analysis indicated that the initial pressure condition would delay ignition time within a range from 100 to 500ms. The combustion test with an inert chamber was also performed to understand the ignition characteristics with the variation of the initial pressure of free chamber volume. Finally, we confirmed that the igniter could provide the acceptable energy to ignite the propellant of kick motor at the ground test. The result of the ground tests showed that the ignition delay time was within the design range at the atmospheric pressure condition.