Zero-phase Tracking Research Articles

Periodic Signal Tracking for Lightly Damped Systems

The focus of this paper is on the development of time-delay filters to accomplish tracking of periodic signals with zero phase errors. The class of problems addressed include systems whose dynamics are characterized by lightly damped modes. A general approach for the zero-phase tracking of periodic inputs is presented followed by an illustration of single harmonic tracking of underdamped second-order systems with relative degree two. A general formulation of the approach is then posed for higher-order systems and systems including zeros. The paper concludes with the illustration of enforcing constraints to desensitize the time-delay filter to uncertainties in the location of the poles of the system and forcing frequencies. A numerical practical design case based on a medical X-ray system is used to illustrate the potential of the proposed technique.

An Approach to Dual-Stage Servo Design in Computer Disk Drives

A novel design strategy is presented for a dual-stage actuator servo system in magnetic disk drives. Based on the existing decoupled-design strategy, we adopt the idea of the well-known zero-phase error tracking controller to minimize destructive effect resulting when two control loops are combined. Since the zero-phase tracking control requires previews of signals in a feedback loop, a kind of estimation scheme is suggested based on the actuators' dynamic model. The best practical advantage is that we achieve systematically a low-order DSA controller capable of high-accuracy track following as well as of high-speed short-span track seek; besides, the existing single-stage controller is fully utilized. The performance of the proposed method is analyzed and demonstrated through simulation and experiment.