Design of a new 2 DOF parallel mechanism

We propose a new two-degree of freedom parallel mechanism in this paper. This mechanism was designed in order to improve the kinematic performance and to achieve static balance. We use the pantograph mechanisms in order to change the location of active joints, which leads to transformation of direct kinematic singularities into nonsingularities. The direct kinematic singular configurations of the proposed parallel mechanism occur near the workspace boundary such as those of the serial manipulators, which means that we do not any more suffer from the singular configuration which occurs at the inside of workspace. Hence, the proposed mechanism can overcome disadvantage such as the singular configurations existing in the inside of workspace for a typical parallel mechanism. Using the property that position vector of rigid body rotating about a fixed point is normal to the velocity vector, Jacobian matrix is derived. Using the vector method, two different types of singularities of the proposed mechanism can be identified and we discuss the physical significance of each of the three types of singularities. We will compare the kinematic performance of the proposed mechanism with that of five-bar parallel mechanism. By specifying that the potential energy be fixed, the conditions for the static balancing of the proposed mechanism is derived. The static balancing is accomplished by changing the center of mass of the links.