To enhance the step climbing performance of omni-directional wheelchair, we developed a front-wheel-steering-drive dual-wheel caster drive mechanism with rocker links and a differential mechanism. The dual-wheel caster drive mechanism has the advantage of simple structure and is suitable for wheelchair applications. Based on the motion characteristics of this mechanism, we have found that the step climbing performance can be improved by adopting a front-wheel-steering-drive mechanism. In addition, the rocker links and the differential mechanism are employed as a suspension mechanism to improve wheel ground contact. In this study, a 3D dynamics simulator was constructed to compare the performance of wheelchairs employing several mechanisms, including the proposed mechanism, in step climbing. Based on the motion characteristics of the dual-wheel caster drive mechanism, simulations were carried out under two conditions: steady state and transient state. Simulation results confirm that the proposed mechanism has high step climbing performance under both conditions. Furthermore, it is confirmed that the rocker links and differential mechanism work to improve step climbing performance when the step has an angle, which means that the two front wheels do not contact the step at the same time.

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