Grasp synthesis for purposeful fracturing of object

Abstract

This paper deals with the problem of purposefully failing (breaking) or yielding objects by a robotic gripper. Robotic harvesting is considered as an application domain that motivates this study. A definition of a failure task is first formulated using failure theories. Next, a grasp quality measure is presented to characterize a suitable grasp configuration and systematically control the failure behavior of the object. This approach combines the failure task and the capability of the gripper for wrench insertion. The friction between the object and the gripper is used to formulate the capability of the gripper for wrench insertion. A new method inspired by the human pre-manipulation process is introduced to utilize the gripper itself as the measurement tool and obtain a friction model. The developed friction model is capable of capturing the anisotropic behavior of materials which is the case for most fruits and vegetables. The evaluation method proposed in this study is formulated as a quasistatic grasp problem and can include both fully-actuated and under-actuated grippers. The proposed approach for purposefully breaking objects is validated using experimental results. Objects with different material properties are used to prove the generality of the method. KUKA LightWeight Robot IV is used as the manipulator.