Cogging-torque actuator

A system for controlling rotational movement of a joint, comprising:

• first and second support members rotatably coupled to each other and that define a joint rotatable about an axis of rotation;
• an electromagnetic joint module comprising an input member coupled to the first support member, and an output shaft coupled to the second support member, such that the input member and the output shaft are rotatable about the axis of rotation, the electromagnetic joint module comprising at least two magnetic poles attached to the output shaft, and a ferromagnetic pole body attached to the input member and comprising a plurality of ferromagnetic stator poles each wrapped in a conductive wire to define a stator coil, wherein at least two magnetic poles and the plurality of ferromagnetic stator poles are configured to define a maximum cogging torque, wherein a total torque of the electromagnetic joint module is within a same order of magnitude as the maximum cogging torque, wherein the same order of magnitude is less than ten times;
• and
• a controller operably coupled to each stator coil for controlling non-continuous rotational movement of the joint.