Conventional training simulators commonly use a hexapod configuration to provide motion cues. While widely used, studies have shown that hexapods are incapable of producing the range of motion required to achieve high fidelity simulation required in many applications. A novel alternative is the Atlas motion platform. The Atlas platform achieves six degree of freedom motion by mounting the Atlas spherical platform on top of an XYZ translation platform. The Atlas rotational stage comprises a sphere manipulated by three omnidirectional wheels. Each wheel imparts a prescribed velocity to the sphere through friction enabling it to rotate about any desired axis with unlimited angular displacement. This work presents a generalized kinematic model of the platform which can be applied to any spherical platform actuated by three omnidirectional wheels. In addition, conditions for slip-free and singularity-free motions are identified. Two illustrative examples are given for different omnidirectional wheel configurations. The actual platform is in final stages of construction, with a 3 meter diameter sphere.
