A NEW FAMILY OF 6 DEGREES-OF-FREEDOM POSITIONAL DEVICES

Positional control is fundamental to most manufacturing processes as w ell as a wide range of other applications. Many types of positional de vices have been proposed and used, ranging from robotic arms to Stewar t platforms. This paper discusses a new family of six degrees of freed om positional control devices which generally combine simple designs, high stiffness and strength, and a wider range of motion. Stiffness is particularly advantageous in very small (submicron) positional device s as thermal motion is a significant source of positional uncertainty. The stiffness and thermally induced positional uncertainty of three d esigns-a robotic arm, a Stewart platform, and one member of the new fa mily-are analysed and compared. The Stewart platform provides the grea test stiffness for a given structural mass but has the most restrictiv e range of motion. The robotic arm is least stiff. The new proposal co mbines greater stiffness than the robotic arm with a significantly gre ater range of motion than the Stewart platform.