• ETRI Journal
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• v.30 no.1
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• pp.59-67
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• 2008

The necessity for the precise time synchronization of measurement data from multiple sensors is widely recognized in the field of global positioning system/inertial navigation system (GPS/INS) integration. Having precise time synchronization is critical for achieving high data fusion performance. The limitations and advantages of various time synchronization scenarios and existing solutions are investigated in this paper. A criterion for evaluating synchronization accuracy requirements is derived on the basis of a comparison of the Kalman filter innovation series and the platform dynamics. An innovative time synchronization solution using a counter and two latching registers is proposed. The proposed solution has been implemented with off-the-shelf components and tested. The resolution and accuracy analysis shows that the proposed solution can achieve a time synchronization accuracy of 0.1 ms if INS can provide a hard-wired timing signal. A synchronization accuracy of 2 ms was achieved when the test system was used to synchronize a low-grade micro-electromechanical inertial measurement unit (IMU), which has only an RS-232 data output interface.

• Journal of the Korean Society for Precision Engineering
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• v.31 no.5
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• pp.389-394
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• 2014

In this paper, we report a new manufacturing method for friction reduction using micro-AAJ (abrasive air-jet) machining. AAJ machining employs compressed air to accelerate a jet of high-speed particles to mechanically machine features, including micro-channels and micro-holes, into glass, metal, or polymer substrates for use in microfluidics, MEMS (micro electromechanical systems). And we introduce the micro-AAJ machining system, which consists of a micro-AAJ nozzle and a five-axis positioning system. Various micro-AAJ nozzles can be used, depending on the required surface structure, and three-dimensional machining is possible. We machined samples under six different conditions and describe machining results obtained while using it. We also measured the coefficient of friction of micro-textured surfaces. We report the coefficient of friction of micro-textured surfaces patterned using micro-AAJ machining for engine piston ring.

• Proceedings of the KSME Conference
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• 2001.06b
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• pp.70-75
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• 2001

In this study, we developed a measuring system utilizing machine vision for measuring the precision of positioning of micro stepping motor. The measuring system equipped with CCD Camera, ring illumination and diffuser measures the repeatability and the hysterisis of a micro stepping motor by means of the pointer attached to the motor directly. With the measuring system, it was possible to measure the precision of the micro stepping motor in the resolution of $50{\mu}m$.

• The Journal of Korea Robotics Society
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• v.9 no.3
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• pp.154-159
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• 2014

The Global Positioning System (GPS) is widely used to aid the navigation of aerial vehicles. However, the GPS cannot be used indoors, so alternative navigation methods are needed to be developed for micro aerial vehicles (MAVs) flying in GPS-denied environments. In this paper, a real-time three-dimensional (3-D) indoor navigation system and closed-loop control of a quad-rotor aerial vehicle equipped with an inertial measurement unit (IMU) and a low-cost light detection and ranging (LIDAR) is presented. In order to estimate the pose of the vehicle equipped with the two-dimensional LIDAR, an octree-based grid map and Monte-Carlo Localization (MCL) are adopted. The navigation results using the MCL are then evaluated by making a comparison with a motion capture system. Finally, the results are used for closed-loop control in order to validate its positioning accuracy during procedures for stable hovering and waypoint-following.

• Journal of the Korean Society for Precision Engineering
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• v.31 no.3
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• pp.277-283
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• 2014

This paper presents the design, optimization and fabrication of a piezo driven micro-positioning stage constructed using a 3D-printer. 3D printing technology provides many advantageous aspects in comparison to traditional manufacturing techniques allowing more rapid prototyping freedom in design, etc. Micro-positioning stages have traditionally been made using metal materials namely aluminum. This paper investigates the possibility of fabricating stages using ABS material with a 3D printer. CAE simulations show that equivalent motion amplification can be achieved compared to a traditional aluminum fabricated stage while the maximum stress is 30 times less. This leads to the possibility of stages with higher magnification factors and less load on the driving piezo element. Experiment results agree with the simulation results. A micro-position stage was fabricated using a 3D printer with ABS material. The motion amplification is very linear and 50 nm stepping was demonstrated.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.34-35
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• 2006

The development of Micro MIM as a new manufacturing process for metallic micro parts made of advanced functional materials has been the subject of considerable research over the last years. This paper addresses important quality aspects on processing of new materials by Micro-MIM. Three examples of new functional materials that can be processed are reviewed in this paper. The first example is two-component-Micro-MIM to obtain multi-functional devices. A micro positioning encoder consisting of a magnetic / non-magnetic material combination is presented. The second issue is series production of the replicate of the smallest human bone in the ear (stapes) from Titanium as an example of medical application. Quality assurance and reproducibility in terms of injection moulding parameters are addressed. In the third part, first results on the processing of the shape memory alloy NiTi by Micro-MIM are presented. Potential applications include biocompatible devices and transportation, for example automotive and aerospace. Processing routes and initial microstructures obtained are discussed.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.1517-1521
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• 2007

On this study, technical aspects were reviewed to drill a series of micro holes (${\phi}$0.10) over 200 within a few micron tolerance in diameter and position on the stainless steel material. Dedicated tools & jigs were designed and manufactured and optimum cutting conditions were found. On this micro hole drilling process, guide drill and step feeding were applied to help chip discharge, prevent drill breakage and finally improve the accuracy of positioning and roundness. The processing results indicated that most holes are distributed within a few micron tolerance in diameter and position intervals.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1995.03a
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• pp.40-62
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• 1995

A micro positioning system using piezoelectric actuators have very wide application region such as ultra-precision machine tool optical device measurement system. In order to keep a high precision displacement resolution it to useful to take a position sensor and feedback of the error. From the practical point of view high-resolution displacement sensor systems are very expensive and it is difficult to make such a sensitive sensor work properly in a poor operational environment of industry. In this study a piezo-electric micro-depth control system which does not require position sensor but piezoelectric voltage feedback has been developed. It is driven by hysteresis-considering reference input voltage calculated in advance and actuator/sensor characteristics of piezoelectric materials. From the result of experiments a fast and stable response of micro-depth control system has been achieved and an efficient technique to control the piezoelectric actuator suggested.

• International Journal of Fuzzy Logic and Intelligent Systems
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• v.4 no.3
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• pp.316-321
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• 2004

In this paper, we have developed a new mounting head system for flip chip. The proposed head system consists of a macro/micro positioning actuator for stable force control. The macro actuator provides the system with a gross motion while the micro device yields fine tuned motion to reduce the harmful impact force that occurs between very small sized electronic parts and the surface of a PCB(printed circuit board). In order to show the effectiveness of the proposed macro/micro chip mounting system, we compared the proposed system with the conventional chip mounting head equipped with a macro actuator only. A series of experiments were executed under the mounting conditions such as various access velocities and PCB stiffness. As a result of this study, a satisfactory voice coil actuator as the micro actuator has been developed, and its performance meet well the specifications desired for the design of the chip mounting head system and show good correspondence between theoretical analysis and experimental results.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.05a
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• pp.977-981
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• 2000

Direct drive linear motors have large potential for use as high speed machine tool feed units since they can increase machining rates and improve servo accuracy by eliminating gear related machining problems. So, in this paper, characteristic of 2-axis linear motor feed unit are studied and control gain are adjusted considering positioning, velocity, acceleration and static stiffness. We confirm linear motor feed unit are affected value of control gain sensitively, because drive directly. From the experiment, this feed unit has l${\mu}{\textrm}{m}$ micro step resolution, 5.7${\mu}{\textrm}{m}$ positioning accuracy and under 60${\mu}{\textrm}{m}$ circularity.