https://par.nsf.gov/servlets/purl/10197584

Variable Stiffness Robotic Arm for Safe Human-Robot Interaction Using Layer Jamming

Modeling and control of inherently safe robots with variable stiffness links

Current robotics industry trends show an increased interest in the interaction between humans and robots in a variety of fields, ranging from collaborative robots in manufacturing to assisted medical devices in the medical field. One limiting factor in present applications is the ability to actively morph these robotic structures and control their stiffness using the same type of actuation system. This paper focuses on developing an actively controlled, variable stiffness structure that uses a pneumatic system for both morphing and locking the structure shape. The structure design integrates Pneumatic Artificial Muscles (PAMs) that are pressurized to control shape morphing. The pressurization of the PAM provides a radial force that allows bi-directional morphing based on the pressurization scheme. Layer Jamming, which utilizes varied friction between thin sheets based on pressure, is used to control the variable stiffness of the structure. In this paper, a control model is developed to predict the morphed curvature of the structure based on the input actuator pressure. This experimental control model is also validated using a theoretical pseudo-rigid-body model. The repeatability and accuracy of morphing is also discussed. Through experimental testing, a measure of the stiffness variation range of the structure is also developed. This novel research would positively impact the robotics field by creating lightweight morphing structures that are flexible and easily deformed, but also stiff with high load-carrying capability for increased human-robot interaction.

result

https://par.nsf.gov/servlets/purl/10105211

An Actively Controlled Variable Stiffness Structure via Layer Jamming and Pneumatic Actuation

The purpose of this research is to design, fabricate and test a tendon driven a continuum soft robot with three modular segments, each of which has a tunable stiffness enabled by layer jamming technology. Compared with previous studies, the robotic arm design of this project has a modular structure, which means the length of the robotic arm can be adjusted by addition of extra arm modules/segments to the existing robotic prototype. Furthermore, the new arm prototype supports motion within a 3-dimensional space. To achieve the goals, the design and fabrication for the variable stiffness robotic arm with compliant main structure and layer jamming mechanism has already been finished. Design and fabrication of the connector has also been finished to integrate several link modules into one robotic arm with multiple segments. The actuator located at the base of the arm has already been designed and tested. Finally, a stiffness test of one arm segment was conducted to verifying the load carrying capacity of the variable stiffness robotic arm, then the stiffness ratio of the layer jammed structure was calculated to analyze the stiffness improvement compared with unstiffened soft robot.

Variable Stiffness Robotic Arm for Safe Human-Robot Interaction Using Layer Jamming

Citations

Modeling and control of inherently safe robots with variable stiffness links

An Actively Controlled Variable Stiffness Structure via Layer Jamming and Pneumatic Actuation

Development of a Tendon Driven Variable Stiffness Continuum Robot with Layer Jamming

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