• Transactions on Control, Automation and Systems Engineering
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• v.2 no.1
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• pp.56-61
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• 2000

Majority of industrial robots are controlled by a simple independent joint control of joint actuators rather than complex controllers based on the nonlinear dynamic model of the robot manipulator. In this independent joint control scheme, the performance of actuator control is influenced significantly by the joint disturbance torques including gravity, Coriolis and centrifugal torques, which result in the trajectory tracking error in the joint control system. The control performance of a redundant manipulator under independent joint control can be improved by minimizing this joint disturbance torque in resolving the kinematic redundancy. A 3 DOF planar robot is studied as an example, and the dynamic programming method is used to find the globally optimal joint trajectory that minimize the joint disturbance torque over the entire motion. The resulting solution is compared with the solution obtained by the conventional joint torque minimization, and it is shown that joint disturbance can be reduced using the kinematic redundancy.

• 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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• 1996.10b
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• pp.1140-1143
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• 1996

A new approach based on artificial potential function is proposed for the obstacle avoidance of redundant manipulators. Unlike the so-called "global" path planning method, which requires expensive computation for the path search before the manipulator starts to move, this new approach, "local" path planning, researches the path in real-time using the local distance information. Previous use of artificial potential function has exhibited local minima in some complex environments. This thesis proposes a potential function that has no local minima even for a cluttered environment. This potential function has been implemented for the collision avoidance of a redundant robot in Simulation. The simulation also employ an algorithm that eliminates collisions with obstacles by calculating the repulsive potential exerted on links, based on the shortest distance to object.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.1
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• pp.142-149
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• 1995

This paper presents a new kinematic control strategy for serial redundant manipulators which gives repeatability in the joint space when the end-effector undergoes some general cyclic motions. Theoretical development has been accomplished by deriving a new inverse kinematic equation that is based on springs being conceptually located in the joints of the manipulator. Although some inverse kinematic equations for serial redundant manipulators have been derived by many researchers, the new strategy is the first to include the free angles of torsional springs and the free lengths of the translational springs. This is important because it ensures repeatability in the joint space of a serial redundant manipulator whose end-effector undergoes a cyclic type motion. Numerical verification for repeatability is done in terms of Lie Bracket Condition. Choices for the free angle and torsional stiffness of a joint (or the free length and translational stiffness) are made based upon the mechanical limits of the joints.

• Journal of the Korean Society for Precision Engineering
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• v.10 no.2
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• pp.170-177
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• 1993

In robotic arc welding, the roll (rotation) of the torch about its direction vector does not have any effect on the welding operation. Thus we could use this redundant degree of greedom for the motion control of the robot manipulator. This paper presents an algorithm for the pseudo- inverse kinematic motion control of the 6-axis robot, which utilizes the above mentioned redunancy. The prototype welding operation and the tool path are also graphically simulated. Since the proposed algorithm requires only the position and normal vector of the weldine as an input data, it is useful for the CAD-based off-line programming of the arc welding robot. In addition, it also has the advantages of the redundant manipulator motion control, like singularity avoidance and collision free motion planning, when compared with the other motion control method based on the direct inverse kinematics.

• 제어로봇시스템학회:학술대회논문집
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• 1991.10a
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• pp.168-173
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• 1991

A neural optimization network is proposed to control the redundant robot manipulators in an environment with the obstacle. The weightings of the network are adjusted by considering both the joint dexterity and the capability of collision avoidance of joint differential motion. The fuzzy rules are proposed to determine the capability of collision avoidance of each joint. To show the validities of the proposed method, computer simulation results are illustrated for the redundant robot of the planner type with three degrees of freedom.

• 제어로봇시스템학회:학술대회논문집
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• 1989.10a
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• pp.230-234
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• 1989

This paper presents the design of a prototype robot and architecture of a distributed control system. The robot, named as KAEROT, has been developed for the purpose of the reduction of personal radiation exposure and the remote maintenance tasks in nuclear facilities. The mobile system with robotic manipulator has been designed to go up and down stairs. For the dextrous handling, this manipulator will be designed as a redundant type to act like a human arm. Manipulator control system is to be extended easily for further usage with a modular architecture to get independency and reliability by minimizing EMI effects.

• Journal of the Korean Society for Precision Engineering
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• v.10 no.4
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• pp.227-235
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• 1993

In this paper, the development of a high performance flexible controller is described. The hardware of the controller, based on VME-bus, consists of four M68020 single-board computers (32-bit) with M68881 numerical coprocessors, two M68040 single board donputers, I/O devices (such as A/D and D/A converters, paraller I/O, encoder counters), and bus-to-bus adaptor. This software, written in C and based on X-window environment with Unix operating system, includes : text editor, compiler, downloader, and plotter running in a host computer for developing control program ; device drivers, scheduler, and mathemetical routines for the real time control purpose ; message passing, file server, source level debugger virtural terminal, etc. The hardware and software are structured so that the controller might have both flexibility and extensibility. In papallel to the controller, a three degrees of freedom kinematically redundant robot has been developed at the same time. The development of the same time. The development of the robot was undertaken in order to provide, on the one hand, a computationally intensive plant to which to apply the controller, and on the other hand a research tool in the field of kinematically redundant manipulator, which is, as such, an important area. By using the controller, dynamic control of the redundant manipulator was successfully experimented, showing the effectiveness and flexibility of the controller.

• 제어로봇시스템학회:학술대회논문집
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• 2004.08a
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• pp.1650-1654
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• 2004

This paper presents how it is effective to use many features for improving the speed and the accuracy of the visual servo systems. Some rank conditions which relate the image Jacobian and the control performance are derived. It is also proven that the accuracy is improved by increasing the number of features. Effectiveness of the redundant features is evaluated by the smallest singular value of the image Jacobian which is closely related to the accuracy with respect to the world coordinate system. Usefulness of the redundant features is verified by the real time experiments on a Dual-Arm Robot manipulator made in Samsung Electronic Co. Ltd.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.778-782
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• 2003

This paper presents how it is effective to use many features for improving the speed and the accuracy of the visual servo systems. Some rank conditions which relate the image Jacobian and the control performance are derived. It is also proven that the accuracy is improved by increasing the number of features. Effectiveness of the redundant features is evaluated by the smallest singular value of the image Jacobian which is closely related to the accuracy with respect to the world coordinate system. Usefulness of the redundant features is verified by the real time experiments on a Dual-Arm Robot manipulator made in Samsung Electronic Co. Ltd.