Determination of 6D Workspaces of Gough-Type Parallel Manipulator and Comparison between Different Geometries (original) (raw)
Designing a Parallel Manipulator for a Specific Workspace
The International Journal of Robotics Research, 1997
We present an algorithm to determine all the possible ge ometries of Gough-type 6-DOF parallel manipulators whose workspace must include a desired workspace. This desired workspace is a set of geometric objects, limited here to points and segments, which describes the desired locations of the cen ter of the moving platform. It is assumed that the orientation of the platform is fixed for each given object. This algorithm takes into account the leg-length limits, the mechanical limits on the passive joints, and interference between links.
Workspace Analysis of a New Parallel Manipulator
1999
This paper studies the workspace of a six-DC)F parallel manipulator of three-PPSR (prismatic-prismaticspheric-revolute) type. It is well recognized that the most significant drawback of parallel manipulators is their limited workspace. To develop new parallel mechanisms with a larger workspace is of interest to additional applications. The mechanism of the three-PPSR manipulator and its variations are briefly analyzed first. The workspace is then determined and the effects of joint limit and limb interference constraints on the workspace shape and size are studied. The constituent regions of the workspace corresponding to different classes of manipulator poses are discussed. It is shown that the workspace of this parallel manipulator is larger than that of a comparable Stewart platform especially in the vertical direction.
Workspace-oriented methodology for designing a parallel manipulator
Proceedings of IEEE International Conference on Robotics and Automation, 1996
We present a method for designing optimal parallel manipulators of the Gough platform type, according to design constraints like a specified workspace, best accuracy over the workspace, minimum articular forces for a given load, etc .... A reduced set of design parameters is defined and the workspace constraints are used to compute the zone of the parameters space which define all the robots whose workspace include the desired workspace. Then a numerical search is performed in this zone to determine the robot which optimize some other criterion. We show how the method has been used to design a robot whose accuracy was specified to be better than 1 l m for a nominal load of 500 kg.
Workspace geometric modelling of a new type of 6RSS parallel manipulator is described below. In the beginning, the researches undertaken in this area by other authors are highlighted and then a definition of this type of mechanisms is provided. The structural model of the 6RSS manipulator is briefly described. Inverse geometric model and translation subspace methods are used in order to determine the dimensions that define the workspace volume of the parallel manipulator. The reachable workspace is defined as a subset of the whole workspace in relation with the positions achieved by the characteristic point.
Novel 6-DOF parallel manipulator with large workspace
Robotica, 2009
SUMMARYThe workspace of a parallel manipulator is usually smaller than the size of the robot itself. It is important to derive new structures that enjoy the advantages of parallel manipulators and also have a large workspace. In this paper we present two configurations of similar structures RRRS and RRSR with rotating links. The RRRS structure has a relatively large workspace—larger than the size of the robot itself—which is not common in parallel robots. The inverse and forward kinematics of the robots are presented. The workspaces of the robots are compared to similar and well-known structures, such as Eclipse, Alizade, Delta, and Hexa robots.
Dynamic modelling of a parallel robot with six degrees of freedom
2010
Parallel robots seem to be the most suitable spots requiring high performance such as speed and accuracy. Such performances sought now are that the dynamics of parallel structures is no longer negligible. This work represents a contribution in this latter context; it deals in the whole dynamic study of a parallel robot with six degrees of freedom constituting the so-called Gough Stewart platform. In determining the direct and inverse geometric model, we use a setup based on Khalil and Kleinfinger ratings [7] for structures with closed loops. The kinematical modeling, using the calculation of the Jacobian matrix and its inverse, were deduced from the joint velocities of the six cylinders in order to follow a desired trajectory for the platform. The Newton Euler formalism is used to model the dynamics of the robot and the first to consider each kinematics chain (legs) as a serial structure, and then by considerations of balance and closed chain, we determine the dynamics of the platform.
Design considerations of new six degrees-of-freedom parallel robots
1998
This paper describes the structure of three types of parallel robots and compares their performances in the sense of size and static forces. The motivation for this investigation is to construct a robot that best fits a given medical application. The requirements are to cover a given work volume with a given orientation and to maintain the robot within the smallest cube possible. Among the structures examined, three are presented since two are modipcations of known structures and the third is a new one.
The Kinematics and the Full Minimal Dynamic Model of a 6DOF Parallel Robot Manipulator
Nonlinear Dynamics, 1999
In this paper we present a particular architecture of parallel robots which has six-degrees-of-freedom (6-DOF) with only three limbs. The particular properties of the geometric and kinematic models with respect to that of a classical parallel robot are presented. We show that inverse problems have an analytical solution. However, to solve the direct problems, an efficient numerical procedure which needs
Determination of the Presence of Singularities in 6D Workspace of a Gough Parallel Manipulator
Advances in Robot Kinematics: Analysis and Control, 1998
Determining if singularities exist in the workspace of a parallel manipulator is an important step in the design of a parallel robot. Singularities are obtained when the posture-dependent determinant of the inverse jacobian matrix of the robot is equal to 0. This determinant is a complex function of the posture. We present an algorithm enabling to determine the presence of singularities in any type of workspace defined either by a geometrical object in the Euclidean space for the position of the end-effector and three ranges for the angles defining its orientation or by an hypercube in the 6-dimensional articular space. This algorithm is relatively fast and numerically robust.