Kinematic study of overconstrained linkages and design of reconfigurable mechanisms

• Main Author: Song, Chao-Yang.
• Other Authors: Chen I-Ming
• Format: Theses and Dissertations
• Language: English
• Published: 2014
• Subjects: DRNTU::Engineering::Mechanical engineering::Kinematics and dynamics of machinery
• Online Access: http://hdl.handle.net/10356/55261
• Institution: Nanyang Technological University

This dissertation explores the possibilities to design reconfigurable mechanisms using the kinematic and geometric properties of existing overconstrained linkages with revolute joints. Despite the large number of overconstrained linkages reported in literatures, there lacks of a comprehensive study into the relationship among them, which limits the understanding of the overconstrained linkages and their potential applications. The first part of this dissertation has been devoted to the systematic generalization of a series of double-Goldberg linkage families, in which the relationship between a number of existing linkages and their variational cases has been revealed. The common link-pair and common Bennett-linkage methods have been proposed to connect a Goldberg 5R linkage and a subtractive Goldberg 5R linkage to form six types of overconstrained linkage closures. Three sub-families, Wohlhart’s double-Goldberg linkages, mixed double-Goldberg linkages and double-subtractive-Goldberg linkages, have been generalized to represent the original cases, variational cases and subtractive cases of double-Goldberg linkage family. A substantial source of design for reconfigurable mechanisms in the Bennett-based linkage family has been presented in this part. In the second part, the kinematic study has been focused on the general line-symmetric Bricard linkage. The closure equations of the original and revised general line-symmetric Bricard linkages have been derived in explicit forms. For the general line-symmetric Bricard linkage, two independent and distinct linkage closures have been discovered. It has also been revealed that the revised cases are equivalent to the original cases with different setups on joint-axis directions. The potential of designing the reconfigurable mechanism through kinematic singularity has been demonstrated with the bifurcation behavior of the special line-symmetric Bricard linkage with zero offsets. The conceptual designs of reconfigurable mechanisms based on overconstrained linkages have been explored in the final part. Both the analytical and construct method have been presented to design morphing structures using overconstrained linkages. Based on the double-Goldberg linkage and the general line-symmetric Bricard linkage, reconfigurable mechanisms have been designed with multiple operation forms between 6R and 4R linkages. Furthermore, a generic method of link-pair replacement has been developed for reconfiguration purpose, which has been applied to reconfigure the topology of different Bennett linkage networks in order to obtain different overconstrained mechanisms. Results in this dissertation could lead to the substantial advancement in the design of reconfigurable mechanism with kinematic singularities. In the future work, the methods could be applied to design advanced reconfigurable robotic platforms with less actuators but more structural support.