US Patent 9090214 Magnetically coupled accessory for a self-propelled device

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 mechanism is coupled to the internal drive system and includes a spring and a spring end in contact with the inner surface of the spherical housing. An accessory component magnetically interacts with the biasing mechanism through the spherical housing such that as the self-propelled device rotates along, the accessory component remains stable with respect to the biasing mechanism.