Stewart platform

A Stewart platform is a type of parallel manipulator that has six prismatic actuators, commonly hydraulic jacks or electric linear actuators, attached in pairs to three positions on the platform's baseplate, crossing over to three mounting points on a top plate. All 12 connections are made via universal joints. Devices placed on the top plate can be moved in the six degrees of freedom in which it is possible for a freely-suspended body to move: three linear movements x, y, z (lateral, longitudinal, and vertical), and the three rotations (pitch, roll, and yaw). Stewart platforms are known by various other names. In many applications, including in flight simulators, it is commonly referred to as a motion base. It is sometimes called a six-axis platform or 6-DoF platform because of its possible motions and, because the motions are produced by a combination of movements of multiple actuators, it may be referred to as a synergistic motion platform, due to the synergy (mutual interaction) between the way that the actuators are programmed. Because the device has six actuators, it is often called a hexapod (six legs) in common usage, a name which was originally trademarked by Geodetic Technology for Stewart platforms used in machine tools. This specialised six-jack layout was first used by V E (Eric) Gough of the UK and was operational in 1954, the design later being publicised in a 1965 paper by D Stewart to the UK Institution of Mechanical Engineers. In 1962, prior to the publication of Stewart's paper, American engineer Klaus Cappel independently developed the same hexapod. Klaus patented his design and licensed it to the first flight simulator companies, and built the first commercial octahedral hexapod motion simulators. Although the title Stewart platform is commonly used, some have posited that Gough–Stewart platform is a more appropriate name because the original Stewart platform had a slightly different design, while others argue that the contributions of all three engineers should be recognized.