Variable valve system

A variable valve system for varying opening and closing timings of valves in an internal combustion engine, comprising:

• a crank angle measurement unit that measures a rotation angle of a crankshaft in the internal combustion engine;
• a cam angle measurement unit that measures a rotation angle of a camshaft coupled to the crankshaft, the camshaft configured to open and close the valves;
• and
• a controller that controls the internal combustion engine, wherein
• at least one of the crank angle measurement unit or the cam angle measurement unit is configured as an absolute angle sensor that measures an absolute rotation angle and outputs a voltage signal corresponding to the absolute rotation angle,
• the controller is configured to perform a correction operation that corrects a rotation angle value calculated based on the voltage signal,
• the variable valve system further comprises a rotating electric machine for varying a camshaft phase, the camshaft phase being a relative rotation angle of the camshaft with respect to the crankshaft,
• the rotating electric machine includes an output shaft and is configured to:
• regulate a rotation speed of the output shaft to match the camshaft phase to a target value, and
• output a pulse shaped rotation angle signal each time a rotation angle of the output shaft changes by a predetermined amount, and
• the controller performs the correction operation further based on the pulse shaped rotation angle signal.