• Industrial Engineering and Management Systems
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• v.10 no.3
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• pp.209-220
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• 2011

Self-tapping screws have some operational peculiarities. In spite of their economical advantage that requires no prior tapping operation, a weakness of self-tapping screw-tightening operations is that screws can easily be tightened at a non-right angle, thus resulting in an improper tightening strength. Increases in outsourced workers have reduced labor costs, but the accompanying high worker fluidity means that new workers are more frequently introduced into factories. It is necessary to train new workers for self-tapping screw-tightening operations, which occupies a considerable portion of ordinary assembly works. The purpose of this study is to develop and implement a skill transfer system for the operation. This study (1) proposes a set of characteristic values for evaluating the quality of the operation and develops a device that can measure these values; (2) proposes criteria for evaluating the resultant quality of the tightening; and (3) develops a skill training system for better work performance. Firstly, sets of characteristic values for evaluating the quality of the operation, namely, torque, vertical pressure forces and horizontal vibration forces, are proposed. A device that can measure these values is developed. Secondly, criteria for evaluating the resultant quality of the tightening are identified, involving tightening torque, maximum vertical pressure and timing, vibration area during the processing and tightening period, and work angle. By using such parameters, workers with the proper aptitude can be identified. Thirdly, a skill training system for the operation is developed. It consists of screwdriver operation training and screw-tightening training with feedback information about the results of the operation. Finally, the validity of the training system is experimentally verified using new operators and actual workers.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.32 no.1
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• pp.34-43
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• 2009

In this thesis, we explain developing processes of the power transmission system for lift truck. Conventional power transmission system had some problems such as spatial constraints or low speed and high torque problem. Because conventional power transmission system was mainly designed for high speed vehicles. In this paper we developed power shift drive axle specialized for $2.0{\sim}3.5$ ton lift truck. Innovative structure of transmission which is built in inside axle, enables to reduce system weight and size by 40% compared to the conventional power transmission system. Also, it is possible to do additional functions such as auto parking system and anti-roll back system.

• Journal of the Korean Society for Precision Engineering
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• v.29 no.12
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• pp.1304-1312
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• 2012

According to the successful development of hybrid vehicle, hybridization of construction equipments like excavator, wheel loader, and backhoe etc., is gaining increasing attention. However, hybridization of excavator and commercial vehicle is very different. Therefore a specialized energy management control algorithm for excavator should be developed. In this paper, hybridization of excavators is investigated and a new energy management control algorithm is proposed. Four control parameters, i.e., lower baseline, upper baseline, idling generation speed, and idling generation torque, are newly introduced and a new operating principle using those four control parameters is proposed. The use of Genetic Algorithm for the optimization of the four control parameters from the view point of minimization of fuel consumption for standard excavating operation is suggested. In order to verify the proposed algorithm, dedicated simulation program of hybrid excavator was developed. The proposed algorithm is applied to a specific hydraulic excavator and 20.7% improvement of fuel consumption is achieved.

• Journal of the Korea Safety Management & Science
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• v.23 no.4
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• pp.93-104
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• 2021

In this paper, we propose a method for diagnosing overload and working load of collaborative robots through performance analysis of machine learning algorithms. To this end, an experiment was conducted to perform pick & place operation while changing the payload weight of a cooperative robot with a payload capacity of 10 kg. In this experiment, motor torque, position, and speed data generated from the robot controller were collected, and as a result of t-test and f-test, different characteristics were found for each weight based on a payload of 10 kg. In addition, to predict overload and working load from the collected data, machine learning algorithms such as Neural Network, Decision Tree, Random Forest, and Gradient Boosting models were used for experiments. As a result of the experiment, the neural network with more than 99.6% of explanatory power showed the best performance in prediction and classification. The practical contribution of the proposed study is that it suggests a method to collect data required for analysis from the robot without attaching additional sensors to the collaborative robot and the usefulness of a machine learning algorithm for diagnosing robot overload and working load.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.7
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• pp.669-677
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• 2009

In general, the pitch momentum biased system that induces inherently nutational motion in roll/yaw plane, has been adapted for geosynchronous communications satellites. This paper discusses the method of roll attitude control using yaw axis momentum management method for a low earth orbit(LEO) satellite which is a pitch momentum biased system equipped with only two reaction wheels. The robustness of wheel momentum management method with PI-controller is investigated comparing with wheel torque control method. The transfer function of roll/yaw axis momentum management system that is useful for attitude controller design is derived. The disturbance effect of roll/yaw axis momentum management system for attitude control is investigated to identify design parameters such as magnitude of momentum bias and to get the insight for controller design. As an example, the PID controller design result of momentum management system for roll/yaw axis control is provided and the simulation results are presented to provide further physical insight into the momentum management system.

• Journal of IKEEE
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• v.24 no.2
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• pp.610-618
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• 2020

This paper presents the modeling of hybrid railway vehicles with hydrogen Fuel-Cells (FCs)/battery using a rule-based algorithm. The driving power of traction system is determined with the speed-torque curve by operation area of the electric machine and the electrical systems are modeled. The demanded power of electrical systems is set with the energy management system (EMS). The consumption of hydrogen is effectively managed with the subdivided operation region depending on the state of charge (SOC). The validity of the modeling is verified using MATLAB/Simulink.

• International Journal of Automotive Technology
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• v.7 no.2
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• pp.145-154
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• 2006

In the companion paper, the composition and structure of the MATDYMO (Multi-Agent for Traffic Simulation with Vehicle Dynamic Model) were proposed. MATDYMO consists of the road management system, the vehicle motion control system, the driver management system, and the integration control system. Among these systems, the road management system and the integration control system were discussed In the companion paper. In this paper, the vehicle motion control system and the driver management system are discussed. The driver management system constructs the driver agent capable of having different driving styles ranging from slow and careful driving to fast and aggressive driving through the yielding index and passing index. According to these indices, the agents pass or yield their lane for other vehicles; the driver management system constructs the vehicle agents capable of representing the physical vehicle itself. A vehicle agent shows its behavior according to its dynamic characteristics. The vehicle agent contains the nonlinear subcomponents of engine, torque converter, automatic transmission, and wheels. The simulation is conducted for an interrupted flow model and its results are verified by comparison with the results from a commercial software, TRANSYT-7F. The interrupted flow model simulation is implemented for three cases. The first case analyzes the agents' behaviors in the interrupted flow model and it confirms that the agent's behavior could characterize the diversity of human behavior and vehicle well through every rule and communication frameworks. The second case analyzes the traffic signals changed at different intervals and as the acceleration rate changed. The third case analyzes the effects of the traffic signals and traffic volume. The results of these analyses showed that the change of the traffic state was closely related with the vehicle acceleration rate, traffic volume, and the traffic signal interval between intersections. These simulations confirmed that MATDYMO can represent the real traffic condition of the interrupted flow model. At the current stage of development, MATDYMO shows great promise and has significant implications on future traffic state forecasting research.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.3
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• pp.613-619
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• 2017

In this paper, DF(Dual Fuel) Generator modeling, which uses both conventional diesel fuel and LNG fuel, has been performed and monitoring system has been developed based on MATLAB/SIMULINK for the development of PMS(Power Management System) HILS(Hardware In the Loop Simulation). The principal components modeling of DF Generator are DF engine which provides the mechanical power and synchronous generator which convert the mechanical power into electrical power. Submodels, such as throttle body, intake manifold, torque generation and mass of LNG and diesel Quantity are used to perform DF engine. Also, governor is used for load sharing between paralleled DF generators to share a total load that exceeds the capacity of a single generator. To verify modeling of DF Generator designated ship lumped load Simulation is carried out. A validity of DF Generator has been verified by comparison between simulation results and estimated result from the designated lumped load.

• Journal of Auto-vehicle Safety Association
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• v.5 no.2
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• pp.24-31
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• 2013

This paper describes a coordinated control algorithm for rear-side collision avoidance. In order to assist driver actively and increase driver's safety, the proposed coordinated control algorithm is designed to combine lateral control using a steering torque overlay by Motor Driven Power Steering (MDPS) and differential braking by Vehicle Stability Control (VSC). The main objective of a combined control strategy is twofold. The one is to prevent the collision between the subject vehicle and approaching vehicle in the adjacent lanes. The other is to limit actuator's control inputs and vehicle dynamics to safe values for the assurance of the driver's comfort. In order to achieve these goals, the Lyapunov theory and LMI optimization methods has been employed. The proposed coordinated control algorithm for rear-side collision avoidance has been evaluated via simulation using CarSim and MATLAB/Simulink.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 1994.04a
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• pp.561-568
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• 1994

A man model can be used as an effective tool to design ergonomically sound products and workplaces, and subsequently evaluate them properly. For a man model to be truly useful, it must be integrated with a posture prediction model which should be capable of representing the human arm reach posture in the context of equipments and workspaces. Since the human movement possesses redundant degrees of freedom, accurate representation or prediction of human movement was known to be a difficult problem. To solve this redundancy problem, a psychophysical cost function was suggested in this study which defines a cost value for each joint movement angle. The psychophysical cost function developed integrates the psychophysical discomfort of joints and the joint range availability concept which has been used for redundant arm manipulation in robotics to predict the arm reach posture. To properly predict an arm reach posture, an arm reach posture prediction model was then developed in which a posture configuration that provides the minimum total cost is chosen. The predictivity of the psychophysical cost function was compared with that of the biomechanical cost function which is based on the minimization of joint torque. Here, the human body is regarded as a two-dimensional multi-link system which consists of four links ; trunk, upper arm, lower arm and hand. Real reach postures were photographed from the subjects and were compared to the postures predicted by the model. Results showed that the postures predicted by the psychophysical cost function closely simulated human reach postures and the predictivity was more accurate than that by the biomechanical cost function.