US Patent 9429940 Self propelled device with magnetic coupling

A self-propelled device includes a spherical housing and an internal drive system including one or more motors. The internal drive system acts to provide power to an interior surface of the spherical housing, thereby causing the self-propelled device to move. A biasing assembly can be included to enable the internal drive system to continuously engage an inner surface of the spherical housing. An external accessory magnetically interacts with interior magnetic components through the spherical housing such that as the self-propelled device rotates and maneuvers, the accessory component maintains a positional relationship to a top portion of the self-propelled device.