Indirect rotor position detection method based on angular admittance modulation of optimally designed piezoelectric ultrasonic motors

This paper addresses the design of a door lock mechanism actuated by a rotary ultrasonic motor featuring a sensorless rotor position detection method based on angular admittance modulation. Electronic door lock cylinders need some sort of mechanical actuator to toggle the locking state between open and closed. The main requirements are high security standards, low power consumption, reasonable production costs, and facile integration of the actuator into the mechatronic system. A piezoelectric ultrasonic motor (PUM) was singled out to respond best to these challenges. After the development of an integration concept, a design of experiments based optimisation methodology is used to design an optimal stator for the PUM. Resonance matching is realised with a LLCC resonant converter and a resonance frequency tracking controller allows for following the ideal working point. A direct digital synthesis (DDS) based drive signal regulator allows for reducing the overall size of drive and control electronics. The locking position is detected indirectly by a motional admittance modulation (MAM) method, obviating the need for a position sensor.