• 제어로봇시스템학회:학술대회논문집
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• 1996.10b
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• pp.730-733
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• 1996

This paper presents the kinematic and dynamic analysis of parallel manipulators with redundant limbs, obtained by putting additional limbs to an existing parallel manipulator. We develop the kinematic and dynamic models of a parallel, manipulator with redundant limbs. The redundancy in parallelism due to the increased number of limbs and the redundancy in actuation due to the increased number of active joints are considered in the modeling. Based on the derived models, we define the kinematic and dynamic manipulabilities of a parallel manipulator with redundant limbs. The effect of the redundant limbs on the performance of parallel manipulators is analyzed in terms of kinematic and dynamic manipulabilities.

• 제어로봇시스템학회:학술대회논문집
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• 1995.10a
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• pp.219-222
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• 1995

This paper presents a control law of multiple actuation servo systems. Multiple actuation systems have an ability to solve some difficult engineering problems; Coulomb friction, backlash, and disturbance. This fact is shown by basic experiments as well as theoretical analysis. The proposed control strategy remarkably improves the performance comparing with conventional single actuation systems.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.11
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• pp.2846-2859
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• 1994

This work deals with kinematic analysis of fault-tolerant 3 degree-of-freedom spherical modules which have force redundancies in its parallel structure. The performance of a redundantly actuated four-legged module with no actuator failure, a single actuator failure, partial and half failure of dual actuator are compared to that of a three-legged module, in terms of maximum force transmission ratio, isotropic characteristics, and fault-tolerant capability. Additionally, a system with an excess number of small floating actuators is considered, and the contribution of these small actuators to the force transmission and fault-tolerant capability is evaluated. This study illustrates that the redundant actuation mode allows significant saving of input actuation effort, and also delivers a fault tolerance.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.4
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• pp.846-855
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• 1994

An effective stiffness, analogous to that of a wound spring, can be created by antagonistic redundant actuation of general closed-chain mechanisms. The qualitative and quantitative characteristics of the effective stiffness are investigated through a Four-bar mechanism, and a load distribution method is introduced which simultaneously guarantees the required system motion and the effective stiffness of the Four-bar mechanism. Furthermore, a simulation is performed to understand the inter-relationship among the effective stiffness, the Four-bar geometry, and the actuation effort. Based on this analysis, the Four-bar synthesis problem for effective stiffness generation is discussed.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.1598-1602
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• 2003

The parallel-type mechanism provides more accurate and stiff motion than the serial-type mechanism. However, in case of using the haptic device, the performance of the force reflection can be deteriorated due to the singular points existing in workspace. In this paper, we propose a redundantly actuated parallel 3-DOF haptic device, which is singularity-free in the workspace and has an improved force reflection capability. In addition, we propose a new force distribution algorithm, which can reflect force of both high and low resolution, using two sets of actuator with different size. Redundant actuators are attached to the base frame in order to minimize the inertia of the system. Moreover, a wire and gear reduction system is employed to achieve high force reflection along with soft feeling. We confirm the performance of the force reflection capability throughout simulation.

• Journal of Institute of Control, Robotics and Systems
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• v.3 no.5
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• pp.482-489
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• 1997

This paper presents the analysis of the kinematics and dynamics of redundant parallel manipulators, and provides design guides for advanced parallel mainpulators with high performance. Three types of redundancies are considered which include the redundancies in serial chain, joint actuation, and parallelism. First, the kinematic and dynamic models of a redundant parallel manipulator are obtained in both joint and Cartesian spaces, and the kinematic and dynamic manipulabilities are defined for the performance evaluation. The effects of the three types of redundancies on the kinematic and dynamic performance of a parallel manipulator are then analyzed and compared, providing a set of guides for the design of advanced parallel manipulators. Finally, the simulation results using planer parallel manipulators are given.

• 제어로봇시스템학회:학술대회논문집
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• 1996.10b
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• pp.48-51
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• 1996

A 5-bar structure with redundant actuators is proposed as a finger mechanism. It is shown that one additional redundant actuator greatly enhances the load handling capacity of the system. The actuator location should be carefully decided to maximize the performance enhancement. Furthermore, we develop stiffness and frequency control algorithms based on the internal loading created by redundant actuation. The effectiveness of these algorithms have been demonstrated by simulations.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2007.11a
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• pp.57-58
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• 2007

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2008.06a
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• pp.39-40
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• 2008

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.355-360
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• 2002

To calibrate a non-redundantly actuated parallel mechanism, one can find actual kinematic parameters by means of geometrical constraint of the mechanism's kinematic structure and measurement values. However, the calibration algorithm for a non-redundant case does not apply fur a redundantly actuated parallel mechanism, because the angle error of the actuating joint varies with position and the geometrical constraint fails to be consistent. Such change of joint angle error comes from constraint torque variation with each kinematic pose (meaning position and orientation). To calibrate a redundant parallel mechanism, one therefore has to consider constraint torque equilibrium and the relationship of constraint torque to torsional deflection, in addition to geometric constraint. In this paper, we develop the calibration algorithm fir a redundantly actuated parallel mechanism using these three relationships, and formulate cost functions for an optimization algorithm. As a case study, we executed the calibration of a 2-DOF parallel mechanism using the developed algorithm. Coordinate values of tool plate were measured using a laser ball bar and the actual kinematic parameters were identified with a new cost function of the optimization algorithm. Experimental results showed that the accuracy of the tool plate improved by 82% after kinematic calibration in a redundant actuation case.