Effect of gravity on the dynamic behavior of manipulators

Abstract

The gravity induced forces on revolute robot links dominate over the dynamic induced forces, particularly at low speeds. This study presents an innovative method to introduce the effect of gravity in the dynamic capability of robot arms. Using the concept of fields, the gravity induced forces acting on individual links are replaced by a single force, called here the generalized weight of the arm. The generalized weight is a force that acts at the end point and its magnitude and direction are functions of the configuration of the arm. Based on the generalized weight field and the generalized inertia tensor introduced by other researchers, the generalized gravitational acceleration field is introduced. This is a vector field whose strength at any point of the work volume indicates the acceleration that is induced on the end effector due to the effect of gravity. The generalized weight and the generalized gravitational acceleration fields are then related to the generalized ellipsoid of inertia and the dynam...