Spiral wheel with a reconfigurable shape and variable grip for all-terrain robots

Wheeled robotic platforms are widely favored for their high mobility, cost-effectiveness, and long operational endurance. However, their traversal performance substantially deteriorates on uneven or obstructed terrain due to the intrinsic limitations of rigid wheels, which lack adaptability to varying surface topologies. To overcome these constraints, we present a reconfigurable, nonpneumatic spiral wheel featuring tunable radial stiffness. The wheel switches between two functional configurations: a contracted, high-stiffness mode for high-speed locomotion on flat surfaces; and an expanded, low-stiffness mode that increases compliance and traction for obstacle negotiation. The design is implemented using a monolithic, 3D-printed chiral structure actuated via a rope-driven mechanism. The system is then subjected to a series of indoor and outdoor locomotion tests upon integration with a wheel-legged robotic platform. The experimental results confirm that the proposed wheel maintains dynamic stability and speed efficiency on planar surfaces while substantially enhancing terrain adaptability and obstacle-crossing performance in complex environments.