SUMMARYOptimization is an important step in the design and development of a planar parallel manipulator. For optimization processes, workspace analysis is a crucial and preliminary objective. Generally, the workspace analysis for such manipulators is carried out using a non-dimensional approach. For planar parallel manipulators of two degrees of freedom (2-DOF), a non-dimensional workspace analysis is very advantageous. However, it becomes very difficult in the case of 3-DOF and higher DOF manipulators because of the complex shape of the workspace. In this study, the workspace shape is classified as a function of the geometric parameters, and the closed-form area expressions are derived for a constant orientation workspace of a three revolute–revolute–revolute (3-RRR) planar manipulator. The approach is also shown to be feasible for different orientations of a mobile platform. An optimization procedure for the design of planar 3-RRR manipulators is proposed for a prescribed workspace area. It is observed that the closed-form area expression for all the possible shapes of the workspace provides a larger solution space, which is further optimized considering singularity, mass of the manipulator, and a force transmission index.
SUMMARY
Conventional planar manipulators have their links in a single plane. Increasing payload at the end effector/mobile platform can induce high stress in the links due to the cantilever nature of links. Thus, it limits the total vertical load that can be applied on the mobile platform. In contrast to the links in conventional planar parallel mechanisms, non-planar links are proposed in this paper, that is, links are made inclined to the horizontal plane and non-planar legs are constructed. Though the links are made non-planar, the end effectors’ planar motion is retained. For studying the application of such non-planar links in planar manipulators, new models of inertia, stiffness and leg dynamics have to be developed. In this article, these models are developed by the static analysis of the planar manipulators with non-planar links, and the performance is compared with the corresponding conventional planar manipulators.
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