A worker operating amilling machine in the early 20th century
Amachine is athermodynamic system that usespower to applyforces and controlmovement to perform an action. The term is commonly applied to artificial devices, such as those employingengines or motors, but also to natural biological macromolecules, such asmolecular machines. Machines can be driven byanimals andpeople, by natural forces such aswind andwater, and bychemical,thermal, orelectrical power, and include a system ofmechanisms that shape theactuator input to achieve a specific application of output forces and movement. They can also includecomputers and sensors that monitor performance and plan movement, often called mechanical systems.
Renaissance natural philosophers identified sixsimple machines which were the elementary devices that put a load into motion, and calculated the ratio of output force to input force, known today asmechanical advantage.[1]
The English wordmachine comes throughMiddle French fromLatinmachina,[2] which in turn derives from theGreek (Doricμαχανάmakhana,Ionicμηχανήmekhane 'contrivance, machine, engine',[3] a derivation fromμῆχοςmekhos 'means, expedient, remedy'[4]).[5] The wordmechanical (Greek:μηχανικός) comes from the same Greek roots. A wider meaning of 'fabric, structure' is found in classical Latin, but not in Greek usage. This meaning is found in late medieval French, and is adopted from the French into English in the mid-16th century.
In the 17th century, the word machine could also mean a scheme or plot, a meaning now expressed by the derivedmachination. The modern meaning develops out of specialized application of the term tostage engines used intheater and to militarysiege engines, both in the late 16th and early 17th centuries. TheOED traces the formal, modern meaning toJohn Harris'Lexicon Technicum (1704), which has:
Machine, or Engine, in Mechanicks, is whatsoever hath Force sufficient either to raise or stop the Motion of a Body. Simple Machines are commonly reckoned to be Six in Number, viz. the Ballance, Leaver, Pulley, Wheel, Wedge, and Screw. Compound Machines, or Engines, are innumerable.
The wordengine used as a (near-) synonym both by Harris and in later language derives ultimately (viaOld French) from Latiningenium 'ingenuity, an invention'.
Thehand axe, made by chipping flint to form awedge, in the hands of a human transforms force and movement of the tool into a transverse splitting forces and movement of the workpiece. The hand axe is the first example of awedge, the oldest of the six classicsimple machines, from which most machines are based. The second oldest simple machine was theinclined plane (ramp),[6] which has been used sinceprehistoric times to move heavy objects.[7][8]
The earliestprogrammable machines were developed in the Muslim world. Amusic sequencer, a programmablemusical instrument, was the earliest type of programmable machine. The first music sequencer was an automatedflute player invented by theBanu Musa brothers, described in theirBook of Ingenious Devices, in the 9th century.[31][32] In 1206, Al-Jazari invented programmableautomata/robots. He described fourautomaton musicians, including drummers operated by a programmabledrum machine, where they could be made to play different rhythms and different drum patterns.[33]
During theRenaissance, the dynamics of theMechanical 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 mechanicalwork. In 1586 Flemish engineerSimon 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 scientistGalileo Galilei in 1600 inLe Meccaniche ("On Mechanics").[34][35] He was the first to understand that simple machines do not createenergy, they merely transform it.[34]
James Albert Bonsack's cigarette rolling machine was invented in 1880 and patented in 1881.
TheIndustrial 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 theUnited Kingdom, then subsequently spread throughoutWestern 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 ofGreat 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 ofiron-making techniques and the increased use ofrefined coal.[38]
Chambers' Cyclopædia (1728) has a table of simple mechanisms.[39] Simple machines provide a "vocabulary" for understanding more complex machines.
The idea that a machine can be decomposed into simple movable elements ledArchimedes to define thelever,pulley andscrew assimple machines. By the time of the Renaissance this list increased to include thewheel and axle,wedge andinclined plane. The modern approach to characterizing machines focusses on the components that allow movement, known asjoints.
Wedge (hand axe): Perhaps the first example of a device designed to manage power is thehand axe, also calledbiface andOlorgesailie. A hand axe is made by chipping stone, generally flint, to form a bifacial edge, orwedge. 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, ormechanical 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 orprismatic joint.
Lever: Thelever 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. Ifa is the distance from the pivot to the point where the input force is applied andb is the distance to the point where the output force is applied, thena/b is themechanical advantage of the lever. The fulcrum of a lever is modeled as a hinged orrevolute joint.
Wheel: Thewheel is an important early machine, such as thechariot. A wheel uses the law of the lever to reduce the force needed to overcomefriction 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.
The classification ofsimple machines to provide a strategy for the design of new machines was developed byFranz Reuleaux, who collected and studied over 800 elementary machines.[40] He recognized that the classicalsimple machines 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.[41]
Simple machines are elementary examples ofkinematic chains orlinkages that are used to modelmechanical 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 akinematic pair called a hinged joint. Similarly, the flat surface of an inclined plane and wedge are examples of thekinematic 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 amechanism.[42]
Two levers, or cranks, are combined into a planarfour-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 asix-bar linkage or in series to form a robot.[42]
Mechanical systems
The Boulton & Watt Steam Engine, 1784
Amechanical system managespower to accomplish a task that involves forces and movement. Modern machines are systems consisting of (i) a power source andactuators that generate forces and movement, (ii) asystem of mechanisms that shape the actuator input to achieve a specific application of output forces and movement, (iii) a controller with sensors that compare the output to a performance goal and then directs the actuator input, and (iv) an interface to an operator consisting of levers, switches, and displays. This can be seen in Watt's steam engine 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 bymechanics.[43] Similarly Merriam-Webster Dictionary[44] 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 mechanicianFranz Reuleaux[45] 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 definepower.
More recently, Uicker et al.[42] stated that a machine is "a device for applying power or changing its direction."McCarthy and Soh[46] describe a machine as a system that "generally consists of a power source and amechanism for the controlled use of this power."
Windmill: Earlywindmills captured wind power to generate rotary motion for milling operations. Modernwind turbines also drives a generator. This electricity in turn is used to drivemotors 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.[47] Asteam 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 theaeolipile of Hero of Alexandria. This is called anexternal combustion engine.
Anautomobile engine is called aninternal combustion engine because it burns fuel (anexothermic chemical reaction) inside a cylinder and uses the expanding gases to drive apiston. Ajet engine uses a turbine to compress air which is burned with fuel so that it expands through a nozzle to provide thrust to anaircraft, and so is also an "internal combustion engine."[48]
Electrochemical: Chemicals and materials can also be sources of power.[49] They may chemically deplete or need re-charging, as is the case withbatteries,[50] or they may produce power without changing their state, which is the case forsolar cells andthermoelectric generators.[51][52] All of these, however, still require their energy to come from elsewhere. With batteries, it is the already existingchemical potential energy inside.[50] In solar cells and thermoelectrics, the energy source is light and heat respectively.[51][52]
Mechanisms
Themechanism of a mechanical system is assembled from components calledmachine elements. These elements provide structure for the system and control its movement.
The structural components are, generally, the frame members, bearings, splines, springs, seals,fasteners and covers. The shape, texture and color of covers provide astyling and operational interface between the mechanical system and its users.
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 theChebychev–Grübler–Kutzbach criterion.
The transmission of rotation between contacting toothed wheels can be traced back to theAntikythera mechanism of Greece and thesouth-pointing chariot ofChina. Illustrations by the renaissance scientistGeorgius Agricola show gear trains with cylindrical teeth. The implementation of theinvolute tooth yielded a standard gear design that provides a constant speed ratio. Some important features of gears and gear trains are:
Acam andfollower is formed by the direct contact of two specially shaped links. The driving link is called the cam (also seecam shaft) and the link that is driven through the direct contact of their surfaces is called the follower. The shape of the contacting surfaces of thecam andfollower determines the movement of the mechanism.
Linkages
Schematic of the actuator and four-bar linkage that position an aircraft landing gear
Alinkage is a collection of links connected by joints. Generally, the links are the structural elements and the joints allow movement. Perhaps the single most useful example is the planarfour-bar linkage. However, there are many more special linkages:
Watt's linkage is a four-bar linkage that generates an approximate straight line. It was critical to the operation of his design for the steam engine. This linkage also appears in vehicle suspensions to prevent side-to-side movement of the body relative to the wheels. Also see the articleParallel motion.
The success of Watt's linkage lead to the design of similar approximate straight-line linkages, such asHoeken's linkage andChebyshev's linkage.
ThePeaucellier linkage generates a true straight-line output from a rotary input.
TheSarrus linkage is a spatial linkage that generates straight-line movement from a rotary input.
TheKlann linkage and theJansen linkage are recent inventions that provide interesting walking movements. They are respectively a six-bar and an eight-bar linkage.
Planar mechanism
A planar mechanism is a mechanical system that is constrained so the trajectories of points in all the bodies of the system lie on planes parallel to a ground plane. The rotational axes of hinged joints that connect the bodies in the system are perpendicular to this ground plane.
Spherical mechanism
Aspherical mechanism is a mechanical system in which the bodies move in a way that the trajectories of points in the system lie on concentric spheres. The rotational axes of hinged joints that connect the bodies in the system pass through the center of these circle.
Spatial mechanism
Aspatial mechanism is a mechanical system that has at least one body that moves in a way that its point trajectories are general space curves. The rotational axes of hinged joints that connect the bodies in the system form lines in space that do not intersect and have distinct common normals.
Flexure mechanisms
A flexure mechanism consists of a series of rigid bodies connected by compliant elements (also known as flexure joints) that is designed to produce a geometrically well-defined motion upon application of a force.
Machine elements
The elementary mechanical components of a machine are termedmachine elements. These elements consist of three basic types (i)structural components such as frame members, bearings, axles, splines,fasteners, seals, and lubricants, (ii)mechanisms that control movement in various ways such asgear trains,belt orchain drives,linkages,cam andfollower systems, includingbrakes andclutches, and (iii)control components such as buttons, switches, indicators, sensors, actuators and computer controllers.[53] While generally not considered to be a machine element, the shape, texture and color of covers are an important part of a machine that provide astyling and operational interface between the mechanical components of a machine and its users.
Structural components
A number of machine elements provide important structural functions such as the frame, bearings, splines, spring and seals.
The recognition that the frame of a mechanism is an important machine element changed the namethree-bar linkage intofour-bar linkage. Frames are generally assembled fromtruss orbeam elements.
Bearings are components designed to manage the interface between moving elements and are the source offriction in machines. In general, bearings are designed for pure rotation orstraight line movement.
Splines andkeys are two ways to reliably mount anaxle to a wheel, pulley or gear so that torque can be transferred through the connection.
Springs provides forces that can either hold components of a machine in place or acts as asuspension to support part of a machine.
Seals are used between mating parts of a machine to ensure fluids, such as water, hot gases, or lubricant do not leak between the mating surfaces.
Fasteners such asscrews, bolts, spring clips, andrivets are critical to the assembly of components of a machine. Fasteners are generally considered to be removable. In contrast, joining methods, such aswelding,soldering,crimping and the application ofadhesives, usually require cutting the parts to disassemble the components
Controllers
Controllers combinesensors,logic, andactuators to maintain the performance of components of a machine. Perhaps the best known is theflyball governor for a steam engine. Examples of these devices range from athermostat that as temperature rises opens a valve to cooling water to speed controllers such as thecruise control system in an automobile. Theprogrammable logic controller replaced relays and specialized control mechanisms with a programmable computer.Servomotors that accurately position a shaft in response to an electrical command are the actuators that makerobotic systems possible.
The biological moleculemyosin reacts to ATP and ADP to alternately engage with an actin filament and change its shape in a way that exerts a force, and then disengage to reset its shape, or conformation. This acts as the molecular drive that causes muscle contraction. Similarly the biological moleculekinesin has two sections that alternately engage and disengage with microtubules causing the molecule to move along the microtubule and transport vesicles within the cell, anddynein, which moves cargo inside cells towards the nucleus and produces the axonemal beating ofmotile cilia andflagella. "In effect, the motile cilium is a nanomachine composed of perhaps over 600 proteins in molecular complexes, many of which also function independently as nanomachines.Flexible linkers allow themobile protein domains connected by them to recruit their binding partners and induce long-rangeallostery viaprotein domain dynamics. "[54] Other biological machines are responsible for energy production, for exampleATP synthase which harnesses energy fromproton gradients across membranes to drive a turbine-like motion used to synthesiseATP, the energy currency of a cell.[55] Still other machines are responsible forgene expression, includingDNA polymerases for replicatingDNA,[citation needed]RNA polymerases for producingmRNA,[citation needed] thespliceosome for removingintrons, and theribosome forsynthesising proteins. These machines and theirnanoscale dynamics are far more complex than anymolecular machines that have yet been artificially constructed.[56] These molecules are increasingly considered to benanomachines.[citation needed]
Mechanization (or mechanisation inBE) is providing human operators with machinery that assists them with the muscular requirements of work or displaces muscular work. In some fields, mechanization includes the use of hand tools. In modern usage, such as in engineering or economics, mechanization implies machinery more complex than hand tools and would not include simple devices such as an un-geared horse or donkey mill. Devices that cause speed changes or changes to or from reciprocating to rotary motion, using means such asgears,pulleys orsheaves and belts,shafts,cams andcranks, usually are considered machines. After electrification, when most small machinery was no longer hand powered, mechanization was synonymous with motorized machines.[59]
Automation is the use ofcontrol systems andinformation technologies to reduce the need for human work in the production of goods and services. In the scope ofindustrialization, automation is a step beyondmechanization. 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 theworld economy and in daily experience.
An automaton (plural: automata or automatons) is a self-operating machine. The word is sometimes used to describe arobot, more specifically anautonomous robot. AToy Automaton was patented in 1863.[60]
Mechanics
Usher[61] reports thatHero of Alexandria's treatise onMechanics focussed on the study of lifting heavy weights. Todaymechanics refers to the mathematical analysis of the forces and movement of a mechanical system, and consists of the study of thekinematics anddynamics of these systems.
Dynamics of machines
Thedynamic analysis of machines begins with a rigid-body model to determine reactions at the bearings, at which point the elasticity effects are included. Therigid-body dynamics studies the movement of systems of interconnected bodies under the action of external forces. The assumption that the bodies are rigid, which means that they do not deform under the action of applied forces, simplifies the analysis by reducing the parameters that describe the configuration of the system to the translation and rotation of reference frames attached to each body.[62][63]
The dynamics of a rigid body system is defined by itsequations of motion, which are derived using eitherNewtons laws of motion orLagrangian 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 ofmechanical systems.
Kinematics of machines
The dynamic analysis of a machine requires the determination of the movement, orkinematics, of its component parts, known as kinematic analysis. The assumption that the system is an assembly of rigid components allows rotational and translational movement to be modeled mathematically asEuclidean, or rigid, transformations. This allows the position, velocity and acceleration of all points in a component to be determined from these properties for a reference point, and the angular position,angular velocity andangular acceleration of the component.
Machine design
Machine design refers to the procedures and techniques used to address the three phases of amachine's lifecycle:
invention, which involves the identification of a need, development of requirements, concept generation, prototype development, manufacturing, and verification testing;
performance engineering involves enhancing manufacturing efficiency, reducing service and maintenance demands, adding features and improving effectiveness, and validation testing;
recycle is the decommissioning and disposal phase and includes recovery and reuse of materials and components.
^Dutch, Steven (1999)."Pre-Greek Accomplishments".Legacy of the Ancient World. Prof. Steve Dutch's page, Univ. of Wisconsin at Green Bay. Archived fromthe original on August 21, 2016. RetrievedMarch 13, 2012.
^Moorey, Peter Roger Stuart (1999).Ancient Mesopotamian Materials and Industries: The Archaeological Evidence.Eisenbrauns.ISBN9781575060422.
^D.T. Potts (2012).A Companion to the Archaeology of the Ancient Near East. p. 285.
^abPaipetis, S. A.; Ceccarelli, Marco (2010).The Genius of Archimedes -- 23 Centuries of Influence on Mathematics, Science and Engineering: Proceedings of an International Conference held at Syracuse, Italy, June 8-10, 2010.Springer Science & Business Media. p. 416.ISBN9789048190911.
^Shepherd, William (2011).Electricity Generation Using Wind Power (1 ed.). Singapore: World Scientific Publishing Co. Pte. Ltd. p. 4.ISBN978-981-4304-13-9.
^Pacey, Arnold (1991) [1990].Technology in World Civilization: A Thousand-Year History (First MIT Press paperback ed.). Cambridge MA: The MIT Press. pp. 23–24.
^Pennock, G. R., James Watt (1736-1819),Distinguished Figures in Mechanism and Machine Science, ed. M. Ceccarelli, Springer, 2007,ISBN978-1-4020-6365-7 (Print) 978-1-4020-6366-4 (Online).
^Beck B., Roger (1999).World History: Patterns of Interaction. Evanston, Illinois: McDougal Littell.
^Chambers, Ephraim (1728), "Table of Mechanicks",Cyclopaedia, A Useful Dictionary of Arts and Sciences, vol. 2, London, England, p. 528, Plate 11.
^"Internal combustion engine",Concise Encyclopedia of Science and Technology, Third Edition, Sybil P. Parker, ed. McGraw-Hill, Inc., 1994, p. 998 .
^Brett, Christopher M. A; Brett, Ana Maria Oliveira (1993).Electrochemistry: principles, methods, and applications. Oxford; New York: Oxford University Press.ISBN978-0-19-855389-2.OCLC26398887.
^Kinbara, Kazushi; Aida, Takuzo (2005-04-01). "Toward Intelligent Molecular Machines: Directed Motions of Biological and Artificial Molecules and Assemblies".Chemical Reviews.105 (4):1377–1400.doi:10.1021/cr030071r.ISSN0009-2665.PMID15826015.
^Bu Z, Callaway DJ (2011). "Proteins MOVE! Protein dynamics and long-range allostery in cell signaling".Protein Structure and Diseases. Advances in Protein Chemistry and Structural Biology. Vol. 83. pp. 163–221.doi:10.1016/B978-0-12-381262-9.00005-7.ISBN9780123812629.PMID21570668.
^Jerome (1934) gives the industry classification of machine tools as being "other than hand power". Beginning with the 1900 U.S. census, power use was part of the definition of a factory, distinguishing it from a workshop.
^B. Paul, Kinematics and Dynamics of Planar Machinery, Prentice-Hall, NJ, 1979
^L. W. Tsai, Robot Analysis: The mechanics of serial and parallel manipulators, John-Wiley, NY, 1999.
Further reading
Oberg, Erik; Franklin D. Jones; Holbrook L. Horton; Henry H. Ryffel (2000). Christopher J. McCauley; Riccardo Heald; Muhammed Iqbal Hussain (eds.).Machinery's Handbook (26th ed.). New York: Industrial Press Inc.ISBN978-0-8311-2635-3.
Reuleaux, Franz (1876).The Kinematics of Machinery. Trans. and annotated by A. B. W. Kennedy. New York: reprinted by Dover (1963).
Uicker, J. J.; G. R. Pennock; J. E. Shigley (2003).Theory of Machines and Mechanisms. New York: Oxford University Press.
Oberg, Erik; Franklin D. Jones; Holbrook L. Horton; Henry H. Ryffel (2000). Christopher J. McCauley; Riccardo Heald; Muhammed Iqbal Hussain (eds.).Machinery's Handbook (30th ed.). New York: Industrial Press Inc.ISBN9780831130992.
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