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US 4,402,082 AGranted
Automatic line termination in distributed industrial process control system
AssigneeFoster Wheeler Energy Corporation
InventorMichael E. Cope
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AssigneeFoster Wheeler Energy Corporation
InventorMichael E. Cope
Estimating the term…
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.
An information transfer system for transferring digital information between stored-program controllers interconnected by a communications link each controller adapted to test the communications integrity of the communications link between it and other of the controllers and connect an impedance to the communications link in the event of an interruption or degradation of the communications integrity of the communications link between the controllers, each system comprising:
A system for controlling an industrial process, said system including a plurality of process controlling remotes interconnected by a common communications link and each adapted to test the communications integrity of the communications link between remotes and provide an impedance thereto in the event of an interruption or degradation of the communications integrity of the communications link between remotes, said system comprising:
A method of providing a line-matching impedance in a communications link of an industrial process control system having a plurality of process controlling remotes interconnected by the communications link in the event of an interruption or degradation of the communications integrity of the communications link comprising the steps of:
A method of providing a line matching impedance in a communications link of an industrial process control system having a plurality of remotes R.sub.0, R.sub.1, . . . R.sub.x-1, R.sub.x, R.sub.x+1 . . . R.sub.n-1, R.sub.n interconnected by a common communications link in the event of an interruption or degradation of the communications integrity of the communications link, comprising the steps of:
An information transfer system comprising a multiplicity of stations, a communications link interconnecting said stations, each station provided with (a) a stored-program controller, (b) transmitting and receiving means connected between said stored-program controller and said communications link for transmitting digital information from said stored-program controller over said communications link in messages of predetermined format to another one of said stations and for receiving digital information from another one of said station over said communications link in messages of predetermined format, and (c) switch means selectively operable under the control of said stored-program controller to connect an impedance to said communications link, the stored-program controllers including message checking means for determing if the transmitted messages are successfully received by the transmitting and receiving means of the receiving station.
Dependencies are inferred from the claim text.