Dynamic analysis, design and control of an industrial parallel robot

An investigation into the applicability of the bond-graph methodology, using the so-called Model Transformation Tools software, has been undertaken to model parallel robots. This software is a novel, non-commercial, program developed at the University of Glasgow, and in addition to the standard bond graph, it contains a powerful tool called the Hierarchical Bond Graph for dealing with very large-scale dynamical systems. It is the first time this tool has been applied for the modelling of parallel manipulators. A General Method for modelling parallel robots using the Hierarchical Bond-Graph concept has been developed. The method is based on related work on the modelling of closed chain robots using the Lagrange method. Introduction of a new design concept to be known as the Multi-cell Parallel Planar Manipulator. The methodology allows for an increase in the workspace of the manipulator by increasing the number of cells without affecting the number of DOF. It can also be shown to enhance the manoeuvrability of the system. Application of the multi-cell approach to a specific 2-DOF planar parallel manipulator and recognition of the need for a general model led to the development of a general dynamic model for the multi-cell manipulator using the Lagrange method. The reason for using the Lagrange formulation is that the necessary generalisation cannot be formalised using the Bond Graph technique due to the dependency of a bond graph on the specified structure of the system being modelled. Static balancing of the new general manipulator was addressed and a new method for balancing has been introduced. The method reduces the number of parameters to be adjusted to only one

Dynamics of the Orthoglide parallel robot

Recursive matrix relations for kinematics and dynamics of the Orthoglide parallel robot having three concurrent prismatic actuators are established in this paper. These are arranged according to the Cartesian coordinate system with fixed orientation, which means that the actuating directions are normal to each other. Three identical legs connecting to the moving platform are located on three planes being perpendicular to each other too. Knowing the position and the translation motion of the platform, we develop the inverse kinematics problem and determine the position, velocity and acceleration of each element of the robot. Further, the principle of virtual work is used in the inverse dynamic problem. Some matrix equations offer iterative expressions and graphs for the input forces and the powers of the three actuators

A New 3-DoF Planar Parallel Manipulator with Unlimited Rotation Capability

International audienceMost of three-degree-of-freedom (3-DoF) planar parallel manipulators encountered today have a common disadvantage that is their low rotational capability. However, for many industrial applications, by example in automated assembly systems, cutting machines, simulators, or micro-motion manipulators, a high rotation capability is needed. To overcome such a difficulty, this paper focuses its attention on the proposal of a new 3-DoF planar parallel manipulator capable of high rotational capability. Firstly, structure and mobility of the suggested manipulator are discussed. Then the forward and inverse kinematic problems are analyzed, as well as it is disclosed its singular configurations. The shaking force and shaking moment balancing are also considered. The proposed design concept is illustrated by a driven demonstrator which is a first model of the suggested manipulator

Parallel Manipulators

In recent years, parallel kinematics mechanisms have attracted a lot of attention from the academic and industrial communities due to potential applications not only as robot manipulators but also as machine tools. Generally, the criteria used to compare the performance of traditional serial robots and parallel robots are the workspace, the ratio between the payload and the robot mass, accuracy, and dynamic behaviour. In addition to the reduced coupling effect between joints, parallel robots bring the benefits of much higher payload-robot mass ratios, superior accuracy and greater stiffness; qualities which lead to better dynamic performance. The main drawback with parallel robots is the relatively small workspace. A great deal of research on parallel robots has been carried out worldwide, and a large number of parallel mechanism systems have been built for various applications, such as remote handling, machine tools, medical robots, simulators, micro-robots, and humanoid robots. This book opens a window to exceptional research and development work on parallel mechanisms contributed by authors from around the world. Through this window the reader can get a good view of current parallel robot research and applications

Design of a Modified Stewart Platform Manipulator for Misalignment Correction

This thesis work is about the design of a modified Stewart platform manipulator for misalignment correction. The common version of the Stewart platform uses six actuators. The traditional Stewart platform of this kind has a moving top plate and a fixed base plate. However, in this research, the modified design of the traditional Stewart platform is studied. It is designed to be an easy connect-disconnect platform that can wrap around different structures with different cross sections and symmetrically designed. It is able to adjust position easily by using four identical but independent linear actuators populated evenly in two parts fastened to the top and bottom base by ball joints with each part been symmetrical to the other. To design two symmetrical parts and an adjustable clamp are a major objective of the thesis. One symmetrical part flipped upside down produces the other. The adjustable clamp was printed in 3D and can be used to align regular structural shapes especially circle of various diameter. To correct the misalignment, a failure study was carried out to determine the two equal but opposite loads required to correct misalignment in two plastic beams. Five loads were applied which showed that the smaller the load, the better the misalignment. This study showed that it is better to fix the base at a location where it does not move. To investigate that the modified Stewart platform can resist structure stiffness, the actuator assembly was analyzed using ANSYS software. The results showed that the deformation and maximum stress is less that the structure stiffness, which proves why the assembly can resist structural stiffness. The results support that the modified Stewart platform can be used for misalignment correction