Thesis
Analysis and design of an auxiliary catching arm for an apple picking robot
Washington State University
Master of Science (MS), Washington State University
05/2020
DOI:
https://doi.org/10.7273/000004112
Handle:
https://hdl.handle.net/2376/125379
Abstract
Significant effort has been made to develop a 7-degree of freedom (DOF) articulated robotic arm system to harvest fresh market apples in a modern apple orchard at Washington State University. The novelty of this design is that it works in tandem with a 2-DOF planar catching manipulator since a key task in robotic harvesting is the collection of the picked fruit in a container. Rather than using a harvesting manipulator to place picked apples in a storage container, the secondary system catches and stores apples at the point of fruit separation in order to minimize path length and improve cycle time. The drop height for the previous design was variable and depended solely on the fruit's height relative to the picking manipulator. The common reviewer feedback is to convert the 2-DOF articulated robotic arm from 2-dimensional motion to fully 3-dimensional motion to minimize the chance of damaging the fruit with bruising. The newly designed 3-dimensional catching robot consists of three revolute joints where the forward linkage is a parallelogram mechanism for keeping the catching end-effector parallel to the picking manipulator's base. A virtual apple field of 505 apples, designed to test the picking abilities of 7 DOF arm, was used to determine the capabilities of this new catching arm design. The target catching efficiency was 90% for the provided virtual apple field with a maximum drop height of 30 cm. The target coordinates for each virtual apple were found by computer simulation in MATLAB. Geometric parameters were selected such that the catching manipulator could reach every possible drop position in the picking manipulator's workspace. The design was completed, fabricated, and validated, utilizing the elegant mechanical linkage design. The workspace analysis showed that it had an acceptable 93% catching efficiency, and as the drop height increased, the efficiency approaches 100%. Definitive inverse-kinematics provided exact joint angles required to catch all catchable apples inside of the workspace. Using these angles, the general equation of motion, using Lagrangian mechanics, yielded the required torque outputs of each of the three motors on the arm. Validation of these torques through laboratory experimentation was considered adequate.
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Details
- Title
- Analysis and design of an auxiliary catching arm for an apple picking robot
- Creators
- ANDREW MICHAEL PORTER - Washington State University, WSU Tri-Cities
- Contributors
- Changki Mo (Advisor) - Washington State University, Mechanical and Materials Engineering, School of
- Awarding Institution
- Washington State University
- Academic Unit
- Engineering and Applied Sciences (TRIC), School of
- Theses and Dissertations
- Master of Science (MS), Washington State University
- Publisher
- Washington State University
- Identifiers
- 99900890785301842
- Language
- English
- Resource Type
- Thesis