Wrench capability analysis of redundantly actuated spatial parallel manipulators

From a design perspective, it is important to find the maximum load which can be applied or sustained by a particular parallel manipulator. Wrench capability analysis is necessary for this purpose. Recently, two methods, namely, a numerical, optimization-based scaling factor method and an analytical method, have been proposed for determining the wrench capabilities of redundant planar parallel manipulators. In this work, these methods are extended to redundant 6-DOF (degree-of-freedom) spatial manipulators. The methods are applied to the spatial 3-RRRS device. Comparison between the two methods is made. The results show that the analytical method is more efficient in determining maximum wrench capabilities than the scaling factor method. The results for four different cases studied under the analytical method are also presented.