Fault tolerable redundancy control
First Claim
1. A redundant control system in which a plurality of equivalent control signals from a plurality of equivalent signal processors are subjected to majority logic operation, to deliver a system control signal, said redundant control system comprising:
- at least three equivalent signal processors connected in parallel for receiving an information signal and for generating respective control signals which will be identical to one another when the processors are operating without fault;
error detecting means connected to receive said control signals from said signal processor for comparing each of said control signals with each of the other control signals to check for the presence of an abnormal control signal which is different in level from that of the majority of the control signals and to generate an error detection signal on an output line corresponding to said different control signal;
means for generating a set signal which represents a mode of control upon occurrence of a fault in at least one of said signal processors;
swithcing means connected to receive said control signals from said signal processors, any error detection signal generated by said error detection means and said set signal for transmitting control signals which are not accompanied by a corresponding error detection signal and for replacing said control signal accompanied by an error detection signal with said set signal; and
a majority logic circuit connected to receive the outputs of said switching means for performing a majority logic operation among the outputs of said switching means to generate a system control signal.
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Accused Products
Abstract
A redundant control system in which three output signals from three equivalent signal processors are compared with each other to judge whether each of the output signals is normal or abnormal, an abnormal output signal thus determined is replaced by a set signal having a predetermined level, and then a majority operation is performed for normal output signals and the set signal to obtain a control signal. The control signal is formed of the logical product or logical sum of two normal output signals according as the predetermined level of the set signal is "1" or "0". In the case where a circuit for generating the above-mentioned control signal are formed in triplicate and a majority operation is performed for three control signals, a fault occurring at other circuit portions than a majority logic circuit at the final stage is permissible. Further, the reliability of the control system is enhanced by forming abnormality detecting means in triplicate and performing a majority operation for the outputs of three abnormality detecting means.
147 Citations
13 Claims
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1. A redundant control system in which a plurality of equivalent control signals from a plurality of equivalent signal processors are subjected to majority logic operation, to deliver a system control signal, said redundant control system comprising:
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at least three equivalent signal processors connected in parallel for receiving an information signal and for generating respective control signals which will be identical to one another when the processors are operating without fault; error detecting means connected to receive said control signals from said signal processor for comparing each of said control signals with each of the other control signals to check for the presence of an abnormal control signal which is different in level from that of the majority of the control signals and to generate an error detection signal on an output line corresponding to said different control signal; means for generating a set signal which represents a mode of control upon occurrence of a fault in at least one of said signal processors; swithcing means connected to receive said control signals from said signal processors, any error detection signal generated by said error detection means and said set signal for transmitting control signals which are not accompanied by a corresponding error detection signal and for replacing said control signal accompanied by an error detection signal with said set signal; and a majority logic circuit connected to receive the outputs of said switching means for performing a majority logic operation among the outputs of said switching means to generate a system control signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A redundant control system in which three ON-OFF control signals from threee equivalent processors are subjected to a majority logic operation to deliver a majority control signal, said redundant control system comprising:
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three equivalent processors connected in parallel for receiving a common information signal and for generating respective ON-OFF control signals which would be identical to one another when the processors are operating without fault; error detecting means connected to said equivalent processors to receive said control signals for comparing each said control signal with each of the other control signals to detect an abnormal control signal which is different from other control signals and for generating three changeover signals corresponding respectively to said control signals, each of which changeover signals is in an ON state when the associated control signal is abnormal and in an OFF state when the associated control signal is normal; means for generating a set signal which is preselected to be in an ON or OFF state according to a desired mode of control when a fault occurs in at least one of said processors; three switching circuits, each of said switching circuits being connected to receive said control signals, said three changeover signals and said set signal and operating to generate three output signals, each output signal of a respective switching circuit being equal to a corresponding one of said control signals when a corresponding one of said changeover signals is in the OFF-state and for converting an ouptut signal into a signal determined by the ON or OFF state of said set signal when the changeover signal corresponding to said output signal is in the ON-state; three first majority logic circuits corresponding to said switching circuits, each of said first majority logic circuits being connected to receive three outputs from a corresponding one of said switching circuits, to perform a majority logic operation; and a second majority logic circuit connected to receive three outputs from said first majority logic circuits for performing a majority operation to deliver said majority control signal. - View Dependent Claims (10, 11, 12, 13)
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Specification