US Patent 7392722 Control unit with three parallel branches

This controller, between a fixed base (1) and a control handle (4), comprises three similar arms (2) of which each comprises three links (5,6,7) jointed between the base and the handle platform by a pivot (8), two rotation joints (9 and 10) and a ball-joint (11). This controller with six degrees of freedom includes force feedback motors at the first and second joints (8 and 9) of which the first is fixed to the base (1) and the second to the first link (5), so that the first is immobile and the other has scarce movement; the third joint (10) is free. The resulting structure is simple and light not requiring any parallelogram, and kinematic singularities are greatly reduced.