An apparatus includes a movable member, and first and second actuators coupled to the movable member at positions offset from a first axis that passes through a centroid of the movable member. A controller independently controls the first and second actuators to exert a first force on the movable member in a direction generally parallel to the first axis, thereby controlling both linear and rotational orientation of the movable member. The apparatus can further include third and fourth actuators coupled to the movable member at positions offset from a second axis that passes through the centroid of the movable member, and the controller can independently controlling third and fourth actuators.