• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2000년도 춘계학술대회논문집 - 한국공작기계학회
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• pp.252-257
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• 2000

This paper describes a look-ahead algorithm of PCNC(personal computer numerical control). The algorithm is based on acceleration/deceleration before interpolation never including a command error and determines a velocity value in end point of each block(or start point of each block). The algorithm is represented as following; 1) calculating two maximum arrival velocity(v1, v2) by a acceleration value, a command velocity and distance in a previous block and a next block, 2) getting a tangent velocity(v3) of the adjacent blocks, 3) choosing a minimum value among these three velocities, and 4) setting the value to a velocity of a start point of the next block(or a end point of the previous block). The proposed look-ahead algorithm was implemented and tested by using a commercial RTOS(real time operation system) on the MS-Windows NT 4.0 in a PC platform. For interfacing to a machine, a counter board, a DAC board and a DIO board were used. The result of the algorithm increased a machining precision and a machining speed in many short blocks.

• 한국생산제조학회지
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• 제9권6호
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• pp.71-81
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• 2000

This paper describers a look ahead algorithm of PC-NC(personal computer numerical control). The algorithm is based on acceleration/deceleration before interpolation which doesn\`t include a command error and determines a feedrate value at the end point of each block(or start point of each block). The algorithm is represented as following; 1) calculating two maximum arrival feedrates(F$_1$,F$_2$) by an acceleration value, a command feedrate, and the distance of a NC block, 2) getting a tangent feedrate (F$_3$) of the adjacent blocks, 3) choosing a minimum value among these three feedrates, and 4) setting the value to a feedrate of a start point of the next block(or a end point of the previous block). The proposed look ahead algorithm was implemented and tested by using a commercial TROS(real time operation system) on the MS-Windows NT 4.0 in a PC platform. For interfacing to a machine, a counter board, a DAC board and a DIO board were used. The result of the algorithm increased a machining precision and a machining speed in many short blocks.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2022년도 추계학술대회
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• pp.532-535
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• 2022

경로 추종 알고리즘은 행성 탐사, 무인 배송, 자율 주행 등의 다양한 모바일 플랫폼에 대하여 많은 연구가 수행되었다. 하지만, 환경에 존재하는 불확실성으로 인해 실제 응용 분야에서 높은 정확도를 보장하기 어렵다. 본 논문에서는 pure pursuit 알고리즘으로 제어되는 모바일 로봇의 경로 추종 성능을 분석함으로써 알고리즘 설계 및 구현에 대한 지침을 도출하는 것을 목표한다. 이를 위해, 전방 주시 거리(look ahead distance)를 설정하고 오류가 있는 액추에이터를 장착할 때, pure pursuit 알고리즘의 추종 정확도를 전산 실험을 통해 평가한다.

• 한국정보과학회논문지:시스템및이론
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• 제30권3_4호
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• pp.109-116
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• 2003

공간 도약법(space leaping)은 가속화된 영상순서 볼륨 렌더링(image-order volume rendering) 방법의 하나로서 광선 추적 시 빈 공간을 식별하여 도약하도록 함으로써 렌더링 속도를 향상시킨다. 이 방법은 렌더링 속도는 빠르지만 공간 도약을 위한 자료구조를 만들기 위한 전처리 시간이 오래 걸리는 문제가 있다. 본 논문에서는 공간 도약법에서 도약 거리를 기존의 방법보다 두 배로 하는 미리 보기 샘플링 방법을 제안한다. 이 방법은 렌더링 속도의 큰 변화없이 전처리 과정인 거리 맵 생성의 시간을 단축시킬 수 있으며, 기존의 방법보다 렌더링 속도를 빠르게 하는 효과도 있다.

• 자동차안전학회지
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• 제13권2호
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• pp.35-41
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• 2021

In this study, improved path tracking control algorithm based on pure pursuit algorithm is newly proposed by using improved lane detection algorithm through real time post-processing with interpolation methodology. Since the original pure pursuit works well only at speeds below 20 km/h, the look-ahead distance is implemented as a sigmoid function to work well at an average speed of 45 km/h to improve tracking performance. In addition, a smoothing filter was added to reduce the steering angle vibration of the original algorithm, and the stability of the steering angle was improved. The post-processing algorithm presented has implemented more robust lane recognition system using real-time pre/post processing method with deep learning and estimated interpolation. Real time processing is more cost-effective than the method using lots of computing resources and building abundant datasets for improving the performance of deep learning networks. Therefore, this paper also presents improved lane detection performance by using the final results with naive computer vision codes and pre/post processing. Firstly, the pre-processing was newly designed for real-time processing and robust recognition performance of augmentation. Secondly, the post-processing was designed to detect lanes by receiving the segmentation results based on the estimated interpolation in consideration of the properties of the continuous lanes. Consequently, experimental results by utilizing driving guidance line information from processing parts show that the improved lane detection algorithm is effective to minimize the lateral offset error in the diverse maneuvering roads.

• ETRI Journal
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• 제37권3호
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• pp.617-625
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• 2015

In this paper, a steering control system for the path tracking of autonomous vehicles is described. The steering control system consists of a path tracker and primitive driver. The path tracker generates the desired steering angle by using the look-ahead distance, vehicle heading, and a lateral offset. A method for applying an autonomous vehicle to path tracking is an advanced pure pursuit method that can reduce cutting corners, which is a weakness of the pure pursuit method. The steering controller controls the steering actuator to follow the desired steering angle. A servo motor is installed to control the steering handle, and it can transmit the steering force using a belt and pulley. We designed a steering controller that is applied to a proportional integral differential controller. However, because of a dead band, the path tracking performance and stability of autonomous vehicles are reduced. To overcome the dead band, a dead band compensator was developed. As a result of the compensator, the path tracking performance and stability are improved.

• 한국정밀공학회지
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• 제24권10호
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• pp.64-74
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• 2007

Because of the size and environment in the shipbuilding process, the portable type robot is required for the automatic seam tracking. For this reason, the structure of laser sensor should be considered in the initial design step and the coordinate transformation between welding robot and laser sensor, which is joint finder, must be identified exactly and the real time tracking algorithm based on these consideration could be developed. In this research, laser displacement sensor in which its structure is laser beam's vertical projection, is developed to recognize the location of weld joint. In practical applications, however, images of weld joints are often degraded because of the surface specularity or spatter. To overcome the problem, the constrained joint finding algorithm is proposed. In the approach of coordinate conversion rule for the visual feedback control among welding torch, robot body and laser sensor is applied by the same reference point method. In the real time seam tracking algorithms we propose constrained sampling method which uses look ahead distance. The RLS(Recursive Least Square) filter is applied to obtain the smooth tracking path from the sensitive edge data. From the experimental results, we could see the possibility that the developed laser sensor with proposed processing algorithm and real time seam tracking method can be used as a welding under the shipbuilding condition.

• Physical Therapy Rehabilitation Science
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• 제4권1호
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• pp.49-54
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• 2015

Objective: Cervical stabilization exercises are frequently to improve strength and endurance of cervical muscles. The purpose of this study was to identify changes in head repositioning accuracy (HRA) and neck proprioception through cervical stabilization exercises in healthy adults. Design: One group pretest-posttest design. Methods: Thirteen participants with no previous history of neck pain or injury to the cervical spine were recruited. HRA was measured by equipment including laser pointer, helmet, eye patch and marking pens. The distance between the spot where the beam had stopped and the center of the graph paper was measured three times with the averaged value used as the head repositioning accuracy. Neck proprioception was measured by a cervical range of motion device (CROM). Subjects wore the CROM tester and were to look straight ahead while bending his/her neck. Subjects were instructed to perform extension, lateral flexion and rotation, and the values were then measured and recorded. The measurements were performed pre-intervention, and after cervical stabilization exercise. Results: There was no significant difference on HRA after intervention. In addition, there was no significant difference on neck proprioception compared with pre-intervention. Conclusions: The present study did not identify any effect on HRA and neck proprioception of cervical stabilization exercise. Further investigations are required to elucidate this in old aged participants and patients with neck pain.

• 한국항공우주학회지
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• 제49권2호
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• pp.121-128
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• 2021

본 논문에서는 초기지점과 최종지점이 주어졌을 때 2차원 평면에서 무인기의 경로 생성 및 추적 문제에 대해 제안한다. Dubins 곡선을 이용한 경로 생성 알고리즘은 계산 속도가 빨라 무인기에 실시간으로 적용 가능하다는 장점이 있다. 경로 추적 알고리즘은 가시거리 유도 알고리즘과 유사한 알고리즘으로 효율적으로 방향각을 제어하기 위해 전방주시거리 개념과 관련된 이득 값을 추가하였다. 무인기의 경우 최대 곡률이 제한된다. 정밀한 제어를 위해 쿼드로터 모델을 사용하였다. 각속도 제한을 고려한 슬라이딩 모드 제어기를 통해 최대 곡률을 벗어나지 않고 경로를 추종하는 시뮬레이션을 진행하였다. 제약조건이 없는 제어기와 제약조건이 있는 제어기를 비교하여 경로 생성 및 추적 성능을 검증하였다.

• 로봇학회논문지
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• 제17권2호
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• pp.142-151
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• 2022

With the advent of the 4th industrial revolution, autonomous driving technology is being commercialized in various industries. However, research on autonomous driving so far has focused on platforms with wheel-type platform. Research on a tracked platform is at a relatively inadequate step. Since the tracked platform has a different driving and steering method from the wheel-type platform, the existing research cannot be applied as it is. Therefore, a path-tracking algorithm suitable for a tracked platform is required. In this paper, we studied a path-tracking algorithm for a tracked platform based on a GPS sensor. The existing Pure Pursuit algorithm was applied in consideration of the characteristics of the tracked platform. And to compensate for "Cutting Corner", which is a disadvantage of the existing Pure Pursuit algorithm, an algorithm that changes the LAD according to the curvature of the path was developed. In the existing pure pursuit algorithm that used a tracked platform to drive a path including a right-angle turn, the RMS path error in the straight section was 0.1034 m and the RMS error in the turning section was measured to be 0.2787 m. On the other hand, in the variable LAD algorithm, the RMS path error in the straight section was 0.0987 m, and the RMS path error in the turning section was measured to be 0.1396 m. In the turning section, the RMS path error was reduced by 48.8971%. The validity of the algorithm was verified by measuring the path error by tracking the path using a tracked robot platform.