regarding Constraints of my arm configuration

I mailed yesterday regarding the configuration which is littlebit different
from Serial 321 configuration.
In this configuration the following spec. along with motor rotation are
there:
::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
LINK                 LENGTH           MOTOR (rotation angle)
Rotation axis(according to OROCOS)
                                                  [ Counter-Clockwise +ve ]
::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
BASE              3"                       0-180 Degree
      Z

SHOULDER     4.75"                  0-180 Degree                           X

ELBOW           4.75"                  -150  to  +30 Degree
X

WRIST            5.75"                  -90   to
90                             parallel to Shoulder and elbow

WRIST ROTATION -----             -90  to 90
Perpendicular to Wrist.

GRIPPER                               opening 2" max.
Perpendicular to both wrist and wristRotation axes.



The serial family has six *revolute* joints: a "wrist" with *three* revolute
joints with intersecting axes; an "arm" with *two* parallel axes; and a
"shoulder" with *one* revolute joint whose axis is orthogonal to the axes of
the "arm" set. but my arm is having three axes parallel (2nd, 3rd and 4th)
and more over  last three are  not intersecting  at a point. Only 4th and
5th are intersecting. Sixth is at some offset of 2.2" from that intersecting
point.

As this is not exactly a 6 DOF arm Its a 5 + gripper but still if we ignore
the last joint and want to move it through desire points, it should move
accordingly.
For some given point which is already in its workspace, Orocos is
calculating joint positions (radians) which are contradicting with motor
constraints so robot can't move to that point. eg  -ve value for base, or
some other value which is out of range for that particular joint motor.
How it can be resolved?

Thanks
H.S.Randhawa

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