Excavating
Patent
1980-03-07
1982-08-17
Atkinson, Charles E.
Excavating
318564, 244194, 371 36, 371 68, G06F 1118
Patent
active
043453279
DESCRIPTION:
BRIEF SUMMARY
The present invention is related to a self-monitored process control device comprising at least one actuator device driven by a control signal. The control signal is computed according to a flight control law, using a generating device to implement the law.
The invention is more particularly related to a control system with integrated monitoring and safety systems allowing an erroneous control signal, which could result from a malfunction of the processing device and/or a failure occurring in one of its own curcuits, to be detected and neutralized simultaneously.
The present invention can be applied favorably, but not exclusively, to the control circuits of an aircraft automatic flight control system, to prevent the aircraft from being put into any hazardous configuration upon a failure.
To achieve this result, it is known to double each of the functions of the system for implementing the automatic flight control law.
This widely used means is safe but it has the drawback of being costly.
The invention aims at achieving this result by an economical, reliable, and safe means without having to duplicate the flight control functions.
On the other hand, there is known a safety system using a vote which selects a signal .delta..sub.2 out of three signals .delta.; .delta..sub.1 and .delta..sub.2 ; the value of the selected signal .delta..sub.2 representing the average value of the other two signals. See French Pat. No. 75-37862 of Dec. 10, 1975.
But this known system does not make it possible, in a simple and economical way, to assure a general-purpose self-monitoring control with a double level warning as described in this application. Further, the known system requires a series of circuits, at times complex, intervening in combination with signal .delta..sub.2, to intervene upstream and downstream from the voter.
The self-monitoring process control system according to this invention comprises two pairs of voters disposed between a digital computation unit and an analog computation unit.
The output signals of the first pair of voters control a first warning signal and are interconnected to the inputs of the other pair of voters; in turn, the output signals of the latter two voters control a second warning signal and, at the same time, an actuator through power loops.
For this purpose, the invention provides a monitoring control system using: making it possible to replace control signals coming from the law implementing system, when they are erroneous, with signals representing maximum allowable safety values (hereafter called safety limit values or more simply stops) calculated by separate circuits independent of those used for implementing the flight control law; of the two voters are not identical; and is not erroneous, in case a failure breakdown occurs in one of the said two circuit units, which safety circuit is provided with a self-monitoring circuit making it possible to signal, by a second warning signal, a failure of the safety circuit.
More precisely, for each function of the generating device the present invention provides for two double limit stops computed separately, i.e., two high-level stops B.sub.1, B'1 and two low-level stops B.sub.2, B'.sub.2. The two signals representative of the coupled high-level, low-level limit stops (B.sub.1, B.sub.2 or B'.sub.1, B'.sub.2), and the control signal from the generating device, are transmitted to a voter or selector, hereinafter referred to as a preformance voter, which compares these three signals and transmits only the signal whose value, at a given instant, is between the values, at the same instant, of the two other signals.
The two signals voted by the two respective voters are then compared by means of a first comparator which sends a warning signal when the two voted signals are not identical.
Obviously in case of a very simplified construction mode of the present invention, the signal from one of the voters can be transmitted directly to the power loop associated with an execution device.
According to a more complex construction mode of the present
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patent: 4035705 (1977-07-01), Miller
patent: 4092578 (1978-05-01), Fabian
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Atkinson Charles E.
Societe Francaise d'Equipements pour la Navigation Aerienne
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