A system, for providing an actuator control signal to an actuator within an optical pickup unit of an optical disk drive, focuses optics on an optical disk. In one implementation, an error term is obtained by sampling the FES (focus error signal) signal. The error term is scaled by an adaptation coefficient, which regulates a rate at which the error term modifies the actuator control signal. An actuator control signal generator generates the actuator control signal to control movement of the actuator, wherein the actuator control signal is a function of a prior actuator position, the error signal and the adaptation coefficient.