How to use OpenRAVE's IK with a 5DoF manipulator?

edit

After successfully converting my URDF file to COLLADA, I can start the IK service like this:

roscd katana_description/collada
rosrun orrosplanning ik_openrave.py --scene="katana6m90a.robot.xml"

The files to reproduce have been added to the katana_description package.

Now, when I make a call to the GetPositionIK service (the ROS version, of type kinematics_msgs/GetPositionIK), I get the following error message:

...
ValueError: number of joints to solve for is not equal to required joints 5!=6

Of course, it is impossible to solve 6DoF IK with a 5DoF arm. Is it possible to use one of the other IK types that OpenRAVE offers to move my gripper into a grasping position?