Parallel Mechanism-Type Skill-Assist Arm Using a Passive-State Actuator to Aid Movement of Limbs
Kengo Tanaka, Hiroaki Kozuka, Hiroshi Tachiya
Abstract
Robotic arms equipped with passive-state actuators to assist beginners in performing upper-limb motions have been-developed for tasks such as welding requiring precise positioning. The arms are equipped with position-controlled actuators, one of which can be switched to a passive-state actuator by turning off its excitation. When the passive-state actuator is active, the operator can directly input motion, and the robot assists in positioning along a target trajectory by coordinating with the operator's motion and selectively switching actuator excitations. A three-degree-of-freedom (3-DOF) serial-type arm using the above method has been reported in prior work. However, it exhibited issues such as motion discontinuities caused by inertial effects during excitation switching. To address these problems, this study proposes a lightweight arm based on a parallel mechanism, incorporating torque control at the passive-state actuator to achieve stable assistance. A prototype was fabricated, and experiments were conducted in which the arm assisted subjects—assumed to be beginners—in upper-limb positioning tasks. The experimental results confirmed that the proposed arm effectively assists in positioning and confirms practical feasibility.
BibTeX
@inproceedings{ral2026_parallelmechanis,
title = {Parallel Mechanism-Type Skill-Assist Arm Using a Passive-State Actuator to Aid Movement of Limbs},
author = {Kengo Tanaka and Hiroaki Kozuka and Hiroshi Tachiya},
booktitle = {RA-L 2026},
year = {2026}
}