The revolute-revolute (RR) planar arm considered is as follows,
Figure 2: Joint 
(the shoulder) is attached to the floor, and is
the origin of a fixed reference system. Joint 
(the elbow)
connects the two links, 
and 
. The Cartesian coordinates of
the endpoint (point P) are (x, y).
Figure 2: The 2D two-link arm manipulator in an environment
with unknown stationary obstacles.
Moving the arm involves changing the joint angles 
and 
.
There are fixed obstacles in the arm environment ( 
and 
, Figure
2). There are no constraints on the shape of the obstacles
or the arm links. The task is to move the arm from a position S
(Start) to the position T (Target), Figure 3.
