An apparatus that generates vibrational motion is disclosed. The apparatus includes a first mass, a second mass, a drive system, and a control system. The first mass is eccentrically mounted on, and configured to rotate about, a first shaft. The second mass is eccentrically mounted on, and configured to rotate about, a second shaft, with first and second shafts sharing a common axis. The drive system imparts rotational motion to first and second shafts, and the control system controls rotational frequencies, directions, and initial angles of the first and second masses. Linear, elliptical, or circular vibratory motion of the apparatus may be induced by controlling such rotational properties of the first and second masses. The apparatus may include a measurement device that measures angular position and/or velocity of the first and second masses. The control system may control the vibrational motion based on measurements taken by the measurement device.