Session: 04-08: Emerging Integrated System Applications

Paper Number: 99246

99246 - Planar Design of Multi-Axial Rigid Load-Bearing Tendon Constrained Inflatables 

Inflatable devices are advantageous for their extensive deploy and compact stow capability. Inflatables also can provide rigidity using constraints such as fibers and plates. A novel architectural approach, a tendon constrained inflatable (TCI), was recently introduced to decouple deploy-and-stow capability from functionality. A TCI is a structure composed of an inflatable bladder held between two rigid end caps connected by inextensible tendons. Due to the flexible nature of the bladder and tendons, a vacuumed TCI can reduce to the height of the end caps for compact stow. When a TCI is pressurized, the tendons become taut and resist deformations due to external loads up to a rigid load-bearing threshold. A TCI with taut tendons demonstrates a high increase in stiffness compared to a TCI with slack tendons. Depending on the orientation and placement of tendons, a TCI can provide customizable and tailorable rigid load-bearing capacities. This paper presents the model-based design of planar tendon configurations to provide tailorable multi-axial rigid load-bearing capacities in a TCI to achieve, for example, the largest rigid load-bearing capacities given a package constraint, the smallest package to meet specific rigid load-bearing capacities, and the simplest tendon configuration to meet the required rigid load-bearing capacities. A linear algebraic model describing the relationship between the tendon configuration and the multi-axial rigid load-bearing region in the planar force-moment space with respect to pressure is developed by modelling the small deflection kinematic constraints due to the tendon configuration geometry. A visualization of the TCI’s design space representing the planar rigid load-bearing region reduces the 3 degrees of freedom (DOFs) to 2 dimensions by normalizing against axial force and directly exposes the impact of varying tendon configuration on the multi-axial rigid load-bearing region. A design methodology is developed by considering the effects of design variables such as the package limit, the complexity of tendon configuration, the desired rigid load-bearing region, etc., on the TCI’s design space. The model and the design methodology are experimentally validated for two types of planar tendon configurations given a required rigid load-bearing region: a configuration with the least number of tendons required to provide rigidity in 3 DOFs and a configuration that provides the largest rigid load-bearing region with the smallest TCI package size. This work enables the compact customization of TCI’s tendon configuration to meet desired variable rigid load-bearing capacities in different DOFs and maintain its ability to deploy and stow.

Presenting Author: Ellen Kim University of Michigan, Mechanical Engineering