Electrical transmission or interconnection systems – Nonlinear reactor systems – Parametrons
Patent
1988-02-17
1989-11-14
Miller, Stanley D.
Electrical transmission or interconnection systems
Nonlinear reactor systems
Parametrons
307441, 307241, 307242, 307243, 307355, 307528, 307631, 307632, 307643, 307644, H01J 1982, H03K 1756, H03K 906, H03K 522
Patent
active
048809942
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a redundant control method and device for controlling a power controlled unit in accordance with a given control order, by a logic combination of two separate control signals elaborated by two respective circuits, from said control order, and two signals representative of the operating state of these two circuits.
It is generally known that the use of redundant circuits for effecting a control essentially responds to safety requirements. To this end, the simplest solution consists in doubling the control circuits and in substituting one for the other when a failure is detected in the operating circuit.
However, it proves that this solution has a certain number of drawbacks and, in particular the one resulting from the fact that an operating failure of the control circuit in operation will necessarily result, at least during the time required for bringing the second control circuit into service, in a discordance between the control order and the effective state of the controlled device. This is why this solution is not suitable for the automatic controllers used, particularly in the chemical and petrochemical industries, which allow no interruption of the process (it is not always possible to interrupt a chemical reaction) and a very great safety.
Furthermore, it is necessary to provide in these control systems, means for making sure that the stand by control circuit, to be substituted for the other at the time of a failure, operates correctly.
The object of the invention is therefore to overcome these drawbacks and to make sure that, independently of the breakdown state of one of the two control circuits, the state of the controlled device always corresponds to the control order. It provides more particularly for this purpose a method for the redundant control of a power controlled unit in accordance with control orders elaborated by at least one digital control device and/or applied thereto, this method being more particularly characterized in that it comprises:
the application to the power controlled device of a control signal resulting from a logic combination of two logic signals delivered by two separate outputs of the digital control device and elaborated thereby, so that said control signal conforms to said control orders;
the detection of failures which may affect the signals delivered by said outputs; and
when a failure of the signal emitted by one of the outputs has been detected, the self adaptation of the signal emitted by the other output, depending on the nature of this failure, so that the signal resulting from said logic combination also conforms to the control orders.
Advantageously, the signals delivered by said outputs of the digital control device will consist of binary signals and the combination of these signals for obtaining the control signal will be achieved by the EXCLUSIVE OR function. The control signal will then consist of a binary signal having a state 1 in the case where, at the same time, the logic states of the signals delivered by said outputs are different and a logic state 0 in the case where these states are identical.
Should a failure of one of the outputs result in blocking of the signal delivered by this output at one of the two states, the signal emitted by the other output will then consist of the image of the control order in the case of blocking in state 0 or a complemented image of this order in the case of blocking in state 1.
The invention may also apply to a monoprocessor digital control device such for example as a programmable controller which will then have two outputs capable of delivering said two logic signals, as well as to a control device with two processors coupled together and each having an output assigned to the control.
Thus, in one embodiment of the invention using two processors coupled together and each having an output for providing the redundant control of the same power device, the method of the invention will include:
for generating the signal delivered by the output of the first processor, the elaboration
REFERENCES:
patent: 3201701 (1965-08-01), Maitra
patent: 3299341 (1967-01-01), Corey
patent: 3417320 (1968-12-01), Muskovac
patent: 3421027 (1969-01-01), Maynard et al.
Drucker William A.
La Telemecanique Electrique
Miller Stanley D.
Phan Trong Quang
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