• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.41 no.4
• /
• pp.284-290
• /
• 2013

The authors propose a nonlinear unknown input observer to estimate the angular speed of a satellite and to detect faults of reaction wheels. Input values are necessary to estimate the angular speed. Therefore, estimation errors are inevitable if faults occur in actuators or reaction wheels. Unknown input observers are useful to estimate the states of a system without being affected by unknown faults. The authors have designed a nonlinear unknown input observer by using the SDRE method and verified the proposed observer via numerical simulations. In spite of various and simultaneous faults, we have estimated the states and detected faults exactly by the proposed nonlinear unknown input observer.

• Korean Journal of Acupuncture
• /
• v.36 no.4
• /
• pp.252-263
• /
• 2019

Objectives : This research aimed to 1) analyze the true meanings of the chapter, 'Wigi Haeng (Wei Qi Xing), the movement of guard qi' in Youngchu (Ling Shu) from the point of view of ancient Chinese Astronomy, 2) calculate the speed of Wigi over 24 Chinese seasons, 3) analyze the true meaning of daytime and nighttime in the chapter. Methods : 1) The chapter 'Wigi Haeng' was analyzed using concepts of ancient Chinese astronomy, 2) the records of angular distances of 28 constellations in the Book of Han (Han Shu) were used to analyze the meanings, and 3) the records of lengths of daytime and nighttime in the Book of Hou Han (Hou Han Shu) were used to calculate the speed of Wigi. Results : 1) The author of the chapter 'Wigi Haeng' did not consider the irregularity in the angular distances of the 28 Chinese constellations (Su). 2) The commentary in the Huangjenaegyong Taeso (Huang Di Nei Jing Tai Su) about the constellations in the chapter is correct. 3) The speed of Wigi changes in daytime and nighttime depending on the seasons. 4) When the speed of Wigi increases in daytime, the speed in nighttime decreases, and vice versa. 5) The beginning of daytime in 'Wigi Haeng' is not the time of sunrise but the time of dawn (2.5 Gak before sunrise). The nighttime ends 2.5 Gak after sunset. Conclusions : 1) The chapter 'Wigi Haeng' demonstrates the ancient astronomical point of view on the universe and the movement of Wigi. The speed of Wigi is variable. 2) This chapter does not address the irregularity in the angular distances of the 28 Su. 3) More research is needed on the meaning of daytime and nighttime in 'Wigi Haeng'.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.17 no.2
• /
• pp.351-358
• /
• 1993

Recently a high speed spindle system for machine tools has attracted considerable attention to reduce the machining time, to improve the machining accuracy, to perform the machining of light metals and hard materials and to unite the cutting and grinding processes. In this study, a high speed spindle system is developed by applying the oil-air lubrication method, angular contact ball bearings, injection nozzles with dual orifices and so on. And a lubrication experiment for evaluating the performance of the spindle system is carried out. Especially, in order to establish the lubrication conditions related to the development of a high speed spindle system, the effects of oil supply rate, rotational spindle speed and so on are studied and discussed on the bearing temperature rise, bearing temperature distribution and frictional torque. And the effect of spindle system structure on the bearing temperature distribution is investigated.

• Journal of the Korean Society for Precision Engineering
• /
• v.11 no.1
• /
• pp.123-128
• /
• 1994

A high speed spindle system for machine tools can be used to reduce the machining time, to improve the machining accuracy, to perform the machining of light metals and hard materials, and to unite the cutting and grinding processes. In this study, a high speed spindle system is developed by applying the oil-air lubrication method, angular contact ball bearings, injection nozzles with dual orifices, cooling jacket and so on. And an air cooling experiment for evaluating the performance of the spindle system is carried out. Especially, in ofder to establish the air cooling conditions related to the development of a high speed spindle system, the effects of cooling air pressure, oil supply rate, air supply rate and rotational spindle speed are studied and discussed on the bearing temperature rise and frictional torque. Also the effects of cooling air pressure, rotational spindle speed and spindle system structure is investigated on the bearing temperature distribution. The experiment on the test model reveals the usefulness of the air cooling method.

• Journal of Ocean Engineering and Technology
• /
• v.25 no.2
• /
• pp.67-72
• /
• 2011

This study had the goal of investigating the effect of the curvature along the heating line on the transverse angular distortion of plates having an initial curvature from line heating. A thermo-elasto-plastic analysis was carried out using 54 models with various radii of curvature, plate thicknesses, and heating speeds. The results show the effect of the curvature along the heating line on the angular distortion in relation to changes in the magnitudes of the curvature, heating speed, and plate thickness. The present numerical results show that the time history of the angular distortion after cooling and reaching the final deformed shape for a plate having an initial curvature is quite different from that of a flat plate. This emphasized the importance of considering the curvature effect on the transverse angular distortion. From the viewpoint of the curvature effect on the deformation, it has been seen that the curvature does not affect the transverse shrinkage. In this study the predicting formula for the transverse angular distortion was derived through a regression analysis. It showed that as the curvature increased, the angular distortion was reduced because of the higher bending rigidity at the same heat input parameter, and the peak points moved toward the origin as the curvature increased.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.67 no.10
• /
• pp.1308-1316
• /
• 2018

Accurate tuning of parameter is very important in vector-controlled induction motor. Among the parameters of induction motor, detuning of rotor resistance used in controller design deteriorates drive performance. This paper presents a novel rotor resistance estimation strategy using slip angular velocity in vector-controlled induction motor drives. The slip angular velocity can be calculated by two methods. Firstly, it can be induced from the rotor voltage equation. Secondly, it can be induced from the difference between synchronous angular velocity and rotor angular velocity. The first method includes the rotor resistance, while the second method dose not include this parameter. From this fact, the rotor resistance can be identified by comparing the slip angular velocities in the two methods. In the tuned states of the rotor resistance, performances of flux estimator and speed drive are discussed. The simulation and experimental results are given to verify the validity of the proposed method in various situations.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2016.10a
• /
• pp.145-148
• /
• 2016

In this paper, we propose a design of Intra Prediction angular mode decision for high-performance HEVC encoder. Intra Prediction works by performing all 35 modes for efficient encoding. However, in order to process all of the 35 modes, the computational complexity and operational time required are high. Therefore, this paper proposes comparing the difference in the value of the original image pixel, using an algorithm that determines Angular mode efficiently. This new algorithm reduces the Hardware size. The hardware which is proposed was designed using Verilog HDL and was implemented in 65nm technology. Its gate count is 14.9k and operating speed is 2GHz.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.21 no.4
• /
• pp.767-773
• /
• 2017

In this paper, we propose a design of Intra prediction angular mode decision for HEVC encoder. Intra prediction coding of HEVC is a method for predicting a current block by referring to samples reconstructed around a current block. Intra prediction supports a total of 35 modes with 1 DC mode, 1 Planar mode, and 33 Angular modes. Intra prediction coding of HEVC works by performing all 35 modes for efficient encoding. However, in order to process all of the 35 modes, the computational complexity and operational time required are high. Therefore, this paper proposes comparing the difference in the value of the original pixel, using an algorithm that determines angular mode efficiently. This new algorithm reduces the Hardware size. The hardware which is proposed was designed using Verilog HDL and was implemented in 65nm technology. Its gate count is 14.9K and operating speed is 2GHz.

• KEPCO Journal on Electric Power and Energy
• /
• v.2 no.4
• /
• pp.619-625
• /
• 2016

In this paper, we propose a new fault diagnosis monitoring system using gyro sensor-based angular velocity calculation for blades of the wind turbine system. First, the proposed system generates the angular velocity dataset for the rotation speed of the normal blade. Using the dataset, we estimate and evaluate the state of blades for the wind turbine by comparing the current state with the pre-calculated normal state. In the experimental results, the angular velocity of the normal state was higher than $360^{\circ}/s$ while that of the damaged blades was lower than $360^{\circ}/s$ and the standard deviation of the angular velocity was significantly increased.

• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.22 no.4
• /
• pp.740-746
• /
• 2013

Angular contact ball bearings are often adopted for a high-speed spindle owing to their durability against axial and radial loads. The dynamic characteristics of an angular contact ball bearing, however, are very complicated because they are dependent on the applied loads as well as on the system configuration. This study systematically analyzes the radial-load-dependent characteristics of spindles as well as angular contact ball bearings. Toward this end, a spindle dynamic model along with the bearing dynamics model is established. An iterative solution algorithm is implemented to resolve the statically indeterminate problem associated with spindle-bearing systems subjected to radial load. Two numerical examples are provided to investigate the spindle and bearing characteristics as a function of radial load with regard to the system configuration.