A 2-DOF Deployable Planar Mechanism with Continuous Rotation Characteristics

A deployable planar mechanism with two degrees-of-freedom (DOFs) is proposed and analyzed. This mechanism has an axisymmetric structure that the lower part and the upper part are identical and symmetric with each other. The end effector can translate continuously along the direction perpendicular to the axis of symmetry of the base and the end effector and rotate continuously around any point on the axis of symmetry. It is proved that the end effector can rotate around a fixed point to reach any postures. The workspace is analyzed and the motion planning of the continuous rotations is carried out. Two numerical examples are given to show the continuous motions of this mechanism and then a prototype is designed to verify the motion characteristics. This mechanism can also be used as a module to construct multi-layer planar deployable structure with high deploying ratio. This work lays the foundation for the practical application of this 2-DOF planar mechanism.