Input/output force analysis of Stewart platform type of manipulators

Abstract

This paper proposes a method to evaluate kinematic structures of a Stewart platform type of manipulator based on the relationship between actuator forces and output forces/moments of the mechanisms. The input/output force analyses proposed so far have been based on the manipulator Jacobian, in which forces and moments are dealt with together. However, it is not natural to deal with both force and moment together, since the force and the moment have different dimensions. The authors analyze manipulators by dealing with the output forces and the output moments independently. They evaluate an output force ellipsoid and an output moment ellipsoid for input force vector whose Euclidean norm is equal to one. The kinematic structure is then evaluated based on the force ellipsoid and the moment ellipsoid of the moving platform. The method is natural and intuitive and is useful for the design of the manipulator kinematic structure.