The robotic hands developed in the laboratory up to this point, had an underactuation only in the fingers. Each finger was thus actuated by its own motor. In 1998 the company MDA Space Missions (previously SPAR Aerospace) contacted the laboratory in order to request the development of a hand for the well-known Canadarm. One of the specifications requested for this new hand was that it should be actuated by only two motors.ment deux moteurs.

This led to the principle of a hand featuring under actuation among the fingers; the opening and closing of the fingers is controlled by only one motor. In fact, one motor is sufficient since it is not necessary for all three fingers to close independently, because all fingers will close to grasp an object as firmly as possible. If one finger is firmly wrapped around an object, the other fingers will continue to close until all fingers are firmly closed. The underactuation among the fingers is achieved through an innovative gear differential mechanism. A second motor allows the orientation of the fingers to be changed to achieve cylindrical, spherical and planar grasps.on des doigts afin de réaliser des prises cylindriques, sphériques et planes.

The SARAH hand was built in collaboration with the Canadian Space Agency. Its design is covered by a US patent (No. 6,505,870) as well as by a pending WIPO patent. The current version is adapted as an end-effector to the SPDM of the Canadian Space Arm for the International Space Station.

A poster on the SARAH Hand was prepared in 2002 and can be downloaded with the PDF file below.

The SARAH Hand can grasp objects of different shapes and textures. The following video segments illustrate several of these grasps.

The following video segment shows the highly underactuated 10-DOF Robotic Hand for general purpose.