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Variable Stiffness and Impedance Control of a Soft Pneumatic Actuator With Tunable Collision Dynamics and Trajectory Following.

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Title: Variable Stiffness and Impedance Control of a Soft Pneumatic Actuator With Tunable Collision Dynamics and Trajectory Following.
Authors: Kim, Sung Y.1 sung.joel.kim@gmail.com, Kumar, Nithin S.1 nithin.s.kumar@vanderbilt.edu, Barth, Eric J.1 eric.j.barth@vanderbilt.edu
Source: Journal of Dynamic Systems, Measurement, & Control. May2026, Vol. 148 Issue 3, p1-13. 13p.
Subjects: Pneumatic actuators, Impedance control, Stiffness (Engineering), Robotic trajectory control, Soft robotics, Impact (Mechanics), Adaptive control systems
Abstract: State-of-the-art soft manipulators are unable to vary stiffness continuously, are complex to manufacture, and have limited control bandwidth. In this work, we present a novel planar bidirectional pneumatically actuated soft manipulator that advances all three limitations--the stiffness is continuously tunable by a factor of 1.6, the actuator is manufactured from a single 3D print, and we are able to demonstrate free-space tracking of a time-varying signal. We are also able to modify the impedance of the actuator during a collision using a dynamic model-based feed-forward and feedback controller and demonstrate an increase in virtual stiffness by a factor of 4. The incorporation of feedback resulted in 0.7mm tip position root-mean-square error (RMSE) (a reduction of 47% over the purely feed-forward controller) while tracking a 5'mm amplitude sinusoid up to 0.75'Hz across the entire stiffness range. [ABSTRACT FROM AUTHOR]
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Database: Engineering Source
Description
Abstract:State-of-the-art soft manipulators are unable to vary stiffness continuously, are complex to manufacture, and have limited control bandwidth. In this work, we present a novel planar bidirectional pneumatically actuated soft manipulator that advances all three limitations--the stiffness is continuously tunable by a factor of 1.6, the actuator is manufactured from a single 3D print, and we are able to demonstrate free-space tracking of a time-varying signal. We are also able to modify the impedance of the actuator during a collision using a dynamic model-based feed-forward and feedback controller and demonstrate an increase in virtual stiffness by a factor of 4. The incorporation of feedback resulted in 0.7mm tip position root-mean-square error (RMSE) (a reduction of 47% over the purely feed-forward controller) while tracking a 5'mm amplitude sinusoid up to 0.75'Hz across the entire stiffness range. [ABSTRACT FROM AUTHOR]
ISSN:00220434
DOI:10.1115/1.4070266