Some planning problems require more complex or custom constraint samplers for more difficult planning problems. This document explains how to creat a custom motion planning constraint sampler for use with MoveIt!.
Create a ROBOT_moveit_plugins package and within that a subfolder for your YOURROBOT_constraint_sampler plugin. Modify the template provided by hrp2jsk_moveit_plugins/hrp2jsk_moveit_constraint_sampler_plugin
In your ROBOT_moveit_config/launch/move_group.launch file, within the <node name="move_group">, add the parameter:
<param name="constraint_samplers" value="YOURROBOT_moveit_constraint_sampler/YOURROBOTConstraintSamplerAllocator"/>
Now when you launch move_group, it should default to your new constraint sampler.