• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.631-637
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• 2005

This paper presents a stiffness analysis method for a low-DOF parallel manipulator, which takes into account of elastic deformations of joints and links. A low-DOF parallel manipulator is defined as a spatial parallel manipulator which has less than six degrees of freedom. Differently from the case of a 6-DOF parallel manipulator, the serial chains in a low-DOF parallel manipulator are subject to constraint forces as well as actuation forces. The reaction forces due to actuations and constraints in each limb can be determined by making use of the theory of reciprocal screws. It is shown that the stiffness model of an F-DOF parallel manipulator consists of F springs related to the reciprocal screws of actuations and 6-F springs related to the reciprocal screws of constraints, which connect the moving platform to the fixed base in parallel. The $6{times}6$ stiffness matrix is derived, which is the sum of the stiffness matrices of actuations and constraints. The six spring constants can be precisely determined by modeling the compliance of joints and links in a serial chain as follows; the link can be considered as an Euler beam and the stiffness matrix of rotational or prismatic joint can be modeled as a $6{times}6$ diagonal matrix, where one diagonal element about the rotation axis or along the sliding direction is zero. By summing the elastic deformations in joints and links, the compliance matrix of a serial chain is obtained. Finally, applying the reciprocal screws to the compliance matrix of a serial chain, the compliance values of springs can be determined. As an example of explaining the procedure, the stiffness of the Tricept parallel manipulator has been analyzed.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.573-578
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• 2004

This paper presents a methodology for the stiffness analysis of a low-DOF parallel manipulator. A low-DOF parallel manipulator is a spatial parallel manipulator which has less than six degrees of freedom. The reciprocal screws of actuations and constraints in each leg can be determined by making use of the theory of reciprocal screws, which provide information about reaction forces due to actuations and constraints. When pure force is applied to a leg, the leg stiffness is modeled as a linear spring along the line. For pure couple, it is modeled as a rotational spring about the axis. It is shown that the stiffness model of an F-DOF parallel manipulator consists of F springs related to actuations and 6-F springs related to constraints connected from the moving platform to the base in parallel. The $6{\times}6$ Cartesian stiffness matrix is obtained, which is the sum of the Cartesian stiffness matrices of actuations and constraints. Finally, a 3-UPU parallel manipulator is used as an example to demonstrate the methodology.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.10a
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• pp.1013-1016
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• 1995

This paper deals with dynamics and control of a PRP6-DOF parallel manipulator. Dynamic modeling includes the effect of inertia of all links in the mechanism to increase modeling accuracy. Kinematic analysis about forward and inverse kinematics is also explained. Using Lagrange-D' Alambert method we get equations of motions in a link space which fully represent 6DOF motions of the manipulator.

• 제어로봇시스템학회:학술대회논문집
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• 1996.10b
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• pp.217-220
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• 1996

In this paper, a fully geometrical method for the determination of the workspace of a 6-DOF parallel manipulator is presented using the concept of 4-bar linkage. The reachable and dexterous can be determined from the proposed algorithm. In order to evaluate the workspace, each leg is considered as an open chain, and two kinematic constraints are developed. The proposed method is verified by simulation.

• Journal of the Korean Society for Precision Engineering
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• v.25 no.11
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• pp.58-65
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• 2008

The study on dual arm robot manipulator which consists of two 6-DOF srms and one 2-DOF torso is introduced. This dual arm robot manipulator is designed for automation of assembly process in automotive manufacturing line. Each industrial 6-DOF arm can be used as a stand-alone type of industrial robot manipulator with 6-DOF and as a manipulator part of dual arm robot at the same lime. These structures help the robot maker willing to succeed in emerging market of dual arm robots have the high competitive power for the current industrial robot market and the emerging market of dual arm robot at the same time. The research results of the design concept, workspace analysis and the PC-based controller will be introduced.

• Journal of Mechanical Science and Technology
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• v.16 no.8
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• pp.1053-1063
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• 2002

This paper presents a robust nonlinear controller for a f degree of freedom (DOF) parallel manipulator in the task space coordinates. The proposed control strategy requires information on orientations and translations in the task space unlike the joint space or link space control scheme. Although a 6 DOF sensor may provide such information in a straightforward manner, its cost calls for a more economical alternative. A novel indirect method based on the readily available length information engages as a potential candidate to replace a 6 DOF sensor. The indirect approach generates the necessary information by solving the forward kinematics and subsequently applying alpha-beta-gamma tracker With the 6 DOF signals available, a robust nonlinear task space control (RNTC) scheme is proposed based on the Lyapunov redesign method, whose stability is rigorously proved. The performance of the proposed RNTC with the new estimation scheme is evaluated via experiments. First, the results of the estimator are compared with the rate-gyro signals, which indicates excellent agreement. Then, the RNTC with on-line estimated 6 DOF data is shown to achieve excellent control performance to sinusoidal inputs, which is superior to those of a commonly used proportional-plus-integral-plus-derivative controller with a feedforward friction compensation under joint space coordinates and the nonlinear controller under task space coordinates.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2009.06a
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• pp.543-544
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• 2009

• 제어로봇시스템학회:학술대회논문집
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• 1997.10a
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• pp.1297-1301
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• 1997

Generally, singularity analysis of 6-DOF parallerl manipulators is very difficult and, as result, velocity relation has many uncertainties. In this paper, an alternative method using the local structurizatioin method(LSM) for the analysis of singular configuraions is presented. With LSM, the velocity relation can be represented in a simple form, and the result is totally equivalent to the conventional velocity relation. The velocity relation suggested in this paper gives a closed-form solution of singularities.

• Journal of Power System Engineering
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• v.19 no.6
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• pp.5-11
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• 2015

The 6DOF (degrees of freedom) Parallel Manipulators have some advantages that are high power, high rigidity, high precision for positioning and compact mechanism compared with conventional serial link manipulators. For these Parallel Manipulators, it can be expected to work in the new fields such that the medical operation, high-precision processing technology and so on. For this expectation, it is necessary to control the action reaction pair of forces which act between the Parallel Manipulator and the operated object. In this paper, we analyze the dynamics of the 6DOF Parallel Manipulator and present numerical simulation results.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.05a
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• pp.574-577
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• 2000

The purpose of robot manipulator control is to make for manipulator take a trace of pre-planned trajectory. In this study, the algorithm of MRAC(Model Reference Adaptive Control) on reference to adaptive control theory was studied. The experiments were performed on 6-DOF robot manipulator with respect to p-d(proportional-differential) controller and adaptive controller. The property of adaptive control was studied and its efficiency proved by being compared to p-d controller.