page_title: Machine
section_title: Mechanical systems
hierarchical_section_title: Machine / Mechanical systems
caption_attribution_description: English: Sketch showing a steam engine designed by Boulton&#160;&amp; Watt, England, 1784. Labelling: B steam valves (input), C steam-cylinder, E exhaust steam valves, H Connecting rod link to beam N cold water pump, O connecting rod, P piston, Q regulator/governor, R rod of the air-pump, T steam input flap (controlled by governor (Q). g link connecting piston (P) and beam via parallel motion g-d-c, m steam inflow lever worked by the air-pump rod (R).
context_page_description: A machine 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 simple machines 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 vehicles, such as automobiles, boats and airplanes, appliances in the home and office, including computers, building air handling and water handling systems, as well as farm machinery, machine tools and factory automation systems and robots.
context_section_description: A mechanical system manages power to accomplish a task that involves forces and movement. Modern machines are systems consisting of (i) a power source and actuators that generate forces and movement, (ii) a 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 (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. Similarly Merriam-Webster Dictionary 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 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. stated that a machine is "a device for applying power or changing its direction." McCarthy and Soh describe a machine as a system that "generally consists of a power source and a mechanism for the controlled use of this power."
caption: The Boulton & Watt Steam Engine, 1784
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