Feedback control of a target system is provided which utilizes the imposition of a periodic modulating signal onto a command signal of a controller. The command signal with the period modulating signal imposed thereon is input to the target system to be controlled. A response of the target system to a manifestation of the periodic modulating signal in the command signal is detected, and a feedback signal is produced from the detected response. The periodic modulating signal and the feedback signal are processed together to produce an error signal, and the command signal is modified in accordance with the error signal to drive the current state of the target system toward a desired state, wherein the periodic modulating signal facilitates control of the target system.