• 대한기계학회논문집A
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• 제38권5호
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• pp.551-557
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• 2014

본 논문은 작업 시 농업용 트랙터의 운전지원을 위한 강인한 횡방향 제어기를 제안하고자 한다. 자동차와 달리 트랙터의 조향 방식은 유압실린더를 이용함으로써 상대적으로 큰 시간지연을 가지고 있으며 작업 시 지면 환경도 일반 도로와는 다르다. 조향 액추에이터 모델을 포함하는 기구학적 트랙터 모델을 기반으로 동적 표면 제어라는 비선형 제어기법을 적용하여 조향 액추에이터의 시간지연 및 노면 경사의 변화에 강인한 횡방향 제어기를 설계한다. 마지막으로 상용 트랙터 시뮬레이터를 이용하여 마찰 계수가 일정한 주어진 노면 상태에서 조향 액추에이터의 시간 지연 변경이나 오르막 또는 내리막과 같은 지형 조건 변화에 대한 횡방향 제어기의 성능 및 강인성을 검증한다.

• 농업과학연구
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• 제50권4호
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• pp.773-784
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• 2023

In this study, we developed a dynamic model and steering controller model for an autonomous tractor and evaluated their performance. The traction force was measured using a 6-component load cell, and the rotational speed of the wheels was monitored using proximity sensors installed on the axles. Torque sensors were employed to measure the axle torque. The PI (proportional integral) controller's coefficients were determined using the trial-error method. The coefficient of the P varied in the range of 0.1 - 0.5 and the I coefficient was determined in 3 increments of 0.01, 0.05, and 0.1. To validate the simulation model, we conducted RMS (root mean square) comparisons between the measured data of axle torque and the simulation results. The performance of the steering controller model was evaluated by analyzing the damping ratio calculated with the first and second overshoots. The average front and rear axle torque ranged from 3.29 - 3.44 and 6.98 - 7.41 kNm, respectively. The average rotational speed of the wheel ranged from 29.21 - 30.55 rpm at the front, and from 21.46 - 21.63 rpm at the rear. The steering controller model exhibited the most stable control performance when the coefficients of P and I were set at 0.5 and 0.01, respectively. The RMS analysis of the axle torque results indicated that the left and right wheel errors were approximately 1.52% and 2.61% (at front) and 7.45% and 7.28% (at rear), respectively.

• 한국기계가공학회지
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• 제18권3호
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• pp.26-32
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• 2019

This study was conducted to analyze the stresses by impact loads on front-end loaders attached to tractors using flexible multi-body dynamics. The model was designed and validated by comparing previous experimental data with the simulation data obtained in this study. Nine sets of conditions were designed using three weights (500, 300, and 100 kg) loaded inside a bucket and three heights (1700, 1350, and 1000 mm) of the bucket from ground level. A parametric study was carried out at five locations for two types of parts of a front-end loader. All the safety factors for the five locations under all conditions were calculated and were greater than 1. Thus, the designs of the front-end loaders were structurally safe. Based on this study, front-end loaders attached to tractors can be designed effectively in terms of cost and safety.

• 한국시뮬레이션학회논문지
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• 제32권4호
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• pp.77-84
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• 2023

농업 분야에서도 내연기관 트랙터에서 벗어나 전기 트랙터 및 수소 트랙터와 같은 대체 에너지원을 사용하는 동력원이 개발되고 있다. 기존의 내연기관 트랙터에서 사용되던 엔진 및 변속기와 같은 부품들이 모터와 배터리 등으로 교체되면서 무게중심이 변화하게 되며, 이에 따라 전도 위험성을 새로이 고려해야 한다. 이 연구의 목적은 동역학 시뮬레이션을 통해 전기 트랙터의 주요 부품 위치별 전도 각도를 분석하여 전도 사고를 최소화하고 안정성을 향상하기 위한 부품 최적의 배치를 도출하는 것이다. PTO 모터, 구동 모터와 배터리 팩의 구성 수준 3가지와 배치 방법 3가지 요인으로 실험 설계하여 총 9가지 동역학 시뮬레이션을 진행하였다. 실험 결과, 구동 모터와 PTO 모터를 트랙터 앞쪽과 뒤쪽에 각각 위치하고 두 개의 배터리 팩을 트랙터 중간에 위치시킨 Type 3 Level 3가 전도 각도가 높은 것을 확인하였다. 본 연구 결과 무게중심을 뒤쪽으로 배치할수록, 아래에 위치할수록 안정성이 증가하였다. 향후 연구로는 부품의 성능과 배치 효율성을 고려한 부품의 최적 위치를 찾는 연구가 필요하다.

• 한국기계가공학회지
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• 제17권3호
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• pp.109-119
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• 2018

The purpose of this study is to evaluate the structural safety of the front-end loader for the 90 kW class of agricultural tractors in impact test conditions. Deformation and stress on the loader under the impact test conditions are analyzed using the commercial finite element analysis software ANSYS. In previous research dealing with the initial design of the loader, the maximum stress occurred in the mount and exceeded the yield strength of the material. In this paper, an improved design of the mount of the loader was proposed to reduce the stress concentration in the initial design. The safety of the improved design was verified by performing rigid-body dynamics analysis, transient structural analysis, and static structural analysis under three impact test conditions: a drop and catch test, a corner pull test, a corner push test. It was found that the local stress concentration in the mount that appeared in the initial design was greatly reduced in the improved design, and that the maximum stresses occurred in the three impact test conditions are smaller than the yield strength. It is expected that the design improvement of the mount proposed in this study and the method of analysis may be effectively used to enhance structural safety in the development of new model front loaders in the future.

• 한국농업기계학회:학술대회논문집
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• 한국농업기계학회 1993년도 Proceedings of International Conference for Agricultural Machinery and Process Engineering
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• pp.1166-1175
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• 1993

The objective of this study is to measure contra-retractive adhesion and lift resistance acting on the rim section of a circular wheel for analyses of their effects on the dynamic load. A circular iron wheel was used for experiments. A part of the wheel rim was cut off, and transducers which can measure normal and tangential forces were installed in this section. Experiments were conducted on a laboratory soil bin which was filled with clayey soil under wet and dry conditions. The mechanism of generating contra -retractive adhesion on a circular wheel were analyzed by the experiments and motion analyses of the wheel. Effects of lift resistance on dynamic load were analyzed by measured forces under wet soil conditions in comparison in comparison with those under dry conditions. The showed that a part of the lift resistance were transferred to the dynamic load. These results may become basic data and ideas for analyses of tractor dynamic under wet soil conditions.

• 대한기계학회논문집 C: 기술과 교육
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• 제3권2호
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• pp.83-88
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• 2015

농용 트랙터는 일반적인 도로 주행이 아닌 논 또는 밭과 같은 험지에서 작업용으로 사용한다. 때문에 정적 하중 뿐만 아니라 동적 하중이 고려된 구조 해석이 진행되어야 한다. 하지만 동적 입력 하중을 계산하기 위해서는 다양한 작업기와 하중조건을 모사해야 하기에 실제 측정에 많은 시간과 노력이 소요된다. 이러한 노력들을 줄이기 위해서 본 연구에서는 상용 자동차와 동일하게 농용 트랙터를 위한 4 축 도로하중 시뮬레이터(4-Post Road Simulator) 모델을 개발하였다. 입력하중을 검증하기 위해 사내 험로 시험장에서 차축의 가속도 값과 바디프레임의 변형률(strain)을 측정하였다. 가속도 값은 동역학 모델의 입력 하중으로 사용하고 모드 중첩 법을 포함한 동역학 해석을 수행하여 변형률을 검증하였다. 이를 통해 험로 프로파일과 유사한 거동을 나타내는 4 축 도로하중을 구할 수 있었으며 신뢰성을 검증하였다.

• 한국군사과학기술학회지
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• 제23권5호
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• pp.502-515
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• 2020

To identify the dynamic characteristics of the Auto-leveling system applied to the Tractor-Trailer type Transporter for mounting a large scale precision equipment, Dynamics Modeling & Simulation were performed using general Dynamics Analysis Program - RecurDyn(V9R2). The axial load data, transverse load data and pad trace data of leveling actuators were obtained from M&S. And they were analyzed and compared with each other by parameters, i.e. friction coefficients on the ground, landing ram speed of actuators, and direction & quantity of ground slope. It was observed that ground contact friction coefficients affected to transverse load and pad trace; the landing ram speed of actuators to both amplitude of axial & transverse load, and this phenomena was able to explain from the frequency analysis of the axial load data; the direction of ground slope to driving sequence of landing ram of actuators. But the dynamic behaviors on the two-directional slope were very different from them on the one-directional slope and more complex.

• Structural Engineering and Mechanics
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• 제2권4호
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• pp.327-343
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• 1994

This is the second part of the paper (Rojek and Kleiber 1993) devoted to nonlinear dynamic analysis of structures consisting of rigid and deformable parts. The first part contains a theoretical formulation of nonlinear equations of motion for the coupled system as well as a solution algorithm. The second part presents the computer implementation of the equations derived in the first part with a short review of the capabilities of the computer program used and the library of finite elements. Details of material nonlinearity treatment are also given. The paper is illustrated by discussing a practical problem of a safety cab analysis for an agricultural tractor.

• Journal of Advanced Marine Engineering and Technology
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• 제25권1호
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• pp.124-130
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• 2001

This paper presents a methodology on automation of a trailer type vehicle which consists of two parts: a tractor and a trailer. Backward moving and parking control is very important to automate this type of vehicle. It is difficult to control the motion such a trailer vehicle whose dynamics in non-holonomic. Therefore, in this paper, the modeling and parameter estimation of the system using a RCGA(real-coded genetic algorithm) is proposed and a backward path tracking control algorithm is then obtained. The simulation results verify the effectiveness of the proposed method.