Abstract
Rigid-body displacements obtained by combining spatial translations and rotations around axes whose direction is fixed in the space are named Shoenflies’ motions. They constitute a 4-dimensional (4-D) subgroup, named Shoenflies’ subgroup, of the 6-D displacement group. Since the set of rotation-axis’ directions is a bi-dimensional space, the set of Shoenflies’ subgroups is a bi-dimensional space, too. Many industrial manipulations (e.g., pick-and-place on a conveyor belt) require displacements that belong to only one Schoenflies’ subgroup and can be accomplished by particular 4-degrees-of-freedom (4-DOF) manipulators (Shoenflies-motion generators (SMGs)). The first author has recently proposed a novel parallel SMG of type CRS-RRC1. Such SMG features a single-loop architecture with actuators on the base and a simple decoupled kinematics. Here, firstly, an organic review of the previous results on this SMG is presented; then, its design is addressed by considering its kinetostatic performances. The adopted design procedure optimizes two objective functions, one (global conditioning index (GCI)) that measures the global performance and the other (CImin) that evaluates the worst local performance in the useful workspace. The results of this optimization procedure are the geometric parameters’ values that make the studied SMG have performances comparable with those of commercial SMGs. In addition, a realistic 3D model that solves all the manufacturing doubts with simple and cheap solutions is presented.
Highlights
Shoenflies’ motions are rigid-body displacements obtained by combining spatial translations and rotations around axes with a fixed direction
The first author has recently proposed a novel parallel Shoenflies-motion generators (SMGs) of type CRS-RRC 1. Such SMG features a single-loop architecture with actuators on the base and a simple decoupled kinematics
An organic review of the previous results on this SMG is presented; its design is addressed by considering its kinetostatic performances
Summary
Shoenflies’ motions are rigid-body displacements obtained by combining spatial translations and rotations around axes with a fixed direction. The main drawback of parallel SMGs is their complex multi-loop structure that drastically reduces their workspace, usually brings cumbersome kinematics and control algorithms, and, often, does not allow a full rotation of the end effector (platform). Such SMG features a single-loop architecture with actuators on the base and a simple decoupled kinematics. An organic review of the previous results on this SMG is presented; its design is addressed by considering its kinetostatic performances. This design procedure will yield a realistic 3D model that solves all the manufacturing doubts with simple and cheap solutions.
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