Patent Grant
8086670
The present invention relates generally to industrial controllers, and more particularly to a system and methodology to facilitate optimized data transfers between an industrial controller and one or more remote client applications.
Industrial control systems have enabled modern factories to become partially or completely automated in many circumstances. These systems generally include a plurality of Input and Output (I/O) modules that interface at a device level to switches, contactors, relays and solenoids along with analog control to provide more complex functions such as Proportional, Integral and Derivative (PID) control. Communications have also been integrated within the systems, whereby many industrial controllers can communicate via network technologies such as Ethernet, Control Net, Device Net or other network protocols and also communicate to higher level computing systems. Industrial controllers utilize the aforementioned technologies along with other technology to control multiple applications ranging from complex and highly distributed to more traditional and repetitious applications. As an example, steel and automobile production often require control and integration with complex welding and/or robotic systems whereas, a transfer or automated assembly line can produce hundreds of thousands of similar items in a more traditional industrial control situation.
At the core of the industrial control system, is a logic processor such as a Programmable Logic Controller (PLC). Programmable Logic Controllers are programmed by systems designers to operate manufacturing processes via user-designed logic programs or user programs. The user programs are stored in memory and generally executed by the PLC in a sequential manner although instruction jumping, looping and interrupt routines, for example, are also common. Associated with the user program are a plurality of memory elements or variables that provide dynamics to PLC operations and programs. These variables can be user-defined and can be defined as bits, bytes, words, integers, floating point numbers, timers, counters and/or other data types to name but a few examples.
As can be appreciated, various remote applications often attempt to acquire PLC information or data in order to service other automation requirements. One such application includes a Human and Machine Interface (HMI) that can reside on a remote client machine to enable PLC Engineers or Operators to manipulate and/or monitor PLC control programs and associated variables, for example. Human and Machine Interfaces along with other remote applications often employ network communications and associated drivers or servers to transfer information between the application and the PLC. For example, one common network transfer protocol is referred to as Control and Information Protocol (CIP) that is an application layer protocol that can be specified for Ethernet/IP (Ethernet Industrial Protocol), as well as for ControlNet, DeviceNet and/or other protocols.
Control and Information Protocol is a message-based protocol that implements a relative path to send a message from one or more “producing” devices to one or more “consuming” devices. The producing device can include path information that directs the messages to reach the consumers. Since the producing device holds the path information, other devices along the path can simply pass the information. In traditional PLC systems, controllers poll input modules to obtain their input status. In CIP systems, digital input modules or other producers are not polled by the controller, for example. Instead, these modules produce (“multicast”) associated data either upon a change of state (COS) or periodically. The frequency of update depends upon options chosen during network configuration and where on the network the input module resides. The input module, therefore, is a producer of input data and the controller and/or communications module is a consumer of the data. The PLC can also produce data for other controllers or applications to consume and/or can produce data for other modules to consume such as an output module, for example.
Presently, if remote access of a data type is requested from the PLC via a CIP or other type request for example, the requested data is placed into a communications packet having an associated overhead. The overhead includes a header and ending field, for example, that supports the protocol and encapsulates the data before being transferred to the remote application for processing. If multiple and/or unrelated data types are requested from the PLC however, respective data types can be placed in separate communications packets, wherein the associated packet includes the overhead described above. Consequently, communications efficiency can be reduced since multiple data type transfer requests between PLC's and remote applications can cause increasing amounts of network and communications overhead as the number of data requests increase.
The following presents a simplified summary of the invention in order to provide a basic understanding of some aspects of the invention. This summary is not an extensive overview of the invention. It is intended to neither identify key or critical elements of the invention nor delineate the scope of the invention. Its sole purpose is to present some concepts of the invention in a simplified form as a prelude to the more detailed description that is presented later.
The present invention relates to a system and methodology to facilitate optimized data transfer and communications over a network between a Programmable Logic Controller (PLC) and one or more remote applications. This is achieved by installing an aggregation component in the PLC (or communications module associated with the PLC) that can dynamically buffer, pack and/or accumulate a subset of related and/or unrelated data items before transferring the data as a group or cluster to the remote application that has requested the data. As an example, a remote application such as a Human and Machine Interface (HMI) or other application installs the aggregation component in the PLC and places names or tags relating to data items of interest in the aggregation component (e.g., data that the remote application desires to process). The PLC then updates the data items associated with the tags, wherein the remote application can then read or transfer the items in a singular communications packet. In this manner, information associated with multiple data items is aggregated or accumulated within the communications packet before transfer across the network, thus mitigating the amount of overhead associated with transferring data items as individual or unrelated entities.
In accordance with one aspect of the present invention, the remote application sends a request to the PLC in order to receive and determine name or tag information associated with a plurality of data items defined in the PLC (e.g., substantially any data type, array or structure). The remote application then builds the aggregation component having selected data type names or tags that relate to application data of interest. The aggregation component can be viewed as an optimized packet having an associated buffer for accumulating information and can be implemented as an object. The optimized packet or object is then installed and instantiated on the PLC, wherein the data items identified within the object are updated by the PLC and upon request of the remote application, the data items are assembled in a communications packet and transferred according to the grouping of items defined in the object. It is noted that one or more remote applications can install optimized packets in the PLC, wherein respective applications can install a plurality of such optimized packets if desired.
Optimized packets can be dynamically configured, installed and/or removed such that if the remote application requests related data items, the related data items are packed according to a beginning address of a first item in a group, followed by a length and then followed by the values relating to the items in the group. In this manner, overhead associated with providing individual tag names for respective items in a group or category can be mitigated (e.g., identifying contiguous data items in array/buffer or other association such as a structure or union via a singular tag name associated with one or a limited number of the items in the group). Moreover, if arbitrary or predetermined limitations are placed on the amount of data that may be included in any one communications packet (e.g., limited by network protocols), then additional optimized packets can be dynamically generated and installed in the PLC to facilitate increased data transfer operations and communications. Furthermore, if the remote application reduces or changes the amount of requested data, the optimized data packets can be dynamically reduced, increased, reconfigured, and/or removed as determined by changes in the application over time.
According to another aspect of the present invention, update information or data that is sent to the PLC can be optimized before communicating the information to the PLC. This is achieved by employing data type pointers or handles rather than explicit name identifiers (e.g., ASCII tags of varying lengths that identify various data items) as part of an update header associated with an update request. For example, a remote application first requests the data types or items that are presently defined in the PLC. As part of the request, the PLC supplies explicit tag or name information for the data item, value information associated with the tag, and instance handle information relating to an address or pointer for the tag. When an update is desired, the instance handle can be employed along with an associated update value in place of the explicit tag or name information to indicate which item in the PLC is to be altered or changed. In this manner, the instance handle provides an indirect indication having fixed length (e.g., handles providing 2 byte pointer as opposed to variable length explicit tag names), thus mitigating the amount of information communicated across the network to the PLC when indicating which data item is to be altered.
The following description and the annexed drawings set forth in detail certain illustrative aspects of the invention. These aspects are indicative, however, of but a few of the various ways in which the principles of the invention may be employed and the present invention is intended to include all such aspects and their equivalents. Other advantages and novel features of the invention will become apparent from the following detailed description of the invention when considered in conjunction with the drawings.
The present invention relates to a system and methodology providing enhanced network communications capabilities between an industrial control system and a client application that interacts with a plurality of data items on the control system. The client application initiates a request or query to the industrial control system for an identification of selected data items of interest. Based on information received in the request, an aggregation component can be constructed by the client and/or an associated communications server, wherein names and buffer allocations relating to the data items of interest are provided. The aggregation component is then installed in/updated by the industrial control system, thus providing information access to the client application when fresh or updated information is desired. Information is accessed via a communications packet that is generated from the combination of data items identified in the aggregation component, thus mitigating overhead associated with transferring the items as smaller or discrete quantities. As will be described in more detail below, information sent to the industrial control system can be optimized by identifying the information via handle identifiers as opposed to explicit reference or tag names that may be of varying lengths.
Referring initially to
The display 50 can be employed to provide feedback and output data to a user regarding various aspects of communications, preferences, configurations and/or adjustments relating to the controller 30. The display 50 can include display objects (e.g., icons, buttons, sliders, input boxes, selection options, menus, tabs and so forth) having multiple dimensions, shapes, colors, text, data and sounds to facilitate optimal interactions with the controller 30. In addition, various menus and alternative screens or display outputs can be provided that perform a plurality of aspects of the present invention, wherein the inputs 54 can be employed for adjusting and configuring the menus and screens. This can include receiving user commands from a mouse, keyboard, speech input and/or other device to effect operations of the client application 40 and controller 30.
According to one aspect of the present invention, the client application 40 determines that one or more data items of interest are to be retrieved from the industrial controller 30. For example, a user may request via the input 54 and associated menu that a plurality of related or unrelated data items of interest are to be presented to the display 50 in order to provide status or other information regarding the controller 30. Based on the user's request, the client application 40 can initiate a data transfer via the communications component 44, wherein a request 60 is generated that specifies the data items of interest and sent to the controller 30. The request 60 is processed by a communications interface 64 on the controller 30, whereby an initial response 70 is generated and transmitted back to the communications component 44. The initial response 70 includes tag, address, pointer and/or name information relating to controller memory locations (described below) for associated data items of interest that was initially requested by the client application 40.
Based upon the response 70 and the associated tag information, the client application 40 and/or the communications component 44, builds and subsequently installs one or more aggregation components 80 in the controller 30 that can be employed as a data communications buffer for the requested data items. The aggregation component 80 is periodically updated by the controller 30 in accordance with data values associated with the data items of interest specified therein. According to subsequent requests for data from the communications component 44, an optimized response 84 can be generated by the communications interface 64 on the controller that includes substantially all or significant portions of the contents of the aggregation component 80. Thus, a plurality of data items that are requested by the client application 40 can be aggregated, transmitted and provided in a substantially larger or singular communications packet (e.g., via a network signal or data packet). In this manner, communications performance can be enhanced since overhead associated with transmitting data items as individual packets is mitigated (e.g., mitigating repeated and redundant header and ending data that is generally associated with a network communications packet). As will be described in more detail below, the aggregation components 80 can be dynamically added or removed depending on the amount of data requested by the client application 40. In addition, respective aggregation components 80 can be increased or decreased in size (e.g., buffer elements added or removed) depending on increased or decreased data demands from the client application 40.
Referring now to
Based upon the determination, a request is generated to the communications server 160 and sent to the communications driver 130. The request is provided to the processor 120 and causes the processor to access the variable memory 140 for one or more of the requested data items 144. As an example, the processor 120 may have access to one or more megabytes of variable memory 140, wherein 250 bytes are requested from the data items 144. The processor 120 locates tag information relating to the requested data items 144 and provides the tag information to the communications driver 130 that is then transmitted to the communications server 160 as a response. According to the tag information in the driver response, the client application 154 and/or communications server 160 construct and install the optimized packet 116 via the communications driver 134 and processor 120. The optimized packet is thus configured as a portion, subset or selection of the data items 144.
According to periodic intervals such as a real time interrupt, the processor 120 can access the data items 144 and update/refresh the optimized packet 116 according to the data items that are selected and specified within the packet. It is noted that the optimized packet 116 can also be updated according to asynchronous communications requests from the communications server 160. When the client application 154 determines that updated or refreshed data is desired, a data request can be generated to the communications server 160 and sent to the communications driver 130. The data request causes the processor 120 to copy the specific items requested from the optimized packet 116 into a buffer (not shown) accessible by the communications driver 130, wherein an aggregated communications packet is constructed and transmitted as a response to the data request. In this manner, a plurality of related or unrelated (not in contiguous memory portions or of the same data type) data items can be transmitted in a singular communications packet, thereby mitigating overhead associated with transmitting these items according to individual data item requests.
Turning to
In accordance with the dynamic aspects of the present invention, if additional data were requested (e.g., an additional 1000 bytes above 1200 bytes), then additional optimized packets 214-218 can be added to support the increased data demand. Likewise, if the client application 254 were to reduce requested data demands, optimized packets 214-218 can be removed from the controller 212 via an associated request from the client application 254 and associated communications server 260.
In accordance with another aspect of the present invention, data within an optimized packet 214-218 can be dynamically adjusted. For example, if the optimized packet 214 were initially configured to transmit a certain amount of data (e.g., 750 bytes of data initially specified), and over a period of time, more or less than the initially specified amount of data were actually requested by the client application 254, then the optimized packet 214 can be reconfigured according to the changed or varying amount of requested data. Thus, communications packets can be dynamically tailored and optimized within a respective packet according to the actual amount of data requested by the client application 254 in order to mitigate transmission of superfluous or un-requested data across the network 270.
Instance attributes 320 include such aspects as object update times, event triggers, whether to update the object based on rate or demand or other criteria, where in the data stream triggers are located, whether to continue on an overflow, number of trending drivers currently installed, timestamp information, size of buffers, start times, an object lifetime settings. An exemplary listing of instance attributes 320 is illustrated below in Example 2.
Object Services 330 include such services as Get All Attributes, Get All List, Set Attributes List, Reset, Start, Stop, Create Object and Delete Object and are described in more detail below in Example 3.
The buffer region 340 includes 1 to L data items, L being an integer. The data items can be configured in substantially any manner. For example, this can include bit, byte, 16 bit, 32 bit or greater word configurations, unsigned or signed integer or floating point elements, and single or multiple dimension array configurations to name but a few examples.
To further illustrate the buffer region 340,
Another type structure relates to one or more user defined tags 470 having 1 to J defined elements, J being an integer. The user defined tag (UDT) 470 can consist of different types of elements (e.g., SINT, INT, DINT, REAL) and/or other complex structures such as Timers, Counters, Arrays and/or other user defined tags. The communications server described above optimizes reading of the UDT 470 by requesting a blob (Binary Large Object) of data consisting of the elements defined in the UDT, and then parsing out the desired items or elements of interest from the blob for the client application. The request for UDT elements can include a first element in the UDT followed by a length specifier to indicate how many bytes of data to read.
Referring to
Referring now to
When the client machine 820 or related application determines that a data update is to be transmitted to the controller 810, an update component 850 employs the handle information received in the response 844 to build an update packet 852 having a handle field 854 and an associated value 860. The update packet 852 is transmitted to the controller 810, wherein a mapping component 870 employs the handle field 854 to place or locate the value 860 at the address pointed to by the handle 854. By employing the handle 854 in place of explicit tag references to place or locate updated data in the controller 810, network bandwidth can be conserved. This can be achieved since explicit tags are often lengthy and consist of variable lengths thus causing variable and often larger amounts of data to be transmitted. The handle 854 can be employed as a consistent one or two byte data reference (or other consistent amount) that generally tends to mitigate the overall amount of data to be transmitted when compared to explicit tag references.
Turning to
What has been described above are preferred aspects of the present invention. It is, of course, not possible to describe every conceivable combination of components or methodologies for purposes of describing the present invention, but one of ordinary skill in the art will recognize that many further combinations and permutations of the present invention are possible. Accordingly, the present invention is intended to embrace all such alterations, modifications and variations that fall within the spirit and scope of the appended claims.
This application is a continuation of U.S. patent application Ser. No. 10/092,323, filed on Mar. 6, 2002, entitled “SYSTEM AND METHODOLODY PROVIDING OPTIMIZED DATA EXCHANGE WITH INDUSTRIAL CONTROLLER”, the entirety of which is incorporated herein by reference
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