Sensor for detecting rotational movement

Claim 1

A sensor for detecting rotational movement comprising: a cylindrical resonator made of a piezo-electric material and having an outer surface; a first pair of driving electrodes provided on said outer surface of said resonator and circumferentially spaced 180 degrees relative to each other; a second pair of driving electrodes provided on said outer surface of said resonator and each being circumferentially spaced 90 degrees from said first pair of driving electrodes, a pair of feedback electrodes provided on said outer surface of said resonator and each being circumferentially spaced from said first pair of driving electrodes 90 degrees; a phase controller for detecting a first voltage outputted from each of said feedback electrodes due to radial deformation of said resonator and for feeding a second voltage to each of said first pair of driving electrodes; an inverter circuit for inverting said second voltage fed from said phase controller to said first pair of driving electrodes to provide an inverted voltage and for feeding said inverter voltage to each of said second pair of driving electrodes; at least a pair of detecting electrodes provided on the outer surface of said resonator; and means connected to each of said detecting electrodes for detecting a rotational movement of said resonator, wherein first radial forces and second radial forces are generated concurrently at said first pair of driving electrodes and said second pair of driving electrodes, respectively, in such manner that each of said first radial forces changes direction of action from radially outwardly to radially inwardly at a constant interval, each of said second radial forces changes direction of action from radially outwardly to radially inwardly at said interval, and that whenever said first forces act radially inwardly, said second forces act radially outwardly.