A machine (or mechanical device) is a mechanical structure that uses power to apply forces and control movement to perform an intended action. Machines can be driven by animals and people, by natural forces such as wind and water, and by chemical, thermal, or electrical power, and include a system of mechanisms that shape the actuator input to achieve a specific application of output forces and movement. They can also include computers and sensors that monitor performance and plan movement, often called mechanical systems.
Renaissance natural philosophers identified six which were the elementary devices that put a load into motion, and calculated the ratio of output force to input force, known today as mechanical advantage.
Modern machines are complex systems that consist of structural elements, mechanisms and control components and include interfaces for convenient use. Examples include a wide range of , such as Car, and , Home appliance in the home and office, building air handler and Plumbing, as well as farm machinery, and Automation systems and .
In the 17th century, the word could also mean a scheme or plot, a meaning now expressed by the derived machination. The modern meaning develops out of specialized application of the term to stagecraft used in theater and to military , both in the late 16th and early 17th centuries. The OED traces the formal, modern meaning to John Harris' Lexicon Technicum (1704), which has:
The idea of a simple machine originated with the Greek philosopher Archimedes around the 3rd century BC, who studied the Archimedean simple machines: lever, pulley, and screw. Archimedes discovered the principle of mechanical advantage in the lever.
During the Renaissance the dynamics of the Mechanical Powers, as the simple machines were called, began to be studied from the standpoint of how much useful work they could perform, leading eventually to the new concept of mechanical work. In 1586 Flemish engineer Simon Stevin derived the mechanical advantage of the inclined plane, and it was included with the other simple machines. The complete dynamic theory of simple machines was worked out by Italian scientist Galileo Galilei in 1600 in Le Meccaniche ("On Mechanics").
The classic rules of sliding friction in machines were discovered by Leonardo da Vinci (1452–1519), but remained unpublished in his notebooks. They were rediscovered by Guillaume Amontons (1699) and were further developed by Charles-Augustin de Coulomb (1785).
James Watt patented his parallel motion linkage in 1782, which made the double acting steam engine practical.Pennock, G. R., James Watt (1736-1819), Distinguished Figures in Mechanism and Machine Science, ed. M. Ceccarelli, Springer, 2007, (Print) 978-1-4020-6366-4 (Online). The Boulton and Watt steam engine and later designs powered , steam ships, and steam power.
The Industrial Revolution was a period from 1750 to 1850 where changes in agriculture, manufacturing, mining, transportation, and technology had a profound effect on the social, economic and cultural conditions of the times. It began in the United Kingdom, then subsequently spread throughout Western Europe, North America, Japan, and eventually the rest of the world.
Starting in the later part of the 18th century, there began a transition in parts of Great Britain's previously manual labour and draft-animal–based economy towards machine-based manufacturing. It started with the mechanisation of the textile industries, the development of iron-making techniques and the increased use of refined coal.
The idea that a machine can be decomposed into simple movable elements led Archimedes to define the lever, pulley and screw as simple machines. By the time of the Renaissance this list increased to include the wheel and axle, wedge and inclined plane. The modern approach to characterizing machines focusses on the components that allow movement, known as joints.
Wedge (hand axe): Perhaps the first example of a device designed to manage power is the hand axe, also see biface and Olorgesailie. A hand axe is made by chipping stone, generally flint, to form a bifacial edge, or wedge. A wedge is a simple machine that transforms lateral force and movement of the tool into a transverse splitting force and movement of the workpiece. The available power is limited by the effort of the person using the tool, but because power is the product of force and movement, the wedge amplifies the force by reducing the movement. This amplification, or mechanical advantage is the ratio of the input speed to output speed. For a wedge this is given by 1/tanα, where α is the tip angle. The faces of a wedge are modeled as straight lines to form a sliding or prismatic joint.
Lever: The lever is another important and simple device for managing power. This is a body that pivots on a fulcrum. Because the velocity of a point farther from the pivot is greater than the velocity of a point near the pivot, forces applied far from the pivot are amplified near the pivot by the associated decrease in speed. If a is the distance from the pivot to the point where the input force is applied and b is the distance to the point where the output force is applied, then a/b is the mechanical advantage of the lever. The fulcrum of a lever is modeled as a hinged or revolute joint.
Wheel: The wheel is clearly an important early machine, such as the chariot. A wheel uses the law of the lever to reduce the force needed to overcome friction when pulling a load. To see this notice that the friction associated with pulling a load on the ground is approximately the same as the friction in a simple bearing that supports the load on the axle of a wheel. However, the wheel forms a lever that magnifies the pulling force so that it overcomes the frictional resistance in the bearing.
to provide a strategy for the design of new machines was developed by Franz Reuleaux, who collected and studied over 800 elementary machines. Moon, F. C., The Reuleaux Collection of Kinematic Mechanisms at Cornell University, 1999 He recognized that the classical can be separated into the lever, pulley and wheel and axle that are formed by a body rotating about a hinge, and the inclined plane, wedge and screw that are similarly a block sliding on a flat surface.Hartenberg, R.S. & J. Denavit (1964) Kinematic synthesis of linkages , New York: McGraw-Hill, online link from Cornell University.
Simple machines are elementary examples of or linkages that are used to model mechanical systems ranging from the steam engine to robot manipulators. The bearings that form the fulcrum of a lever and that allow the wheel and axle and pulleys to rotate are examples of a kinematic pair called a hinged joint. Similarly, the flat surface of an inclined plane and wedge are examples of the kinematic pair called a sliding joint. The screw is usually identified as its own kinematic pair called a helical joint.
This realization shows that it is the joints, or the connections that provide movement, that are the primary elements of a machine. Starting with four types of joints, the rotary joint, sliding joint, cam joint and gear joint, and related connections such as cables and belts, it is possible to understand a machine as an assembly of solid parts that connect these joints called a mechanism .
Two levers, or cranks, are combined into a planar four-bar linkage by attaching a link that connects the output of one crank to the input of another. Additional links can be attached to form a six-bar linkage or in series to form a robot.
This can be seen in Watt's steam engine (see the illustration) in which the power is provided by steam expanding to drive the piston. The walking beam, coupler and crank transform the linear movement of the piston into rotation of the output pulley. Finally, the pulley rotation drives the flyball governor which controls the valve for the steam input to the piston cylinder.
The adjective "mechanical" refers to skill in the practical application of an art or science, as well as relating to or caused by movement, physical forces, properties or agents such as is dealt with by mechanics.Oxford English Dictionary Similarly Merriam-Webster DictionaryMerriam-Webster Dictionary Definition of mechanical defines "mechanical" as relating to machinery or tools.
Power flow through a machine provides a way to understand the performance of devices ranging from levers and gear trains to automobiles and robotic systems. The German mechanician Franz ReuleauxReuleaux, F., 1876 The Kinematics of Machinery (trans. and annotated by A. B. W. Kennedy), reprinted by Dover, New York (1963) wrote, "a machine is a combination of resistant bodies so arranged that by their means the mechanical forces of nature can be compelled to do work accompanied by certain determinate motion." Notice that forces and motion combine to define power.
More recently, Uicker et al.J. J. Uicker, G. R. Pennock, and J. E. Shigley, 2003, Theory of Machines and Mechanisms, Oxford University Press, New York. stated that a machine is "a device for applying power or changing its direction." McCarthy and SohJ. M. McCarthy and G. S. Soh, 2010, Geometric Design of Linkages, Springer, New York. describe a machine as a system that "generally consists of a power source and a mechanism for the controlled use of this power."
Waterwheel: appeared around the world around 300 BC to use flowing water to generate rotary motion, which was applied to watermill. Modern use water flowing through a dam to drive an electric generator.
Windmill: Early wind mill captured wind power to generate rotary motion for milling operations. Modern also drives a generator. This electricity in turn is used to drive Electric motor forming the actuators of mechanical systems.
Engine: The word engine derives from "ingenuity" and originally referred to contrivances that may or may not be physical devices. See Merriam-Webster's definition of engine. A steam engine uses heat to boil water contained in a pressure vessel; the expanding steam drives a piston or a turbine. This principle can be seen in the aeolipile of Hero of Alexandria. This is called an external combustion engine.
An automobile engine is called an internal combustion engine because it burns fuel (an exothermic chemical reaction) inside a cylinder and uses the expanding gases to drive a piston. A jet engine uses a turbine to compress air which is burned with fuel so that it expands through a nozzle to provide thrust to an aircraft, and so is also an "internal combustion engine." "Internal combustion engine", Concise Encyclopedia of Science and Technology, Third Edition, Sybil P. Parker, ed. McGraw-Hill, Inc., 1994, p. 998 .
Power plant: The heat from coal and natural gas combustion in a boiler generates steam that drives a steam turbine to rotate an electric generator. A nuclear power plant uses heat from a nuclear reactor to generate steam and electric power. This power is distributed through a electrical grid for industrial and individual use.
Fluid Power: Hydraulic and pneumatic systems use electrically driven to drive water or air respectively into cylinders to power linear actuator.
The structural components are, generally, the frame members, bearings, splines, springs, seals, and covers. The shape, texture and color of covers provide a styling and operational interface between the mechanical system and its users.
The assemblies that control movement are also called "mechanisms." Reuleaux, F., 1876 The Kinematics of Machinery, (trans. and annotated by A. B. W. Kennedy), reprinted by Dover, New York (1963)J. J. Uicker, G. R. Pennock, and J. E. Shigley, 2003, Theory of Machines and Mechanisms, Oxford University Press, New York. Mechanisms are generally classified as and , which includes and , cam and cam follower mechanisms, and linkages, though there are other special mechanisms such as clamping linkages, Geneva drive, and friction devices such as and .
The number of degrees of freedom of a mechanism, or its mobility, depends on the number of links and joints and the types of joints used to construct the mechanism. The general mobility of a mechanism is the difference between the unconstrained freedom of the links and the number of constraints imposed by the joints. It is described by the Chebychev-Grübler-Kutzbach criterion.
Researchers have used DNA to construct nano-dimensioned . Marras, A., Zhou, L., Su, H., and Castro, C.E. Programmable motion of DNA origami mechanisms, Proceedings of the National Academy of Sciences, 2015 McCarthy, C, DNA Origami Mechanisms and Machines | Mechanical Design 101, 2014
Automation is the use of and information technologies to reduce the need for human work in the production of goods and services. In the scope of industrialization, automation is a step beyond mechanization. Whereas mechanization provides human operators with machinery to assist them with the muscular requirements of work, automation greatly decreases the need for human sensory and mental requirements as well. Automation plays an increasingly important role in the world economy and in daily experience.
The dynamics of a rigid body system is defined by its equations of motion, which are derived using either Newtons laws of motion or Lagrangian mechanics. The solution of these equations of motion defines how the configuration of the system of rigid bodies changes as a function of time. The formulation and solution of rigid body dynamics is an important tool in the computer simulation of mechanical systems.