Development of 2-DOF Manipulator Using Straight-Fiber-Type Pneumatic Artificial Muscle for Agriculture

Abstract

Recently, Japan has been witnessing an increase in the average age of agricultural workers and a decrease in the number of new entrants into farming, both of which are progressing year by year due to the country’s declining birthrate and aging population. As a result, expectations for substitution by robots and human-robot collaboration are rising. Therefore, we propose a robot arm built using straight-fiber-type pneumatic artificial muscle (SF-PAM) and a noncircular pulley. SF-PAM is sealed and has no sliding parts; thus, it has excellent dustproof and waterproof properties and is suitable for work on farms. However, due to its structure, the SF-PAM has a nonlinear relationship between the contraction force and the amount of contraction, and the output torque is insufficient near the limit of its range of motion. As a solution to this problem, a noncircular pulley is introduced to compensate for the output torque and expand the range of motion. Based on this, this study aims to realize fruit harvesting operation using a robot arm. In this paper, a two-degree-of-freedom robot arm was developed, and position control experiments were conducted to verify the tracking with the target value. As a result, the mechanical equilibrium model of the wire-pulley mechanism was found to be valid for this robot arm. However, issues were found due to the arrangement of the SF-PAM and the shape of the noncircular pulley.