Abstract: An event-driven control system controls movement of a base and carriage of a storage and retrieval machine. The control system is microprocessor-based and includes a motion controller, a machine control task, an input/output interface, an input/output task, and a microprocessor that executes the machine control task and the input/output task. In operation, a plurality of interrupts is issued to the machine control task in response to events which occur in an operating environment of the storage and retrieval machine. To respond to the interrupts, at least one subroutine in response to the reception of each interrupt. The execution of the subroutines controls movement of the base and the carriage of the storage and retrieval machine. Movement of the base and the carriage of the storage and retrieval machine (1) is substantially entirely controlled by issuing and responding to the interrupts as different events occur in the operating environment that cause the interrupts to be issued.

Abstract: A method of mapping a warehouse rack structure having a plurality of racks comprises the steps of creating a logical matrix and updating the logical matrix. The updating step further includes the steps of causing a moveable device to travel to a first one of the plurality of racks, and producing a first machine-readable distance measurement output. The machine-readable distance measurement output is produced using a first sensor and represents a distance between the first sensor and a first position on the warehouse rack structure. A system for mapping a warehouse rack structure comprises a storage and retrieval machine; a rack structure; a logical matrix; and a computer. The storage and retrieval machine has first and second ultrasonic sensors mounted thereon. The rack structure includes a plurality of racks. The logical matrix stores horizontal position information and vertical position information for each of the plurality of racks.