Design of a Six Degree of Freedom Haptic Interface
1
David T. Burns
Master's thesis, Department of Mechanical Engineering, Northwestern University, August, 1996.
1996 NWU
http://lims.mech.northwestern.edu/dburns-lib/master/dburnsmaster.pdf
A six degree-of-freedom manipulandum with force-feedback capabilities
was designed for the use as an interface in virtual environments and
teleoperators.  Of specific interest is its application to astronaut
training.  The manipulandum should be able to simulate the mechanical
behavior of a wide range of tools in a zero gravity environment.  The
device is made up of two, three degree-of-freedom mechanisms coupled
by a variable length linkage which also serves as the manipulandum's
handle.  The tip of each 3 dof mechanism can be positioned arbitrarily
in 3-space.  A fixed-length rod connecting the two tips would have
five controlled dof, but would be unable to rotate about its own axis.
However, expanding and contracting the variable length linkage will
rotate the handle about the axis of the linkage resulting in the sixth
degree of freedom.  A cable driven differential transmission is used
for each of the three degree of freedom mechanisms allowing all six
actuators to be fixed to ground.  The kinematic parameters were chosen
such that the usable workspace, with no singularities, is
approximately one cubic foot in translational motion, and plus/minus
ninety degrees in endpoint orientation space.