• Journal of the Institute of Electronics Engineers of Korea CI
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• v.39 no.2
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• pp.21-34
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• 2002

Different from ordinary mobile robots used in a well-structured industrial workspace, a guide mobile robot for the visually impaired should be designed in consideration of a moving obstacle, which mostly refers to pedestrians in intentional motions. Thus, the navigation of the guide robot can be facilitated if the intention of each detected obstacle can be known in advance. In this paper, we propose an inference method to understand an intention of a detected obstacle. In order to represent the environment with ultrasonic sensors, the fuzzy grid-type map is first constructed. Then, we detect the obstacle and infer the intention for collision avoidance with the CLA(Centroid of Largest Area) point of the fuzzy grid-type map. To verify the proposed method, some experiments are performed.

• Journal of the Korean Society of Industry Convergence
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• v.18 no.3
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• pp.181-190
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• 2015

This paper presents a new approach to control the position of robot arm in workspace a robot manipulator under unknown system parameters and bounded disturbance inputs. To control the motion of the manipulator, an inverse dynamics control scheme was applied. Since parameters of the robot arm such as mass and inertia are not perfectly known, the difference between the actual and estimated parameters was considered as a external disturbance force. To identify the known parameters, an improved robust control algorithm is directly derived from the Lyapunov's Second Method. A robust control algorithm is devised to counteract the bounded disturbance inputs such as contact forces and disturbing forces coming from the difference between the actual and the estimated system parameters. Numerical examples are shown using SCARA arm with four joints.

• Journal of the Korean Society for Precision Engineering
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• v.31 no.2
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• pp.149-156
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• 2014

Flexible tactile sensors can provide valuable feedback to intelligent robots about the environment. This is especially important when the robots, e.g., service robots, are sharing the workspace with human. This paper presents a flexible tactile sensor that was manufactured by direct writing technique, which is one of 3D printing method with multi-walled carbon nano-tubes. The signal processing system consists of two parts: analog circuits to amplify and filter the sensor output and digital signal processing algorithms to reduce undesired noise. Finally, experimental setup is implemented and evaluated to identify the characteristics of the flexible tactile sensor system. This paper showed that this type of sensors can detect the initiation and termination of contacts with appropriate signal processing.

• Journal of the Korean Society for Precision Engineering
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• v.34 no.1
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• pp.53-58
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• 2017

A fine stage is developed for the 3-DOF error compensation of a linear axis in order to improve the positioning accuracy. This stage is designed as a planar parallel mechanism, and the joints are based on a flexure hinge to achieve ultra-precise positioning. Also, the effect of Abbe's offsets between the measuring and driving coordinate systems is minimized to ensure an exact error compensation. The mode shapes of the designed stage are analyzed to verify the desired 3-DOF motions, and the workspace and displacement of a piezoelectric actuator (PZT) for compensation are analyzed using forward and inverse kinematics. The 3-DOF error of a linear axis is measured and compensated by using the developed fine stage. A marked improvement is observed compared to the results obtained without error compensation. The peak-to-valley (PV) values of the positional and rotational errors are reduced by 92.6% and 91.3%, respectively.

• Journal of the Korean Society for Precision Engineering
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• v.19 no.4
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• pp.124-131
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• 2002

In this paper, an extended volumetric error model considering backlash in a three-axis machine tool was proposed and utilized for calculating the volumetric error of the machine tool at any position in three-dimensional workspace. Backlashes are interrelated; i.e. the angular backlash affects the straightness errors which then affect talc calculated squareness errors. Therefore, a new concept was introduced to define the backlash of squareness errors to incorporate the backlash of squareness error into the volumetric error, and the characteristics of the backlash of squareness error were investigated. The effects of backlash errors were assessed, by experiments. for 21 geometric errors of a machine tool. The backlash error was shown to be one of the systematic errors of a machine tool. And a generalized volumetric error model formulator for three-axis machine tools was developed, which allowed us to formulate machine tool synthesis error models far all possible machine tool configurations only with machine tool topology information. Based on these volumetric error model and model formulator, a computer-aided volumetric error analysis system was developed for a three-axis machine tool in this paper. Then the volumetric error at an arbitrary position can be obtained, and displayed in a three-dimensional graphic form.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.05a
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• pp.676-680
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• 2000

In this paper, an extended volumetric error model considering backlash in a three-axis machine tool was proposed and utilized for calculating the volumetric error of the machine tool at any position in three-dimensional workspace. Backlashes are interrelated; i.e. the angular backlash affects the straightness errors which then affect the calculated squareness errors. Therefore, a new concept was introduced to define the backlash of squareness errors to incorporate the backlash of squareness error into the volumetric error, and the characteristics of the backlash of squareness error were investigated. The effects of backlash errors were assessed, by experiments, fur 21 geometric errors of a machine tool. The backlash error was shown to be one of the systematic errors of a machine tool. Based on this volumetric error model, a computer-aided volumetric error analysis system was developed for a three-axis machine tool in this paper. Then the volumetric error at an arbitrary position can be obtained, and displayed in a three-dimensional graphic form.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.5
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• pp.891-898
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• 2001

This paper develops a master manipulator which can reflect a force from a slave manipulator effectively. It many have a big workspace, can represent a human operators manipulation perfectly, and is composed of a position control part, an orientation control part and an end effector control part. This paper also develops a graphic simulator using the Visual C++ and OpenGL in the Window operating system. It can be used to make a virtual slave manipulator and set a virtual working environment, and provide a visual information from a desired view point. A virtual teleoperation system is developed by connecting the developed master manipulator to the graphic simulator using an interfacing hardware bilaterally. It is used for performing a virtual object exploration experiment. In the experiment, two virtual objects are used. They are virtual wall and virtual hexahedron which have 0.7N/mm and 2.2 N/mm stiffness respectively. The experiments are performed under six different working conditions. The experiment results will show the effectiveness of the reflected force from the slave manipulator for improving the efficiency and stability of the teleoperation task.

• Proceedings of the Korea Information Processing Society Conference
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• 2005.05a
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• pp.1619-1622
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• 2005

본 논문에서는 로봇이 작업을 계획하기 위해 필요한 3차원 작업 공간을 세 가지의 컨텍스트(context)들을 이해함으로써 빠르게 모델링하는 새로운 기법을 소개 하고 있다. 로봇이 사람과 비슷한 속도와 정확도로 작업 공간을 이해하고 모델링하는 것에 초점을 두고 있으며 이를 위해 작업 공간상의 특징적인 세 가지의 컨텍스트(작업공간의 간략화를 위한 전체 공간상의 평면특징, 데이터베이스에 미리 정의된 물체 그리고 로봇의 주어진 작업에 따라 다양한 상세함을 갖는 그 외의 장애물)를 정의하였고, 그것들을 빠르게 이해함으로써 어떻게 3차원 작업 공간을 형성하는지 설명하고 있다. 본 논문에서 3 차원 정보를 갖는 scale invariant feature transformation(SIFT)를 stereo-sis SIFT 로 간주했으며 이를 이용하여 위에서 언급한 컨텍스트들을 이해하였고 다양한 카메라의 위치로부터 얻어지는 여러 개의 장면들을 정합하였다. 또한, 실험을 통해 제안한 방법의 타당성도 검증하였다.

• Journal of the Korean Society for Precision Engineering
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• v.34 no.2
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• pp.115-123
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• 2017

This paper presents the design and the control performance of a novel dynamic compliant-arm support with parallel elastic actuators that was developed to assist with the daily living activities of those whose arms are compromised by muscular disease or the aging process. The parallel elastic-arm support consists of a compliant mechanism with combined passive and active components for human interaction and to reach the user's desired positions. The achievement of these tasks requires impedance control, which can change the virtual stiffness, damping coefficients, and equilibrium points of the system; however, the desired-position tracking by the impedance control is limited when the end-effector weight varies according to the equipping of diverse objects. A prompt algorithm regarding weight calibration and friction compensation is adopted to overcome this problem. A result comparison shows that, by accurately assessing the desired workspace, the proposed algorithm is more effective for the accomplishment of the desired activities.

• Journal of the Korean Society for Precision Engineering
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• v.16 no.6
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• pp.90-99
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• 1999

A vehicle driving simulator is a virtual reality device which a human being feels as if the one drives a vehicle actually. The driving simulator is used effectively for studying interaction of a driver-vehicle and developing vehicle system of a new concept. The driving simulator consists of a vehicle motion bed system, motion controller, visual and audio system, vehicle dynamic analysis system, cockpit system, and etc. In it is paper, the main procedures to develop the driving simulator are classified by five parts. First, a motion bed system and a motion controller, which can track a reference trajectory, are developed. Secondly, a performance evaluation of the motion bed system for the driving simulator is carried out using LVDTs and accelerometers. Thirdly, a washout algorithm to realize a motion of an actual vehicle in the driving simulator is developed. The algorithm changes the motion space of a vehicle into the workspace of the driving simulator. Fourthly, a visual and audio system for feeling higher realization is developed. Finally, an integration system to communicate and monitor between sub systems is developed.