The harmonic drive principle can be integrated with an electric motor in a particular manner in order to generate a high-torque "gear motor." Suppose that the flexispline of the harmonic drive is made of an electromagnetic material, such as the rotor of a motor. Instead of the mechanical wave generator, suppose that a rotating magnetic field is generated around the fixed spline. The magnetic attraction will cause the tooth engagement between the flexispline and the fixed spline. What type of motor principle may be used in the design of this actuator? Give an expression for the motor speed. How would one control the motor speed in this case?