| This dissertation deals with the key issues relevant to design of configuration and control of motion branch transformation for reconfigurable mechanisms and their applications to the metamorphic walking robots.It develops a new synthesis method of reconfigurable mechanisms based on singular configuration,which reveals the transformation mechanism from tranditional mechanisms and reconfigurable mechanisms,and pioneers the joints velocity control for motion branches transformation and creates the metamorophic walking robots.The main contents of this dissertation are summarized as follows:(1)Based on the local properties of singular configurations on geometric constraints and algebraic relationships,this dissertation proposes a novel synthesis method of multi-bifurcated reconfigurable mechanisms by singular configurations.At first,a singular configuration,which satisfies geometric constraints of all the desired motion branches,is designed with suitable parameters of joints axes and links length.Then higher order kinematic analyses and singular value decomposition(SVD)numerical method are combined to identify and solve all the motion branches and to reveal their connectivity in configuration space.Using this synthesis method,two novel multi-bifurcated double-cnetered 6R linkages are invented.Both linkages have the desired motions branches,include two various spherical four-bar linkages and a linesymmetric Bricard linkage or Bennett linkage.The proposed synthesis method is simple,and task-orieted to design motion branches.(2)Based on the equivalent model of mechanisms,this dissertation designs a reconfigurable eight-bar linkage derived from the 8-Kaleidocycle.Using the geometrical properties,the reconfigurable eight-bar linkage is simplified as a spherical four-bar linakge to solve the close equations.Based on the analysis of the sagittal planes of configuration space,the relationship between bifurcation and structural parameters of a special line and plane symmetric Bricard linkage is revealed.Based on the joints velocity constraints obtained by higher order kinematic analyses,this dissertation proposed a novel method for transformation of motion branches,which the additional joints velocity constraints are added to increase the demension of actuation without additional actuators.(3)Inspired by various walking patterns and spinal structure of legged animals,an metamorphic walking robot is designed to conduct operations in different environments,particularly the extreme and restricted occasions,through its structure reconfiguration.The metamorphic walking robot uses metamorphic eight-bar linkages as its trunk,which enables the robot to transform into three typical shapes that correspond to three kinds of animals: mammals,arthropods,reptiles,and combines all the features of locomotion of the three kinds of animals into one robot.Based on the mobility and bifurcation properties of the metamorphic eight-bar linkage,the actuation scheme and the best transformation path between various biomimetic shapes are developed.Compared with the traditional walking robot,the metamorphic quadruped robot can use the mobility of trunk and legs simultaneously,which enables the robot with higher speed and stability,more flexible,and more adaptive to complex terrain environment. |
