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Types of Robols and Their Integration into Computer-Integrated Manufacturing Systems
Published in Ulrich Rembold, Robot Technology and Applications, 2020
Homogeneous vectors and matrices were generalized to obtain a standardized representation method for kinematic problems. Kinematic structures (serial links and joints) are analyzed by defining the position and orientation of one link with respect to another. A widely used method consists of assigning coordinate frames that are fixed to their respective links. The position of the consecutive links is then defined by a homogeneous transformation matrix—for example, transforming a frame attached to link n - 1 to the frame attached to link n (Fig. 1.3). A manipulator with n links and n joints can be described by n homogeneous matrices. They are generalized as unit vector base frames, which are used to define the geometric relationship between any kind of reference coordinate system and robot coordination base. The Jacobian matrix is used to describe the transformation of a global kinematic chain in terms of changes of the individual joint angles. It can be applied to the calculation of joint movements to achieve small, but directionally defined changes of the tool or end-effector. The Jacobian is also useful for the calculation of joint movement to achieve a specific tool velocity or a path. By using the virtual work principle, it can relate forces, applied by or to the end-effector, to the resultant forces and torques generated at each joint.
Systematic Mechanism Design
Published in Preben W. Jensen, Classical and Modern Mechanisms for Engineers and Inventors, 2018
A kinematic chain is composed of links and turning joints. The question now is how can all possible solutions be developed from a given assortment of links and joints. To this purpose, each ternary, quarternary, etc., link is represented by a circle surrounding a “3,” “4,” etc., respectively (Fig. 17.1). As an example, class IV d(l), (Table 17.1) is chosen with g = 13, n = 10, n1, = 0, n2 = 6, n3 = 2, n4 = 2, and f = 1. Consider the two ternary and two quarternary links. They are represented by a circle around a “3” and a “4,” respectively. The problem now is to connect the four circles in such a way that three connections radiate from each ternary link and four connections radiate from each quarternary link. The four circles are divided into two groups, one group with n3 = 1 and n4 2, and the other group with n3 = 1.
Robot Kinematics
Published in Osita D. I. Nwokah, Yildirim Hurmuzlu, The Mechanical Systems Design Handbook, 2017
A robot manipulator consists of a kinematic chain of n + 1 links connected by means of n joints. Joints can essentially be of two types: revolute and prismatic; complex joints can be decomposed into these simple joints. Revolute joints are usually preferred because of their compactness and reliability. One end of the chain is connected to the base link to which a suitable base frame is attached, whereas an end-effector is connected to the other end and a suitable end-effector frame is attached. The basic structure of a robot is the open kinematic chain that occurs when only one sequence of links connects the two ends of the chain. Alternatively, a robot contains a closed kinematic chain when a sequence of links forms a loop. In Figure 19.2, an open-chain robot manipulator is illustrated with conventional representation of revolute and prismatic joints.
Design and control of a 7 DOF redundant manipulator arm
Published in Australian Journal of Mechanical Engineering, 2021
Priyadarshi Biplab Kumar, Navneet Kumar Verma, Dayal R. Parhi, Deepayan Priyadarshi
The primary motive behind any scientific development lies in the query to ease human efforts and reduce operational time in turn cost. Robotics has been one of the most emerging areas of research over the last few decades owing to the ability of robotic agents to be used as human assistive devices. Manipulators are the type of robotic agents that are used in almost every sector of industrial revolution. A robotic manipulator is a mechanical arm consisting of a series (chains) of rigid links connected by joints. Each link can be connected by either revolute joint or prismatic joint depending upon the operations required. Both the joints provide one degree of freedom to the manipulator arm. For ‘n’ number of links in the manipulator arm, it has one link (first) fixed which is the base of the manipulator arm and ‘n-1’ moving links. Last link of the manipulator arm is named as the end effector whose function is to perform operations like pick and place, welding, surgery, grasping, drilling, etc. Generally, the links of the manipulator arm are connected in such a way that they form an open chain, i.e. end effecter (last link) is not connected to the base (first link). In a closed kinematic chain, first link is connected to the last link, and all the relative motions in the closed chain are constrained. To perform different physical operations on a manipulator arm, it is important to conduct the kinematic analysis on it so that the workspace and singularities can be known beforehand (Wood et al. 2019). Several researchers have analysed robotic manipulators both in terms of kinematic analysis and control methodology. Some of them can be highlighted here.
Gradient method for identification of isomorphism of planar kinematic chains
Published in Australian Journal of Mechanical Engineering, 2020
Arvind Shukla, Shubhashis Sanyal
A kinematic chain can be thought upon as a graph, vertices and edges of which are assigned to links and joints respectively. In graph theory, distance between two vertices is defined as the least number of edges that separate them. This definition when adapted to a chain means the least number of joints that separate them.