• Proceedings of the KSME Conference
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• 2003.11a
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• pp.1500-1505
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• 2003

In order to avoid the unit inconsistency problem in the conventional Jacobian matrix, previously we presented new formulation of a dimensionally homogeneous inverse Jacobian matrix for parallel manipulators with a planar mobile platform by using three end-effector points based on the velocity relationship [1]. This paper presents force relationships between joint forces and Cartesian forces at the three End-Effector points. The derived force relationships can then be used for analyses of the input/output force transmission. These analyses, forward and inverse force transmission analyses, depend on the singular values of the derived dimensionally homogeneous Jacobian matrix. Using the proposed force relationship, a numerical example is presented for actuator size design of a 3-RRR planar parallel manipulator.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.3
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• pp.89-96
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• 2003

An electro-hydraulic manipulator using hydraulic actuators has many nonlinear abetments, and its parameter fluctuations are greater than those of an electrically driven manipulator. So it is relatively difficult to realize not only stable but also accurate trajectory control for the autonomous assembly tasks using hydraulic manipulators. In this report, we propose a two-degree-of-freedom control including parallel feedforward compensator (PFC) where PFC plays a very important role in the stability of a proposed control system. In the experimental results of the 6-link electro hydraulic manipulator, it is verified that the stability and the model matching performance are improved by using the proposed control method.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2012.05a
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• pp.53-54
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• 2012

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2007.06a
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• pp.385-386
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• 2007

• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.621-625
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• 2005

This paper presents a new hybrid serial-parallel robot(HSPR), which has six degrees of freedom driven by ball screw linear actuators and motored joints. This hybrid robot design presents a compromise between high rigidity of fully parallel manipulators and extended workspace of serial manipulators. The hybrid robot has a large, singularity-free workspace and high stiffness. Therefore, the presented kinematic structure of the hybrid robot is particularly suitable for multi-tasking machining processes such as milling, drilling, deburring and grinding. In addition to the machining processes, the hybrid robot can be used for welding, fixturing, material handling and so on. The study on design of the hybrid robot is performed. A kinematic analysis and mechanism description of the hybrid robot with six-controlled degree of freedom is presented. In the virtual design works by DADS, workspace and force analysis are discussed. A numerical model is treated to demonstrate our analysis and to determine the range of permissible extension of the struts. Also, we determine some important design parameters for the hybrid robot.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.1494-1499
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• 2003

Kinematic calibration is a process whereby the actual values of geometric parameters are estimated so as to minimize the error in absolute positioning. Measuring all components of Cartesian posture, particularly the orientation, can be difficult. With partial pose measurements, all parameters may not be identifiable. This paper proposes a new device that can be used to identify all kinematic parameters with partial pose measurements. Study is performed for a six degree-of-freedom fully parallel Hexa Slide manipulator. The device, however, is general and can be used for other parallel manipulators. The proposed device consists of a link with U joints on both sides and is equipped with a rotary sensor and a biaxial inclinometer. When attached between the base and the mobile platform, the device restricts the end-effector's motion to five degree-of-freedom and can measure position of the end-effector and one of its rotations. Numerical analyses of the identification Jacobian reveal that all parameters are identifiable. Computer simulations show that the identification is robust for the errors in the initial guess and the measurement noise.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.1476-1481
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• 2003

Kinematic calibration enhances absolute accuracy by compensating for the fabrication tolerances and installation errors. Effectiveness of calibration procedures depends greatly on the measurements performed. This paper investigates identifiable parameters and optimum postures for four different calibration procedures - measuring postures completely with inverse kinematic residuals, measuring postures completely with forward kinematics residuals, measuring only the three position components, and restraining the mobility of the end-effector using a constraint link. The study is performed for a six degree-of-freedom fully parallel HexaSlide type parallel manipulator, HSM. Results verify that all parameters are identifiable with complete posture measurements. For the case of position measurements, one and for the case of constraint link, three parameters were found non-identifiable. Selecting postures for measurement is also an important issue for efficient calibration procedure. Typically, the condition number of the identification Jacobian is minimized to find optimum postures. Optimal postures showed the same trend of orienting themselves on the boundaries of the search space.

• Journal of Institute of Control, Robotics and Systems
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• v.6 no.7
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• pp.559-567
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• 2000

This paper proposes simple and practical methods in order to overcome complex formulation and heavy computational burden of the forward kinematics of 6 앨 3-6 type parallel manipulators. Three ap-proaches for the forward kinematics are presented : one extra sensor a modified structure and novel numerical method. The proposed methods are applied to the forward kinematics of a new 6 앨 parallel manipulator with special geometry that has three internal links three external links and a moving platform of a cone shape. The proposed methods use three tetrahedrons for finding the position and orientation vector of the moving platform. The main advantages of the appraches using tetrahedrons are to abbreviate the formulation to easily find so-lutions of the forward kinematics and to be able to practically control of the manipulator in real time.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1994.10a
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• pp.901-906
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• 1994

In designing and evaluating manipulators, itis important to understand the capability of kinematic and static performances. Both workspace and manipulability can be considered as such performance measures. In general, the measure of manipulability is related to the kinematics for serial type manipulators. However.in case of parallel manipulators such as Stewart Platform, the manipulability can be interpreted as the static capability of transforming the input forces of actuators to the wrench of the end-effector. In this paper, the mathematical and physical meanings of manipulability suggested in some research works have been examined, and more meaningful measure of manipulability using the absolute minimum eigenvalues of J $^{T}$ .del. J has been suggested, which has been applied to a Stewart Platform in order to investigate the manipulability of this mechanism..

• 제어로봇시스템학회:학술대회논문집
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• 1997.10a
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• pp.764-767
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• 1997

This paper presents the modulation of the dexterity of a parallel manipulator using joint freezing/releasing and joint unactuation/actuation. In this paper, individual limbs have redundant number of joints, and each joint can be frozen/released and unactuated/actuated, as needed. First, given a task, the restrictions on joint freezing and joint unactuation of a parallel manipulator are derived. Next, with/without joint freezing and/or joint unactuation, the kinematics of a parallel manipulator is formulated, based on which the manipulability ellipsoid is defined. The effects of joint freezing and joint unactuation on the manipulability are analyzed and compared. Finally, simulation results for a planar parallel manipulator are given. Joint mechanisms, such as joint freezing and joint unactuation, are rather simple to adopt into a parallel manipulator, but is quite effective to improve the task adaptability of the system.