• Journal of Biosystems Engineering
• /
• 제43권4호
• /
• pp.273-284
• /
• 2018

Purpose: Conventional headland turning typically requires repeated forward and backward movements to move the farming equipment to the next row. This research focuses on developing an upland agricultural robot with an optimized headland turning mechanism that enables a $180^{\circ}$ turning positioning to the next row in one steering motion designed for a two-wheel steering, four-wheel drive agricultural robot named the HADA-bot. The proposed steering mechanism allows for faster turnings at each headland compared to those of the conventional steering system. Methods: The HADA-bot was designed with 1.7-m wide wheel tracks to travel along the furrows of a garlic bed, and a look-ahead path following algorithm was applied using a real-time kinematic global positioning system signal. Pivot turning tests focused primarily on accuracy regarding the turning radius for the next path matching, saving headland turning time, area, and effort. Results: Several test cases were performed by evaluating right and left turns on two different surfaces: concrete and soil, at three speeds: 1, 2, and 3 km/h. From the left and right side pivot turning results, the percentage of lateral deviation is within the acceptable range of 10% even on the soil surface. This U-turn scheme reduces 67% and 54% of the headland turning time, and 36% and 32% of the required headland area compared to a 50 hp tractor (ISEKI, TA5240, Ehime, Japan) and a riding-type cultivator (CFM-1200, Asia Technology, Deagu, Rep. Korea), respectively. Conclusion: The pivot turning trajectory on both soil and concrete surfaces achieved similar results within the typical operating speed range. Overall, these results prove that the pivot turning mechanism is suitable for improving conventional headland turning by reducing both turning radius and turning time.

• 한국항행학회논문지
• /
• 제26권1호
• /
• pp.9-14
• /
• 2022

종래 유도탄의 경우 대부분 유도탄의 전방부에 GPS (Global Positioning System) 안테나가 장착되는 경우가 많아 종말 유도단계에서 수직 낙하하는 유도탄의 경우 GPS 안테나가 전방부에 위치하면 동체에 의한 위성 신호 가림 현상이 생겨 GPS 성능이 떨어진다. 본 논문에서는 위성 신호에 대한 가시영역을 최대로 확보하기 위해 GPS 안테나를 유도탄의 후방 부에 기울임을 주어 배치하였으며 배열안테나의 패치를 기울여 설계하는 것을 제안하였다. 제안된 안테나 배치 형상에 대하여 GPS 신호의 신호 수신 범위를 분석하기 위해 LOS (Line Of Sight) 관점에서 가시영역을 분석하였고 실제 무반향 챔버에서 수신 신호 세기 측정을 통해 위성 신호의 유효 수신영역을 분석하였다. 또한 야외시험과 비행시험을 통해서 위성 신호의 음영지역이 줄어드는 것을 확인함으로써 GPS 안테나가 유도탄의 후방에 배치되었을 때 얻을 수 있는 장점을 확인하였다.

• 전자공학회논문지
• /
• 제51권9호
• /
• pp.208-214
• /
• 2014

차선유지 제어시스템, 적응식순항 제어시스템과 같은 첨단운전 지원시스템은 기본적으로 차량의 거동 정보를 기반으로 구동되지만, 최근 도로의 기하학적 정보를 추가적으로 활용하는 연구가 활발히 진행되고 있다. 특히, 도로의 종단경사는 차량의 가감속 제어 및 항법알고리즘 구현에 있어 필수적인 정보로서 DGPS-RTK와 같은 고가의 장비로 직접 측정하는 방법과 디지털 맵에 저장된 속성정보를 활용하는 방식이 제안되고 있으나, 상용화 관점에서는 아직 많은 문제점이 존재한다. 따라서, 본 논문에서는 추가 센서의 장착없이 연속형 확장칼만필터를 활용하여 차량의 동특성과 도로종단경사를 효율적으로 추정하는 알고리즘을 제안한다. 도로종단경사를 포함하는 3자유도 차량동역학 모델과 차량의 내부 네트워크롤 통해 수집할 수 있는 차량의 상태정보를 기반으로 확장칼만필터를 설계하여 차량의 동특성과 도로종단경사를 추정한다. 제안된 알고리즘은 시뮬레이션과 실차실험을 통해 그 성능을 검증하였다.

• 한국전기전자재료학회논문지
• /
• 제36권3호
• /
• pp.214-225
• /
• 2023

Piezoelectric actuators, which utilize piezoelectric crystals or ceramics, are commonly used in precision positioning applications, offering high-speed response and precise control. However, the use of low-performance ceramics and expensive single crystals is limiting their versatile use in the actuator market, necessitating the development of both high-performance and cost-effective piezoelectric materials capable of delivering higher forces and displacements. The use of textured Pb (lead)-based piezoelectric ceramics formed by so-called templated grain growth method has been identified as a promising strategy to address the performance and cost issue. This review article provides insights into recent advances in texturing Pb-based piezoelectric ceramics for improved performance in actuation applications. We discussed the relevant issues in detail focusing on current challenges and emerging trends in the textured piezoelectric ceramics for their reliability and performance in actuator applications. We discussed in detail focusing on current challenges and emerging trends of textured piezoelectric ceramics for their reliability and performance in actuator applications. In conclusion, the article provides an outlook on the future direction of textured piezoelectric ceramics in actuator applications, highlighting the potential for further success in this field.

• 한국정밀공학회지
• /
• 제27권1호
• /
• pp.125-133
• /
• 2010

A versatile micro-robotic platform for micro/nano scale assembly has been demanded in a variety of application areas such as micro-biology and nanotechnology. In the near future, a flexible and compact platform could be effectively used in a scanning electron microscope chamber. We are developing a platform that consists of miniature mobile robots and a compact positioning stage with multi degree-of-freedom. This paper presents the design and the implementation of a low-cost and compact multi degree of freedom position sensor that is capable of measuring absolute translational and rotational displacement. The proposed sensor is implemented by using a CMOS type image sensor and a target with specific hole patterns. Experimental design based on statistics was applied to finding optimal design of the target. Efficient algorithms for image processing and absolute position decoding are discussed. Simple calibration to eliminate the influence of inaccuracy of the fabricated target on the measuring performance also presented. The developed sensor was characterized by using a laser interferometer. It can be concluded that the sensor system has submicron resolution and accuracy of ${\pm}4{\mu}m$ over full travel range. The proposed vision-based sensor is cost-effective and used as a compact feedback device for implementation of a micro robotic platform.

• Spatial Information Research
• /
• 제16권4호
• /
• pp.401-410
• /
• 2008

본 연구에서는 우리나라의 측지기준점의 개선에 대하여 소개하였다. 개선의 내용은 기준점의 구조와 정확도에 중점을 두어 설명하였으며, 구조의 경우 3차원 기준점으로 변화하면서 정확도, 포함 정보, 그리고 기준점의 위계에 대하여 서술하였다. 정확도의 개선은 위성측지 기술의 발달과 정밀지오이드를 기반을 주 내용으로 하고 있으며, 기준점의 개념은 위치뿐 만 아니라 중력, 환경정보와 같은 다양한 공간정보를 포함하여 전반적인 정보의 분석이 가능한 점이 강조되었다. 또한 RFID와 CDMA 기술을 이용한 공간정보의 효율성과 신속성을 소개하였다. 이러한 모든 노력으로 한국의 측지망은 보다 정확하고 다양한 공간정보를 효율적으로 전달할 수 있을 것이라 판단되며 이러한 개선이 측지 기준점의 역할과 미래의 방향에 큰 영향을 미칠 것으로 기대된다.

• 한국정밀공학회지
• /
• 제28권3호
• /
• pp.292-300
• /
• 2011

Control systems in machinery equipment provide correction signals to motion units in order to reduce or cancel out the mismatches between sensor feedback signals and command or desired values. In this paper, we introduce a simulator for control characteristics of machinery equipment. The purpose of the simulator development is to provide mechanical system designers with the ability to estimate how much dynamic performance can be achieved from their design parameters and selected devices at the designing phase. The simulator has a database for commercial parts, so that the designers can choose appropriate components for servo controllers, motors, motor drives, and guide ways, etc. and then tune governing parameters such as controller gains and friction coefficients. The simulator simulates the closed-loop control system which is built and parameter-tuned by the designer and shows dynamic responses of the control system. The simulator treats the moving table as a 6 degrees-of-freedom rigid body and considers the motion guide blocks stiffness, damping and their locations as well as sensor locations. The simulator has been under development for one and a half years and has a few years to go before the public release. The primary achievements and features will be presented in this paper.

• 한국정밀공학회지
• /
• 제22권10호
• /
• pp.174-185
• /
• 2005

This paper presents the design, fabrication, and testing results of a dual stage actuator system for a fine positioning of magnetic heads in magnetic disk drives. A novel rotary microactuator which is electrostatically driven and utilized as a secondary actuator was designed. The stator and rotor electrodes in the microactuator was revised to have the optimal shapes and hence produces much higher rotational torque compared with the conventional comb-shape electrodes. The microactuators were successfully fabricated using SoG(silicon on glass) processing technology, which is known as being cost-effective. The fabricated microactuator has the structural thickness of $45{\mu}m$ with the gap width of approximately $3{\mu}m$. The dynamic characteristic of microactuator/slider assembly was investigated, and its natural frequency and DC gain were measured to be 3.4kHz and 32nm/V, respectively. The microactuator/slider assembly was integrated into a HDD model V10 of Samsung Electronics Co. and a dual servo algorithm was tested to explore the tracking performance of dual stage actuator system where the LDV signals instead of magnetic head signals were used. Experimental results indicate that this system achieves the tracking accuracy of 30nm. This value corresponds to a track density of 85,000 track per inch(TPI), which is about 3 times greater than that of current hard disk drives.

• Journal of Ubiquitous Convergence Technology
• /
• 제2권2호
• /
• pp.67-77
• /
• 2008

Representation of various types of information in an interactive virtual reality environment on mobile devices had been an attractive and valuable research in this new era. Our main focus is presenting spatial indoor location sensing information in 3D perception in mind to replace the traditional 2D floor map using handheld PDA. Designation of 3D virtual reality by Virtual Reality Modeling Language (VRML) demonstrates its powerful ability in providing lots of useful positioning information for PDA user in real-time situation. Furthermore, by interpolating portal culling algorithm would reduce the 3D graphics rendering time on low power processing PDA significantly. By fully utilizing the CC2420 chipbased sensor nodes, wireless sensor network was established to locate user position based on Received Signal Strength Indication (RSSI) signals. Implementation of RSSI-based indoor tracking method is low-cost solution. However, due to signal diffraction, shadowing and multipath fading, high accuracy of sensing information is unable to obtain even though with sophisticated indoor estimation methods. Therefore, low complexity and flexible accuracy refinement algorithm was proposed to obtain high precision indoor sensing information. User indoor position is updated synchronously in virtual reality to real physical world. Moreover, assignment of magnetic compass could provide dynamic orientation information of user current viewpoint in real-time.

• 한국콘텐츠학회:학술대회논문집
• /
• 한국콘텐츠학회 2007년도 추계 종합학술대회 논문집
• /
• pp.30-34
• /
• 2007

레이저는 단시간에 높은 정밀도로 다량의 측정을 행할 수 있는 장점을 지니며, 이의 구체적인 실현이 지상 LiDAR라고도 불리는 지상레이저 스캐너이다. 본 논문에서는 Z-F 레이저시스템을 사용하여 대상물의 3차원 레이저 측정, Point 데이터의 생성, Registration & Merging, Polygon 데이터의 생성, Surface 데이터 생성의 과정을 거쳐 수행된 고건축물의 3차원 모델링 결과에 대하여 기술한다. 문화재의 보존 및 복원을 위한 자료 기록 및 측정에 있어서 지상 레이저스캐너를 사용한 고건축물의 데이터베이스 구축기술은 문화유산의 복원 및 관련분야에 커다란 영향력으로 자리매김할 수 있을 것으로 사료된다.