Electromechanical spring clutch with integrated speed detection

An electromechanical apparatus, comprising:

• an electromagnet including a magnetically permeable housing and a wire coil disposed therein;
• a magnetically permeable rotor that spins about an axis within the apparatus, the rotor being disposed in the path of a magnetic circuit generated by the electromagnet when energized;
• a drive for rotating the rotor relative to the electromagnet housing;
• wherein the rotor and the electromagnet housing are each shaped to vary the reluctance between the rotor and the electromagnet housing as the rotor rotates,
• a current source configured to apply a current to the electromagnet coil, wherein, during rotation of the rotor, fluctuations in the current result in the electromagnet coil due to varying reluctance between the rotor and the electromagnet housing are superimposed on the applied current;
• a current sensor connected to, and sensing the fluctuations in the current in, the electromagnet coil;
• and
• processing logic, connected to the current sensor and configured for reading the sensed current and determining the frequency of the fluctuations, said frequency being correlated to the rotor speed,
• wherein the rotor functions as an armature by being axially moveable.