Mecanisme

A mechanism is a device that transforms input motion or force into a prescribed output motion or force. It is typically defined as a system of rigid bodies, or links, connected by joints that constrain movement to a desired path. Unlike a complete machine, which may store energy or perform work, a mechanism focuses on the geometry of motion and the transmission of power between components.

Mechanisms are found in countless applications. They combine elements such as linkages (bars connected by hinges), gears, cams, pulleys, and sliders. Classic simple machines—lever, wheel and axle, inclined plane, screw, wedge, and pulley—form the building blocks of many mechanisms, but modern designs often integrate multiple components to achieve complex, synchronized motion.

Design and analysis involve kinematics and dynamics. Engineers determine positions, velocities, accelerations, and force paths, choose joints and link lengths, ensure mobility, and avoid interference. Planar mechanisms constrain motion to a plane and include four-bar linkages, slider-cranks, and gear trains. Computer-aided design, simulation, and optimization are widely used in contemporary practice.

Applications span robotics, automotive transmissions, watches, manufacturing equipment, packaging machinery, and biomechanical devices. The study of mechanisms also has historical significance, with early devices such as the Antikythera mechanism illustrating how gearing can model complex natural phenomena.

Etymology: mechanism derives from the French mécanisme, from Greek mechanikos, "of or belonging to a machine," via Latin mechanisma. The term is sometimes used in a broader sense to refer to the underlying process or law that governs a system, not only the physical hardware.