• Journal of the Optical Society of Korea
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• v.3 no.2
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• pp.35-40
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• 1999

One of main error sources in white light scanning interferometry is the inaccuracy of scanning mechanisms in that PZT(piezoelectric transducer) micro-actuators are preferably used. We propose a new calibration method that is capable of identifying actual scanning errors directly by analyzing the spectral distribution of sampled interferograms. This calibration provides an effective means of self-compensation for the non-linearity errors caused by PZT hysteresis, enhancing the measurement uncertainty to a level of 5 nanometers over an entire measuring range of 100 ${\mu}{\textrm}{m}$.

• Journal of KSNVE
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• v.2 no.1
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• pp.49-59
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• 1992

The motion analysis of a translation device driven by a piezoelectric actuator is performed to identify the mechanics of impact drive mechanism and to find the maximum speed waveform. The translation device is modeled as a semidefinite two-degree-of-freedom system. The motion analysis includes effects of friction force between moving mass and contact surface, dynamics of voltage amplifier and piezoelectric elements, and hysteresis of piezoelectric actuator. Base on the model, simulation studies are carried out and then compared with experimental results. It is found that the error between moving distances obtained by analysis and experiment is less than 15% and that the actual motion of moving mass is well predicted by the analytical work, finally, precision positioning experiments are carried out by using a proximity sensor as a feedback sensor. Position control of moving mass is initiated by the maximum speed waveform and finely tuned by the scaled down waveform so that accurate positioning is accomplished within the resolution of the sensor.

• Journal of Power Electronics
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• v.11 no.5
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• pp.704-712
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• 2011

This paper describes a hybrid induction motor drive system incorporating DTC-hysteresis and Direct Self Control (DSC) schemes to achieve excellent dynamic performance. The control scheme is switched from a circular to a hexagonal flux locus whenever a dynamic condition is encountered. On the other hand, when the motor operates under steady state conditions, a circular flux locus is used. Without major modifications to the simple structure of a basic DTC, hexagonal flux locus operation is established by modifying the flux error status, before it is fed to the look-up table. The feasibility of the proposed hybrid scheme to achieve excellent control performance is verified by experimental results.

• Journal of Sensor Science and Technology
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• v.18 no.3
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• pp.210-216
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• 2009

In this paper the tactile sensor system based on the bending loss of optical fiber sensor is presented. The sensor array was designed with fabric structure. The optical measuring system was composed of LED for light source and CCD camera for the signal light detector. Performance of this tactile sensor system was evaluated in various environments and compared with Harmon's design criteria. The result shows that load range is 3 g$\sim$100 g, resolution is 1.5 g, hysteresis error is 1.5%. The response linearity is good and flexibility of sensor array is excellent.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.11
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• pp.5587-5594
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• 2012

Determination of the soil-water characteristic curve is one of the most important things to solve geotechnical engineering problems. Expecially, convenient and reliable method to measure the soil-water characteristic curve during drying and wetting cycles is required with lower labor input, more independence from operator experience, and shorter testing time than other available methods. Many measurement methods including the flow pump system have been developed to characterize the soil-water characteristic curve for the several decades. This study measured the soil-water characteristic curve during drying and wetting cycles using a suction control technique with the flow pump system. Two test materials were used for determination of the soil-water characteristic curve, and it is concluded that suction control technique is suitable for determination of the soil-water characteristic curve and characterization of the hydraulic hysteresis with varying test conditions. Especially, the suction control technique can reduce error of measurement and save time in measuring the soil-water characteristic curve due to automated system and high degree of precision.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.42 no.1
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• pp.1-8
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• 2005

We fabricate PLT(5) thin film on Pt/TiO/sub x/SiO₂/Si substrate by using sol-gel method and investigate leakage current, switching and retention properties. The leakage current density of PLT(5) thin film is 3.56×10/sup -7/A/㎠ at 4V. In the examination of switching properties, pulse voltage and load resistance were 2V～5V and 50Ω～3.3kΩ, respectively. Switching time has a tendency to decrease from 0.52㎲ to 0.14㎲ with the increase of pulse voltage, and also the time increases from 0.14㎲ to 13.7㎲ with the increase of load resistance. The activation energy obtained from the relation of applied pulse voltage and switching time is about 135kV/cm. The error of switched charge density between hysteresis loop and experiment of polarization switching is about 10%. Also, polarization in retention decreases as much as about 8% after l0/sup 5/s.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.42 no.11
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• pp.1-8
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• 2005

In this paper, we present design and prototyping of a low-cost, integrated multi-functional micro health sensor chip that can be used or embedded in widely consumer devices, such as cell phone and PDA, for monitoring environmental condition including air pressure, temperature and humidity. This research's scope includes basic individual sensor study, architecture for integrating sensors on a chip, fabrication process compatibility and test/evaluation of prototype sensors. The results show that the integrated TPH sensor has good characteristics of ${\pm}\;1\%FS$ of linearity and hysteresis for pressure sensor and temperature sensor and of ${\pm}\;5\%FS$ of linearity and hysteresis But if we use 3rd order approximation for humidity sensor, full scale error becomes much smaller and this will be one of our future study.

• Journal of Advanced Marine Engineering and Technology
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• v.33 no.8
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• pp.1261-1267
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• 2009

The Direct Torque Control[DTC] controls torque and flux by restricting the flux and torque errors within respective hysteresis bands, and motor torque and flux are controlled by the stator voltage space vector using optimum inverter switching table. And the Current Error Compensation method is on the basis of compensating current difference between the induction motor and its numerical model, in which the identical stator voltage is supplied for both the actual motor and the model so that the gaps between stator currents of the two can be forced to decay to zero as time proceeds. Consequently, the rotor speed approaches to the model speed, namely, setting value and the system can control motor speed precisely. This paper proposes a new sensorless speed control of induction motor using DTC and Current Error Compensation, which requires neither shaft encoder, speed estimator nor PI controllers. And through computer simulation, confirm effectiveness of proposed method.

• Journal of Korea Multimedia Society
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• v.9 no.5
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• pp.585-594
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• 2006

Due to the size limit, the voice coil motor (VCM) is adopted in most of the mobile phone camera to control auto-focus instead of step motor. The optical system using the VCM has the property that the focus values are varying even though the same current is induced. It means that an error of the lens position was taken placed due to the characteristics of the VCM. In this paper, a algorithm was proposed to compensate the lens position error using the step size and the search count of each stage. In the proposed algorithm -7 step middle searching stage is inserted the conventional searching algorithm for the fast auto-focus searching and the final searing step size was set to +1 for the precise focus control, respectively. In the experimental results, the focus values was found more fast in the proposed algorithm than the conventional. And more the image quality by the proposed algorithm was superior to that of the conventional.

• Journal of Sensor Science and Technology
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• v.16 no.1
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• pp.24-32
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• 2007

Conductive rubber material was molded in a belt shape to measure respiration. Its resistivity was approximately $0.03{\;}{\Omega}m$ and the resistance-displacement relationship showed a negative exponent. The temperature coefficient was approximately $0.006{\;}k{\Omega}/^{\circ}C$ negligible when practically applied on the abdomen. The conductive rubber belt was applied on a normal male's abdomen with the dimensional change measured during resting breathing. The abdominal signal was differentiated ($F_{m}$) and compared with the accurate standard air flow rate signal ($F_{s}$) obtained by pneumotachometry. $F_{m}$ and $F_{s}$ differed in waveform, but the start and end timings of each breaths were clearly synchronized, demonstrating that the respiratory frequency could be accurately estimated before further processing of $F_{m}$. $F_{m}-F_{s}$ loop showed a nonlinear hysteresis within each breath period, thus 6 piecewise linear approximation was performed, leading to a mean relative error of 14 %. This error level was relatively large for clinical application, though customized calibration seemed feasible for monitoring general variation of ventilation. The present technique would be of convenient and practical application as a new wearable respiratory transducer.