Position　control　of　a　2DOF　underactuated　planar　flexible　robot　in　joint　space　is　investigated.　Firstly,　the　dynamic　equations　are　given　based　on　the　assumed　mode　method.　The　position　control　strategies　of　this　underactuated　planar　flexible　manipulator　are　designed　with　the　switch　of　the　brake　at　the　passive　joint.　And　the　corresponding　algorithms　of　the　active　and　passive　joints　are　proposed　in　stages.　A　2DOF　underactuated　planar　robot　experimental　setup　and　its　control　system　is　developed.　Position　control　of　this　manipulator　is　completed　experimentally.　The　simulative　and　experimental　results　show　that　in　respective　stage　the　active　and　passive　joints　can　track　the　targets　perfectly,　which　verify　the　effectiveness　of　the　proposed　method.　Furthermore,　the　elastic　vibration　at　the　end　of　the　flexible　link　reflects　the　rightness　of　the　assumed　mode　dynamic　model　for　the　underactuated　flexible　manipulator.　©　2011　IEEE.