Foster Wheeler Energy Corporation

Forney Engineering Company

Fornex Engineering Company

Michael E Cope

In a distributed computer control system in which remote stations are interconnected by a communications link, the remote stations take turns having supervisory control over the communications link. Each remote is numbered in sequence in a predetermined succession order and takes its turn having control of the communications link in accordance with this succession order. When a remote station has completed its turn of having supervisory control, it transmits a first control message over the communications link. The next remote station in the succession order then takes control over the communications link by transmitting a second control message over the communications link. Each remote station has two variable timers which are set in response to the first control message and the second control message, respectively, and have time out intervals depending upon the offset of the receiving remote station from the remote station which transmitted the control message. If and when any of these variable timers times out in a given remote station, then that remote station will assume control of the communications link by transmitting the second control message on the communications link.

Distributed computer control system with variable monitor timers

A control system for controlling an industrial process includes a plurality of remotely located process control units (remotes) each coupled to an associated input/output device(s) and adapted to communicate with one another through a dual channel communications link. Each remote has a unique succession number within a predetermined succession order with supervisory communication-control of the communication link sequentially transferred to each remote according to its succession number to provide a revolving or master for the moment control of the system. Each remote after completing its turn as master transmits a control block to the next remote in the sequence. Each remote, when exercising supervisory communication control of the communication link, may transmit data in block form to other remotes and request and receive data back from other remotes. Each remote upon completing its turn transmits a control block to the next remote in the sequence, which, upon receiving the control block, tests for validity and, if valid, transmits an acknowledgement signal to the remote which transmitted the control block. The next remote then takes its turn exercising supervisory control over the communications link and, in the same manner, the supervisory control is transferred from one remote to the next in the sequence.

Distributed industrial control system with remote stations taking turns

A control system for controlling an industrial process includes a plurality of remotely located process control units (remotes) each coupled to an associated input/output device(s) and adapted to communicate with one another through a dual channel communications link. Digital information in the form of data and control information blocks is transmitted between remotes with the blocks transmitted twice on each channel of the dual channel communications link. The destination remote checks the block validity on one of the dual channels and, if valid, responds with an acknowledgement signal (ACK), and, if invalid, tests the blocks on the other, alternate channel and then responds with an acknowledgement or non-acknowledgement signal (NAK) depending on whether the data blocks tested on the alternate channel are found valid or invalid. Each remote in the system is adapted to test the communication integrity of both channels of the communication link between it and its immediately adjacent remotes in the system and provide a line-balanced termination impedance in the event one or both communication channels are degraded or interrupted. The system thereby provides high overall operating efficiency since the remotes maintain a system-like integrity even if one of the communication links is interrupted by automatically inserting a line-matching termination impedance to prevent or minimize problems incident to unterminated interrupted or degraded communication links, these problems including loss of signal strength in the transmission line and reflected signals.

Automatic line termination in distributed industrial process control

A control system for controlling an industrial process includes a plurality of remotely located process control units (remotes) each coupled to an associated input/output device(s) and adapted to communicate with one another through a dual channel communications link. Each remote has a unique succession number within a predetermined succession order with supervisory communication-control of the communication link sequentially transferred to each remote according to its succession number to provide a revolving or master for the moment control of the system. Digital information in the form of data and control information blocks is transmitted between the remotes with the blocks transmitted twice on each channel of the communications link. The destination remote tests the block validity on one of the two dual channels and, if validated, responds with an acknowledgement signal (ACK) and, if invalid, tests the blocks on the other, alternate channel and then responds with an acknowledgement or non-acknowledgement signal (NAK) depending upon whether the data blocks tests on the alternate channel are found valid or invalid. A non-acknowledgement from the destination remote re-triggers the transmission of the blocks from the source remote. The system provides high overall operating efficiency since the remotes will maintain a system-like integrity on each side of a severed communication link and the redundant block transmission with alternate line checking provides very high information transfer reliability.

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Richardson, TX, United States of America

Michael E Cope