Inflatable devices have been used in various applications due to their low-cost, light weight, simplicity, and ability to compactly stow yet deploy to large sizes with complex geometries. Recently, the field of soft robotics has added active shape change to the otherwise static functionality of inflatables. However, the required complex multi-chamber structures and active pressure control sacrifice many of the advantages of inflatables, including simplicity and stowability. Many commercial applications require only passive shape change, or posability, where a user can manipulate the shape of the device manually, and the device simply holds its new posed shape. This paper explores a new approach that provides posability while maintaining stowability and other inherent advantages of inflatables through the use of internal string-like tensile elements, leveraging concepts in the field of tensegrity mechanisms. Tensegrity constrained inflatables provide posable motion by allowing tensile strings internal to the inflatable to thread through loops as the shape is changed, where friction between the strings and loops retain the new pose. Graphical instantaneous center kinematic analysis techniques for traditional linkage systems are extended to include threaded tensegrity mechanisms, enabling analysis and design of complex posable tensegrity structures. A prototype implementing a simple example of posable kinematics, bending with 1 DOF, demonstrates posable behavior which is quantified in terms of the force required to change pose at different angles and pressures, displaying bistable behavior which is explained through the use of the IC kinematic analysis. The kinematic techniques are also applied to the design of one degree of freedom functional building blocks which are combined to create tensegrity configurations providing two degree of freedom posability in two and three dimensions which are demonstrated through multiple hardware prototypes. The novel technology and design methods presented in this paper provide a foundation for the development of a class of new user-interactive inflatable devices with posable functionality and deploy and stow capability


Posable Tensegrity-Constrained Inflatable Kinematic Graphical Analysis

Division / Sponsors: 
Aerospace Division

Paper Proceedings: https://asmedigitalcollection.asme.org/SMASIS/SMASIS2020/volume/84027

SMASIS2020 - Virtual Conference

Supporting the need among researchers worldwide for additional online and multimedia content, ASME now offers the ASME Conference Video Collection. This platform will collect and provide long-term access to conference presentation videos, encompassing all technology areas within ASME's technical conference and events program. About 30,000-40,000 engineers across all mechanical engineering and related disciplines participate in ASME conferences each year. This includes authors of approximately 6,000 to 8,000 technical papers published by ASME, the majority of whom also submit video presentations for our virtual conferences. The video collection will be available as an add-on to existing product packages or as a separate subscription.