Stewart platform

A Gough-Stewart platform is a type of parallel robot that has six prismatic actuators, commonly hydraulic jacks or electric actuators, attached in pairs to three positions on the platform's baseplate, crossing over to three mounting points on a top plate. 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. These are the three linear movements x, y, z (lateral, longitudinal and vertical), and the three rotations pitch, roll, & yaw. The terms "six-axis" or "6-DoF" (Degrees of Freedom) platform are also used, also "synergistic" (see below).

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. Although the short title Stewart Platform is now used for this jack layout, it would be fairer to Eric Gough to call it a Gough/Stewart platform. To be more precise, the original Stewart platform had a slightly different design. See the more detailed references at the end of this article.

Because the motions are produced by a combination of movements of several of the jacks, such a device is sometimes called a synergistic motion platform, due to the synergy (mutual interaction) between the way that the jacks are programmed.

Because the device has six jacks, it is often also known as a hexapod (six legs). The trademarked name "hexapod" (by Geodetic Technology) was originally for Stewart platforms used in machine tools. However, the term is now used for 6-jack platforms outside of the machine tool area, since it simply means "six legs".

Stewart platforms have applications in flight simulators, machine tool technology, crane technology, underwater research, air-to-sea rescue, mechanical bulls, satellite dish positioning, telescopes and orthopedic surgery.

The Stewart platform design is extensively used in flight simulation, particularly in the so-called full flight simulator for which all 6 degrees of freedom are required. This application was developed by Redifon, whose simulators featuring it became available for the Boeing 707, Douglas DC-8, Sud Aviation Caravelle, Canadair CL-44, Boeing 727, Comet, Vickers Viscount, Vickers Vanguard, Convair CV 990, Lockheed C-130 Hercules, Vickers VC10, and Fokker F-27 by 1962.

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