Patent ID: 7528565

Claim:
A signal processing device for processing a position information signal output from a sensor in accordance with a driving position of a driver and detecting a driving speed of the driver, comprising: a position information signal processor that processes the position information signal and calculates driving speed information of the driver; and an internal position information generator that reflects a latest driving speed information calculated by the position information signal processor and generates a latest presumed position of the driver as internal position information, wherein the position information signal output from the sensor is a periodic function signal periodically changing in accordance with drive of the driver, the periodic function signal being a two-phase signal containing a first signal and a second signal having a predetermined phase difference the position information signal processor includes: a first signal processor that processes the first signal and outputs a phase changing amount of the first signal as the driving speed information, and a second signal processor that processes the second signal and outputs a phase changing amount of the second signal as the driving speed information: the signal processing device further comprises a signal switching section that is provided on a downstream side of the position information signal processor, the signal switching section selecting and switching to the output signal based on the periodic function signal with the signal value changing amount of the periodic function signal being greater than the phase changing amount of either the output signal from the first signal processor or the output signal from the second signal processor; the internal position information generator includes: an integrator that integrates the phase changing amount from the position information signal processor and calculates a phase corresponding to position information of the driver, and an internal position information converter that calculates a periodic function value corresponding to the phase calculated by the integrator as the internal position information; and the position information signal processor calculates the driving speed information of the driver based on a difference between the position information signal from the sensor and the internal position information, generated by the internal position information generator.