This paper presents a line-of-sight (LOS) stabilization control method for portable optical systems by analyzing fast steering mirror, image sensor, and gyro sensor system. To compensate for LOS errors caused by hand tremors in portable optical systems, we present the configuration of an image sensor-based LOS stabilization control system and a control strategy considering the phase delay effect caused by low sampling frequency of the image sensor. The phase delay effect of the image sensor caused restricted bandwidth, which limited the stabilization performance. To overcome such limitations, we present disturbance feedforward control using the gyro sensor and controller design method considering characteristics of the gyro sensor. Through overall system modeling, we constructed a control simulation model. The LOS stabilization performance against hand tremor disturbances was analyzed based on the proposed controller design. Simulation results demonstrated that integrating a gyro sensor-based disturbance feedforward control with the image sensor-based LOS stabilization control significantly enhanced the stabilization performance.

Nonlinear hysteresis effects in piezoelectric fast steering mirrors (FSMs) are major culprits of deteriorating the servo performance and reducing the robustness of a control system. In order to compensate for such nonlinearities, this paper presents an identification and compensation method of piezoelectric hysteresis using frequency response measurements. The relationship between hysteresis curves and frequency response was analyzed using various amplitudes of input voltage and measured output displacements. Results proved that hysteresis curves could be reconstructed based on frequency response measurements. By utilizing an inverse function from reconstructed hysteresis curves, parameters for the compensation model were identified. Experimental results showed that the maximum range of output displacement at the nominal position due to hysteresis was significantly decreased by 76% when the hysteresis model identified by the proposed frequency-domain method was used. In addition, the compensated frequency response showed consistent results regardless of input amplitudes, implying that linear dynamics of the piezoelectric FSM could be separately measured.

A clean room is used for adjusting the concentration of suspended particles using an air-conditioner. It has a fan-filter unit combining a centrifugal fan and a high-efficiency particulate air filter that purifies the outside air and directly affects its cleanliness. Defects in these systems are typically detected using special sensors for each fault, which can be costly. Therefore, this paper proposes a system for diagnosing defects in the fan-filter unit using a single differential sensor and deep learning. The fan-filter unit is part of the air-conditioning system, and it is usually defective in bearings, filters, and motors. These faults include ball wear, internal bearing contamination, filter contamination, and motor speed changes. Each defect was artificially induced in experiments, and the differential pressure data of each defect was learned using a long short-term memory (LSTM) deep learning algorithm. The results of deep learning experiments generated by randomly mixing data five times were presented using a confusion matrix, and the results showed an accuracy of 87.2±2.60%. Therefore, the possibility of diagnosing defects in the fan-filter unit using a single sensor was confirmed.

Automatic tool changers(ATCs) store tools used in a machining center to its magazine and changes the tools automatically. Tools of machine centers are changed and then precisely equipped to spindle system by the ATC. Therefore, the stability and reliability of the ATC is very important. But, there is lack of development and evaluation on basic performance and vibration of the ATCs. So, in this study, a BT40 ATC test bench was developed to verify stability and reliability of BT40 ATCs.

This paper describes a design process of end-milling cutters: solid model of the designed cutter is constructed along with computation of cutter geometry, and the wheel geometry as well as wheel positioning data for fabricating end-mills with required cutter geometry is calculated. In the process, the main idea is to use the cutting simulation method by which the machined shape of an end-milling cutter is obtained via Boolean operation between a given grinding wheel and a cylindrical workpiece(raw stock). Major design parameters of a cutter such as rake angle, inner radius can be verified by interrogating the section profile of its solid model. We studied relations between various dimensional parameters and proposed an iterative approach to obtain the required geometry of a grinding wheel and the CL data for machining an end-milling cutter satisfying the design parameters. This research has been implemented on a commercial CAD system by use of the API function programming, and is currently used by a tool maker in Korea. It can eliminate producing a physical prototype during the design stage, and it can be used for virtual cutting test and analysis as well.

In reverse engineering, data acquisition methodology can generally be categorized into contacting and non-contacting types. Recently, researches on hybrid or sensor fusion of the two types have been increasing. In addition, efficient construction of a geometric model from the measurement data is required, where considerable amount of user interaction to classify and localize regions of interest is inevitable. Our research focuses on the classification of each bounded region into a pre-defined feature shape for a hybrid measuring scheme, where the overall procedures are described as follows. Firstly, the physical model is digitized by a non-contacting laser scanner which rapidly provides cloud-of-points data. Secondly, the overall digitized data are approximated to a z-map model. Each bounding curve of a region of interest (featured area) can be traced out based on our previous research. Then each confined area is systematically classified into one of the pre-defined feature types such as floor, wall, strip or volume, followed by a more accurate measuring step via a contacting probe. Assigned to each feature is a specific digitizing path topology which may reflect its own geometric character. The research can play an important role in minimizing user interaction at the stage of digitizing path planning.

This paper describes a method for digitizing the compound surfaces which are comprised of several unknown feature shapes such as base surface, and draft wall. From the reverse engineering's point of view, the main step is to digitize or gather three-dimensional points on an object rapidly and precisely. As wen known, the non-contact digitizing apparatus using a laser or structured light can rapidly obtain a great bulk of digitized points, while the touch or scanning probe gives higher accuracy by directly contacting its stylus onto the part surface. By combining those two methods, unknown features can be digitized efficiently. The paper proposes a digitizing methodology using the approximated surface model obtained from laser-scanned data, followed by the use of a scanning probe. Each surface boundary curve and the confining area is investigated to select the most suitable digitizing path topology, which is similar to generating NC tool-paths. The methodology was tested with a simple physical model whose shape is comprised of a base surface, draft walls and cavity volumes.

There is an increasing need for large flat panel display devices. PDP (Plasma Display Panel) is one of the most promising candidates for this need. Thermal shock failure of PDP glass during manufacturing process is a critical issue in PDP industry since it is closely related to the product yield and the production speed. In this study, thermal shock resistance of PDP glass is measured by water quenching test and an analysis scheme is described for estimating transient temperature and stress distributions during thermal shock. Based on the experimental data and the analysis results, a simple procedure for predicting the thermal shock failure of PDP glass is proposed. The fast cooling process for heated glass plates can accelerate the speed of PDP production, but often leads to thermal shock failure of the glass plates. Therefore, a design guideline for preventing the failure is presented from a viewpoint of high speed PDP manufacturing process. This design guideline can be used for PDP process design and thermal-shock failure prevention.