Abstract: The coupling of driving shaft with a driven shaft is accomplished at high torques and high speeds of rotation using a piezoelectric shack, a passive clutch system, and a hydraulic clutch activation system. The piezoelectric stack is housed in the rotating driving shaft, and extends along the axis of the shaft when it receives an engagement signal. This extension of the piezoelectric stack depresses a disk spring into the hydraulic cavity of the housing of the hydraulic clutch activation system. The pressure thereby generated in the hydraulic fluid compresses a compression ring onto a control disk and translates any rotation of the compression ring into the control disk. A torsion rod in the center axis of the control disk is rotated and, in turn, rotates a plug connected to a sprag clutch. This rotation serves to rotate the sprags into a locking position so that the sprag clutch engages the driving shaft with the driven shaft.