Method and apparatus for an active standby control system on a network

• US 7,032,029 B1
• Filed: 07/07/2000
• Issued: 04/18/2006
• Est. Priority Date: 07/07/2000
• Status: Expired due to Term

• Current Assignee: Schneider Automation Incorporated (Schneider Electric SE)
• Original Assignee: Schneider Automation Incorporated (Schneider Electric SE)
• Inventors: Tanzman, Allan, Mooney, Stephen, Dube, Dennis J. W.
• Primary Examiner(s): Thompson, Marc D.
• Assistant Examiner(s): Phan, Tam T.
• Application Number:
  US09/612,636
• Time in Patent Office: 2,111 Days
• Field of Search: 709/217, 709/220, 709/245, 700/1, 700/2, 700/9, 700/11, 700/19, 700/20, 700/21, 700/82, 710/10, 714/11, 714/13
• US Class Current: 709/245
• CPC Class Codes: G05B 19/058 Safety, monitoring
• CPC Class Codes: G05B 2219/14132 Dual plc, each monitors other
• CPC Class Codes: G05B 9/03 with multiple-channel loop, i.e. redundant control systems

Abstract

A method and apparatus for providing an active standby control system comprising the steps of providing a first and second programmable logic controller (PLC), each controller having an operating state. Each controller further including a network module board operably connected to a network; a control unit, a remote I/O head; and, a hot standby module, each hot standby module is operably connected together. Operably connecting each programmable logic controller to a network. Assigning a network address identifier, i.e., Internet Protocol or Media Access Control address, to each programmable logic controller and sensing the operating state of each programmable logic controller. The network address identifier of each programmable logic controller is determined by the operating state of each respective programmable logic controller. The present invention is also directed to an apparatus for communication with at least one device which resides on a standard communications network using a standard communications protocol. The apparatus has a scanner for scanning the device, a device scan table for storing data relating to the device, and a standard communications interface for interfacing between the device scanner and the standard communications network using the standard communication protocol.

Claims

1. A method of providing an active standby control system comprising the step of:

providing a first and a second programmable logic controller, each programmable logic controller having an operating state, an I/O scanner having a connection to a remote I/O head, and a hot standby nodule, wherein each programmable logic controller'"'"'s hot standby module is operably connected together,

operably connecting each programmable logic controller to a network;

assigning a network address identifier to each programmable logic controller, wherein the network address identifier is a Media Access Control address;

placing the first programmable logic controller in primary mode and the second programmable logic controller in secondary mode;

sensing the operating state of each programmable logic controller;

exchanging the network address identifiers between the first programmable logic controller and the second programmable logic controller upon detection of a failure in the first programmable logic controller; and

resetting the connection between the I/O scanner and the remote I/O head in the first primary programmable logic controller prior to exchanging the network address identifiers.

2. The method of claim 1 wherein each programmable logic controller comprises a network module board operably connected to the network and a control unit.

3. The method of claim 2 wherein the network is an Ethernet network.

4. A hot standby system for a control system, comprising:

a first and a second programmable logic controller, each programmable logic controller including;

a network module board having a network address identifier, wherein the network address identifier is a Media Access Control address;

a control unit having an operating state;

an I/O scanner having a connection to a remote I/O head; and

a hot standby module, the hot standby module of each programmable logic controller being operably connected together;

means for assigning the address identifier to each network module board;

means for operably connecting each network module board to a network;

means for sensing the operating state of each control unit, and exchanging the network address identifier of the first programmable logic controller and the network address identifier of the second programmable logic controller upon detection of a failure in the first programmable logic controller; and

means for resetting the connection between the I/O scanner and the I/O head in the first programmable logic controller prior to exchanging the network address identifiers.

5. The hot standby system of claim 4 wherein the network is an Ethernet network.

6. A method of providing an active standby control system comprising the steps of:

providing a first and a second programmable logic controller, each controller having an operating state and an I/O scanner having a connection to a remote I/O head;

operably connecting the first and second programmable logic controllers to each other and to a network;

assigning a network address identifier to designate each programmable logic controller wherein the network address identifier is a Media Access Control address;

placing the first programmable logic controller in primary mode and the second programmable logic controller in secondary mode;

sensing the operating state of the primary mode programmable logic controller;

swapping the network address identifiers between the first and second programmable logic controllers upon detection of a failure in the first programmable logic controller, and placing the second programmable logic controller in primary mode;

resetting the connection between the I/O scanner and the remote I/O head in the first primary programmable logic controller prior to swapping the network address identifiers; and

transmitting reverse address resolution protocol (RARP) messaging to the network, wherein the newly designated programmable logic controller resume network operations.

7. The method of claim 6 wherein the network is an Ethernet network.

8. The method of claim 6 further including the step of aborting all connections to the first and second programmable logic controllers.

9. An active standby system for a control system, the active standby system comprising:

a first and a second programmable logic controller, each programmable logic controller having a network module board, each network module board having a separate network address identifier, wherein the network address identifier is a Media Access Control address, each network module board is operably connected to a network, each programmable logic controller comprising;

a control unit having an operating state;

a remote I/O head;

a hot standby module, the hot standby module of each programmable logic controller is operably connected to each other and to the network, and is configured wherein the network address identifier of each network module board is exchanged upon detection of a failure in the first programmable logic controller; and

and I/O scanner having a connection to the remote I/O head, wherein the first programmable logic controller is configured to reset the connection prior to an exchange of the network address identifiers.

10. The active standby system of claim 9 wherein the network is an Ethernet network.

11. The active standby system of claim 9 wherein the network module is operably connected to the network by a switch.