Patent ID: 6608573
Filing Date: 2003-08-19
Classification: H03M

Abstract:
A automatic resolution changing method for use in a high-precision digital conversion of two-phase sinusoidal wave signals, said automatic resolution changing method comprising the steps of:detecting a two-phase-sinusoidal-wave-like A-phase output (sin &thgr;Â·f(t)) and a two-phase-sinusoidal-wave-like B-phase output (cos &thgr;Â·f(t)), which are outputted based on rotation of a rotor with respect to a stator; integrating an angular velocity (d&phgr;/dt) of said rotor obtained from the control residual (sin(&thgr;âˆ’&phgr;)) between the two-phase sinusoidal wave signals in a counter; performing digital conversion of a rotation angle (&thgr;) of said rotor with respect to said stator; and outputting a result of the digital conversion, wherein for outputting the result of the digital conversion, in a case where the angular velocity (d&phgr;/dt) is equal to or higher than a first percentage of a follow-up speed at a current resolution of said counter, the resolution of said counter is reduced, while in a case where the angular velocity (d&phgr;/dt) is equal to or lower than a second percentage of the follow-up speed at the current resolution of said counter, the resolution of said counter is increased.