# GM project: Common grasp search algorithm

## Contents

### Reasearch purpose

This work addresses the problem of designing an End Effector for a robotic arm which is able to grasp a given set of objects. The purpose of this work is to develop an algorithm which will find a configuration and design of a universal end-effector for a set of objects. With given a set of all CAD models of the parts, the idea is to design an end-effector that is universal in the sense of being able to hold a wide set of components for multiple manipulation tasks. The algorithm will be able to characterize the objects geometries and find a configuration for grasping them. An optimal configuration is the one which can stably grasp the object even under the application of external wrench due to the task being done, i.e., we require Force-Closure grasp.

### OCOG Algorithm

The OCOG (Object COmmon Grasp) algorithm developed, searches for a common grasp over the set of objects. The search algorithm maps all possible grasps for each object which satisfy a quality criterion. The mapped grasps are represented by feature vectors in a high-dimensional space. This feature vector describes the shape of the gripper. We generate a database of all possible grasps for each object in the feature vector space. Then we use a search algorithm for intersecting all possible grasps over all parts and finding a common grasp suitable for all objects. The search algorithm utilizes an index structure termed kd-tree for representing the database of the sets of feature vectors. The kd-tree structure enables an efficient and low cost search for common points between the sets. Each point (feature vector) is the grasp configuration for a group of objects, which implies for the future end-effector design. The final step classifies the objects to grasps found, according to the common points found. The algorithm will be useful for assembly line robots in reducing end-effector design and manufacturing time and final product cost.

File:Gm-logo-small.jpg

This work is supported by General Motors Corp. Ltd.

### Publications

1. Avishai Sintov, Srinivas Raghothama, Roland Menassa and Amir Shapiro, *A Common 3-finger grasp Search Algorithm for a Set of Planar Objects*, IEEE International Conference on Automation Science and Engineering (CASE), pp. 1091-1096, August 20-24, 2012, Seoul, Korea.

2. Avishai Sintov, Ronland Menassa and Amir Shapiro, "OCOG: A Common Grasp Computation Algorithm for a Set of Planar Objects", Journal of Robotics and Computer-Integrated Manufacturing. Vol 30 (2), 124-141, April 2014.

3. A. Sintov, R. Menassa and A. Shapiro, "Technical report - 3D-OCOG: A Common n-finger grasp Search Algorithm for a Set of 3D Objects", Technical report, Dept. of Mechanical Engineering, Ben Gurion University, 2012.

4. Avishai Sintov and Amir Shapiro. *On the computation of a common 3-finger grasp for a set of 3D objects*, Israeli Conference on Mechanical Engineering (ICME) Oct. 2012, Tel-Aviv, Israel.