(Dr. Kok-Meng Lee, advisor)

"Quasi-static Force Analysis of an Automated Live-bird Transfer System"

Abstract

Flexible fingers have been found to be potentially useful for handling natural, dynamic objects (such as broilers) in meat processing industries since their compliance can accommodate a range of sizes, shapes and natural reactions among the objects.  However, despite the increasing use of flexible rubber fingers in the poultry processing industry, these fingers are often designed empirically. The ability to predict the contact forces and stresses experienced by a flexible finger during to grasping could offer a more cost-effective design of a grasping mechanism.

The primary objective of this thesis is to characterize the forces applied by a rotating flexible finger on a natural, moving object such as a broiler in a poultry-processing plant. Since the contact area in such an application depends on the posture of the bird as it moves through the flexible fingers, a machine-vision algorithm to detect the bird’s posture at the entrance of the grasping mechanism was developed based on analysis of the leg kinematics of the bird. The effect of contact forces due to grasping has been studied by experimental simulation, which determined the effects on the contact forces of the rotational speed, the initial position of the finger with respect to the bird’s arrival, and the stiffness of the finger.   Two methods are used to analyze the effects of stiffness on the contact forces.  The first method uses an analytical model based on the Frisch-Fay flexible bar theory. This method provides an approximate closed-form solution for determining the force at the contact point. The second method, using Finite Element Method (FEM) computation, predicts the stress distribution around the contact area. The results of both methods have been verified experimentally using two different types of rubber finger, and results agree well with the conclusions reached analytically.

The results of these analytical and experimental investigations were used in the development of a leg-presentation subsystem of an automated live-bird transfer system, which consists of a compliant grasping mechanism. This research has immediate application in the poultry industry where a system that automates transfer of live birds is preferred over the expensive and unpleasant task of manual operation.