• Smart Structures and Systems
• /
• 제1권1호
• /
• pp.13-27
• /
• 2005

Simultaneous precision positioning and vibration suppression of a reciprocating flexible manipulator is investigated in this paper. The flexible manipulator is driven by a multifunctional active strut with fuzzy logic controllers. The multifunctional active strut is a combination of a motor assembly and a piezoelectric stack actuator to simultaneously provide precision positioning and wide frequency bandwidth vibration suppression capabilities. First, the multifunctional active strut and the flexible manipulator are introduced, and their dynamic models are derived. A control strategy is then proposed, which includes a position controller and a vibration controller to achieve simultaneous precision positioning and vibration suppression of the flexible manipulator. Next, fuzzy logic control approach is presented to design a fuzzy logic position controller and a fuzzy logic vibration controller. Finally, experiments are conducted for the fuzzy logic controllers and the experimental results are compared with those from a PID control scheme consisting of a PID position controller and a PID vibration control. The comparison indicates that the fuzzy logic controller can easily handle the non-linearity in the strut and provide higher position accuracy and better vibration reduction with less control power consumption.

• 정보처리학회논문지:소프트웨어 및 데이터공학
• /
• 제6권1호
• /
• pp.29-36
• /
• 2017

본 논문에서는 손목형 가속도계를 이용하여 운동 가속도가 거의 없는 식사 행동을 인식하기 위한 방법을 제안한다. 먼저 손목 방향에 작용하는 중력 가속도를 이용하여 중력 방향과 손목 방향 간의 각도를 구하고, 특정 각도 영역에서 첨두값과 첨미값이 존재하는 경우 손목이 왕복하는 동작을 검출한다. 손목 왕복 동작 발생 횟수를 누적하여 그 횟수가 10회 이상일 경우 검출 시점으로 5분 전까지 식사 시간으로 간주하며, 그 지속시간이 7분 이상인 경우에만 식사 시간으로 추론한다. 대학원생 4명으로부터 수집한 2128분 데이터를 통해 식사 시간을 추론한 결과 95.63%의 정확도를 보인다.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2000년도 추계학술대회논문집
• /
• pp.796-801
• /
• 2000

The monitoring and diagnostics of the rotating machinery have been received considerable attention for many years. The objectives are to classify the machinery condition and to find out the cause of abnormal condition. This paper describes a signal classification method for diagnosing the rotating machinery using the artificial neural network and the wavelet transform. In order to extract salient features, the wavelet transform are used from primary noise signals. Since the wavelet transform decomposes raw time-waveform signals into two respective parts in the time space and frequency domain, more and better features can be obtained easier than time-waveform analysis. In the training phase for classification, self-organizing feature map(SOFM) and learning vector quantization(LVQ) are applied, and the accuracies of them are compared with each other. This paper is focused on the development of an advanced signal classifier to automatise the vibration signal pattern recognition. This method is verified by small reciprocating compressors, for refrigerator and normal and abnormal conditions are classified with high flexibility and reliability.

• 한국치위생학회지
• /
• 제21권1호
• /
• pp.17-25
• /
• 2021

Objectives: Interdental toothbrushes are made and sold in various design types and brush thicknesses. However, there is little research on which type of interdental toothbrush currently manufactured and sold on the market is the most effective in eliminating interdental plaque. Therefore, this study aims at comparing the elimination rate of artificial dental plaque between reciprocating- and rotating-types of interdental toothbrush based on the frequency of application and thickness of brush. Methods: This study focused on the effective management of dental plaque using interdental toothbrush, a recommended item for personal dental hygiene. The method was as follows: artificial dental plaque coloring was applied to the distal surface of artificial tooth #46 and the mesial surface of #47. The area was subject to reciprocal movement three and six times to eliminate artificial plaque. Results: The results showed that using a 0.7mm rotating interdental toothbrush, on the proximal surface of each molar, the elimination rates were: on the distal surface of #46, upon three applications 40.24%, upon six applications 30.41%; on the mesial surface of #47, upon three applications 44.52%, upon six applications 29.72%. Conclusions: These results showed that for rotating-type interdental toothbrushes, a high dental plaque elimination rate was observed even though many reciprocal movements were not performed.

• 전력전자학회:학술대회논문집
• /
• 전력전자학회 2003년도 춘계전력전자학술대회 논문집(1)
• /
• pp.424-429
• /
• 2003

A reciprocating compressor with a rotary motor used in a refrigerator has low efficiency, because it has the large mechanical losses due to the crank mechanism. The linear compressor which has the free piston driven by a linear motor, was developed to increase the efficiency of compressor by reducing mechanical losses. The TRIAC has been widely used for controlling the piston, because it has simple structure. However, as it is able to control only stator voltage, it is very difficult to obtain good efficiency. Recently, PWM inverter which is able to control the voltage as well as the frequency, is applied to linear compressor drive system to overcome above problem. In this paper, the variations for efficiency and power factor of linear compressor are investigated by changing both the mechanical resonant frequency and electrical resonant frequency of linear compressor, and also the inverter frequency The optimum relationships between both resonant frequencies and the inverter frequency is derived in order to obtain the maximum efficiency and also good power factor.

• 한국마린엔지니어링학회:학술대회논문집
• /
• 한국마린엔지니어링학회 2005년도 전기학술대회논문집
• /
• pp.149-153
• /
• 2005

Marine Propulsion shafting system coupled with medium diesel engine forms multi-degree torsional vibration system which consist of many inertia masses such as crank, flywheel, propeller and sometimes gear system is adopted additionally for the purpose of improving propeller's propulsion efficiency or connecting with PTO/PTI. The periodic excitation torques generated by combustion pressure in cylinder and reciprocating masses induce various kinds of vibrations in this shafting system. If the frequency of this excitation torques is equal to the natural frequency of the shafting, the amplitude of the torsional vibration increases steeply and the damage of crankshaft or gears may be occurred by that. This frequency is called critical speed. When making a plan for shafting system, it is important for this frequency to be expected exactly and not to be in commonly used speed. For this reason, this paper introduces the experimental equipment for torsional vibration of marine propulsion shafting system and describes the theoretic and the experimental methods to look for natural frequencies.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2007년도 춘계학술대회A
• /
• pp.1026-1030
• /
• 2007

A linear compressor used in a refrigerator has higher energy efficiency than a reciprocating compressor. But its vibration level is still severe than others. The vibration level of linear compressor at the frequency of 60Hz is dominant since it is the exciting frequency of a motor. Experimental approach to reduce the vibration needs much effort and long period. In this paper, simulation tool to predict the vibration of the shell of the linear compressor was developed. The piston, body and shell are assumed to be rigid, while the loop pipe is flexible. The results by the developed tool showed good agreements with those by experiments.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2000년도 추계학술대회논문집B
• /
• pp.278-284
• /
• 2000

The method of Impinging jet was applied lots of part in industrial field as a cooling of as gas turbine blade, a annealing of metal and plastic sheets, drying of textile, veneer paper, X-ray medical devices, laser weapons and electronic components. This study's main factor is reciprocating Jet impingement perpendicular to the heated Surface. We researched the effect of heat transfer and enhancement with pulsating air jet. The pulsating air jet has an improvement in pulsating Frequencies((f= 0.5, 1, 1.5, 3Hz) and nozzle-to-plate distances($l/d=\;2{\sim}4,\;6{\sim}8,\;4{\sim}6,\;8{\sim}10$).

• 한국정밀공학회지
• /
• 제29권12호
• /
• pp.1313-1320
• /
• 2012

Condition monitoring of the reciprocating compressor is important task. As a traditional method, health monitoring system of refrigerator depends on decision of a skilled person based on his experience. However, the skilled person cannot monitor all the compressors completely. If a sampled compressor is faulty, thousands of compressors manufactured at that place are regarded as faulty compressors. Therefore it is necessary to monitor all compressors in the production line. In the paper real time health monitoring system is developed based on high order time frequency method and artificial neural network. The system is installed in the mass production line. The result of the application has been very successful, and currently the system is working very well on the production line.

• Journal of Magnetics
• /
• 제16권1호
• /
• pp.51-57
• /
• 2011

A power supply for magnetic-stimulation devices was designed via a control algorithm that involved a start current application based on a resonant converter. In this study, a new power supply for magnetic-stimulation devices was designed by controlling the pulse repetition frequency and pulse width. The power density could be controlled using the start-current-compensation and ZCS (zero-current switching) resonant converter. The results revealed a high-repetition-frequency, high-power magnetic-stimulation device. It was found that the stimulation coil current pulse width and that pulse repetition frequency could be controlled within the range of 200-450 ${\mu}S$ and 200-900 pps, respectively. The magnetic-stimulation device in this study consisted of a stimulation coil device and a power supply system. The maximum power of the stimulation coil from one discharge was 130 W, which was increased to 260 W using an additional reciprocating discharge. The output voltage was kept stable in a sinusoidal waveform regardless of the load fluctuations by forming voltage and current control using a deadbeat controller without increasing the current rating at the starting time. This paper describes this magnetic-stimulation device to which the start current was applied.