Research On Design Methods Of TriVariant-B-A 5-DOF Hybrid Robot

This thesis investigates into some issues on conceptual design, dimensional synthesis, precision design and dynamics analysis of a novel reconfigurable 5-DOF hybrid manipulator---TriVariant-B. The following works have been accomplished.Referring to the characteristics of the spherical coordinate parallel mechanism (SCPM), a novel 5-DOF hybrid robot named the TriVariant-B is proposed. The robot is composed of a 2-DOF spherical parallel mechanism (SPM) that is serially connected with a 3-DOF open-loop kinematic chain via a prismatic joint. This design has the merit that a relative workspace/limb-stroke ratio can be achieved.On the basis of inverse kinematic analysis, the singular and isotropic configurations of the 2-DOF SPM are investigated. Consequently, dimensional synthesis of the 2-DOF SPM is carried out by monotonical analysis of the design variables vs. a global conditioning index represented by the mean of the minimum singular value of the Jacobian, leading to the solution of two nonlinear equations due to the limb length constraint and nearly axial symmetry requirement of the kinematic performance.The geometric error model of the 2-DOF SPM is formulated using the full 6×6 Jacobian matrix. It shows that the pose accuracy of the end-effector can be explicitly divided into two components, i.e. compensable pose accuracy and uncompensatable pose accuracy, respectively. The influences of the geometric source errors affecting the uncompensatable source errors are investigated by the sensitivity analysis.The inverse dynamics of the 2-DOF SPM is formulated using virtual work principle. An effective approach is then proposed that allows the upper bound of the actuated joint velocity and torque to be determined in a very quick manner. The effectiveness of this approach has been verified using typical path for flame cutting process. The above-mentioned outcomes have been employed for the development of a brand new 5-DOF hybrid robot for flame cutting.