Constraint analysis and theoretical development of multi-furcation and reconfiguration in mechanisms

• Main Author: Qin, Yun
• Published: King's College London (University of London) 2013
• Subjects: 621.8
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.628326

Multi-furcation and reconfiguration in mechanisms interested many researchers over past twenty years since the early investigation by Wohlhart in 1996. This Dissertation systematically investigates multi-furcation and reconfiguration in mechanisms including recognition of motion branches, factors causing motion branches and how these factors result in different motion branches in serial and parallel mechanisms by line geometry. Among these factors, relative orientations of joint-axes and the corresponding multi-furcation and reconfiguration are further discussed. The Dissertation starts from multi-furcation in the derivative mechanism from the "queer square" origami fold by allowing a full rotation of joints and reveals fourteen motion branches with four different motions as single translation, double translations and other two single screw motions about perpendicular axes. Two kinds of multi-furcation are demonstrated by the derivative mechanism, on account of its first six branches maintaining unchanged relative orientations of joint-axes and its last eight branches caused by variable relative orientations of joint-axes. Mobility and motion characteristics of the derivative mechanism are discussed. The Dissertation then studies reconfiguration with different motion characteristics caused by different relative orientations of joint-axes and proposes a new parallel mechanism with two motion branches. The transformation between spatial translational motion branch and spatial rotational motion branch is caused by different configurations of reconfigurable joints. Constraint disposition and motion characteristics are presented in group-algebraic and screw-based analyses. A discussion of motion branches with different motion directions caused by variable relative orientations of joint-axes is provided. The 3-US and 3-RRS parallel mechanisms with reconfigurable joints are proposed followed by motion investigations. The platform implements anticlockwise folding and clockwise deploying motion in the first motion branch and the inverse motion as clockwise folding and anticlockwise deploying motion in the second motion branch. According to special configurations and motion features, novel mechanisms presented in this Dissertation have wide applications in fields of manufacture with multiple tasks, design of architectures and aerospace industry.