Fault scoring and selection circuit and method for redundant system
First Claim
1. A fault scoring and selection circuit for selectively enabling at least one of a plurality of redundant control units to govern the operation of controlled equipment in which the redundant control units are each of the type having both self-testing and cross-testing capabilities respectively producing self-test and cross-test fault signals, said circuit comprising:
- fault-scoring logic circuit means including means for receiving self-test and cross-test fault signals from each of said control units, and means assigning predetermined scoring weights, certain of which are different, to said self-test fault signals and cross-test fault signals, and means for combining these weighted fault signals to produce combined fault score signals representing the health of each of said control units; and
selection logic circuit means for receiving said fault score signals, and for converting said fault score signals into a selection output signal that selects at least one of said control units having the lowest available fault score as determined by said fault score signals.
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Accused Products
Abstract
In a triplex redundant digital control system, one of three computer units is selected for controlling a digital flight control system by using fault scoring and selection logic circuitry that responds to discrete signals produced by the computer units that represent both self-test and cross-test information on the health of the three available units. The self-test and cross-test discrete information signals are received and processed by the selection logic circuit in accordance with a fault-scoring scheme in which the self-test scores are accorded different and, in particular, greater weight than the cross-test scores and a computer unit exhibiting the lowest combined self- and cross-test fault score is selected as the computer in control. The circuitry also includes memory devices for storing the fault scores associated with previous fault conditions so that a previously unfailed computer unit is selected over a previously failed but currently healthy computer. The memory devices are cleared whenever all three computer modules have scored a fault condition of equal weight such that transient failures do not cause permanent disablement of a computer unit, rather the temporarily faulty unit is allowed to recover and to be brought back on line if needed. To minimize switching, the selection logic causes a new selection only if a computer unit with a lower fault score is available. For simplicity and reliability, the fault scoring and selection logic functions of the circuitry are performed by read-only memories (ROMs) and the memory function is implemented by resettable latches.
58 Citations
25 Claims
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1. A fault scoring and selection circuit for selectively enabling at least one of a plurality of redundant control units to govern the operation of controlled equipment in which the redundant control units are each of the type having both self-testing and cross-testing capabilities respectively producing self-test and cross-test fault signals, said circuit comprising:
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fault-scoring logic circuit means including means for receiving self-test and cross-test fault signals from each of said control units, and means assigning predetermined scoring weights, certain of which are different, to said self-test fault signals and cross-test fault signals, and means for combining these weighted fault signals to produce combined fault score signals representing the health of each of said control units; and selection logic circuit means for receiving said fault score signals, and for converting said fault score signals into a selection output signal that selects at least one of said control units having the lowest available fault score as determined by said fault score signals. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
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21. A redundant computer control system for reliable operation of computer-controlled equipment comprising in combination:
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a plurality of redundant computer units, each of said computer units including means for producing a self-test fault signal in discrete format indicating either a faulty or nonfaulty self-test state, and means for producing a plurality of cross-test fault signals in discrete format, one such cross-test fault signal being produced for each other of said plurality of computer units and indicating that such other control unit has either a faulty or nonfaulty state; fault scoring and selection circuitry for selectively enabling at least one of said plurality of computer units to control the equipment, said fault scoring and selection circuitry comprising; fault-scoring logic circuit means including means for receiving said self-test and cross-test fault signals and means for assigning predetermined scoring weights, certain of which are different, to said self-test fault signals and to said cross-test fault signals, and means for combining these weighted fault signals to produce combined fault score signals representing the health of each of said computer units; and selection logic circuit means for receiving said fault score signals, and for converting said fault score signals into a selection output signal that selects at least one of said computer units that has the lowest available fault score as determined by said fault score signals.
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22. A method of selecting at least one of a plurality of redundant control units to govern the opeation of controlled equipment by automatic fault scoring and selection logic, in which each of the plurality of redundant interlinked control units is of the type capable of producing both a self-test discrete signal representing a failed or nonfailed self-test and cross-test discrete signals corresponding to failed or nonfailed conditions of the other control units, comprising the combination of steps of:
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receiving and scoring the self-test and cross-test discrete signals from said control units by assigning predetermined scoring weights, certain of which are different, to said self-test fault signals and to said cross-test fault signals, and combining these weighted fault signals to produce combined fault score signals representing the health of each of said control units; and selecting at least one control unit by comparing said combined fault score signals in accordance with predetermined selection logic, and responsively producing a selection output signal that selects at least one of said control units having the lowest available fault score as determined by said fault score signals. - View Dependent Claims (23, 24, 25)
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Specification