US Patent 7445107 Hydraulic clutch control system and method

A hydraulic clutch control system includes a clutch, a hydraulic circuit that supplies a hydraulic pressure to a piston of the clutch so as to cause a stroke of the piston for engagement of the clutch, a primary hydraulic pressure signal generation unit that generates a primary hydraulic pressure signal to regulate a magnitude of the hydraulic pressure, a secondary hydraulic pressure signal generation unit that generates a secondary hydraulic pressure signal to induce fluctuations in the hydraulic pressure, a hydraulic pressure control unit that operates the hydraulic circuit to control the hydraulic pressure according to the primary and secondary hydraulic pressure signals, a detection unit that detects the amount of fluctuations in the hydraulic pressure and a piston stroke judgment unit that judges the piston stroke based on the hydraulic pressure fluctuation amount.