• Journal of Advanced Marine Engineering and Technology
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• v.23 no.6
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• pp.731-737
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• 1999

This paper describes the path tracking control for a mobile robot which has two casters at the front and rear to keep balance and two driving wheels on the left and right sides of its body. Power wheeled steering method is adapted to control heading of the robot. It is very difficult to find appropriate feedback gains when linear regulator control scheme is adapted to path tracking con-trol of this type of robot. Therefore in this paper we propose the path tracking control algorithm using the fuzzy logic control scheme for this type of root. Simulation to prove the validity of the proposed two algorithms is performed. The results are reported as last part in this paper.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.2
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• pp.327-336
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• 1997

This paper addresses an analytical approach to the mechanical error analysis and tolerance design of a four-bar path generator with lubricated joints. The mobility method is applied to consider lubrication effects and the four-bar path generator is stochastically modeled by using the clearance vector model for methanical error analysis. To show the validity of the proposed method, the mechanical errors obtained by applying the method to a four-bar path generator are compared with those by Monte Carlo simulation. Based on this analytical method, an optimal tolerance design problem is formulated and solved for the four-bar path generator.

• Journal of the Korean Society for Precision Engineering
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• v.12 no.2
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• pp.97-111
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• 1995

In this paper, we investigate path compensation scheme for the machining errors due to tool deflection in 2D contour machining. The significance of the deflection error is first shown by experiments, and a direct compensation scheme is sought. In the presented scheme, the tool path is evaluated and correcte based on the instantaneous deflection force model, until the desired contour can be obtained under the presence of tool deflection in actual machining. In the sense that the developed method estimates and compensates the machining errors via modifying the tool path, it is distinguished from the previous approach based on geometric simulation and cutting simulation. Further, it can be viewed as a direct and active method toward direct shape control in CNC machining. Simulation results are included to show the validity and adequacy of the path-modification scheme under various cutting conditions.

• Journal of Institute of Control, Robotics and Systems
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• v.17 no.5
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• pp.405-411
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• 2011

This paper presents a hierarchical trajectory planning method which can handle a collision-free of the planned path in complex and dynamic environments. A PV (Path & Velocity profile) planning method minimizes a sharp change of orientation and waiting time to avoid a collision with moving obstacle through detour path. The path generation problem is solved by three steps. In the first step, a smooth global path is generated using $A^*$ algorithm. The second step sets up the velocity profile for the optimization problem considering the maximum velocity and acceleration. In the third step, the velocity profile for obtaining the shortest path is optimized using the fuzzy and genetic algorithm. To show the validity and effectiveness of the proposed method, realistic simulations are performed.

• Proceedings of the KIEE Conference
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• 2002.07d
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• pp.2401-2403
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• 2002

Given a certain target point, the mobile robot's navigation could be mainly considered about two areas, 'how fast and accurate' and 'how safe'. Such problems regarding the velocity and stability possess close relationship with the path in which the mobile robot navigates in. Thus, the system proposed in this research paper was constructed so the mobile robot can obtain the optimum path by utilizing the information according to the environmental map, based on the Global Path Planning. Also by inducing the Local Path Planning method, it was constructed so that the robots can avoid the obstacles, which were not shown in the environmental map on-line. Particularly, by fusing the Local and Global Path Planning together, it is possible for the robots to plan similar path. At the same time, the focus was on the materialization of effective mobile robot's navigation. It was made possible by utilizing the Fuzzy Logic Control. Also, the validity of the algorithm proposed was proven through the trial experiment.

• Journal of Institute of Control, Robotics and Systems
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• v.11 no.9
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• pp.802-809
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• 2005

A hybrid genetic algorithm is proposed for the problem of generating laser torch paths to cut a stock plate nested with free-formed parts each having a set of sub-parts. In the problem, the total unproductive travel distance of the torch is minimized. The problem is shown to be formulated as a special case of the standard travelling salesman problem. The hybrid genetic algorithm for solving the problem is hierarchically structured: First, it uses a genetic algorithm to find the cutting path f3r the parts and then, based on the obtained cutting path, sequence of sub-parts and their piercing locations are optimally determined by using a combined genetic and heuristic algorithms. This process is repeated until any progress in the total unproductive travel distance is not achieved. Computational results are provided to illustrate the validity of the proposed algorithm.

• Journal of Institute of Control, Robotics and Systems
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• v.8 no.12
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• pp.1048-1055
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• 2002

The problem of generating torch paths for 2D laser cutting of a stock plate nested with a set of free-formed parts is investigated. The objective is to minimize the total length of the torch path starting from a blown depot, then visiting all the given Parts, and retuning back to the depot. A torch Path consists of the depot and Piercing Points each of which is to be specified for cutting a part. The torch path optimization problem is shown to be formulated as an extended version of the standard travelling salesman problem To solve the problem, a hybrid genetic algorithm is proposed. In order to improve the speed of evolution convergence, the algorithm employs a genetic algorithm for global search and a combination of an optimization technique and a genetic algorithm for local optimization. Traditional genetic operators developed for continuous optimization problems are used to effectively deal with the continuous nature of piercing point positions. Computational results are provided to illustrate the validity of the proposed algorithm.

• Journal of Mechanical Science and Technology
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• v.17 no.11
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• pp.1616-1627
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• 2003

This paper describes a mini linear optical pickup actuator. To reduce the size, inner yokes are designed to guide the mover and outer yokes of permanent magnets are removed. Magnetic circuit method is used to determine the thrust force. Virtual path method is proposed to analyze the open magnetic circuit analysis. The magnetic circuit of the proposed actuator can be a closed circuit due to the virtual path model of the outer magnetic flux. The validity of virtual path method is evaluated by comparing to the FEM analysis. Structural vibration is investigated using FEM and the design of the mover is modified to improve the vibration characteristic. Dynamic characteristic experiments shows that the performance of the proposed actuator is enough to be used as a coarse and fine seeking actuator simultaneously and the thrust force margin for loading a focusing actuator is guaranteed.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.11
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• pp.1844-1853
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• 2001

In the present investigation, it was attempted to design the rolling pass schedule fur a clean steel of 0.1C-1.5Mn-0.25Si with the objective of the austenite grain refinement. As the method of approach, a coupled mathematical modeling technique was proposed which consists of a recrystallization model and a flow stress modes. The validity of the coupled model was examined through comparison with results of continuous and discontinuous compression tests at various temperatures, strains and strain rates. The coupled model was incorporated with the finite element method to set up a systematic design methodology far the rolling path schedule for austenite grain refinement. Two path schedules were obtained and discussed in the paper with regard to rolling path time, average grain size, grain size deviation in thickness, etc.

• Journal of Institute of Control, Robotics and Systems
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• v.4 no.6
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• pp.786-794
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• 1998

This paper proposes an automatic microshaping technology using laser and applies it to implementation of semicutting control system of the panel inside which a car air bag is equipped. Since it is impossible to project laser directly onto the desired working point of a target panel due to fixedness of laser generator, we reflect the generated laser, using reflection mirrors and focusing lenses, to project onto the desired working point. Also, in order to conduct an uniform semicutting control with constant width and depth, we control the end-effector of manipulator, which grasp the laser reflection mirror, to track working path with constant speed and orientation. The validity and effectiveness of the proposed methods are checked through experiments tracking a path formatted with straight lines and arcs.