DESC:COMMUNICATION INTERFACE SYSTEM FOR PROCESS AUTOMATION CONTROL SYSTEMS

Field of the invention:

The present invention relates to the field of process control systems and more particularly, to a communication interface system used in process automation control systems such as Programmable Logic Controllers (PLCs) or Distributed Control Systems (DCS) to establish redundant communication between input-output modules with controllers or Central Processing units (CPU).

Background of the invention:

Process automation control systems like PLC (Programmable Logic Control) or DCS (Distributed Control System) comprises of input-output modules (I/O modules) and a controller. The input modules acquire data of process variables such as temperature, pressure, flow, level etc. which are sent to the controller over a communication bus. The controller processes the input data and sends control outputs to the output modules over the communication bus.

In order to ensure reliable and fail-safe operation, advanced control systems provide redundancies for the controllers as well as for the communication buses. In the event of failure of the controller, a stand-by controller takes over the operations seamlessly. Similarly, in the event of failure of the communication bus, a redundant communication bus takes over from faulty bus seamlessly.

Present automation systems such as PLCs or DCS have redundant communication interfaces for communication between the controllers and the I/O modules as shown in figure 1. Typically, the communication interfaces are external to the controllers. The communication interface modules communicate with the controllers and the I/O modules through backplanes. Such method for communication through the backplanes is typically known as a ‘Parallel Data Bus’.

Drawbacks in the prior art:
1. The parallel data buses are complex hardware involving several data lines.
2. Any discontinuity in the backplanes can affect communication with the I/O modules ahead of a point of occurrence of fault.
3. The communication interfaces are typically separate hardware modules and not as integral part of the controllers.
4. Systems with prior art are provided with redundant communication interfaces for the I/O modules at one end of the communication bus intended for the I/O modules.
5. The controllers in the prior art system do not have integrated redundant communication interfaces.
6. Most of the systems with the prior art have an active parallel communication bus for the I/O Modules. This bus has complex mechanism, particularly for implementing redundancy.

Accordingly, there exists a need to provide a communication interface system for the process automation control systems, that overcomes the abovementioned drawbacks of the prior art.

Objects of the invention:

An object of present invention is to simplify communication techniques used for communication between controllers and input-output modules of a process automation control systems.

Yet another object of the present invention is to improve integrity of the communication between the controllers and the input-output modules.

Summary of the invention:

Accordingly, the present invention provides a communication interface system used in process automation control systems. The system comprises a plurality rows of input-output modules (hereinafter referred as, “the I/O modules”), a plurality of bus connectors, at least two sets of bus interface modules and at least two process redundant controllers connected in operable communication with each other. Each input-output modules is mounted with a bus connector on a metal rail such as DIN rail. Each row of the I/O modules having a first end and a second end. A first bus interface module and a second bus interface module are connected to the first end and the second end of the each row through the bus connectors, respectivley. Each redundant controller has at leat two redundant serial communication ports. At least two redundant serial communication buses includes a first serial communication bus that is connected to the first bus interface module and a second serial communication bus that is connected to the second bus interface module. Connectivity between the I/O modules and each bus interface modules is provided through a multi-drop serial communication bus.

Each I/O module thus has two alternate paths for communication with the two process redundant controllers. Both the communication buses are connected to both the redundant controllers through their respective redundant communication ports. Each of the input-output modules communicates with each of the controllers for providing inputs thereto and receiving outputs therefrom. An inter-controller communication link is provided for communication between the first controller and the second controller. Any one of the redundant controllers is active and other remains in standby so that the active controller passes on all information about current status of acquired data and processing of the same over inter-controller communication link. This ensures that both controllers are in synchronism with each other and a standby controller is ready to take over from a failed controller to avoid a point of occurrence of fault.

Brief description of the drawings:

The objects and advantages of the present invention will become apparent when the disclosure is read in conjunction with the following figures, wherein

Figure 1 shows a block schematic diagram of a communication interface system
for a process automation control system, in accordance with a prior art;

Figure 2 shows a block schematic diagram of a communication interface system for a process automation control system, in accordance with the present invention.

Detailed description of the invention:

The foregoing objects of the present invention are accomplished and the problems and shortcomings associated with the prior art, techniques and approaches are overcome by the present invention as described below in the preferred embodiments.

The present invention provides a communication interface system used in process automation control systems such as Programmable Logic Controllers (PLCs) or Distributed Control Systems (DCS) to establish redundant communication between input-output modules (I/O modules) with controllers or Central Processing units (CPUs). The communication interface system is about checking integrity of communication links between the controllers and I/O modules. Specifically, the communication interface system provides a technique used for interfacing the I/O modules with the controllers.

The present invention is illustrated with reference to the accompanying drawings, throughout which reference numbers indicate corresponding parts in the various figures. These reference numbers are shown in bracket in the following description.
Referring to figure 2, a communication interface system (100) (hereinafter referred as, “the system (100)”) for process automation control systems, in accordance with the present invention is shown. Specifically, the figure 2 shows a schematic block diagram of overall architecture of the system (100).

The system (100) is primarily intended for automatic control systems for processes where high level of reliability is expected such as chemical plants, pharmaceutical processes, power plants, process boilers, metallurgical processes and like, but not limited thereto. In an exemplary embodiment, any automation system, a process variable which is to be monitored and or controlled is sensed by sensors / transmitters and converted into electrical signals. Typical process variables are temperature, pressure, flow, level, pH, conductivity, which are analogue signals (continuously variable) and switches, push-buttons etc., which are digital (only two states). These signal are connected to the input-output modules (I/O Modules), which in turn pass-on these signals to controller through a communication network. The controller contains necessary software for decision making logic. For example, in a steam-heating control logic, if the controller finds that the measured temperature is less than the required one, the controller issues a command for a valve to open more so as to increase the heating. This command is passed-on to the I/O module, which in turn passes the command to appropriate control valve intended for regulating the steam supply.

For critical applications demanding high reliability, it is essential to ensure that all the elements involved in the measurement, communications and control are highly reliable. To augment the reliability, hot redundancy is provided for all the elements including the I/O modules, the communication buses and the controllers. The present invention is pertaining to a novel technique for redundant communication links between the controllers and the I/O modules.

The system (100) comprises a plurality rows (10) of input-output modules (hereinafter referred as, “the I/O modules”), a plurality of bus connectrors (20), at least two sets of bus interface modules (30A, 30B), at least two process redundant controllers (40A, 40B) connected in operable communication with each other.

Each row (10) of the I/O modules has a first end (not numbered) and a second end (not numbered). In an emboidiment only three rows (10) of the I/O modules are shown in the figure 2 for illustrative purpose. However, it is understood that plurality of the rows (10) includes 1st row of the I/O modules, 2nd row of the I/O modules, upto Nth row of the I/O modules. Each the I/O modules of the each row (10) are mouned on a metal rail including a DIN rail (16). Each of the I/O modules is mounted with a bus connector (20) that is stackable connector. Each of the I/O modules comprises an input-output signal conditioning circuit (not shown), a microcontroller (not shown) and a serial communication interface (not shown).

Each row (10) of the I/O modules comprises any one or more I/O modules selected from an analog input module (1), an analog output module (2), a pulse input module (3), a digital input module (4) and a digital output module (5). The analog input module (1) is arranged for receiving analog inputs (11) from any of temperature sensors, pressure sensors, flow sensors/transmitters and like, but not limited thereto. The analog output module (2) is arranged for providing analog outputs (12) to any of control valves and regulation equipments, and like, but not limited thereto. The pulse input module (3) is arranged for receiving pulse inputs (13) from the flow transmitters. The digital input module (4) is arranged for receiving digital inputs (14) from any of limit switches, push buttons and like, but not limited thereto. The digital output module (5) is arranged for providing analog outputs (15) to any of pumps, motors and like, but not limited thereto. The I/O modules (1, 2, 3, 4, 5) are shown in the figure 2 for illustrative purpose. However, it is understood that types and quantities of the I/O modules can be varied based on types of the process automation requirements.

A first bus interface module (30A) is connected to the first end of the each row (10) through the bus connectors (20) of each I/O modules. A second bus interface module (30B) is connected to the second end of the each row (10) through the bus connectors (20) of each I/O modules. In a specific embodiment, the connectivity between the each input-output module of the each row (10) and each bus interface modules (30A, 30B) is provided through a multi-drop serial communication bus.

A first serial communication bus (35A) is arranged to communicate with each of the first bus interface module (30A) for transferring data information to and fro. A second serial communication bus (35B) is arranged to communicate with each of the second bus interface module (30B) for transferring data information to and fro. In a specific embodiment, both communication buses (35A, 35B) are redundant communication buses connected to redundant bus interface modules (30A, 30B).

A first controller (40A) has a first serial communication port (42A) arranged for coupling to the each first bus interface module (30A) through the first serial communication bus (35A) and a second serial communication port (44A) arranged for coupling to the each second bus interface module (30B) through the second serial communication bus (35B). A second controller (40B) has a first serial communication port (42B) arranged for coupling to the each first bus interface module (30A) through the first serial communication bus (35A) and a second serial communication port (44B) for coupling to the each second bus interface module (30B) through the second serial communication bus (35B). The first serial communication ports (42A, 42B) and the second serial communication ports (44A, 44B) act as redundant communication ports for each of the controllers (40A, 40B). Specifically, the redundant communication ports (42A, 42B) and (44A, 44B) are made integral to the controllers (40A, 40B). Each of the I/O modules communicates with each of the controllers (40A, 40B) for providing inputs thereto and receiving outputs therefrom.

An inter-controller communication link (50) is provided for communication between the first controller (40A) and the second controller (40B). The first controller (40A) and the second controller (40B) are redundant to each other. Any one of the first controller (40A) and the second controller (40B) is active and other remains in standby so that the active controller passes on all information about current status of acquired data and processing of the same over inter-controller communication link (50), thereby ensuring that both the controllers (40A, 40B) are in synchronism with each other and a standby controller is ready to take over from a failed controller to avoid a point of occurrence of fault.

Each controller (40A, 40B) comprises a processor (not shown), a watchdog circuit (not shown), an interface circuit (not shown) and at least two communication ports (46A, 46B) for communicating with at least one engineering-cum-operator station via at least two redundant Ethernet switches (110A, 110B). Multiple engineering-cum-operator stations (120A, 120B) are shown in figure 2 for illustration purpose. Operations carried out by the controllers (40A, 40B) are communicated to the engineering-cum-operator stations (120A, 120B) that are configured around standard computers. Redundancy is provided for the communication between the controllers (40A, 40B) and the engineering-cum-operator stations (120A, 120B) with the help of redundant switches (110A, 110B) and respective communication links (not numbered).

In an exemplary embodiment, process signals like temperature, pressure, flow, level etc. in the form of electricals signals (milliamps / volts / ohms) are connected to the input modules (1). The microprocessor / microcontroller (not shown) inside the the input modules (1) translates the process signals into a digitally communicable form and passes on to each of the first and second bus interface modules (30A, 30B). Each of the first and second bus interface modules (30A, 30B) passes on the procees signal to the each controller (40A, 40B) over both communication buses (35A, 35B).

The active controller from the controllers (40A, 40B) takes a decision regarding control action to be taken and informs the same over both communication buses (35A, 35B) to the output modules (2). This information is passed through the each of the first and second bus interface modules (30A, 30B). The output modules (2) translate the command received from the active controller of each controllers (40A, 40B) to appropriate electrical signal (milliamps / volts) and passes on to final control element such as control valve or any other regulation equipment.

The process described above is for analog signals. Similar process is carried out for other types of signals like digital inputs and outputs via the input modules (4) and the output modules (5).

Each of the controllers (40A, 40B) interacts with the at least one engineering-cum-operator station via at least two redundant Ethernet switches (110A, 110B). Multiple engineering-cum-operator stations (120A, 120B) are shown in figure 2 for illustration purpose. An operator can set the required control parameters and inform the controllers (40A, 40B) accordingly. Each of the controllers (40A, 40B) informs the at least one engineering-cum-operator station about the actions taken and status of various process signals and hardware involved.

In the embodiment, the each I/O module communicates with each of the controllers (40A, 40B) at both ends of each row (10) through two alternate paths including a first path via the first bus interface module (30A) at the first end of the bus through the first serial communication bus (35A) and then to the first serial communication ports (42A, 42B) of each controllers (40A, 40B) and a second path via the second bus interface module (30B) at the second end of the bus through the second serial communication bus (35B) and then to the second serial communication ports (44A, 44B) of each controllers (40A, 40B). Specifically, both the first serial communication bus (35A) and the second serial communication bus (35B) are connected to both the redundant controllers (40A, 40B) through their respective redundant communication ports (42A, 42B) and (44A, 44B).

Thus, the system (100) provides a novel technique for communication from the I/O modules of each row (10) by two ends of the communication bus interface modules (30A, 30B) to the at least two process redundant controllers (40A, 40B), thereby avoiding a point of occurrence of fault. As stated above, for enhanced reliability, all the elements including each of the I/O modules, the first and second serial communication buses (35A, 35B), the first and second controllers (40A, 40B) are made redundant with automatic changeover from a failed one to standby element.

Advantages of the invention:

1. The system (100) involves simpler architecture, hence better reliability and easier maintainability.
2. The system (100) has a compact design of system hardware.
3. The system (100) provides better communication integrity.
4. The system (100) provides connectivity to the I/O modules from both ends of the communication bus for the I/O Modules.
5. The system (100) considers built-in redundant communication ports for each of the controllers (40A, 40B).
6. The system (100) considers serial bus for simplicity and ease of implementing redundancy.

The foregoing objects of the invention are accomplished and the problems and shortcomings associated with prior art techniques and approaches are overcome by the present invention described in the present embodiment. Detailed descriptions of the preferred embodiment are provided herein; however, it is to be understood that the present invention may be embodied in various forms. Therefore, specific details disclosed herein are not to be interpreted as limiting, but rather as a basis for the claims and as a representative basis for teaching one skilled in the art to employ the present invention in virtually any appropriately detailed system, structure, or matter. The embodiments of the invention as described above and the methods disclosed herein will suggest further modification and alterations to those skilled in the art. Such further modifications and alterations may be made without departing from the scope of the invention.
,CLAIMS:We claim:

1. A communication interface system (100) for process automation control systems comprising:
a plurality rows (10) of input-output modules, each row (10) having a first end and a second end, wherein each input-output modules is mounted with a bus connector (20);
a first bus interface module (30A) connected to the first end of the each row (10) through the bus connectors (20);
a second bus interface module (30B) connected to the second end of the each row (10) through the bus connectors (20);
a first serial communication bus (35A) arranged to communicate with the first bus interface module (30A);
a second serial communication bus (35B) arranged to communicate with the second bus interface module (30B);
a first controller (40A) having,
• a first serial communication port (42A) for coupling to the each first bus interface module (30A) through the first serial communication bus (35A), and
• a second serial communication port (44A) for coupling to the each second bus interface module (30B) through the second serial communication bus (35B);
a second controller (40B) having,
• a first serial communication port (42B) for coupling to the each first bus interface module (30A) through the first serial communication bus (35A), and
• a second serial communication port (44B) for coupling to the each second bus interface module (30B) through the second serial communication bus (35B);
wherein, each of the input-output modules communicates with each of the controllers (40A, 40B) for providing inputs thereto and receiving outputs therefrom; and
an inter-controller communication link (50) provided for communication between the first controller (40A) and the second controller (40B), wherein the first controller (40A) and the second controller (40B) are redundant to each other and any one of the first controller (40A) and the second controller (40B) is active and other remains in standby so that the active controller passes on all information about current status of acquired data and processing of the same over inter-controller communication link (50), thereby ensuring that both the controllers (40A, 40B) are in synchronism with each other and a standby controller is ready to take over from a failed controller to avoid a point of occurrence of fault.

2. The communication interface system (100) as claimed in claim 1, wherein the connectivity between the each input-output module and each bus interface modules (30A, 30B) is provided through a multi-drop serial communication bus.

3. The communication interface system (100) as claimed in claim 1, wherein the each input-output module communicates with each of the controllers (40A, 40B) at both ends of each row (10) through two alternate paths including,
a first path via the first bus interface module (30A) at the first end of the bus through the first serial communication bus (35A) and then to the first serial communication ports (42A, 42B) of each controllers (40A, 40B), and
a second path via the second bus interface module (30B) at the second end of the bus through the second serial communication bus (35B) and then to the second serial communication ports (44A, 44B) of each controllers (40A, 40B).

4. The communication interface system (100) as claimed in claim 1, wherein the each row (10) of the input-output modules comprises any one or more input-output modules selected from:
an analog input module (1) arranged for receiving analog inputs (11) from any of temperature sensors, pressure sensors, flow sensors/transmitters;
an analog output module (2) arranged for providing analog outputs (12) to any of control valves and regulation equipments;
a pulse input module (3) arranged for receiving pulse inputs (13) from flow transmitters;
a digital input module (4) arranged for receiving digital inputs (14) from any of limit switches, push buttons; and
a digital output module (5) arranged for providing analog outputs (15) to any of pumps and motors.

5. The communication interface system (100) as claimed in claim 1, wherein the each input-output modules of the each row (10) are mouned on a metal rail including a DIN rail (16).

6. The communication interface system (100) as claimed in claim 1, wherein the first serial communication ports (42A, 42B) and the second serial communication ports (44A, 44B) act as redundant communication ports for each of the controllers (40A, 40B).

7. The communication interface system (100) as claimed in claim 1, wherein the each controller (40A, 40B) comprises a processor, a watchdog circuit, an interface circuit and at least two communication ports (46A, 46B) for communicating with at least one engineering-cum-operator station via at least two redundant Ethernet switches (110A, 110B).

Dated this 22nd day of May 2020

Madhavi Vajirakar
(Agent for the Applicant) (IN/PA-2337)