US 5,313,386 A · Programmable controller with backup capability

Abstract

A machine is controlled by a system which has a pair of programmable controllers connected in tandem. One controller operates in the active mode governing the operation of the machine, while the other controller is in a backup mode able to assume control of the machine should the active controller fail. Each programmable controller has a backup module through which the two controllers are connected. In order to determine which controller is to be active upon power up, each backup module has an input means for receiving a first active mode request signal from another programmable controller. A means is provided to produce a tie breaker signal at one backup module which indicates that its programmable controller is to operate in the active mode when both programmable controllers simultaneously desire to operate in the active mode. A mode indicator in the backup module designates the active mode when the input means does not receive the first active mode request signal, or when the input means is receiving the first active mode request signal and the tie breaker signal is being produced at that backup module. Otherwise, the mode indicator designates that the programmable controller is to operate in the backup mode. An output means transmits a second active mode request signal to the other programmable controller when the mode indicator designates the active mode.

Claims13

Dependent claims

In a programmable controller having a memory which stores a control program and data, and a processor for executing the control program to receive data from input/output circuits which connect to a machine being controlled and for sending data to the input/output circuits for operating devices on the machine;

wherein the improvement comprises:
an input means for receiving a first signal indicating that another programmable controller, which is connected to the same input/output circuits, requests to operate in an active mode;
a first terminal for receiving a second signal indicating that the programmable controller is to operate in the active mode when a plurality of programmable controllers are requesting to operate in the active mode at substantially the same time;
mode indicator means for designating that the programmable controller is to operate in the active mode in response to said input means not receiving the first signal, and in response to said input means receiving the first signal and to said first terminal receiving the second signal, otherwise said mode indicator means designating that the programmable controller is to operate in a backup mode;
and
an output means for transmitting a third signal to the other programmable controller when said mode indicator means designates that the programmable controller is to operate in the active mode, the third signal not being transmitted when said mode indicator means designates that the programmable controller is to operate in the backup mode.

3 more elements

In a programmable controller having a memory which stores a control program, an I/O image table and a data table, and having a processor for executing the control program to examine and alter the I/O image table, and having means for exchanging data between the memory and a machine being controller;

wherein the improvement comprises a backup module comprising:
an input means for receiving an first active mode request signal and a first warning signal from another programmable controller that is connected to the same machine;
means for producing a tie breaker signal that indicates whether the programmable controller is to operate in the active mode when a plurality of programmable controllers are requesting to operate in the active mode at substantially the same time;
mode indicator means for indicating a mode in which the programmable controller is to operate, which indicates an active mode in response to said input means not receiving the first active mode request signal, or in response to said input means receiving the first active mode request signal and to the tie breaker signal from said means for producing, said mode indicator means otherwise indicating that the programmable controller is to operate in the backup mode unless the first warning signal is received in which case said mode indicator means indicates a disqualified mode;
and
an output means for transmitting a second active mode request signal to the other programmable controller when said mode indicator means designates the active mode.

3 more elements

Dependencies are inferred from the claim text.

Programmable controller with backup capability

Life of this patent

Programmable controller with backup capability

Life of this patent

Abstract

Claims13