Design of a variable-diameter wheel with a novel distributed compliant mechanism

Compliant variable-diameter mechanisms enable adaptation of variable-diameter wheels to both road and soft terrain. Conventional compliant variable-diameter mechanisms, in which every wheel-foot is an independent load-bearing structure, rely heavily on rigid-body mechanisms. To overcome the structure restriction and improve their performances, we introduce a novel compliant mechanism in which circumferentially distributed leaf springs or combination springs with large deformation range are used as flexible components. The springs constitute the closed outer ring and the overall load-bearing structure in the wheel. A novel screw transmission mechanism was designed to achieve motions with two degrees of freedom. Based on the geometric relationships, a dimensional design method for the mechanism is proposed. The chained beam-constraint-model and integration methods are introduced to obtain the spring deflections and maximum hub rotation angle. These methods can be used for further design of the transmission mechanism. The wheel design is then verified experimentally. The results indicate that the required design targets were achieved. Thus, the proposed mechanism diversifies the structure type and design of compliant mechanisms and expands the applicability of variable-diameter wheels in mobile platforms.