Design Theory And Methodology Of A New 3-DOF Parallel Mechanism

This dissertation proposes the theory and methodology of the design of a 3-DOF parallel mechanism with asymmetrical architecture used for micro machining. The main content consists of conceptual design, workspace synthesis and analysis, forward position analysis, statics and static balancing. The following contributions have been made.1 Based on the theory of structure synthesis of sub-6 DOF parallel mechanisms, the conceptual design of a novel 3-DOF PKM named TAM is analyzed in detail. It consists of a constrained limb and several unconstrained limbs and have the same type and degrees of freedom with SKM400 which indicates that the TAM inherits all structural characteristics of SKM400.2 By considering the restriction of the parallelogram, a dimensional synthesis method is proposed. The investigation of the effects of the dimensional parameters on the kinematic performance of the TAM is conducted by inducing a set of appropriate constraints such as axially symmetric manipulability and maximum/minimum length ratio of the UPU limb. As the results, the optimal kinematic design of the TAM is implemented by solving a set of nonlinear algebraic equations. It reveals that the TAM has competitive kinematic performance in comparison with the SKM400.3 The forward position analysis of the TAM is carried out by using analytical and two numerical methods. The result of analytical method reveals the TAM has unique solution to special layout. Newton-Raphson method and the Jacobian numerical method based on inverse position are used for the forward position problem of the TAM. Despite of difference in accuracy, the two methods are both efficient for real-time monitor.4 Amendment of virtual displacement is used for statics analysis of the sub-6 DOF asymmetrical PKM. The virtual displacement is in conjunction with the influence coefficients and generalized coordinates, so the generalized velocity and virtual displacement are unified. The spring is used and with parametric optimization, the static balancing for TAM is achieved.The outcome of this dissertation has provided a complete theoretical package for the development of the TAM which is being used as a plug-and–play module to build a novel multi-functional device for micro machining. And it's also suitable to the development of other similar parallel mechanism.