Design, Assembly, and Testing of Compliant Spring Tires for Lunar Rovers

With a renewed interest in the Moon and the need for autonomous lunar rovers that drive longer distances and operate over extended durations, designing efficient and robust mobility systems is paramount. Created by NASA Glenn Research Center for planetary rover missions, the spring tire is a compliant airless tire consisting of hundreds of coiled springs woven together to create a toroidal-shaped mesh wheel that can deform to uneven terrain, providing additional durability and traction. This work aims to apply this technology to two robotic testbeds: ERNEST, an autonomous rover built at the Jet Propulsion Laboratory, and IPEx, a regolith mining robot built at Kennedy Space Center. This paper discusses the modeling of these spring tires with numerical methods, along with the design and assembly of two sets of spring tire prototypes for use on the aforementioned rover platforms. The results of compression testing, rough terrain driving, and drawbar pull testing of these wheels are also discussed, which demonstrated their improved tractive performance when used on both lunar vehicle testbeds, with IPEx towing 6.9% more weight and slipping up to 38% less in a cohesive soil with spring tires than with rigid aluminum wheels, and with ERNEST towing 8.8% more weight and slipping up to 18% less in a sandy, friction-dominated soil with SMA spring tires than with rigid steel tires.