Abstract
A novel parallel robot, dubbed the SDelta, is the subject of this paper. SDelta is a simpler alternative to both the well-known Stewart–Gough platform (SGP) and current three-limb, full-mobility parallel robots, as it contains fewer components and all its motors are located on the base. This reduces the inertial load on the system, making it a good candidate for high-speed operations. SDelta features a symmetric structure; its forward-displacement analysis leads to a system of three quadratic equations in three unknowns, which admits up to eight solutions, or half the number of those admitted by the SGP. The kinematic analysis, undertaken with a geometrical method based on screw theory, leads to two Jacobian matrices, whose singularity conditions are investigated. Instead of using the determinant of a 6 × 6 matrix, we derive one simple expression that characterizes the singularity condition. This approach is also applicable to a large number of parallel robots whose six actuation wrench axes intersect pairwise, such as all three-limb parallel robots whose limbs include, each, a passive spherical joint. The workspace is analyzed via a geometric method, while the dexterity analysis is conducted via discretization. Both show that the given robot has the potential to offer both large workspace and good dexterity with a proper choice of design variables.
Highlights
1 Introduction A parallel robot, a.k.a. a parallel-kinematics machine (PKM), is defined as a multi-degree-of-freedom articulated mechanical system composed of one moving platform (MP) and one base platform (BP), connected by at least two serial limbs [1]
Works on six-dof PKMs are found mostly around the Stewart-Gough platform (SGP) [4, 5], whose MP and BP are connected via six limbs
8 Discussion From the above figures for which two sets of arbitrarily chosen design parameters are used, it is apparent that the singularity locus, workspace and dexterity are greatly affected by the ratio a/b and the range of the limb length
Summary
A parallel robot, a.k.a. a parallel-kinematics machine (PKM), is defined as a multi-degree-of-freedom (multi-dof) articulated mechanical system composed of one moving platform (MP) and one base platform (BP), connected by at least two serial limbs [1]. Many six-dof parallel robots, including most of the three-limb PKMs with limbs including, each, a spherical joint (see, for example, [29, 31]), are designed with the foregoing feature Based on this interpretation, we use a simpler formulation to derive one single, simple expression for the singularity condition. We use a simpler formulation to derive one single, simple expression for the singularity condition This condition is applicable to a large class of parallel robots whose six wrench axes intersect pairwise, i.e., most three-limb six-dof PKMs—those with one passive spherical joint somewhere in each limb—and the SGPs whose six limbs have three attachment points on the MP.
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