The Original Stewart Platform

Abstract

At the beginning of the 1900s, a two-degree-of-freedom (DOF) parallel manipulator intended to operate like a flight simulator named the "Antoinette Barrel Trainer" was designed by a French company to help pilots control wheel motion before an aircraft was flown. To do this, the orientation of the Antoinette flight simulator was controlled by two wheels mounted left and right of the pilot, one for pitch and the other for roll. Despite the simplicity of this first virtual plane, at that time the benefits of flight simulators were immediately recognized mainly by the military industry; for instance, during World Wars I and II, flight simulators were designed for purposes like teaching pilots how to operate flight controls, improving pilots' skills in air gunner operations, instructing pilots how to navigate at night guided by the stars, and so forth. In the mid-1960s, when working for the Space and Weapons Research Establishment on aviation simulation at the Elliott Automation Company, Stewart published his celebrated theoretical paper entitled "A platform with six degrees of freedom" (Stewart 1965-1966), where flight simulators were one of its possible applications (Fig. 13.1). Interesting topics like mobility and singularity analyses were included in this contribution, attracting the attention of engineers and scientists. However, an unusual number of ardent communications followed Stewart's theoretical paper (Fichter et al. 2009). Meir offered positive and exhaustive comments about potential applications of the Stewart platform; Meir also appreciated the elegant mathematical treatment Stewart used to approach the kinematic analysis of the new spatial mechanism. On the other hand, Meir also considered that the inclusion of six servo motors could be a serious obstacle to developing the new parallel manipulator due to the obvious high cost of such a mechatronic system. It is difficult to imagine how a new machine would be cheaper than commercially available options. For example, one of the main problems today with introducing the general hexapod as a multiaxis machine tool has been the use of spherical joints. Fortunately, this has not been a