Editing Machine (section)

==Mechanical systems==
[[File:SteamEngine Boulton&Watt 1784.png|thumb|upright=1.2|alt=Boulton & Watt Steam Engine|The Boulton & Watt Steam Engine, 1784]]  
A '''mechanical system''' manages [[power (physics)|power]] to accomplish a task that involves forces and movement. Modern machines are systems consisting of (i) a power source and [[actuator]]s that generate forces and movement, (ii) a [[Machine (mechanical)|system 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 by [[mechanics]].<ref name=OED>{{cite OED|mechanical}}</ref> Similarly Merriam-Webster Dictionary<ref name=Merriam-mechanical>Merriam-Webster Dictionary [http://www.merriam-webster.com/dictionary/mechanical Definition of mechanical] {{webarchive|url=https://web.archive.org/web/20111020103442/http://www.merriam-webster.com/dictionary/mechanical |date=2011-10-20 }}</ref> 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 Reuleaux]]<ref name=Reuleaux1876>Reuleaux, F., 1876 [https://archive.org/details/kinematicsmachi01reulgoog <!-- quote=kinematics of machinery. --> ''The Kinematics of Machinery''] {{webarchive|url=https://web.archive.org/web/20130602121819/http://books.google.com/books?id=WUZVAAAAMAAJ&printsec=frontcover&dq=kinematics+of+machinery&hl=en&sa=X&ei=qpn4Tse-E9SasgLcsZytDw&ved=0CEQQ6AEwAQ |date=2013-06-02 }} (trans. and annotated by A. B. W. Kennedy), reprinted by Dover, New York (1963)</ref> 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 (physics)|power]].

More recently, Uicker et al.<ref name=Uicker2003>J. J. Uicker, G. R. Pennock, and J. E. Shigley, 2003, ''Theory of Machines and Mechanisms'', Oxford University Press, New York.</ref> stated that a machine is "a device for applying power or changing its direction."McCarthy and Soh<ref name=McCarthy2010>J. M. McCarthy and G. S. Soh, 2010, [https://books.google.com/books?id=jv9mQyjRIw4C&pg=PA231 ''Geometric Design of Linkages,''] {{webarchive|url=https://web.archive.org/web/20160819020038/https://books.google.com/books?id=jv9mQyjRIw4C&pg=PA231 |date=2016-08-19 }} Springer, New York.</ref> describe a machine as a system that "generally consists of a power source and a [[mechanism (engineering)|mechanism]] for the controlled use of this power."