Novel ultrasonic motors

Together with an undergraduate project student, Samarth Bhargava, we investigated a novel type of ultrasonic motor, recently reported by James Friend and co-workers.This motor induces rotation of an object placed on the tip of a spiral that is ultrasonically actuated. The tip of the spiral undergoes rotation and extention and induces rotation in a manner very similar to that of a cook throwing a pizza. The photograph below shows a spiral plexiglas stator excited by piezoelectric wafers with a brass rotor. The brass rotor is painted so the rotational velocity can be measured.  

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Samarth Bhargava won first prize for his paper at the Innovative STEM Symposium in Baltimore in 2009. He subsequently presented a paper at the IEEE Ultrasonic Symposium which was accompanied by a related paper on simulations of motor operation.

An intriguing aspect of this motor is that the direction of rotation depends on the frequency of the excitation.

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Animations showing the rotation in two different directions are linked below. (These are for a motor with different dimensions from the motor in the figure above). 

Motor at 70000 Hz

Detail at 70000 Hz

Detail at 42500 Hz