Chap 11 – Case Studies
11.6 Space Station Remote Manipulator System (SSRMS)
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7 axis manipulator, 7 d.o.f. (redundant)
1st & 2nd axes intersect
6th & 7th axes intersect
3rd, 4th, & 5th axes are parallel
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• The manipulator is classified as being
redundant since only six joint axes are
necessary to position and orient the end
effector arbitrarily in space.
• The reverse kinematic position analysis will
proceed, however, by having the user
specify one of the joint angle parameters in
addition to specifying the desired position
and orientation of the end effector.
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• In the present analysis, the user must specify
2 in addition to the desired end effector
position and orientation.
• This strategy offers a distinct advantage in
that the parameter 2 has a physical meaning
for the operator.
• This angle governs the orientation of the
longest links of the manipulate or (a34 and
a45) with respect to the XY plane through the
base of the robot.
• The prior specification of 2 will enable the
user to take better advantage of the
redundancy of the system by being able to
position the longest links of the manipulator
to move over or around obstacles in the
workspace.
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6
• Make a free choice for the offset S7 and
establish a direction for the vector a78 in the
last link. (Establish the 7th coordinate system.)
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• Obtain the coordinates of the origin of the 7th
coordinate system with respect to ground.
• Close the loop. Obtain a81, S8, S1, 8, 81, 1.
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11.6.1 Development of an Equivalent 6 Degree
of Freedom Manipulator
obtain 12’ , a12’, S1’, and S2’
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special configuration if 2 equals 0 or 180, 4 axes parallel
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11
project vector loop onto S2 (z comp. of set 14)
project vector loop onto x & y axes of set 14, square and add
x & y axes of set 14
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11.7 Modified Flight Telerobotic Servicer (FTS) Manipulator System
original FTS design
modified FTS design
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• redundant robot
• assume 7 is given
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• redundant robot
• assume 7 is given
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• redundant robot
• assume 7 is given
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• redundant robot
• assume 7 is given
calculate
where
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• redundant robot
• assume 7 is given
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• redundant robot
• assume 7 is given
• 1st & 2nd axes intersect
• 3rd & 4th axes parallel
• 5th & 6th axes intersect
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