Patent Application
20120249268
The present invention relates to data communication systems, in particular, to systems and termination of industrial process multi-point data communication connections between and among process workstations and process monitor and control devices.
Industrial environments and processes include manufacturing or processing sub-components which are located or are arranged in parallel and/or in sequence until the end of the process. Each manufacturing or processing sub-component often communicates with other sub-components or a controller, typically a programmable logic device, e.g. a specialized computer. Due to the nature of the industrial process, such sub-components are widely physically distributed in a somewhat hostile industrial environment, yet is required to be tightly integrated to maintain efficient execution of the process, which requires flexible and easy installation and reliable operation over the lifetime of the industrial process.
At least one standard of data and power distribution among the process sub-components provides a first pair of wires dedicated exclusively to power distribution and a separate pair of wires dedicated exclusively to data communication which are bundled together with the power distribution pair of wires in a common cable. For example, according to the DeviceNet™ standard defined by the Open DeviceNet Vendor Association, data is exchanged over the data pair of wires which generally extend from a first end to a second end and have a termination resistor at each end substantially at the nominal (standardized) impedance of the data pair impedance, i.e. 120 ohms. Typically the power distribution pair of wires receives a constant power, e.g. 24 VDC of up to 16 amperes by a power connection for distribution to the process sub-components attached thereto. A sub-component is typically connected to both pairs of wires with a connector which connects to the power distribution pair and also provides connection to the data trunk. In the DeviceNet™ and other industrial bus specifications, no impedance is specified for the power distribution pair of wires, and no termination elements applied to the power distribution pair of wires.
The present industrial communication system and devices are typically used in an industrial environment with a process that includes a number of workstations, cells or process operations along the work flow or the conveyor line, and includes the work station power distribution line running along side the work flow or conveyor line, and individual data units connected between the individual work stations and the power distribution line, and may further include a similar connection by a data unit between a process controller and the power distribution line, providing a selective flow of data is provided between and/or among the individual work stations and/or a workstation and the process controller. A separate data distribution, or data trunk line is also present to provide a data path separate from data present on the power distribution line as described above.
According to exemplary embodiments of the present invention, each of the power distribution and data distribution lines are terminated by a termination device typically placed at each end of each of the power distribution and data distribution lines. For instance, according to the Open DeviceNet Vendor Association (ODVA) standard 5-wire (2 pairs plus ‘drain’) data and power distribution cable, impedances (e.g. 120 ohms) are applied at each end of each of the data wire pair and power wire pair.
As further described in INDUSTRIAL PROCESS COMMUNICATION SYSTEM, Ser. No. 12/925,775, filed Nov. 1, 2010 and incorporated herein by reference, further inventive embodiments of the present invention include a secondary or redundant power distribution line to which the individual data units may also be connected and data selectively transmitted therethrough for additional bandwidth, alternate control signals or a substitute primary data path in the event of primary power line failure or deteriorated transmission quality. Moreover, further embodiments include the powering of the data units from power derived from the power distribution line(s), and integration and/or embedding some or all of the communications elements of the present invention into the structure, e.g. circuit boards, of the workstations and other devices connected to primary and/or secondary power lines.
The embodiments of the present invention provide a robust, reliable, flexible, easily installed or modified, and relatively low cost communication system operable together with hardware and signaling protocols of prior standardized systems to provide additional features of the present invention.
These and further features of the present invention will be better understood by reading the following Detailed Description together with the Drawing, wherein
An exemplary system 50 according to the present invention is shown in
The power distribution path 52P is energized with system 50 power, typically up to 48 VDC by a power supply 66 disposed between the ends 54 and 56 of the cable 52 and connected to the power distribution path via a terminator 64 which is connected to the power distribution path 52P and optionally the data distribution path 52D. Optionally, the power supply may be connected to an end, e.g. at 56 via a terminator 64 in place of the terminator 60.
Equipment 70 which conforms to the signaling standards of the cable, e.g. ODVA DeviceNet™ protocol, may be connected to both data distribution lines 52D and power distribution lines 52P as provided by that standard along those lines at “T” junction boxes, barrier connectors, etc. 62, as may equipment 72 which communicates via the power distribution lines 52P may be connected, as is further described by co-pending application Ser. No. 12/925,775 referenced above and incorporated herein. Moreover, equipment 74 which communicates by data over both the data distribution path 52D and the power distribution path 52P (e.g. as defined by the above mentioned standards). Typically the equipment 70, 72 and/or 74 presents an impedance to the respective paths substantially at the value of the respective path impedance to avoid signal reflections along the respective path.
An exemplary terminator 80 is shown in
Optionally, a power supply 66A may be connected to provide power the power distribution lines 52P via connector 90 pins 92 and 93 via a balanced ‘common mode’ inductor 96 having 2 windings, connected to provide the 2 power supply paths (to connections 91 and 92), wound around a common core or air space,
An alternative embodiment 84 of the terminator and shown in
Other connectors such as the ‘mini-sealed’ and ‘open styled’ connectors, connector elements or connector gender, and cable types, sizes and impedances as provided by the ODVA DeviceNet™ specifications, and other networks such as Profibus™ of Siemens AG, Interbus-S™ of Benden, Inc, GeniusBus of General Electric Company, Modubus™ of Modbus Organization, Fieldbus™ of Fieldbus Foundation, CANbus of Robt. Bosch GmbH, Seriplex of Belden, Inc., SDS™ of SDS Council, Honeywell Micro Switch Div., and others bus structures which have a data path and a separate power path, or have a data path and a separate power path is added, are within the scope of the present invention. Further modifications and substitutions by one of ordinary skill are within the scope of the present invention which is not to be limited except by the claims which follow.
