Magnetically driven harmonic drive

A compound harmonic actuator, comprising:

• a housing;
• an output arm;
• a circular gear including a first number of first teeth, which is fixed relative to the housing;
• a flex gear including a second number of second teeth and permanent magnets arranged along a circumferential length thereof, the flex gear being rotatable relative to the housing and coupled to the output arm and respective entireties of the permanent magnets are suspended within the flex gear;
• and
• a coil assembly disposed and configured to generate a magnetic field with which the permanent magnets interact to deform the flex gear such that the second teeth engage with the first teeth,
• the first and second numbers being different and the coil assembly being controllable such that the deformation of the flex gear is such that engagement of the second teeth with the first teeth results in flex gear and output arm rotation,
• the compound harmonic actuator further comprising a secondary circular gear comprising a third number of third teeth, wherein:
• the flex gear comprises a fourth number of fourth teeth and the third and fourth numbers are different,
• the flex gear surrounds the circular gear and the secondary circular gear surrounds the flex gear,
• the first teeth are on an exterior of the circular gear and the second teeth are on an interior of the flex gear,
• the fourth teeth are on an exterior of the flex gear and the third teeth are on an interior of the secondary circular gear, and
• the deformation of the flex gear is such that the third and fourth teeth engage to drive rotation of the secondary circular gear.