Robert E. Skelton

Tensegrity cell mechanical metamaterial with metal rubber

We present here a design of the unit cell of a mechanical metamaterial based on the use of a tensegrity structural configuration with a metal rubber. Tensegrity combines the use of compression and tension-only elements, and allows the creation of structures with high rigidity per unit mass. Metal rubber is a multiscale porous metal material with high energy absorption and vibration damping capabilities under compressive load. The combination of the two structural and material concepts gives rise to a mechanical metamaterial with increased energy absorption and tuneable nonlinearity under quasi-static, vibration, and impact loading. We develop prototypes, models, and perform tests under static and dynamic loading conditions to assess the performance of this mechanical metamaterial.We present here a design of the unit cell of a mechanical metamaterial based on the use of a tensegrity structural configuration with a metal rubber. Tensegrity combines the use of compression and tension-only elements, and allows the creation of structures with high rigidity per unit mass. Metal rubber is a multiscale porous metal material with high energy absorption and vibration damping capabilities under compressive load. The combination of the two structural and material concepts gives rise to a mechanical metamaterial with increased energy absorption and tuneable nonlinearity under quasi-static, vibration, and impact loading. We develop prototypes, models, and perform tests under static and dynamic loading conditions to assess the performance of this mechanical metamaterial.

Design and Control of Growth Adaptable Artificial Gravity Space Habitat

We seek to solve 5 unsolved problems in space: Providing gravity, food, radiation protection, and a growable technology that enlarges the habitat as economics allow. A full-scale center for space research is needed to keep the gravity gradient across the human body less than 6%, to avoid nausea and other health issues. The artificial gravity is provided by centripetal forces in a spinning habitat. The agricultural space occupies the low gravity part of the habitat. The radiation protection requires 5m of regolith from ISRU. The habitat will be roomy and research can determine the level of gravity required for human health, as ONLY a large space habitat can do (the plan grows to 225m radius yielding only 1% gravity gradient). The tensegrity paradigm is used for the design of the growth adaptable space structure. The mass required to sustain the centrifugal forces and the atmospheric pressure is minimized using the tensegrity structural paradigm. The transient dynamics of the structure during pressurization is shown. The growth strategy is planned for continuous occupancy of humans and agriculture. A control scheme is provided to stabilize the sun-pointing attitude, while spinning at a desired rate for artificial gravity. Numerical simulations are used to demonstrate the efficacy of the control laws for the space habitat system.

ℋ 2 optimal sensing architecture with model uncertainty

In this paper we present an integrated approach to control and sensing design. The framework assumes sensor noise as a design variable along with the controller and determines l1 regularized optimal sensing precision that satisfies a given closed loop performance in the presence of model uncertainty. We pursue two approaches here. In the first approach, we represent the uncertainty as polytopic and, in the second formulation, we model it using integral quadratic constraints (IQC). We apply these two approaches to an active suspension control and sensing design problem and demonstrate that the IQC based approach provides better results and is able to incorporate larger system uncertainty.