• Journal of Biosystems Engineering
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• 제31권3호
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• pp.146-152
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• 2006

Most upland in Korea have irregular field shapes. Boom sprayers working alone winding row will show considerable differences of spraying amount per unit area between left and right booms. If flow rates of both booms are equal. This phenomenon becomes significant as steering radius of sprayer decreases. This study was performed to seek a method which reduce the difference of the spray amount between left, right and center booms while spraying along curvy rows. A flow rate control method for keeping application rate of each boom section constant was proposed and experimentally proved using a boom sprayer attached to a cultivating tractor. The flow rate control device was composed of 3 ball valves and a rotary angle sensor. The rotary angle sensor showed a symmetric voltage output with respect to steering radius. The spray overlapping was happened in a boom nearby the steering center when steering radius of the sprayer was less than 5.2 m. Flow rates for left, right and center booms were regulated using ball valves based on the steering radius and spraying areas ration of right/left boom. The Maximum spraying area ratio ($S_{LR}$) of left to right boom section was 1:3.6 at the steering radius of 5.2 m. However, The Maximum achieved right and left spraying flow ratio was 1:2.7.

• 한국항공우주학회지
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• 제37권1호
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• pp.89-98
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• 2009

CMG는 3축으로 토크를 발생시키기 위해 클러스터로 구성하여 사용할 수 있다. CMG 클러스터에서 발생되는 여러 가지 설계에 고려되어야 할 문제들이 있다. 이러한 문제들을 지상에서 미리 검증하는 것이 필수적이다. 따라서 본 논문에서 토크센서로 위성자세를 계산하는 CMG 시뮬레이터를 제안하였다. 개발과정에서 발생한 김발각문제 해결을 위해 보정방법과 칼만필터가 제시되었다. 보정방법은 계산된 김발각을 기본으로 사용하고 센서 값을 보조로 사용해서 오차를 줄인다. 또한 개발된 CMG 시뮬레이터를 이용하여 특이점 회피를 위한 구동법칙과 자세제어 로직 시험결과도 예로서 제시되었다.

• Journal of Biosystems Engineering
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• 제25권1호
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• pp.55-62
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• 2000

Autonomous farm operation needs to be developed for safety, labor shortage problem, health etc. In this research, an autonomous tractor for tillage was investigated using machine vision and a fuzzy logic controller(FLC). Tractor heading and offset were determined by image processing and a geomagnetic sensor. The FLC took the tractor heading and offset as inputs and generated the steering angle for tractor guidance as output. A color CCD camera was used fro the image processing . The heading and offset were obtained using Hough transform of the G-value color images. 15 fuzzy rules were used for inferencing the tractor steering angle. The tractor was tested in the file and it was proved that the tillage operation could be done autonomously within 20 cm deviation with the machine vision and the FLC.

• 한국전자통신학회논문지
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• 제16권4호
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• pp.699-708
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• 2021

본 논문에서는 2개의 비전 센서와 딥 러닝을 이용한 자율주행 차량의 속도제어 알고리즘을 제시하였다. 비전 센서 A로부터 제공되는 도로 속도 표지판 영상에 딥 러닝 프로그램인 텐서플로우를 이용하여 속도 표지를 인식한 후, 자동차가 인식된 속도를 따르도록 하는 자동차 속도 제어 알고리즘을 제시하였다. 동시에 비전 센서 B부터 전송되는 도로 영상을 실시간으로 분석하여 차선을 검출하고 조향 각을 계산하며 PWM 제어를 통해 전륜 차축을 제어, 차량이 차선을 추적하도록 하는 조향 각 제어 알고리즘을 개발하였다. 제안된 조향 각 및 속도 제어 알고리즘의 유효성을 검증하기 위해서 파이썬 언어, 라즈베리 파이 및 Open CV를 기반으로 하는 자동차 시작품을 제작하였다. 또한, 시험 제작한 트랙에서 조향 및 속도 제어에 관한 시나리오를 검증함으로써 정확성을 확인할 수 있었다.

• Journal of Biosystems Engineering
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• 제26권1호
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• pp.29-38
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• 2001

A navigation system was developed for autonomous guidance of a combine. It consisted of a DGPS, a machine vision system, a gyro sensor and an ultrasonic sensor. For an autonomous operation of the combine, target points were determined at first. Secondly, heading angle and offset were calculated by comparing current positions obtained from the DGPS with the target points. Thirdly, the fuzzy controller decided steering angle by the fuzzy inference that took 3 inputs of heading angle, offset and distance to the bank around the rice field. Finally, the hydraulic system was actuated for the combine steering. In the case of the misbehavior of the DGPS, the machine vision system found the desired travel path. In this way, the combine traveled straight paths to the traget point and then turned to the next target point. The gyro sensor was used to check the turning angle. The autonomous combine traveled within 31.11cm deviation(RMS) on the straight paths and harvested up to 96% of the whole rice field. The field experiments proved a possibility of autonomous harvesting. Improvement of the DGPS accuracy should be studied further by compensation variations of combines attitude due to unevenness of the rice field.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2000년도 제15차 학술회의논문집
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• pp.257-257
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• 2000

The objective of this research is to monitor and control the vehicle motion in order to remove out the existing safety risk based upon the human-machine cooperative vehicle control. A predictive control method is proposed to control the steering wheel of the vehicle to keep the lane. Desired angle of the steering wheel to control the vehicle motion could be calculated based upon vehicle dynamics, current and estimated pose of the vehicle every sample steps. The vehicle pose and the road curvature were calculated by geometrically fusing sensor data from camera image, tachometer and steering wheel encoder though the Perception Net, where not only the state variables, but also the corresponding uncertainties were propagated in forward and backward direction in such a way to satisfy the given constraint condition, maintain consistency, reduce the uncertainties, and guarantee robustness. A series of experiments was conducted to evaluate the control performance, in which a car Like robot was utilized to quit unwanted safety problem. As the results, the robot was keeping very well a given lane with arbitrary shape at moderate speed.

• 제어로봇시스템학회논문지
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• 제16권6호
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• pp.566-571
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• 2010

EPS (Electric Power Steering) is important device for improving vehicle's dynamics and static performances. This paper deals with simulator design for C-EPS (Colum type-EPS), development assist and returnability control algorithm. First, C-EPS system model was simply designed because EPS system is complex control system that has many unknown variables. These parameters were simplified through assumptions. Second, C-EPS simulator was designed for development of control algorithm. This simulator has SAS (Steering Angle Sensor), dual torque sensor, dual load cell for measuring rack force, dual linear actuator for generating tire force and Data Acquisition System. Using this simulator, control methods ware tested. Third, control algorithm was designed for torque assist and returnability. Assist torque map and returnability torque map were found by lots of simulation test. These torque maps were tuned for EPS actuator control. The simulation result was compared with non-EPS system result. In this research, the C-EPS simulator was designed for development of control algorithm about torque assistant and returnability. Using this simulator, control algorithm was improved.

• 대한기계학회논문집A
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• 제24권12호
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• pp.2883-2890
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• 2000

In this study, a Hardware-In-The-Loop-Simulation(HILS) system for developing a Electric-Power-Steering(EPS) system is designed. To test a EPS by HILS system, a mathematical vehicle model with a steering system model has been constructed. This mathematical model has been constructed. This mathematical model has been downloaded to the Digital-Signal-Processor(DSP) board. To realize the lateral force acting on the front wheel in a real car. the steering wheel angle sensor and vehicle velocity have been used for input signal. The force sensor has been used for a feedback signal. The full vehicle states could by simulated by the HILS system. Consequently, the HILS system could by used to analyze control-parameters of a EPS that contributes to the maneuverability and stability of a vehicle. At the same time, the HILS system can evaluate the whole performance of the vehicle-steering system. Also the HILS system could do test could not be executed in real vehicle. The HILs system will useful for developing the control logic for the EPS system.

• 한국농업기계학회:학술대회논문집
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• 한국농업기계학회 2000년도 THE THIRD INTERNATIONAL CONFERENCE ON AGRICULTURAL MACHINERY ENGINEERING. V.III
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• pp.707-714
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• 2000

For self-guiding track-type orchard sprayer, a low-cost steering controller was developed using two ultrasonic sensors, two DC motors and 80196kc microprocessor. The operating principle of controller was to travel the sprayer between artificial targets such as wood stick placed every 1 m along both sides of the demanded path of speed sprayer. Measuring distances to both targets ahead with the ultrasonic sensors mounted on the front end of sprayer, the controller could determine how much offset the position of sprayer was laterally. Then the steering angle was calculated to actuate DC motors connected to the steering clutches, where the fuzzy control algorithm was used. Equipped with the controller developed in this research, the sprayer could be traveled along demanded path, the centerline between targets, at speeds of up to 0.4m/sec with an accuracy of ${\pm}$20cm.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1993년도 한국자동제어학술회의논문집(국내학술편); Seoul National University, Seoul; 20-22 Oct. 1993
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• pp.434-439
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• 1993

This paper present a sensor based obstacle avoidance method which is based on a VFH(Vector Field Histogram) method. The basic idea of obstacle avoidance is to find a minimum obstacle direction and distance. From the minimum sonar index and the target direction high level system determine steering angle of mobile robot. The sonar sensor system consists of 12 ultra sonic sensor, and each sensor have its direction and safety value. This method has advantage on calculation speed and small memory. This method is implemented on indoor autonomous vehicle'ALiVE-2'.