Variable-Stiffness Control of a Dual-Segment Soft Robot Using Depth Vision

A soft-bodied robot exhibits prominent dexterity due to the soft nature of its material. However, the softness can become a burden when the robot needs to interact with the environment, given that the targeted object is usually much stiffer than the compliant soft robot. A variable-stiffness soft ro...

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Bibliographic Details
Published in:IEEE/ASME transactions on mechatronics 2022-04, Vol.27 (2), p.1034-1045
Main Authors: Lai, Jiewen, Lu, Bo, K. Chu, Henry
Format: Article
Language:English
Subjects:
Control systems design
End effectors
Jamming
Manipulators
RGB-D perception
Robot control
Robot kinematics
Robotic surgery
Robots
Segments
soft robot
soft robot materials and design
Soft robotics
Softness
Stiffness
tendon/wire mechanism
Tendons
Tensioning
Tuning
visual servoing
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Summary:A soft-bodied robot exhibits prominent dexterity due to the soft nature of its material. However, the softness can become a burden when the robot needs to interact with the environment, given that the targeted object is usually much stiffer than the compliant soft robot. A variable-stiffness soft robot, fusing the merits of softness and stiffness, is in favor of many applications, such as robot-assisted minimally invasive surgeries. In this article, we propose a tendon-tensioning method to adaptively control the stiffness of a dual-segment tendon-driven backboneless soft robot based on depth vision. A depth-vision-based closed-loop controller is designed for stiffness compensation when the manipulator is subjected to the external load. Experiments were conducted to examine the feasibility and performance of the proposed method. The results confirm our control scheme on the robot with controllability of stiffness up to 132%. Based on our method, the manipulator with an external payload can follow designated trajectories with positioning errors reduced up to 50% comparing to that with open-loop control. Without quantifying the instantaneous stiffness, this work contributes a generalized method for tuning the stiffness of the tendon-driven soft robots in the presence of external disturbances without onboard sensing.
ISSN:1083-4435
1941-014X
DOI:10.1109/TMECH.2021.3078466