On the Development of Reactionless Spatial 3-dof Parallelepiped Mechanisms

In this paper, the design and dynamic balancing of a novel 3DOF parallel mechanism referred to as parallelepiped mechanism are addressed. Two types of actuation schemes of the mechanism are considered. The balancing equations are derived by imposing that the center of mass of the mechanism is fixed and that the total angular momentum is constant with respect to a fixed point. Optimization is performed to determine the counterweights and counter-rotations based on the balancing conditions. The dynamic simulation software ADAMS is used to simulate the motion of the 3-DOF parallelepiped mechanisms and to verify that the mechanisms are reactionless at all times and for any trajectory. A numerical example of a reactionless 3-DOF parallelepiped mechanism is given. It is shown that 3-DOF parallelepiped mechanisms can be completely balanced and used to synthesize 6-DOF reactionless manipulators. Additionally, the inverse and direct kinematic problems of the 3-DOF parallelepiped mechanisms as well as simulation tools for demonstrating the characteristics of the mechanisms are also introduced in this paper.