Storage and retrieval machine having improved real-time responsiveness

Abstract

A communication system for a storage and retrieval machine comprises a conductor bar, base and carriage electrical devices, a sliding brush, first and second transmitters, and first and second receivers. The sliding brush is mounted to the carriage and is in slidable electrical contact with the conductor bar. The transmitters and receivers are coupled to the conductor bar or the sliding brush, depending on the direction of transmission. The first and second transmitters transmit positive half-waves and negative half-waves, respectively, across the conductor bar in response to inputs. Hence, two one-bit intra SRM communication links are provided between the SRM carriage and base. A communication system for communicating high priority and low priority messages between a base and carriage of an SRM comprises base and carriage electrical devices, and first and second communication links. Specifically, the first communication link includes a conductor bar, a sliding brush, and a first transmitter and first receiver which are coupled to either the conductor bar or the sliding brush, depending on the direction of transmission. The first communication link communicates high priority messages. The second communication link, which includes first and second optical modems on the carriage and base, respectively, communicates the low priority messages. The present invention advantageously permits increased real-time responsiveness of the SRM control system, enjoys increased noise immunity, and uses low maintenance components.