SARAH Hand (underactuated robotic hand for the Canadarm) |
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Highly Underactuated 10-DOF Robotic Hand (for the Canadarm)
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.
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.
A prototype of the highly underactuated self-adaptive 10-DOF robotic hand with 2 actuators was built in 1999.
The new hand, SARAH (Self Adaptive Robotic Auxilary Hand), is
slightly smaller and weighs only half as much as its 12-DOF predecessor
(MARS Hand). It has the same mobility, but
is actuated by only two motors.
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.
Poster
A poster on the SARAH Hand was prepared in 2002 and can be
downloaded with the PDF file below.
Highly Underactuated Hands (11 Mb)
Selected Photos
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Several photos of the SARAH Hand are provided below.
They can be enlarged by clicking directly on the photos. |
Video Clips
The SARAH Hand can grasp objects of different shapes and textures.
The following video segments illustrate several of these grasps.
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Plastic SARAH
Video clip showing the plastic prototype of SARAH, using electric screwdriver as input.
Format: mpg Length: 1:12 Size: 3.3 Mb
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SARAH
Video clip showing several grasps carried out by SARAH, using external electrical actuators as input (the gray and blue base is a replica of the Canadarm end-effector).
Format: mpg Length: 1:14 Size: 3.4 Mb
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SARAH: space use
Animation showing the use of the SARAH Hand to relocate camera on the international space station.
Format: mpg Length: 0:49 Size: 23.8 Mb
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Highly Underactuated 10-DOF Robotic Hand (for general purpose)
A new version of the SARAH Hand was recently built. It differs from the previous one in the actuator placement and its overall size.
Two DC motors are incorporated inside the robotic hand base. The hand is smaller than its predecessor. The hand is
presently on the CART (the SPDM simulator) of the Canadian Space Agency.
Video Clips
The following video segment shows the highly underactuated 10-DOF Robotic Hand for general purpose.
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SARAH for general purpose
Video clip showing several grasps carried out by SARAH, using two in-built electrical actuators as input.
Format: mpg Length: 1:08 Size: 3.2 Mb
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