Page 134 - Rapid Learning in Robotics

120 Application Examples in the Robotics Domain

simple augmentation of the embedding space X with extraneous compo-
nents (note, they do not affect the normal operation.) Those can be used
to formulate additional cost function terms and can be activated when-
ever desired. The cost function terms can be freely constructed in various
functional dependencies and are supplied during the learning phase of the
PSOM.

The best-match location s is under-constrained, since jIj m
(in contrast to the cases described in Sec. 5.6.) Certainly, the standard best-
match search algorithm will find one possible solution — but it can be any
compatible solution and it will depend on the initial start condition s t .
Here, the PSOM offers a versatile way of formulating extra goals or
constraints, which can be turned on and off, depending on the situation
and the user's desire. For example, of particular interest are:

Minimal joint movement: “fast” or “lazy” robot. One practical goal can
be: reaching the next target position with minimum motor action.
This translates into finding the shortest path from the current joint

configuration curr to a new compatible with the desired Cartesian
position .
r
Since the PSOM is constructed on a hyper-lattice in , finding the
shortest route s in S is equivalent to finding the shortest path in .
Thus, all we need to do is to start the best-match search at the best-
match position s curr belonging to the current position, and the steep-
est gradient descent procedure will solve the problem.

Orientation preference: the “traditional solution”. If a certain end effec-
tor approach direction, for example a top–down orientation, is pre-
ferred, the problem transforms into the standard mixed position /
orientation task, as described above.

Maximum mobility reserve: “comfortable configuration”. If no further
orientation constraints are given, it might be useful to gain a large
joint mobility reserve — a reserve for further actions and re-actions
to unforeseen events.

Here, the latter case is of particular interest. A high mobility reserve
means to stay away from configurations close to any range limits. We