Tensegrital Wheel for Enhanced Surface Mobility

ProtoInnovations introduces the "tensegrital wheel" an inventive concept for wheeled locomotion that exploits the geometric and mechanical attributes of a tensegrity structure to engage with the terrain in an effective and efficient manner. The tensegrital wheel emulates the behavior of a variable pressure tire without the need for an inflation system. The construction of the tensegrital wheel is such that it absorbs and diffuses ground forces fairly evenly. The stiffness of the tensegrital wheel can be tuned to match the demands of a given environment that the wheel is to operate in or can be adjusted on-the-fly. These attributes allow for better adaptation to the terrain thus increasing the amount of thrust that can be generated at the wheel/ground interface, and improving a vehicle's dynamic response and obstacle negotiation abilities. We assert that the tensegrital wheel can be designed to achieve a very high strength-to-weight ratio and exceptional capacity for long-life specifically in the context of planetary exploration. For the Phase I of this SBIR project we aim to prove the feasibility of the tensegrital wheel and quantify its capabilities and limitations through analysis, prototyping, and testing. The technology proposed here is of particular value to planetary missions involving mobility over various terrain geometries and ground compositions.

The tensegrital wheel would benefit future NASA planetary exploration missions by enhancing the mobility and controllability of surface exploration rovers. The ability of the tensegrital wheel to better conform to the terrain and its inherent capacity to evenly distribute reaction loads through its structure would result in measurable improvements in in-soil traversability, obstacle climbing, stability, and response to dynamic events. The proposed wheel system affords significant advantages over existing wheel systems for planetary rovers. While the structural design of existing wheel systems provides compliance approximating that of a pneumatic tire, such compliance is fixed by the design. Pneumatics, while providing adjustability of compliance by varying tire pressure, are impractical in application to a planetary rover due to requirements for gas supply, pumps, valves, etc. and are furthermore subject to leakage at the tire, piping and pneumatic swivels which are requires to make such a system work.

The utility of the tensegrital wheel goes beyond planetary rover missions. Terrestrial systems may take advantage of the unique performance characteristics of this wheel design. Many military vehicles currently use active control of tire air pressure to adjust compliance of the tires and deal with deflation due to punctures. As with planetary rover systems, using the tensegrital wheel for this application negates the need for pumps, pneumatic lines and pneumatic rotary joints. No pneumatic tire means no risk of puncture. In addition, the tensegrital wheel offers a lightweight alternative to unconventional wheel designs. Farm and industrial vehicles can find application for the tensegrital wheel as well. A tractor, for instance, might negotiate cross slopes more safely and effectively by selectively adjusting the compliance of the wheels so that the uphill wheels are more compliant than the downhill wheels providing a measure of center-of-gravity control. Likewise the pose of industrial vehicles such as manlifts can be provided with additional control through the use of the tensegrital wheel technology.

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