Abstract: The present invention provides a method and apparatus for linking together a plurality of disk drives. One drive is designated the "master". The others, designated "slaves", are synchronized to a common signal which may be from the "master" drive or from an external source. The disks are synchronized with respect to rate of revolution (spindle speed) and angular position. A plurality of hard disk drives are coupled in this manner to provide a parallel data output to a host computer. Each disk drive is microprocessor controlled. In normal operation a speed control loop regulates spindle speeds to within one percent of 3600 RPM. Both master and slave drives are equipped with input "MAPIN" and output "MAPOUT" signal terminals. The MAPOUT signal is relative to and dependant on the angular position of the disk. Synchronization is achieved by coupling the output signal from the master drive (MAPOUT) to the input terminal on the slave drives (MAPIN).

Abstract: A sampled data positioning system for moving a member between positions in a minimum time employs a model of the physical system to overcome the low bandwidth constraints of fed back position and velocity samples. The model system is an approximate analog of the physical system and provides continuous pseudo position and velocity signals of high bandwidth. These are applied to a seek controller which generates an error signal between a desired reference velocity trajectory and the pseudo velocity signal. The error signal is fed back to the model system input and is also applied to control the physical system. The model velocity and position outputs are reset at sampling times to the values of the sampled velocity and position in the physical system.