• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.1741-1744
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• 2005

The electron beam machining provides very high resolution up to nanometer scale, hence the E-Beam writing technology is rapidly growing in MEMS and nano-engineering areas. For E-Beam machining, $2^{nd}$ electron detector is required to see a machined sample at the stage. The $2^{nd}$ electron detector is composed of scintillator and photomultiplier with signal amplifier and high voltage power supplier. Since a photomultiplier tube is an extremely high-sensitivity photodetector, the signal light level to be detected is very low and therefore particular care must be exercised in shielding external light. In this paper, the design methodology of $2^{nd}$ electron detector and the image noise removal method are introduced.

• Journal of the Korean Society for Precision Engineering
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• v.19 no.2
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• pp.213-219
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• 2002

A cone-shaped active magnetic healing spindle system for high speed internal grinding with built-in motor that has 7.5kW power and maximum rotational speed of 50,000 rpm is designed and built. Using cone-shaped AMB(Active Magnetic Bearing) system, the axial rotor dick and magnets of conventional 5-axis actuating design can be eliminated. so this concept of design provides a simple magnetic bearing system. In this paper, the cone-shaped electromagnets are designed by magnetic circuit theory, and a de-coupled direct feedback PID controller is applied to control the coupled magnetic bearings. The designed crone-shaped AMB spindle system is built and constructed with a digital control system, which has TMS320C6702 DSP, 16 bit AD/DA, switching power amplifier and gap sensors. As the AMB system provides high damping ratio eliminating overshoot and resonance speed, this spindle runs up to 40,000 rpm stably with about 5${\mu}{\textrm}{m}$ of runout.

• Journal of the Korean Society for Precision Engineering
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• v.19 no.1
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• pp.71-78
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• 2002

This paper is concerned with the design and implementation of magnetic damper system to reduce the vibration of suspension system actively. Cylindrical type electro-magnetic actuator with permanent magnet is analyzed and effective controller design is made. Magnetic force analyzed and transfer function for the total system is determined by experimental data using error minimization method. For experiments, simple suspension structure system is utilized, in which a magnetic damper composed of permanent magnet and digital controller is attached. In order to drive the system, bipolar power amplifier of voltage control type is utilized. Stable and high speed control board is used to perform digital control logic for the given system. This paper shows that the magnetic damper system using phase-lead controller excellently reduces vibration of 1-D.O.F (degree of freedom) suspension system.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.23 no.6
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• pp.539-546
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• 2014

This paper describes an ultra-precision electronic clinometer, which is based on the capacitive-based fluid type, for detection of small inclination angles. The main parts of the clinometer low-noise electronics are two capacitance measurement circuits for converting the capacitances of the capacitors of the clinometer into voltages, and a differential amplifier for obtaining the difference of the capacitances, which is proportional to the input inclination angle. A 16 bit analog to digital (AD) converter is also embedded into the same circuit board, whose output is sent to a PC via RS-232C, for achieving a small noise level down to tens of ${\mu}v$. A compensation method, which is referred to as the delay time method for shortening the stabilization time of the sensor was also discussed. Experimental results have shown the possibility of achieving a measurement resolution of $0.0001^{\circ}$ as well as the quick measurement with the delay time method.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.1
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• pp.89-97
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• 2001

A microgyroscope, which vibrates in two orthogonal axes on the substrate plane, is designed and fabricated. The shuttle mass of the vibrating gyroscope consists of two parts. The one is outer shuttle mass which vibrates in driving mode guided by four folded springs attached to anchors. And the other is inner shuttle mass which vibrates in driving mode as the outer frame does and also can vibrate in sensing mode guided by four folded springs attached to the outer shuttle mass. Due to the directions of vibrating mode, it is possible to fabricate the gyroscope with simplified process by using polysilicon on insulator structure. Fabrication processes of the microgyroscope are composed of anisotropic silicon etching by RIE, gas-phase etching (GPE) of the buried sacrificial oxide layer, metal electrode formation. An eletromechanical model of the vibrating microgyroscope was modeled and bandwidth characteristics of the gyroscope operates at DC 4V and AC 0.1V in a vacuum chamber of 100mtorr. The detection circuit consists of a discrete sense amplifier and a noise canceling circuit. Using the evaluated electromechanical model, an operating condition for high performance of the gyroscope is obtained.

• Journal of the Korean Society for Precision Engineering
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• v.16 no.9
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• pp.34-40
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• 1999

In order to establish the design technique of the robust current controller in d.c series wound motor driver system, this paper proposes a method of the compensated Bang-Bang current control using d.c series wound motor driver system under the improperly variable load to get minimum time for the torque control. The compensated Bang-Bang current controller structure is simpler than that of PID plus Bang-Bang controller. This paper shows that a general 16 bits microprocessor is efficiently used to implement such an algorithm. The calculation time of software is extremely small when compared with that of conventional PID plus Bang-Bang controller. Both nonlinear operating characteristics of digital switching elements and describing function methods are used for the analysis and synthesis. Real-time implementation of the compensated Bang-Bang current controller is achieved. The concept of design strategy of the control and the PWM waveform generation algorithms are presented in this paper.

• Journal of the Korean Society for Precision Engineering
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• v.13 no.12
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• pp.30-37
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• 1996

On-line process control equipment for CO$_{2}$ laser cutting is not available for industrial applications. The major part of the industrial laser cutting machines are adjusted off-line by highly educated engineers. The quality inspection of the sample is visual and referred to different quality scales. Due to the lack of automation the potential laser users hesitate to implement the cutting method. The first step toward an automation of the process is the development of a process monitoring system and the research is cincentrated on the area of on-line quality monitoring during CO$_{2}$ laser cutting. The method is based on the detection of the emitted light from the cutting front by photo diode. The developed monitoring system consists of the OP Amplifier, A/D convertor, power supply and PC. The signal from the photo diode has been undertaken from Fourier analysis and statistical analysis with real time. The photograph of striation pattern was taken by metallurgical microscope. As a result, it is possible to predict the striation pattern according to the beam traveling speed.

• Proceedings of the IEEK Conference
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• 2003.07c
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• pp.2733-2736
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• 2003

This paper proposes a dry-type active surface EMG electrode for the myoelectric prosthetic hand. The designed electrode is small size for embedding in the socket of prosthetic hand, and it has three leads including the reference of signal. To acquire EMG signal rejected the power noise, a precision differential amplifier and various filters such as the band pass filter band rejection filter, low pass and high pass filter are embedded on the electrode. The final output of the electrode is integrated absolute EMG (IEMG) obtained by full rectifier and moving average circuits. From experimental results using the implemented dry-type active surface EMG electrode, the proposed electrode is feasible for the myoelectric prosthetic hand.

• International Journal of Control, Automation, and Systems
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• v.5 no.1
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• pp.35-42
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• 2007

This paper presents an INS(Inertial Navigation System) grade, surface micro-machined differential resonant accelerometer(DRXL) manufactured by an epitaxially grown thick poly silicon process. The proposed DRXL system generates a differential digital output upon an applied acceleration, in which frequency transition is measured due to gap dependent electrical stiffness change. To facilitate the resonance dynamics of the electromechanical system, the micromachined DRXL device is packaged by using the wafer level vacuum sealing process. To test the DRXL performance, a nonlinear self-oscillation loop is designed based on the extended describing function technique. The oscillation loop is implemented using discrete electronic elements including precision charge amplifier and hard feedback nonlinearity. The performance test of the DRXL system shows that the sensitivity of the accelerometer is 24 Hz/g and its long term bias stability is about 2 mg($1{\sigma}$) with dynamic range of ${\sigma}70g$.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.9 no.4
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• pp.53-58
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• 2010

In this paper, the output characteristics of PSD(Position Sensetive Detector) used in measurement system are described. Most of the precision measurment systems are accomplished by a laser diode(LD), a photo diode(PD) and PSD(Position Sensetive Detector), which are used in reflection of mirror or projection of infrared spectrometer. But it is especially restricted by resolution of PD and PSD in nano-measurement. A new inclined light methods into the PSD are employed in the surface measurement system for increasing the resolution. As the results, we can know that the output characteristics of detective senser (PSD) become more than 2 or 3 times by changing inclined angle(range: 5 degree) compared with common angle. In addition, the experiment results are confirmed that the change of inclined angle is not affecting to the linearity and repeating.