Effect of gravity on the static behavior of manipulators
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Abstract
The gravity-induced forces on revolute robot links dominate over the dynamic induced forces, particularly at low speeds. These forces, however, are generally ignored in conceptual analysis works due to the ensuing simplifications that their omission bring about. The force ellipsoid, the dynamic manipulability ellipsoid, and the generalized ellipsoid of inertia introduced by some researchers are but a few examples. For robot-arm control applications, the effect of gravity is usually isolated from the dynamic equations and then compensated for by the robot controller.
This study presents a method to introduce the effect of gravity in the static analysis 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 endpoint, and its magnitude and direction are functions of the configuration of the robot arm. The generalized weight field is then integrated with the force ellipsoid to result in the true force that a manipulator can apply to its environment. Since the system is conservative, the generalized weight is considered to be the gradient of a potential field called the generalized potential field. This field alone can illustrate the overall effect of gravity on the manipulator throughout its work volume.
Keywords
Potential Field Conceptual Analysis Static Behavior Control Application Work VolumePreview
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