The sequences of the movements and the positioning that the Friend
robot must follow in order to carry out the operation of ôSubstitution of
For avoidance, the procedure follows two different routes
according to the type and geometry of the obstacle. There are two obstacle
categories : an obstacle is either particularly long lengthwise or
The " Substitution of Parts "
represents most complex and articulated macro_operation of maintenance of
the orbiting station on which the Friend robot operates, therefore the
studies lead on this last one can be considered like a synthetic analysis
of the operations that compose it, which as an example the operation of
Taking, Transporting and Depositing of Objects, the operation of
Assemblage and the operation of Disengaging.
In order to supply to the
development of such duties of maintenance, it is previewed to equip the
robot with 13 degrees of freedoms indicated in the following figure.
For avoidance, in the event of the grasping point not being found in
the arm plane, there are two ways of reaching it: the first is to move the
articulated quadrilateral thus compensating for the increase in the
distance by using the 3 link movements; the second is to carry out a
rotation around the transverse docking axis, counter-rotate the spherical
wrist and correct the distance using the 3 link movement. The first option
is preferable; fewer movements are used and the whole operation is
It is considered the operation of "Substitution of Parts " in the
case in which the damaged member is shielded from panels of protection.
The robot arranges his body frontally to those panels in order to open
With such End Effectors, the 2 arms deposit the damaged
piece, seize the " module " of reciprocation and transport it near the the
fixed support to which they approach it sweetly. For avoidance, the robot
avails itself of various options to overcome an obstacle; these depend
mainly on the way in which one wishes to reach an object : either using
one or both arms. The possibility of reaching it with both arms is
essential in terms of robot operating features. Moreover when studying the
sequence pertaining to transit above an obstacle, it has been shown, that
the robot has to use independently rotation of the two half-bodies around
the transverse docking axis.
The modality of analysis of the "
Substitution of Parts " has general validity and it can be used to study
all the other operations of maintenance.
It is necessary to equip such
first level analysis, with a successive
developed dynamics analysis
resorting to the multibody method in such way to place the bases for the
development of the control system.
For the avoidance, The limitations
involved in the possibility of overcoming an obstacle using this procedure
are the dimensions of the obstacle itself; if this is much larger than the
dimensions of the robot itself, the obstacle will not be able to be