A classification method for input joints of planar five-bar mechanisms

This paper presents a classification method for input joints of planar five-bar two-degree-of-freedom mechanisms or in-parallel manipulators. This classification method emphasizes on the applicability of the classification method in input actuator selection and dimension design. Input joints considered in this study are the two ground joints of five-bar mechanisms. The criteria applied to classify the input joints are based on practical types of motions of drivers. The classification method classifies input joints of all five-bar mechanisms into four classes and they are incomplete-rotation joints, unconditioned complete-rotation joints, position-conditioned complete-rotation joints, and coordination-conditioned complete-rotation joints. Three groups of sets of symbolic inequalities in link lengths, which can be used to identify the classes of the input joints of all five-bar mechanisms, are derived, applying geometric algebra formula and simple logic operations. Also included in this study are the verification of the completeness of the classification method and explicit equations, in link lengths, of rotation ranges for input joints of all classes. Examples are given to demonstrate how to use the classification method to determine the class of input joints and eligible motion ranges of the input joints. Finally, a discussion is given for possible applications of this classification method in design.