We present an optimization procedure that uses the Taguchi method to maximize the mean stiffness and workspace of a redundantly actuated parallel mechanism at the same time. The Taguchi method is used to separate the more influential and controllable variables from the less influential ones among kinematic parameters in workspace analysis and stiffness analysis. In the first stage of optimization, the number of experimental variables is reduced by the response analysis. Quasi-optimal kinematic parameter group is obtained in the second stage of optimization after the response analysis. As a validation of the suggested procedure, the kinematic parameters of a planar 2-DOF parallel manipulator are optimized, which optimization procedure is used to investigate the optimal kinematic parameter groups between the length of the link and the stiffness.
In this paper, an experimental verification of antagonistic stiffness planning is presented for a 2-DOF parallel mechanism with four actuators. With 2-DOF force redundancy, the magnitude and direction of the stiffness enhancement can be controlled by the additional actuators, where the internal torques of the mechanism exist on the two-dimensional null space. In the experiments, the passive and active stiffness are measured, respectively, during endowing the external force at the end-effector. Two stiffness assignment methods for a given pathway are suggested and are verified by the experiments.
This paper presents a novel three degrees of freedom (3-DOF) planar parallel mechanism with a 360-degree rotational capability, which can be used as a positioning device. A high rotational capability is necessary to reduce process time and to apply the mechanism to various fields such as micro-machining and printed circuit board (PCB) depaneling. The proposed mechanism has the advantage of a continuous rotational capability over existing planar parallel mechanisms with limited rotation. The position and velocity kinematics are derived, and the singularities are analyzed based on the Jacobian matrices. The workspace can be determined not to have a singularity inside, and the kinematic variables for enlarging the singularity-free workspace are determined. The application example on the PCB depaneling process is proposed for future work.
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