Structural Analysis And Synthesis Of A Class Of Reconfigurable Parallel Mechanisms

With the development of modern science and technology,and the requirements of reconfigurability and multiple functionality for machines used in industrial world,reconfigurable parallel mechanisms have been one of the new research hotpots in the field of mechanisms and robotics.In this paper,the structural analysis and synthesis of a new class of reconfigurable parallel mechanisms are studied.A class of reconfigurable single-loop closed chains is proposed.Based on the new single-loop closed chains or the existing single-loop closed chains,a new class of reconfigurable parallel mechanisms based on the single-loop closed chains is obtained.The reconfigurable parallel mechanism is divided into two categories:the reconfig-urable parallel mechanism with invariable geometric constraints of the limbs and the re-configurable parallel mechanism with variable geometric constraints of the limbs.The composition principle of reconfigurable parallel mechanisms is revisited using the theor-y of linear algebra,resulting in three classes of reconfigurable parallel mechanisms with variable geometric constraints which can be generated by three types of reconfigur-able limbs in terms of actuation and constraints.By using Hook hinge and spherical five-bar mechanism to replace two connected hinges of planar four-bar mechanism and planar-five-bar mechanism,a new class of reconfigurable single-loop closed chain is obtained.The new reconfigurable single-loop closed chains have different kinematic characteristics due to the different combination of Hook hinge and spherical five-bar linkages.Some of them have the characteristic of bifurcation motion and the others have the property of metamorphic motion.A class of reconfigurable hybrid chain is obtained by integrating the reconfigurable single-loop closed chains with a serial limb with changeless degrees of freedom.A new class of reconfigurable parallel mechanism is obtained by using reconfigurable hybrid limbs to connect the moving platform and the fixed based.One kind of the new reconfigurabl parallel mechanisms has bifurcation motion and the others have metamorphic motion.A family of metamorphic hybrid chain is obtained by integrating the decoupling single-loop closed chain with a serial limb with changeless degree of freedom.A new class of metamorphic parallel mechanism is constructed by using metarmorphic hybrid limbs to connect the moving platform and the fixed based.It is found that these metamorphic parallel mechanisms do not encounter constraint singular configurations and self-motion of sub-chain of a leg during reconfigurationTwo new kinds of active reconfigurable limb with suitable constraints are obtained A new class of parallel mechanism is presented with active reconfigurable branch with suitable constraints.The forward and inverse kinematics of the reconfigurable parallel manipulator are carried out,and the complete Jacobian matrices under different working modes are established,and its singularity is analyzed.