• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.1
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• pp.181-192
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• 1995

In this study, we introduce new types of planar 2 degree-of-freedom robot modules resembling the musculoskeletal structure of the human arm with actuation redundancy. First, for the given actuator sizes the performance analysis for the manipulator with redundant actuation and without redundant actuation is performed with respect to maximum load handling capacity, maximum hand velocity, and maximum hand acceleration. Secondly an algorithm which decides optimal actuator sizes for the given operational performances is introduced, and the optimal actuator sizes for a robot module with four redundant actuation are obtained. The algorithms employed in this paper will be useful to analyze the robot performances and to determine the actuator sizes for general robot manipulators.

• 제어로봇시스템학회:학술대회논문집
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• 1996.10a
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• pp.69-72
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• 1996

This paper considers a global resolution of kinematic redundancy under inequality constraints as a constrained optimal control. In this formulation, joint limits and obstacles are regarded as state variable inequality constraints, and joint velocity limits as control variable inequality constraints. Necessary and sufficient conditions are derived by using Pontryagin's minimum principle and penalty function method. These conditions leads to a two-point boundary-value problem (TPBVP) with natural, periodic and inequality boundary conditions. In order to solve the TPBVP and to find a global minimum, a numerical algorithm, named two-stage algorithm, is presented. Given initial joint pose, the first stage finds the optimal joint trajectory and its corresponding minimum performance cost. The second stage searches for the optimal initial joint pose with globally minimum cost in the self-motion manifold. The effectiveness of the proposed algorithm is demonstrated through a simulation with a 3-dof planar redundant manipulator.

• Journal of Institute of Control, Robotics and Systems
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• v.5 no.4
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• pp.446-453
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• 1999

An athlete motion during weightlifting is analyzed based on robotic manipulability, which shows dexterities by changing the position and orientation of the end-effector of robot manipulators arbitrary or along a specified direction. The athlete body is modeled as a highly redundant robot manipulator. The motion of weightlifting is analyzed based on the selected model with a power manipulability. Power manipulability and its geometric characteristics are derived by combining kinematic manipulability and dynamic manipulability. Also, manipulability-based optimal trajectory of weightlifter for given body structure of weightlifter derived through genetic algorithm.

• 제어로봇시스템학회:학술대회논문집
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• 1994.10a
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• pp.89-94
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• 1994

This paper presents an impact control algorithm for reducing the potentially damaging effects by interation of redundant manipulators with their environments. In the. proposed control algorithm, the redundancy is resolved at the torque level by locally minimizing joint torque, subject to tire operational space dynamic formulation which maps tire joint torque set into the operational forces. For a given pre-impact velocity of the manipulator, the proposed approach is on generating joint space trajectories throughout the motion near the contact which instantaneously minimize the impulsive force which is a scalar function of manipulator's configurations. This is done by using the null space dynamics which does not affect the motion of an end-effector. The comparative evaluation of the proposed algorithm with a local torque optimization algorithm without reducing impact is performed by computer simulation. The simulation results illustrate the effectiveness of the algorithm in reducing both the effects of impact and large torque requirements.

• Proceedings of the KIEE Conference
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• 2001.11c
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• pp.103-106
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• 2001

A new control method for a redundant manipulator is developed using a local optimal torque and null space joint velocity. By solving the dynamic control equations of the system, the local optimal torque is obtained. If only the local optimal torque is used for controlling the robot there is a possibility that the system is unstable. To eliminate the characteristics of instability during the movements, the control law with a null space concept is used. The new method is applied to the 3-DOF planar manipulator. The simulation results show the effectiveness of the proposed algorithm.

• 제어로봇시스템학회:학술대회논문집
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• 1988.10a
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• pp.37-40
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• 1988

It is well-known that the redundancy can be exploited to avoid the singular regions of the redundant manipulator by increasing the manipulability. The method, however, requires exprecessive energy and gives rather large tracking errors since the manipulability is increased repidly so that the manipulator avoid the singular region quickly. In this paper, a new method is proposed in which the increasing speed of the manipulability is confined to a certain bound. Therefore, in the proposed method, the movement energy and the tracking errors are reduced. The computer simulation studies are performed to show the validity of the method.

• Journal of Power System Engineering
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• v.5 no.2
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• pp.79-86
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• 2001

A method is presented for generating the path which significantly reduces residual vibration of the redundant, flexible robot manipulator in the presence of obstacles. The desired path is optimally designed so that the system completes the required move with minimum residual vibration, avoiding obstacles. The dynamic model and optimal path are effectively formulated and computed by using special moving coordinate, called VLCS, to represent the link flexibility. The path to be designed is developed by a combined Fourier series and polynomial function to satisfy both the convergence and boundary condition matching problems. The concept of correlation coefficients is used to select the minimum number of design variables. A planar three-link manipualtor is used to evaluate this method. Results show that residual vibration can be drastically reduced by selecting an appropriate path, in the presence of obstacles.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.05a
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• pp.979-983
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• 2001

We develop a new method of simultaneous optimization of trajectory and shape of redundant flexible manipulators for collision-free utilizing the B-spline function and a mathematical programming method We adopt an approximate flexible manipulator model which consists of rigid bar elements and spring elements. We use B-spline function for determining the approximate trajectory and the expressions of the outline of obstacles. The used total performance index consists of 2 performance indices. The first is the driving energy, and the second is the trajectory deviation which is caused by the approximate modeling for the flexible manipulator. We design optimal collision-free trajectory of flexible manipulators by searching optimum positions of the control points for B-spline approximation which minimize the performance index subject to constraint condition for collision-free. Some examinations through numerical examples show the effectiveness of the method

• Journal of the Korean Institute of Telematics and Electronics
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• v.25 no.6
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• pp.598-605
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• 1988

A kinematic control method for the redundant robot manipulator is proposed, where redundancy is utilized to avoid the limit of joint positions and velocities. For the given tadk, the joint positions are obtained in such a way that each joint is placed as close to its center point as possible by considering the velocity limit. The robot is, therefore, controlled so that the joints move with the acceptable velocities and lie within the reachable ranges. To show the validities of the proposed method, two examples are illustrated by computer simulations for the RHINO-XR robot with sliding base.

• Journal of Industrial Technology
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• v.15
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• pp.63-70
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• 1995

This paper presents an impact control algorithm for reducing the potentially damaging effects by interation of redundant manipulators with their environments. In the proposed control algorithm, the redundancy is resolved at the torque level by locally minimizing joint torque, subject to the operational space dynamic formulation which maps the joint torque set into the operational forces. For a given pre-impact velocity of the manipulator, the proposed approach is on generating joint space trajectories throughout the motion near the contact which instantaneously minimize the impulsive force which is a scalar function of manipulator's configurations. The comparative evaluation of the proposed algorithm with a local torque optimization algorithm with a local torque optimization algorithm without reducing impact is performed by computer simulation. The simulation results illustrate the effectiveness of the algorithm in reducing both the effects of impact and large torque requirements.