Rider - Design and analysis of mechanisms a planar approach

1. Chapter 09

1. bappA
2. bappB
3. Chapter 01
4. Chapter 02
5. Chapter 03
6. Chapter 04
7. Chapter 05
8. Chapter 06
9. Chapter 07
10. Chapter 08
11. Chapter 09
12. Chapter 10

Michael J. Rider, Ph.D.

Professor of Mechanical Engineering, Ohio Northern University, USA

This edition first published 2015
2015 John Wiley & Sons, Ltd.

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Library of Congress Cataloging-in-Publication Data

Rider, Michael J.
Design and analysis of mechanisms : a planar approach / Michael J. Rider, Ph.D.
pagescm
Includes bibliographical references and index.

ISBN 978-1-119-05433-7 (pbk.)
1.Gearing.2.Mechanical movements.I.Title.
TJ181.R53 2015
621.815dc23
2015004426

A catalogue record for this book is available from the British Library.

The intent of this book is to provide a teaching tool that features a straightforward presentation of basic principles while having the rigor to serve as basis for more advanced work. This text is meant to be used in a single-semester course, which introduces the basics of planar mechanisms. Advanced topics are not covered in this text because the semester time frame does not allow these advanced topics to be covered. Although the book is intended as a textbook, it has been written so that it can also serve as a reference book for planar mechanism kinematics. This is a topic of fundamental importance to mechanical engineers.

deals with fundamental cam design while looking at different types of followers and different types of follower motion and determining the cams profile.

There are numerous problems at the end of each chapter to test the students understanding of the subject matter.

discusses the basics of MATLAB and how it can be used to solve planar mechanism problems.

Engineering involves the design and analysis of machines that deal with the conversion of energy from one source to another using the basic principles of science. Solid mechanics is one of these branches. It contains three major sub-branches: kinematics, statics, and kinetics. Kinematics deals with the study of relative motion. Statics is the study of forces and moments apart from motion. Kinetics deals with the result of forces and moments on bodies. The combination of kinematics and kinetics is referred to as dynamics. However, dynamics deals with the study of motion caused by forces and torques. For mechanism design, the desired motion is known and the task is to determine the type of mechanism along with the required forces and torques to produce the desired motion. This text covers some of the mathematics, kinematics, and kinetics required to perform planar mechanism design and analysis.

A mechanism is a mechanical device that transfers motion and/or force from a source to an output. A linkage consists of links generally considered rigid which are connected by joints such as pins or sliders. A kinematic chain with at least one fixed link becomes a mechanism if at least two other links can move. Since linkages make up simple mechanisms and can be designed to perform complex tasks, they are discussed throughout this book.

A large majority of mechanisms exhibit motion such that all the links moved in parallel planes. This text emphasizes this type of motion, which is called two-dimensional planar motion. Planar rigid body motion consists of rotation about an axis perpendicular to the plane of motion and translation in the plane of motion. For this text, all links are assumed rigid bodies.

Mechanisms are used in a variety of machines and devices. The simplest closed form linkage is a 4-bar, which has three moving links plus one fixed link and four pinned joints. The link that does not move is called the ground link. The link that is connected to the power source is called the input link. The follower link contains a moving pivot point relative to ground and it is typically considered as the output link. The coupler link consists of two moving pivots, points C and D, thereby coupling the input link to the output link. A point on the coupler link generally traces out a sixth-order algebraic coupler curve. Very different coupler curves can be generated by using a different tracer point on the coupler link. Hrones and Nelsons Analysis of 4-Bar Linkages [1] published in 1951 shows many different types of coupler curves and their appropriate 4-bar linkage.

The 4-bar linkage is the most common chain of pin-connected links that allows relative motion between the links (see ). These linkages can be classified into three categories depending on the task that the linkage performs: function generation, path generation, and motion generation. A function generator is a linkage in which the relative motion or forces between the links connected to ground is of interest. In function generation, the task does not require a tracer point on the coupler link. In path generation, only the path of the tracer point on the coupler link is important and not the rotation of the coupler link. In motion generation, the entire motion of the coupler link is important, that is, the path that the tracer point follows and the angular orientation of the coupler link.