• Journal of Institute of Control, Robotics and Systems
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• v.19 no.3
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• pp.275-280
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• 2013

Conventional proportional navigation guidance law is not adequate for missiles with a strapdown seeker, because the strapdown seeker cannot measure line-of-sight rate directly. This paper suggests a guidance loop design method, in which the look angle, measured by the strapdown seeker directly, is controlled to deliver a missile to a target. Basically, the look angle control loop is regarded as an attitude control loop. By using the proposed method, it is possible to shape the midcourse trajectory by choosing the reference look angle properly. The look angle control loop can robustly maintain target lock-on against disturbances because the target is always captured in the field of view of the seeker. The performance of the proposed method is verified via 6-DOF simulations of a true short range tactical missile model.

• Journal of the korean Society of Automotive Engineers
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• v.7 no.3
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• pp.64-73
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• 1985

In order to control ignition advance angle, this system is designed with Z-80 CPU, CTC (counter Timer Circuit), PIO(Parallel Input Output), A/D Converter and Memory, etc. Serial pulses from speed sensor and analog voltage from pressure sensor are converted to digital data. In order to reduce the error of ignition advance angle output, the reference of ignition advance angle output is set 56.25 before TDC(Top Dead Center). The table of ignition advance angle and program which have a main routine and subroutines are written into ROM ( 1 K-byte). The experimental result of this system is correspondent to the theoretical values of proposed ignition advance angle table. This system can be utilized to any other type of 4 cylinder vehicles for advance angle control by changing software.

• The Transactions of the Korean Institute of Power Electronics
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• v.14 no.4
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• pp.278-284
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• 2009

This paper presents a firing angle controller of a thyristor converter for DC power supply using PID controller with parallel data loop to improve the dynamic response. The proposed parallel data loop for firing angle controller of 3-phase semi-converter, generates pre-measured firing angle according to reference voltage and load current. With the approximated firing angle according to operating conditions, the output voltage can fast keep the reference value with small voltage error. And the PID controller compensates the output voltage error from the firing angle of parallel data loop. In order to reduce the sudden changing of the data from current ripple, a simple digital low pass filter is used to determine the output data. The proposed control scheme is verified by the experimental test of a practical 50[A] grade thyristor converter system.

• Journal of Power Electronics
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• v.18 no.3
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• pp.714-722
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• 2018

This paper presents a wide-range speed control scheme of brushless DC (BLDC) motors based on a hall sensor with separated low- and normal-speed controllers. However, the use of the hall sensor signal is insufficient to detect motor speed in the low-speed region because of low sensor resolution and time delay. In the proposed method, a micro-stepping current control method according to the torque angle variation is presented. In this mode, the motor current frequency and rotating angle are determined by the reference speed without the actual speed fed by the hall sensor. The detected torque angle is used to adjust the current value in a limited band to control the current value in accordance with the load. The torque angle is detected exactly at the changing point of the hall sensor signal. The rotor can follow the rotating flux with the variable torque angle. In a normal speed range, the conventional vector control scheme is used to control the motor current with a PI speed controller using the hall sensor. The torque characteristics are analyzed on the basis of the back EMF and current shape. To adopt the vector control scheme, the continuous rotor position is estimated by the measured speed and hall sensor position. At the mode changing point between low and normal speed range, the proper initial current command and reference rotor position are calculated. The calculated current command can reduce the torque ripple during transient mode. The proposed method is simple but effective in extending the speed control range of a conventional BLDC motor with hall sensor without the need for a high-resolution encoder. The effectiveness of the proposed method is verified by various experiments on a practical BLDC motor.

• The korean journal of orthodontics
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• v.40 no.4
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• pp.227-238
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• 2010

Objective: The purpose of this study was to analyze the effect of growth hormone treatment (GHT) on craniofacial growth in children of short stature. Methods: Nineteen untreated children of short stature were referred from the Pediatric Department, Yeungnam University Hospital as a subject group. All subjects had lateral cephalograms taken before, after 1 year and after 2 years of growth hormone treatment. As a reference group, we selected 19 normal children with paired sampling who matched the subjects' age and sex, from the Department of Orthodontics, Kyungpook National University Hospital. Results: Before GHT, anterior cranial base length and upper posterior facial height, posterior total facial height, mandibular ramus length, and mandibular corpus length were significantly smaller in the reference group. In angular craniofacial measurements, saddle angle and mandibular plane angle were larger. SNA and SNB were smaller in the reference group. After two years of GHT, growth hormone accelerated growth in several craniofacial components. The posterior total facial height, the anterior, posterior cranial base length, and the mandibular ramus length were increased. And the difference in mandibular plane angle and ANB values compared with the reference group was decreased. Conclusions: GHT over 2 years leads to a craniofacial catch-up growth tendency, which is pronounced in interstitial cartilage and condylar cartilage.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.27 no.3
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• pp.231-238
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• 2001

This study was performed to evaluate soft tissue cephalometric norms for Korean adults which can be implemented in surgical orthodontic treatment planning using selected horizontal reference plane especially for Koreans (Male: $SN-7.5^{\circ}$, Female: $SN-9.0^{\circ}$) and a simplified analytical method. 70 males and 70 females consisting of freshmen of Yonsei University from 1996 to 1997 and students from the Dental College of Yonsei University were chosen according to clinical examination and cephalometric analysis. The samples had normal profiles, normal anteroposterior skeletal relationship(ANB angle of $0^{\circ}\;to\;4^{\circ}$ and Wits appraisal of -4.0mm to 0mm), and Class I molar and canine relationship. They had no missing or supernumerary teeth and had no experience of orthodontic or prosthetic treatment. After the selection of 15 soft tissue landmarks and the construction of horizontal and vertical reference lines, 25 measurements were taken. These consisted of vertical and horizontal linear measurements and angular measurements. The results were as follows. 1. Mean and standard deviation of the measurements were calculated in males and females. 2. Vertical measurements were comparably bigger in males than females whereas anterior facial height ratio(sN-Sn/Sn-sMe) and lower anterior facial height ratio(Sn-Stms/Stmi-sMe) showed no significant difference between sexes. 3. Most of the horizontal measurements in relation to the vertical reference line(G-perpendicular) showed no significant difference between sexes. 4. Nasofacial angle, columellar angle, nasolabial angle and facial contour angle showed no significant difference between sexes. 5. The upper and lower lip were positioned about $-1.0{\pm}2.0mm$ and $+1.0{\pm}2.0mm$ in relation to the Ricketts' esthetic line in both sexes. In this study, soft tissue cephalometric norms of Korean adults for orthognathic surgery were obtained.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.51 no.5
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• pp.249-257
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• 2002

In this paper, a novel control scheme compensating source voltage unbalance and harmonic currents for the combined system of series active and shunt passive power filter is proposed, where no low/high-pass filters are used in deriving the reference voltage for compensation. The phase angle and the reference voltages compensating for harmonic current and unbalanced voltage are derived from the positive sequence component of the unbalanced voltage set, which is simply obtained by using digital all-pass filters. In order to remove the phase delay in generating the reference voltage for compensation, the reference of 5th and 7th harmonic components is predicted one-sampling ahead. The validity of the proposed scheme has been verified for 3[kVA] proto-type active power filter system.

• Journal of Korean Society of Steel Construction
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• v.18 no.3
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• pp.311-320
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• 2006

This study has ben conducted to investigate the effect of the number of bolts on stiffness and strength of a double-angle connection and to propose two simplified models that can predict the initial stiffness and ultimate connection moment of a double-angle connection, respectively. In adition, we also aim to provide some basic reference data for structural designers to choose the most adequate prediction equation and to more precisely double-angle connection.

• Journal of Power Electronics
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• v.7 no.1
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• pp.81-88
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• 2007

This paper presents a new approach to the automatic control of the turn-off angle used to excite the Switched Reluctance Motor (SRM) employed in electric vehicles (EV). The controller selects the turn-off angle that supports and improves the performance of the motor drive system. This control scheme consisting of classical current control and speed control depends on a lookup table to take the best result of the motor. The turn-on angle of the main switches of the inverter is fixed at $0^{\circ}C$ and the turn-off angle is variable depending on the reference speed. The motor, inverter and control system are modeled in Simulink to demonstrate the operation of the system.

• International Journal of Aeronautical and Space Sciences
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• v.7 no.1
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• pp.129-136
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• 2006

A new guidance synthesis for anti-ship missiles to control impact angle and impact time is proposed in this paper. The flight vehicle is assumed as a 1st order lag system to consider more practical system. The proposed guidance synthesis enhances the survivability of anti-ship missiles because multiple anti-ship missiles with the proposed synthesis can hit the target simultaneously. The control input to satisfy constraints of zero miss distance and impact angle, and the feedforward bias control input to control impact time constitute the guidance law. The former is from trajectory shaping guidance, the latter is from neural network. And particle swarm optimization method is introduced to furnish reference input and output for learning in neural network. The performance of the proposed synthesis in the accuracy of impact time and angle is validated by numerical examples.