Deployable parallel lower-mobility manipulators with scissor-like elements

A novel family of extendable kinematic chains, termed dual scissor-like mechanisms (D-SLiM), is proposed in this paper. The chains, which generally have two translational degrees of freedom (DOF), are constructed by linking two identical parallel scissor-like elements. The mobility and singularities of the proposed kinematic chains are discussed. Three such D-SLiM legs are employed to build two 3-DOF scissor-like mechanisms - parallel lower-mobility(SLiM-PaLM) manipulators with “Y” and “△” shapes, termed Y- and △- shaped SLiM-PaLM manipulators, respectively. Due to the large range of motion of each leg, such translational parallel manipulators are capable of being collapsed for storage and deployed in the work area. Common kinematic and simplified dynamic models are derived. The forces in the horizontal links are addressed for analyzing the singularities and stiffness of the D-SLiM. Furthermore, the workspace, stiffness and deployed-stowed length ratio of the SLiM-PaLM manipulators are investigated. Prototypes of the Y- and △-shaped SLiM-PaLM manipulators are fabricated and tested to validate the presented design and analysis.