Positioning control with arbitrary orientation

[modpra]

Dear all,
I am currently working on a 4 degree of freedom robot that has to move
in cartesian motion, thus requiring me to firgure out its inverse
kinematics. Being a 4DOF robot working it cannot achieve arbitrary
positions and orientations but this is not what I care about. I want
the robot to only achieve proper positioning.
The problem I am facing is that my invese kinematics force the robot
to maintain orientation and not position (I am guessing since the
joint angles are primarily derived via the 3X3 rotation part of the
forward kinematic matix).
Is there a way to estimate an orientation while making the position of
the tool the primary goal to be achieved.
I have heard of a process called "Toolfitting" but so far haven't
found anything on the topic via google or looking up the univesity
catalogue.
Regards and thanks for the help.

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