• 제어로봇시스템학회논문지
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• 제10권10호
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• pp.887-898
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• 2004

In this paper a mathematical framework fur deriving acceleration bounds from given joint torque limits of multiple cooperating robots are described. Especially when the different frictional contacts for every contact are assumed and the torque limits are given in 2-norm sense, we show that the resultant geometrical configuration for the acceleration is composed of corresponding parts of ellipsoids. Since the frictional forces at the contacts are proportional to the normal squeezing forces, the key points of the work includes how to determine internal forces exerted by each robot in order not to cause slip at the contacts while the object is carried by external forces. A set of examples composed of two robot systems are shown with point-contact-with-friction model and insufficient or proper degree of freedom robots.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2010년도 춘계학술대회 논문집
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• pp.957-958
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• 2010

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2004년도 춘계학술대회 논문요약집
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• pp.21-21
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• 2004

본 논문은 수동 힘반영 기구의 안정성을 제어하기 위한 방법으로 수동성 제어기를 제안한다. 수동 힘반영 기구는 브레이크와 같은 수동 엑츄에이터를 사용함으로써 힘을 반영하게 되는데, 여기에 사용되는 수동 엑츄에이터는 사용자가 움직이고자 하는 방향의 반대방향으로만 힘을 생성할 수 있기 때문에, 힘을 생성할 수 있는 방향에 제한이 있다. 따라서 가상의 벽면을 나타내는 데에도 정확히 원하는 방향의 힘을 제시하지 못하고, 힘의 근사화를 통하여 가장 근접한 방향의 힘을 생성해낸다. 이는 이상적인 수동 힘반영 기구의 연구에서도 나타나며, FME(Force Manipulability Ellipsoid)에 의해 명확하게 설명이 되는 현상이다.(중략)

• 한국정밀공학회지
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• 제29권3호
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• pp.346-353
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• 2012

The purpose of this study is to verify the energy efficiency of the integrated system combining human and a lower extremity exoskeleton robot when it is applied to the proposed gait pattern. Energy efficient gait pattern of the lower limb was proposed through leg function distribution during stance phase and the dynamic-manipulability ellipsoid (DME). To verify the feasibility and effect of the redefined gait trajectory, simulations and experiments were conducted under the conditions of walking on level ground and ascending and descending from a staircase. Experiments to calculate the metabolic cost of the human body with or without the assistance of the exoskeleton were conducted. The energy consumption of the lower extremity exoskeleton was assessed, with the aim of improving the efficiency of the integrated system.

• Transactions on Control, Automation and Systems Engineering
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• 제3권4호
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• pp.217-222
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• 2001

We propose a new two-degree of freedom parallel mechanism for a haptic device and will refer to the mechanism as the SenSation. The SenSation is designed in order to improve the kinematic performanced and to achieve static balance. We use the panto graph mechanisms in order to change the location of active joints, which leads to transform a direct kinematic singularity into a nonsingularity. The direct kinematic singular configurations of the SenSation occur near the workspace boundary. Using the property that position vector of rigid body rotating about a fixed point is normal to the velocity vector, Jacobian matrix is derived. Using the vector method, two different types of singularities of the SenSation can be identified and we discuss the physical significance of each of the three types of singularities. We will compare the kinematic performances(force manipulability ellipsoid, kinematic isotropy) of the SenSation with those of five-var parallel mechanism. By specifying that the potential energy be fixed, the conditions for the static balancing of the SenSation is derived. The static balancing is accomplished by changing the center of mass of the links.

• 한국정보통신학회논문지
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• 제5권4호
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• pp.756-765
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• 2001

An effective dexterous motion control method of redundant robot manipulators based on neural optimization network is proposed to satisfy multi-criteria such as singularity avoidance, minimizing energy consumption, and avoiding physical limits of actuator, while performing a given task. The method employs a neural optimization network with parallel processing capability, where only a simple geometric analysis for resolved motion of each joint is required instead of computing of the Jacobian and its pseudo inverse matrix. For dexterous motion, a joint geometric manipulability measure(JGMM) is proposed. JGMM evaluates a contribution of each joint differential motion in enlarging the length of the shortest axis among principal axes of the manipulability ellipsoid volume approximately obtained by a geometric analysis. Redundant robot manipulators is then controlled by neural optimization networks in such a way that 1) linear combination of the resolved motion by each joint differential motion should be equal to the desired velocity, 2) physical limits of joints are not violated, and 3) weighted sum of the square of each differential joint motion is minimized where weightings are adjusted by JGMM. To show the validity of the proposed method, several numerical examples are illustrated.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2004년도 ICCAS
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• pp.1424-1429
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• 2004

In this paper a mathematical framework for deriving acceleration bounds from given joint torque limits of multiple cooperating robots are described. Especially when the different frictional contacts for every contact are assumed and the torque limits are given in 2-norm sense, we show that the resultant geometrical configuration for the acceleration is composed of corresponding parts of ellipsoids. Since the frictional forces at the contacts are proportional to the normal squeezing forces, the key points of the work includes how to determine internal forces exerted by each robot in order not to cause slip at the contacts while the object is carried by external forces. A set of examples composed of two robot systems are shown with point-contact-with-friction model and insufficient or proper degree of freedom robots.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2003년도 ICCAS
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• pp.1565-1570
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• 2003

Passive Haptic Devices have more benefit than the active in Stability. But Apart from benefits, it shows poor performance in haptic display. The author proposed the passive FME(Force Manipulability Ellipsoid) which can graphically show force generating ability of a passive haptic device. In this paper, performance indexes for the force approximation and pseudo friction cone are obtained with the passive FME and an optimized planar device with the indexes is proposed. Based on the above theory, experiment is conducted.

• 제어로봇시스템학회논문지
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• 제5권8호
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• pp.955-960
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• 1999

This paper describes the effect of impact configurations on a single robot manipulator. The effect of different configurations of kinematically redundant arms on impact forces at their end effectors during contact with the environment is investigated. Instead of the well-known impact ellipsoid, I propose an analytic method on the geometric configuration of the impact directly from the mathematical definition. By calculating the length along the specified motion direction and volume of the geometry, we can determine the characteristics of robot configurations in terms of both the impact along the specified direction and the ability of the robot withstanding the impact. Simulations of various impact configurations are discussed at the end of this paper.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2003년도 ICCAS
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• pp.1559-1564
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• 2003

In this paper, a control method is presented to improve performance of haptic display on a passive haptic device equipped with passive actuators. In displaying a virtual wall with the passive haptic device, an unstable behavior occurs with excessive actions of brakes due to the time delay mainly arising from the update rate of the virtual environment and force approximation originated from the characteristics of the passive actuators. The previous T.D.P.C. (Time Domain Passivity Control) method was not suitable for the passive haptic device, since a programmable damper used in the previously introduced T.D.P.C. method easily leads to undesirable behaviors. A new passivity control method is evaluated with considering characteristics of the passive device. First, we propose a control method which is designed under the analysis of the passive FME (Force Manipulability Ellipsoid). And then a passivity control scheme is applied to the proposed control method. Various experiments have been conducted to verify the proposed method with a 2-link mechanism.