Analysis and Design of the 2PRU-1PRS Manipulator for Vibration Testing

Parallel manipulators, compared to serial manipulators, have some interesting properties, such as high stiffness, low inertia, high velocity, good accuracy and large payload capacity. Thus, parallel manipulators, especially the ones with one translation and two rotations as outputs (1T2R), are being increasingly studied. The 3PRS mechanism is a very typical example of this category, but it has accuracy problems caused by the parasitic motion, and low orientation capability. To overcome these problems, new mechanisms are being studied, such as the 2PRU-1PRS manipulator. As the 3PRS manipulator, the degrees of freedom of the 2PRU-1PRS are one translation along the Z-axis and two rotations about the X- and Y-axes. The advantages are that the parasitic motion appears only in one direction instead of in three and that the orientation capability is higher. In this paper we present the design of a 2PRU-1PRS mechanism suitable for vibration tests. In order to do this, we develop a code with an intuitive GUI (graphical user interface) that, for given variable limits, solves the inverse kinematic and dynamic problem for all the variable combinations and obtains the combination that consumes less power for an harmonic trajectory. Taking the simulations results into account, we propose a design that fulfils all the requirements for vibration tests in the three axes.Copyright © 2014 by ASME