Self-Motions of General 3-RPR Planar Parallel Robots

This paper studies the kinematic geometry of general 3-RPR planar parallel robots with actuated base joints. These robots, while largely overlooked, have simple direct kinematics and large singularity-free workspace. Furthermore, their kinematic geometry is the same as that of a newly developed parallel robot with SCARA-type motions. Starting from the direct and inverse kinematic model, the expressions for the singularity loci of 3-RPR planar parallel robots are determined. Then, the global behaviour at all singularities is geometrically described by studying the degeneracy of the direct kinematic model. Special cases of self-motions are then examined and the degree of freedom gained in such special configurations is kinematically interpreted. Finally, a practical example is discussed and experimental validations performed on an actual robot prototype are presented

Online pose correction of an industrial robot using an optical coordinate measure machine system

In this article, a dynamic pose correction scheme is proposed to enhance the pose accuracy of industrial robots. The dynamic pose correction scheme uses the dynamic pose measurements as feedback to accurately guide the robot end-effector to the desired pose. The pose is measured online with an optical coordinate measure machine, that is, C-Track 780 from Creaform. A root mean square method is proposed to filter the noise from the pose measurements. The dynamic pose correction scheme adopts proportional-integral-derivaitve controller and generates commands to the FANUC robot controller. The developed dynamic pose correction scheme has been tested on two industrial robots, FANUC LR Mate 200iC and FANUC M20iA. The experimental results on both robots demonstrate that the robots can reach the desired pose with an accuracy of ±0.050 mm for position and ±0.050° for orientation. As a result, the developed pose correction can make the industrial robots meet higher accuracy requirement in the applications such as riveting, drilling, and spot welding

A 3-R ᠪ PR Parallel Mechanism With Singularities That are Self-Motions

The Cartesian workspace of most three-degree-of-freedom parallel mechanisms is divided b

A novel three-legged 6-DOF parallel robot with simple kinematics

This paper presents a novel three-legged six degrees of freedom (6-DOF) parallel robot with simple kinematics. The main idea behind this novel architecture is that each of the three identical legs is controlled by two prismatic actuators with parallel directions. As a result, it is possible to control simultaneously or separately the position and the orientation of a leg. The reduced number of legs leads to a simple mechanical design with reduced risk for mechanical interferences.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Orientation Capability, Error Analysis, and Dimensional Optimization of Two Aticulated Tool Heads with Parallel Kinematics

Because of the increasing demand in industry fo

Abstract Accuracy analysis of 3-DOF planar parallel robots

Three-degree-of-freedom planar parallel robots are increasingly being used in applications where precision is of the utmost importance. Clearly, methods for evaluating the accuracy of these robots are therefore needed. The accuracy of well designed, manufactured, and calibrated parallel robots depends mostly on the input errors (sensor and control errors). Dexterity and other similar performance indices have often been used to evaluate indirectly the influence of input errors. However, industry needs a precise knowledge of the maximum orientation and position output errors at a given nominal configuration. An interval analysis method that can be adapted for this purpose has been proposed in the literature, but gives no kinematic insight into the problem of optimal design. In this paper, a simpler method is proposed based on a detailed error analysis of 3-DOF planar parallel robots that brings valuable understanding of the problem of error amplification

Singularity Loci of Planar Parallel Manipulators with Revolute Joints

This paper addresses the problem of determining the singularity loci of 3-DOF planar parallel manipulators with revolute joints for a constant orientation of the mobile platform