A mechanism is a device designed to transform input forces and movement into a desired set of output forces and the movement. In this context, his use of machine is generally interpreted to mean mechanism, the combination of force and movement defines power, and a mechanism is designed to manage power in order to achieve a desired set of forces and movement. A mechanism is usually a piece of a process or mechanical system. Sometimes an entire machine may be referred to as a mechanism, examples are the steering mechanism in a car, or the winding mechanism of a wristwatch. From the time of Archimedes through the Renaissance, mechanisms were considered to be constructed from simple machines, such as the lever, pulley, screw, wheel and axle, wedge and inclined plane. It was Reuleaux who focussed on bodies, called links, in order to use geometry to study the movement of a mechanism, its links are modeled as rigid bodies. This means distances between points in a link are assumed to be unchanged as the moves, that is the link does not flex. Thus, the movement between points in two connected links is considered to result from the kinematic pair that joins them. A mechanism is modeled as an assembly of rigid links and kinematic pairs, Reuleaux called the ideal connections between links kinematic pairs. He distinguished between higher pairs which were said to have contact between the two links and lower pairs that have area contact between the links. J. Phillips shows that there are ways to construct pairs that do not fit this simple. Lower pair, A lower pair is a joint that has surface contact between the pair of elements. This imposes five constraints on the movement of the links. This imposes five constraints on the movement of the links. A cylindrical joint requires that a line in the body remain co-linear with a line in the fixed body. It is a combination of a joint and a sliding joint. This joint has two degrees of freedom, a spherical joint, or ball joint, requires that a point in the moving body maintain contact with a point in the fixed body. This joint has three degrees of freedom, a planar joint requires that a plane in the moving body maintain contact with a plane in fixed body
Theo Jansen's kinetic sculpture Strandbeest. A wind-driven walking machine.
Schematic of the actuator mechanism for an aircraft landing gear.