Industrial control system with interconnected remotely located computer control units

An information transfer system for transferring digital information between stored-program controlled means and for testing the validity of the transferred information, said system comprising:

• at least one stored-program controlled means for transmitting digital information in blocks of predetermined format which blocks include an error detecting code word;
• at least one other stored-program controlled means for receiving digital information in said block format and adapted to test the validity of said received block using the error detecting code word;
• plural independent communication channels connected to and extending between said first-mentioned and said second-mentioned stored-program controlled means for transferring information blocks therebetween;
• and
• said second-mentioned stored-program controlled means having validity testing means for selecting a one of said plural communication channels and testing the validity of the block received thereon and for selecting another of said plural communication channels and testing the validity of the block received on said other communication channel when the block received on said first-selected communication channel fails its validity test.

A method for transferring digital information formatted in predetermined blocks between an information transmitting device and an interconnected information receiving device, said method comprising the steps of:

• transmitting identical information blocks from a transmitter over plural independent communication channels to a receiver;
• receiving and storing the received information blocks at the receiver;
• selecting the information block received on one of said plural communication channels and testing the validity thereof;
• selecting the information block received on the other of said communication channels and testing the validity thereof in the event the first-selected information block fails its validity check;
• and
• requesting retransmission of said information blocks in the event both the first-selected and the second-selected information blocks fail their validity test.

In a control system of the type having a plurality of process control remotes interconnected through a communications link with each remote assigned the unique position in a predetermined succession order and each remote exercising supervisory control of the communication link on a revolving master basis, each remote having a variable transfer monitor timer, a method for transferring supervisory control of the communication link from one remote to another comprising:

• transmitting a control-transfer command signal along the communication link from the present system master to the next successive remote in the succession order;
• setting, when said control-transfer command signal is transmitted from the present system master to the next successive master, the transfer-monitor time-out interval of at least the second successive remote from the present master to a time-out interval that is a function of a predetermined supervisory control transfer value and the position of the particular remote relative to the present master
• said method operating in a normal mode comprising the further steps of:
• (1) receiving and evaluating the validity of the control transfer command signal at the next successive remote;
• (2) sending an acknowledgement signal to the present system master from the next successive remote;
• and
• (3) accepting supervisory control of the communications link by the next successive remote from the present system master if the control transfer command signal is found valid by the next successive remote whereby the next successive remote becomes the present system master,
• said method operating in an abnormal mode comprising the further step of accepting supervisory control of the communications link by the second successive remote from the present system master in the event the transfer-monitor timer of such second successive remote times out before the first successive remote accepts supervisory control in said normal mode of operation.

In a control system for controlling an industrial process of the type that includes a plurality of remote units each connected to an associated input/output device and interconnected through a communications link and in which each remote is assigned a unique position in a predetermined succession order, 0, 1, 2, 3, . . . m, . . . n, and each remote accepts supervisory control of the communications link on a master for the moment basis in accordance with the succession order, a method for transferring supervisory control of the communications link from a present system master R.sub.m to the first successive remote R.sub.m+1 comprising the steps of:

• transmitting a control-transfer command signal through the communications link from the present system master R.sub.m to the next successive remote R.sub.m+1 ;
• evaluating the validity of the control-transfer command signal at the next successive remote R.sub.m+1 ;
• sending an acknowledgement signal through the communications link from the next successive remote R.sub.m+1 to the present system master R.sub.m when the control-transfer command signal is found valid;
• and
• accepting supervisory control of the communications link by the next successive remote R.sub.m+1 from the present master R.sub.m whereby the next successive remote R.sub.m+1 becomes the present master R.sub.m.

In a control system for controlling an industrial process of the type that includes a plurality of remote units each connected to an input/output device and interconnected through a common communications link and in which each remote is assigned a unique position in a predetermined succession order, 0, 1, 2, 3, . . . m, . . . n, and in which each remote accepts supervisory control of the communications link on a master for the moment basis and in which each remote includes a settable variable transfer-monitor timer, a method for sequentially transferring supervisory control of the communications link from the present master R.sub.m to the next successive remote R.sub.m+1 in the succession order and for transferring supervisory control of the communications link from the present system master R.sub.m to the second successive remote R.sub.m+2 in the event the next successive remote R.sub.m+1 fails to accept supervisory control from the present system master R.sub.m comprising the steps of:

• transmitting a control-transfer command signal through the communications link from the present system master R.sub.m to the next successive remote R.sub.m+1 ;
• setting the transfer-monitor timer of at least the second successive remote R.sub.m+2 to a time-out interval based on a function of the successive remote's position relative to the present system master R.sub.m ;
• said method in a normal mode of operation comprising the further steps of:
• (1) evaluating the validity of the control-transfer command signal at the next successive remote R.sub.m+1 ;
• (2) sending an acknowledgement signal through the communications link from the next successive remote R.sub.m+1 to the present system master R.sub.m when the control-transfer command signal is found valid;
• and
• (3) accepting syspervisory control of the communications link by the first successive R.sub.m+1 from the present system master;
• said method in an abnormal method of operation comprising the further step of:
• accepting supervisory control of the communications link by the second successive remote R.sub.m+2 when the transfer-monitor timer of the second successive remote R.sub.m+2 times-out before the first successive remote R.sub.m+1 accepts supervisory control of the communications link.

In a control system of the type having a plurality of process control remotes interconnected through a communications link with each remote assigned a unique position in a predetermined succession order and each remote exercising supervisory control of the communication link on a revolving master basis, a method for transferring supervisory control of the communications link from a present system master to the next successive remote in the succession order comprising the steps of:

• transmitting a control-transfer command signal along the communication link from the present system master to the next successive remote in the succession order;
• receiving and evaluating the validity of the control-system command signal at the next successive remote;
• and
• accepting supervisory control of the communication link by the next successive remote from the present master if the control-transfer command signal is found valid by the next successive remote, whereby the next successive remote becomes the present system master.

A system for controlling an industrial process, said system comprising:

• a plurality of process controlling remotes, a common communication link interconnecting said remotes, each remote being assigned a unique position in a predetermined succession order and each remote exercising supervisory control of the communication link on a master for a moment basis in accordance with the succession order;
• each remote including a means for transmitting digital information in block format over said communications link to the other of the remotes and each including receiver means for receiving digital information transmitted from one other of the remotes;
• and
• each remote including means for transferring the supervisory control to the next successive remote in the succession order by transmitting a control-transfer block over said communication link to the next successive remote in the succession order and the next successive remote accepting supervisory control of the communication link in response to said control-transfer block.