Data processing: generic control systems or specific application – Generic control system – apparatus or process – Plural processors
Reexamination Certificate
1998-08-31
2001-09-11
Grant, William (Department: 2121)
Data processing: generic control systems or specific application
Generic control system, apparatus or process
Plural processors
C700S018000, C700S050000, C700S100000, C700S099000, C709S241000, C709S241000
Reexamination Certificate
active
06289252
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to automated process control and in particular to improved methods and systems for batch process control wherein a phase logic module operable in accordance with a state machine model is integrated within a programmable controller or within a data processing element.
2. Discussion of Related Art
Batch Processing
There are many types of industrial processes. Some run continuously until stopped, typically producing very large quantities of product between start-up and shutdown. Other industrial processes operate on groups of parts, with the group moving as a unit between workstations but with each part maintaining its own unique identity.
A third type of industrial process is the batch process, which involves subjecting raw materials to processing steps using one or more pieces of equipment to produce a “batch” of product. Cooking is an example of a batch process practiced in the home. Raw food is prepared, is placed in a pan, is cooked for a time specified by a recipe, and ends up as a dish or “batch” ready for eating.
Preparation of polyvinyl chloride is an example practiced on an industrial scale. Polyvinyl chloride is made by polymerizing or “joining together” much smaller molecules of vinyl chloride. This is accomplished by filling a batch reactor to the appropriate level with a mixture of vinyl chloride, solvent and polymerization inducer, heating the mixture in the reactor, cooling the resulting batch, and purifying the batch by removing leftover starting materials.
These are but a few examples of batch processes. In general, there are many different kinds of batch processes. They may include, for example, product manufacturing, distribution, and testing as well as several other product and non-product oriented processes.
Batch Process Control
Generally speaking, it is important to control a batch process. For one example, if a dish is left on the stove for too long during cooking, it will burn and the resultant batch of food will be ruined. For another example, if a reaction mixture of vinyl chloride is not reacted long enough, the yield of polyvinyl chloride from the process will be inadequate and money will be lost. Control of a batch process can become critical where production of dangerous chemicals or comparable entities is involved.
One way to control a batch process is manually. That is, one or more workers are assigned the job of watching all aspects of batch process to be sure that everything is proceeding according to plan. However, this is tedious work, and errors can creep in unnoticed.
For these and other reasons, workers in the field of batch control have been trying for some time now to automate the control of batch processes by using electronic devices. Computers, programmable controllers and comparable electronic devices have been used in conjunction with intelligent field devices (i.e., intelligent sensors and controllable valves) by a number of batch control system suppliers to automate the control of batch processes.
An intelligent sensor is typically placed on a piece of equipment and reports on equipment conditions to a central control room in the plant. A controllable valve typically controls the input to, or output from, a piece of equipment, and can be controlled from a central control room, often based on information received from an intelligent sensor.
Efforts to automate batch processing have led to the formation of standards committees by members of industries involved in batch processing and suppliers of batch processing equipment, among others. The general purpose of these standards committees has been to define uniform standards for automated batch processing.
One such standard has been promulgated by the International Society for Measurement and Control, an international organization concerned with issues of process control. This standard is entitled
Batch Control Part
1:
Models and Terminology
and is often referred to as the ISA S88.01-1995 standard (or “S88” for purposes of this application).
The S88.01 standard defines models of equipment and procedures for use in automated batch processes, as well as terminology for use in referring to those models and their elements. The S88.01 standard defines a “batch process” as a process that leads to the production of finite quantities of material by subjecting quantities of input materials to an ordered set of processing activities over a finite period of time using one or more pieces of equipment. A “batch” is defined as the material that is being produced or has been produced by a single execution of a batch process.
Procedural Model
Batch-processing equipment (i.e., controllable elements such as valves, heaters, mixers, etc.) is operated according to procedures to make a batch. For purposes of this application, all such equipment is referred synonymously to as equipment, equipment modules, processing equipment, or physical element. The procedures to operate such physical elements are often referred to by the S88.01 standard as the “procedural model.” According to the S88.01 standard, the procedural model is structured as a hierarchical ranking of procedures, with the highest level encompassing each of the lower levels, the next highest level encompassing each of the levels below it, and so on. The levels of the S88.01 procedural model of particular interest for purposes of this application are, in descending order:
the “procedure”
the “unit procedure”
the “operation”
the “phase”
The term “procedural element” is used in this application to refer to any embodiment or implementation of any of these levels of the S88.01 procedural model, not just to those of the “procedure” level or any other single level of the procedural model.
The highest-level procedural element of interest is referred to as a procedure, which is made up of one or more unit procedures. Each unit procedure is in turn made up of one or more operations, which are each in turn made up of one or more phases. The S88.01 procedural model does not preclude definition and use of other hierarchical levels, nor does it require that each level be present in particular applications. Rather, the standard is intended to provide a broad, standardized model for describing the procedures followed in automated batch-process control.
FIG. 8
graphically depicts the hierarchical relationship of procedural elements defined by the S88.01 standards. A procedure
800
is comprised of one or more unit procedures
802
. Each unit procedure
802
is comprised of one or more operations
804
. Each operation
804
is generally comprised of one or more phases
806
. As noted above each phase is generally in communication with one or more units
820
(a collection of process equipment physical elements) collectively referred to as a process cell
825
to effectuate the desired control of a batch process. As also noted above, other higher level elements of the procedural model are generally abstractions of the lower level elements (i.e., operations are abstractions of one or more phases, etc.).
Linkage of Physical and Procedural Elements
In general, procedural elements are implemented as computer programs that are executed by and within data-processing devices, including personal computers, workstations, and programmable controllers. Execution of a typical procedural element results in an electrical or optical output from the data-processing device that can be used to control a physical element, typically by connecting an output of the data-processing device to the physical element directly, or indirectly over a local-area or wide-area network.
A procedural element performs its assigned task by invoking “basic control” with respect to at least one physical element. This type of control is dedicated to establishing and maintaining a specific desired state of the physical element. Basic control would, for example, start or maintain a flow of material in a storage bin element or heating of starting materials in a polyvinyl chloride reactor element.
In practice, the lower l
Deitz David L.
Irwin William G.
Sherriff Godfrey R.
Wilson Grant
Chrisman Bynum & Johnson, P.C.
Fisher-Rosemount Systems Inc.
Grant William
Patel Ramesh
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