Data processing: generic control systems or specific application – Generic control system – apparatus or process – Sequential or selective
Reexamination Certificate
2000-01-20
2004-08-03
Patel, Ramesh (Department: 2121)
Data processing: generic control systems or specific application
Generic control system, apparatus or process
Sequential or selective
C700S017000
Reexamination Certificate
active
06772017
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to process control networks and more particularly to configuring and managing process control networks.
2. Description of the Related Art
Large processes such as chemical, petroleum and other manufacturing and refining processes include numerous field devices disposed at various locations within a facility to measure and control process parameters which thereby effect control of the process. These devices may be, for example, sensors such as temperature, pressure and flow rate sensors as well as control elements such as valves and switches. Historically, the process control industry used manual operations such as manually reading level and pressure gauges, turning valve wheels, etc., to operate the measurement and control field devices within a process.
Presently, control of the process is often implemented using microprocessor-based controllers, computers or workstations which monitor the process by sending and receiving commands and data to hardware devices to control either a particular aspect of the process or the entire process as a whole. The specific process control functions that are implemented by software programs in these microprocessors, computers or workstations may be individually designed, modified or changed through programming while requiring no modifications to the hardware. For example, an engineer might cause a program to be written to have the controller read a fluid level from a level sensor in a tank, compare the tank level with a predetermined desired level, and then open or close a feed valve based on whether the read level was lower or higher than the predetermined, desired level. The parameters are easily changed by displaying a selected view of the process and then by modifying the program using the selected view. The engineer typically would change parameters by displaying and modifying an engineer's view of the process.
The controller, computer or workstation stores and implements a centralized and, frequently, complex control scheme to effect measurement and control of process parameters according to an overall control scheme. Usually, however, the control scheme implemented is proprietary to the field device manufacturer, thus making the process control system difficult and expensive to expand, upgrade, reprogram and/or service because the field device provider must become involved in an integral way to perform any of these activities. Furthermore, the equipment that can be used or interconnected may be limited due to the proprietary nature of the field device and the situation where the provider may not support certain devices or functions of devices manufactured by other vendors.
To overcome some of the problems inherent in the use of proprietary field devices, the process control industry has developed a number of standard, open communication protocols including, for example, the HART®, DE, PROFIBUS®, WORLDFIP®, LONWORKS®, Device-Net®, and CAN protocols. These standard protocols enable field devices made by different manufacturers to be used together within the same process control environment. In theory, any field device that conforms to one of these protocols can be used within a process to communicate with and to be controlled by a process control system or other controller that supports the protocol, even if the field devices are made by different manufacturers.
To implement control functions, each process control device includes a microprocessor having the capability to perform one or more basic control functions as well as the ability to communicate with other process control devices using a standard and open protocol. In this manner, field devices made by different manufacturers can be interconnected within a process control loop to communicate with one another and to perform one or more process control functions or control loops. Another example of an open communication protocol that allows devices made by different manufacturers to interoperate and communicate with one another via a standard bus to effect decentralized control within a process is the FOUNDATION Fieldbus protocol (hereinafter the “Fieldbus protocol”) by the Fieldbus Foundation. The Fieldbus protocol is an all digital, two-wire loop protocol.
When using these protocols, a challenge associated with designing the process control system or network relates to the actual physical layout and interconnection of the various process control devices. Specifically, each of these protocols sets forth constraints of values for the physical characteristics within which a process control system must operate to conform to the standard. These constraints include the voltage drop across communication sections, the spur length, the overall cable length, the total current draw and the total number of process control devices on a particular hub. The physical location of vessels, pipes, pumps, motors and valves as well as controllers and operator stations also set forth constraints that must be taken into account when configuring the process control system or network. The interrelationship of these constraints are important and variable based upon the values of the constraints. Once the process control system or network is configured and in use, the managing of the system can be cumbersome due to the complexity of most refining and manufacturing facilities.
In addition to executing control processes, software programs also monitor and display a view of the processes, providing feedback in the form of an operator's display or view regarding the status of particular processes. The monitoring software programs also signal an alarm when a problem occurs. Some programs display instructions or suggestions to an operator when a problem occurs. The operator who is responsible for the control process needs to view the process from his point of view and correct the problem quickly. A display or console is typically provided as the interface between the microprocessor based controller or computer performing the process control function and the operator and also between the programmer or engineer and the microprocessor based controller or computer performing the process control function.
Systems that perform, monitor, control, and feed back functions in process control environments are typically implemented by software written in high-level computer programming languages such as Basic, Fortran or C and executed on a computer or controller. These high-level languages, although effective for process control programming, are not usually used or understood by process engineers, maintenance engineers, control engineers, operators and supervisors. Higher level graphical display languages have been developed for such personnel, such as continuous function block and ladder logic. Thus each of the engineers, maintenance personnel, operators, lab personnel and the like, require a graphical view of the elements of the process control system that enables them to view the system in terms relevant to their responsibilities.
The graphical view of the elements of the process control system are provided without correlation to the spatial layout of the facility and only show logical connections of the devices and functions. For example, a process control program might be written in Fortran and require two inputs, calculate the average of the inputs and produce an output value equal to the average of the two inputs. This program could be termed the AVERAGE function and may be invoked and referenced through a graphical display for the control engineers. A typical graphical display may consist of a rectangular block having two inputs, one output, and a label designating the block as AVERAGE. A different program may be used to create the graphical representation of this same function for an operator to view the average value. Before the system is delivered to the customer, these software programs are placed into a library of predefined user selectable features. The programs are identified by function blocks. A user may t
Dove Andrew Philip
Gardner David Richard
Fisher-Rosemount Systems Inc.
Marshall & Gerstein & Borun LLP
Patel Ramesh
LandOfFree
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