MXPA97002915A - Apparatus for providing access to field devices in a distribution control system - Google Patents

Abstract

The present invention relates to a distributed control system comprising: a control room for providing primary control of the distributed control system, a plurality of network-based field devices with each network-based field device having a port of primary control network, a control network coupled with each primary control network port of each network-based field device of the plurality of network-based field devices, a controller coupled with the control salt, to control and providing primary access to the plurality of network-based field devices, a network / controller connection means for counting the control network with the controller, and a secondary access means for providing secondary and non-redundant access to the plurality of field devices based on r

Description

"APPARATUS FOR PROVIDING ACCESS TO FIELD DEVICES IN A DISTRIBUTED CONTROL SYSTEM" BACKGROUND OF THE INVENTION This invention relates to providing access to field devices in a distributed control system. Specifically, this invention relates to providing remote access to these field devices using wireless transceivers, providing access to functions of field devices that can not be accessed by the controller of the distributed control system, and providing redundant wireless access to these devices. Remote field devices using wireless transceivers. In a typical industrial plant, a distributed control system (DCS) is used to control many of the industrial processes carried out in the plant. Typically, the plant has a centralized control room that has a computer system with I / O peripherals, I / O disk, and other peripherals that are known in the computer industry. Coupled with the computer system in a controller and an I / O process subsystem.

The I / O process subsystem includes a plurality of I / O ports that connect to the various field devices across the plant. Field devices known in the field of control include various types of analytical equipment, silicon pressure sensors, capacitive pressure sensors, resistive temperature detectors, thermoelectric cells, strain gauges, limit switches, on / off switches, flow transmitters, pressure transmitters, capacitance level switches, scales, transducers, valve setters, valve controllers, actuators, solenoids, and indicator lights. As used herein, the term "field device" encompasses these devices, as well as any other device that performs a function in a distributed control system and is known in the art of control. Traditionally, analog field devices have been connected to the control room by two wire twisted pair current circuits, with each device connected to the control room by a single twisted pair of two wires. Analog field devices are capable of responding to or transmitting an electrical signal within a specified scale. In a typical configuration, it is common for there to be a differential voltage of approximately 20 to 25 volts between the two wires of the torque and current of 4 to 20 milliamperes that runs through the circuit. An analog field device that transmits a signal to the control room modulates the current flowing through the current circuit, with the current proportional to the process variable detected. On the other hand, an analog field device that performs an action under the control of the control room is controlled by the magnitude of the current through the circuit, which is modulated by the I / O port of the process system of I / O, which in turn is controlled by the controller. The traditional two-wire analog devices have active electronics and can receive up to 40 milliwatts of energy from the circuit. The analog field devices that require more power typically connect to the control room using four wires, with two of the wires supplying power to the device. These devices are known in the art as four-wire devices, and are not energy limited as the two-wire devices. In contrast, traditional discrete field devices transmit or respond to a binary signal. Typically, discrete field devices operate on a 24 volt signal (either alternating current or direct current), an AC signal of 110 or 240 volts, or a direct current signal of 5 volts. Of course, a discrete device can be designed to function in accordance with any electrical specification required by a specific control environment. A discrete input field device is simply a switch that either effects or interrupts the connection to the control room, while a discrete output field device will take an action based on the presence or absence of a signal from the control room. Historically, more traditional field devices have either a single input or a single output that is directly related to the primary function carried out by the field device. For example, the only function implemented by the traditional analog resistive temperature sensor is to transmit a temperature by modulating the current flowing through the pair of twisted wires, whereas the only function implemented by a traditional analog valve sealer is to place a valve between an open and closed position, inclusive, based on the magnitude of the current flowing through the pair of twisted wires.

More recently, hybrid systems have been used that superimpose the digital data in the current circuit, in the distributed control systems. A hybrid system in the control field is known as the Distant Highway Dirigible Transducer (HgART) and is similar to the Bell 202 modem specification. The EART system uses the magnitude of the current in the current circuit to detect a variable of the process (like the traditional system), but also superimposes a digital carrier signal on the current circuit signal. The carrier signal is relatively slow, and can provide updates of a secondary process variable at a rate of approximately 2 to 3 updates per second. In general, the digital carrier signal is used to send secondary and diagnostic information and is not used to obtain a primary control function of the field device. Examples of information that are provided through the carrier signal include secondary process variables, in diagnostic training (including sensor diagnostics, device diagnostics, wiring connection diagnostics and process diagnostics), operating temperatures, temperature of the sensor, calibration information, device ID numbers, construction materials, configuration or programming information, etc. Accordingly, an individual hybrid field device can have a variety of input and output variables and can implement a variety of functions. The HÍVRT system is a normal industrial system of no property. However, it is relatively slow. Other companies in the industry have developed digital property transmission projects that are faster but these projects are usually not used or available to competitors. More recently, a newer control protocol has been defined by the Instrument Society of America (ISA). The new protocol is usually called Fieldbus, and is especially referred to as SP50, which is an acronym for Standards and Practice Subcommittee 50. The Fieldbus protocol defines two sub-protocols. A Fieldbus Hl network transmits the data at a rate of up to 31.25 ilobits per second and provides power to the field devices coupled to the network. A Fieldbus H2 network transmits the data at a rate up to 2.5 megabits per second, does not provide power to the field devices connected to the network, and is provided with redundant transmission media. The Fieldbus is an open, non-proprietary standard that is attracting attention in the industry.

As additional protocols and popularity of architecture gain in the industry, the industry will have to face bigger and bigger challenges of those technologies together in a single distributed control system. For example, the newer devices will be coupled with an existing distributed control system. In these situations, signals coming from the control room can expect traditional analog or hybrid technologies, but field devices can be coupled with a Fieldbus Hl or H2 network. On the contrary, the control room of the industrial plant can be renewed, with the entrances and exits to the control room comprising a modern Fieldbus Hl or H2, and the individual signals that run to certain older analog and hybrid field devices. Fieldbus-based field devices newer. In addition to the challenge of integrating several technologies into a single distributed control system, the newer field devices will have maintenance modes and enhanced features that are not accessible through the old control system. In addition, even when all components of a distributed control system adhere to the same standard (such as the Fieldbus standard), a computer in the manufacturer's control room may not be able to give access to secondary functions or secondary information. provided by other field devices of the manufacturer.

COMPENDIUM OF THE INVENTION The present invention provides an apparatus for providing non-redundant secondary access to field devices in a distributed control system that has a control room to provide primary access to field devices, thereby enabling secondary access of all information and functions available in field devices. The present invention also provides an apparatus for providing redundant wireless access to field devices in a distributed control system, which has a control room that provides wired access to the field devices, thereby allowing redundant access to the control devices. field in case of a fault of the half wiring. In a first embodiment of the invention, each field device is provided with a wireless port and can be accessed by a portable wireless unit or a wireless terminal. In a configuration of this mode, the wireless port is energized by the control network to which the field device is connected. In a second embodiment of the invention, a field module having a wireless port is connected to an existing control network. The field module provides access to the wireless handheld unit or a wireless terminal (which may be in the control room) to all field devices connected to the control network. In a configuration of this mode, the field module is energized by the control network to which it is connected. In a third embodiment of the invention, the distributed control system is provided with a bridge connecting a distribution network in the distributed control system with one or more of the control networks, where the control networks are coupled with the field devices. The bridge also includes a wireless bridge that also provides from a wireless portable unit or a wireless terminal (which can be in the control room) to all field devices connected to the control networks. In a fourth embodiment of the present invention, a bridge / converter is connected to the analog wires of the twisted pair of two wires that come from an old control room designed to control the analog field devices, and couples the old control room with field devices based on newer network. In a configuration of this mode, the bridge / converter includes a wired port that is coupled to a terminal. The terminal, which can be placed in the control room, provides operators of the control system with access to all functions and secondary information of field devices based on the newest network that are not accessible by the old analog components from the control room. In another configuration of this mode (which may be complementary to the first configuration), the bridge / converter is provided with a wireless port that allows "network-based devices to access via a wireless terminal or a wireless portable unit.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a diagram of a distributed control system of the prior art. Figure 2A is a diagram of an industrial plant having two distributed control systems and showing three embodiments of the present invention.

Figure 2B is a diagram of the industrial plant having two distributed control systems showing three embodiments of the present invention. Figure 3 is a diagram of an industrial plant having an older analog distributed control system that has been remodeled with newer network-based field devices and shows one embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED MODALITIES Figure 1 is a functional diagram of a distributed control system of the prior art 10 (DCS). The DCS 10 consists of a control room 12, a controller 14, a discrete / analog I / O unit 16, a bridge 18 H2 to H1, and a variety of field devices represented by the solenoid 24, the switches 26 and 54, the valve placers 28, 46 and 52, the transmitters 30, 34 and 44, the process analyzers 36 and 50. These devices represent any type of field device known in the control branch. Also shown in Figure 1 are the portable units 38 and 39 that are capable of providing access to the information in a Fieldbus-based field device or hybrids through a physical wire connection, and a local operator / user station 40. , which is capable of issuing and receiving controls of the control room type to and from the field device with which it is connected through a physical wire connection. Control room 12 includes computers, I / O user peripherals, various forms of data storage devices, and other computing devices known in the art. The control room 12 is coupled to the controller 14 via the collector bus 20, which is typically a proprietary digital communications network or an open digital communication network employing a proprietary protocol. The controller 14 receives different commands from the control room 12 and provides the data to the control room 12. As illustrated in Figure 1, the DCS 10 is a hybrid system comprising two different types of field devices. Devices 24 to 36 are traditional analog, discrete, and analog / digital hybrid devices, wherein the primary control function of the device is carried out by modulating a current. These field devices are coupled with the discrete / analog I / O unit 16, with each device connected to an individual channel of the unit 16 by a single pair of wires (and possibly two additional power wires in the case of a device). of four traditional wire field). For example, the solenoid 24 is coupled through the pair 42 of two twisted wires to the channel 43 of the unit 16. For a traditional discrete or analog field device, the only communication with the device occurs by modulating or switching the current running. through the pair of twisted wires, with the magnitude of the current representing a measured process variable (such as in the case of the transmitter), or an action requested by the controller 14 (as in the case of the valve setter or solenoid ). Traditional analog devices have a frequency response limited to approximately 10 Hz to receive power from the pair of twisted wires. The analog / digital hybrid device works in a similar way to traditional analog devices, but also allows digital communication of secondary information by overlaying a digital carrier signal in the modulated current carried by the pair of twisted wires. One of these analog / digital hybrid systems in the control field is known as a Distant Highway Dirigible Transducer (gHART) and transmits the data in a manner similar to a conventional computer modem that adheres to the Bell 202 specification. , the primary function of these devices is still carried out modulating the current through the circuit while the other types of secondary information, such as the diagnostic data, the operating temperature, the identification codes, the error codes and the secondary variables are transmitted digitally. In this system, digital communication is relatively slow and limited to approximately 300 baud. When a maintenance person wishes to test an analog device, the maintenance person must make a physical connection with the device itself, such as the local station 40 of the operator / user connected to the transmitter 30, or the pair of two twisted wires that lead to the device, such as the portable unit 38 connected to the pair of twisted wires that open into the valve setter 28. In contrast, devices 44-54 are digital field devices based on a modern network, wherein all information is digitally transmitted to and from each device. Although many of the control system manufacturers have developed proprietary digital systems, the Standards and Practices Subcommittee 50 of the Instrument Society of .America has developed and specified an architecture known in the field as Fieldbus. The Fieldbus specification includes two types of networks, a lower speed network referred to as in Hl and a higher speed network referred to as H2. Both networks can support multiple connections with only one bus connector on the network, in contrast to traditional analog connections, which only support one device per pair of twisted wires. Although the present invention is described herein with reference to a field-based network control system, in the other embodiments of the present invention it can be employed in any distributed control system having network-based field devices. A Fieldbus H2 network can transmit data at rates up to 2.5 megabits per second. In addition, an H2 network is redundant, with the two sets of physical wire means comprising the network. In case the medium of the primary wire fails, the secondary wire means is automatically used by the DCS. Due to the high capacity and redundancy of the Fieldbus H2 networks, the Fieldbus H2 networks are beginning to be used as a distribution network that connects the controller to the different distribution units in the DCS. However, traditional distribution networks are proprietary networks using either parallel or serial communication.

In Figure 1, distribution network 22 couples controller 14 with bridge 18, H2 to H1, and proprietary collector bus 21 couples controller 14 with discrete / analog I / O unit 16. In other configurations known in the art, the unit 16 and bridge 18 may be coupled with a common distribution network. As discussed above, the discrete / analog I / O unit 16 includes discrete channels, with each channel coupled to a single device. The bridge H2 to H1 links the data carried by the proprietary distribution network 22 with the 45 and 47 control networks of the Fieldbus H1. The Fieldbus control network Hl is coupled to the transmitters 44, the valve setter 46, and the relay 48, and the Fieldbus HL number 47 is coupled to the process analyzer 50, the valve setter 52 and the solenoid 54 Even though the Fieldbus Hl network is not redundant, and has a lower data transmission rate of approximately 31.25 kilobits per second, it is capable of providing power to the devices with which it is coupled, while the Fieldbus H2 network does not he does it. Due to the aforementioned reasons, Fieldbus Hl is ideal for providing final connections with individual field devices, while the Fieldbus H2 network is ideal for distributing control signals through the physical plant where the DCS is installed. More recently, field devices with microprocessors and additional functionality have been provided. These "smart" field devices are capable of monitoring a plurality of process variables, performing a variety of control functions, carrying out comprehensive diagnostics, and providing extensive training of various types of current state information. The Fieldbus specification specifies a variety of functions that can be supported by the various Fieldbus field devices. In addition, many manufacturers have provided secondary functions beyond those specified in the Fieldbus specification. Even though Fieldbus field devices manufactured by different manufacturers are compatible to the extent that they only give access to the specified Fieldbus functions, they are not compatible with respect to secondary functions. For example, a Fieldbus controller manufactured by company A will generally not be able to provide access to the secondary functions provided by a Fieldbus valve setter manufactured by company B. Therefore, an industrial plant using a variety of Fieldbus components that are provided by different manufacturers will not be able to derive the benefit of all the functions provided by the various components. The problem is compounded in older distributed control systems that were designed to use traditional analog and discrete and hybrid devices. Frequently, a company wants to conserve an investment in an existing installation, and modify the installation with newer Fieldbus field devices. In this installation, the control room would not yet be able to give access to the functions of the standardized Fieldbus network that is provided by the different devices. Accordingly, there is a need to provide access to the secondary functions provided by the different manufacturers, as well as the standardized Fieldbus functions when a device is connected based on Fieldbus with an older distributed control system. Figure 2 is a diagram of an industrial plant that has two distributed control systems.

The DCS 56 consists of a control room 60, the controller 62, the bus 64, the field device 66, the valve setter 68, the transmitter 70, the process analyzer 72, the Fieldbus control network 74 , the transmitter 76, the valve setter 78, the solenoid 80, the field module 82, and the Fieldbus control network Hl. The DCS 58 consists of control room 86, the controller 88, the bus collector 90, the distribution network 94 of Fieldbus H2, the bridge 92 of H2-a-Hl, the transmitters 96 and 100, the valve setter 98 and the Fieldbus control network Hl. The collector buses 64 and 90 are usually proprietary digital communication networks or open communication networks employing a proprietary protocol. Also, a terminal 104 and a portable control unit 110 are shown in Figure 2. The terminal L04 is coupled with the wireless link module 106, which in turn connects to the wireless transceiver 108. The portable control unit 110 includes a wireless transceiver 112. Two embodiments of the present invention are illustrated in the DCS 56. The first embodiment is illustrated by those field devices coupled with the Fieldbus control network 74 Hl. Each field device in the control network 74 includes a wireless transceiver. The field device 66 represents any generic field device coupled to the control network 74 and includes the wireless transceiver 114. The valve setter 68 includes the wireless transceiver 116, the transmitter 70 includes a wireless transceiver 118, and the process analyzer 72 includes the wireless transceiver 120. Each wireless transceiver implements a wireless Fieldbus connection with the terminal 104 and the portable unit 110, thereby allowing access to the secondary functions of each field device not accessible through the control room 60, as well as providing a person with excessive maintenance. convenient to each field device without having to communicate with the independent control room of the distributed control system. The wireless fieldbus connections described herein are implemented through secondary wireless network ports that are used in addition to the primary network ports that are wired with a control room. Accordingly, a network-based field device may alternatively access through either wired connection to the control room or the wireless Fieldbus connection. In contrast, many prior art network-based field devices are provided with a redundant wired network connection that is used as a backup or reinforcement in case the first connection fails. However, the field device is usually not allowed to access alternately by any of the redundant first connections, except to test the redundant connection. In addition, typically, the redundant connection is also sent to the control room.

Another novel feature of the present invention is that the wireless Fieldbus port attached to the field device is energized by the Fieldbus Hl port wired to each device. Therefore, a customer having a Fielbus control equipment from a manufacturer can connect the field devices having a wireless Fieldbus port (in accordance with the present invention) with an existing Fieldbus Hl control network and can give access to all of them. the functions of field devices added using a portable unit that has a wireless Fieldbus link or a terminal that has a wireless Fieldbus link. Since the fieldbus wireless link of the field devices is powered by the existing Fieldbus Hl control network, no additional connection is required. The wireless links disclosed herein represent any method of wireless communication known in the art, including, but not limited to, radio, infrared, visible light, and ultrasonic forms of wireless communication. A second embodiment of the present invention is illustrated by the devices connected to the Fieldbus control network Hl. The transmitter 76, the valve setter 78, and the solenoid 80 each couple with the control network 84. Coupled also with the control network 84 is a field module 82, which includes a wireless transceiver 122 energized by the Fieldbus control network Hl. The field module 82 essentially forms a wireless bridge between the control network 84 and the portable unit 110 or the terminal 104, and allows the unit 110 or the access terminal 104 to each device coupled with the Fieldbus control network 84 Hl. Accordingly, the field module 82 is ideally suited for use in an existing environment having a variety of Fieldbus Hl devices from different manufacturers. The portable unit 110 and the terminal 104 can be easily programmed to give access to the functions of each device in the control network with which the field module 82 is connected. A third embodiment of the present invention is illustrated by the DCS 59. In the DCS 58, the controller 88 is coupled with the bridge from H2 to Hl by the distribution network 94 Fieldbus H2. The bridge from H2 to Hl connects the Fieldbus distribution network 94 with the Fieldbus Hl control network 102. The bridge from H2 to Hl also includes a second Fieldbus port connected to the wireless transceiver 124 communicating with a remote device such as the portable unit 110 or the terminal 104. Therefore, the remote wireless field device can give access to all the field devices that are serviced by the bridge from H2 to Hl, such as the transmitters 96 and 100 and the valve setter 98. In other configurations, it is common for the bridge from H2 to Hl to serve a plurality of Fieldbus Hl control networks, in which case, all the field devices connected to all the control networks to which the bridge is serviced. from H2 to Hl, they can get remote access. Many industrial plants have a plurality of distributed control systems. Using wireless fieldbus networks, a maintenance person can go from the DCS to the DCS with a single portable control unit and the access field devices coupled with each DCS. Since the portable control unit can be programmed to give access to each field device, the maintenance person can give access to all the functions of the devices supplied by the different manufacturers. The present invention also provides an apparatus and method for providing redundant wireless access to field devices in a distributed control system, thereby allowing access to field devices in the event of a failure of the wired medium connecting the devices of the field. field with a control room. The redundant wireless access can be used in several ways. First, can be used to allow a continuous operation of a distributed control system in case of maintenance failure in the wired medium. However, even when continuous operation is not desired, redundant wireless access can still be valuable for monitoring process variables and carrying out control actions, such as those required to paralyze a process. For example, consider a distributed control system that is subject to a certain type of failure, such as an explosion. The explosion can make it possible for the wired media connecting the field devices to the control room to be inoperable. Using the redundant wireless access provided by the present invention, a control room operator may still be able to provide access to the field device to perform an orderly shutdown of the distributed control system. The operator can observe critical temperatures and pressures and adjust or close valves and other devices to complete the standstill. By having redundant wireless access to field devices, the operator may be able to perform a stoppage in such a manner as to minimize losses. Figure 2B is a diagram of an industrial plant having two distributed control systems similar to that of Figure 2A and where the same components have the same reference numbers. The DCS 56 in Figure 2B consists of a control room 60 (which now includes a terminal 104 coupled with the wireless link module 106, which in turn is connected to the wireless transducer 108), the controller 62, the bus collector 64, the field device 66, etc. as described for Figure 2A. The DCS 58 comprises of the control room 86 (which now includes the terminal 103 coupled with the wireless link module 107, which in turn is connected to the wireless transceiver 109, the controller 88, the bus collector 90, etc. as is described for Figure 2 A. Two embodiments of the invention of Figure 2B are illustrated in DCS 56. The first embodiment is illustrated by those field devices coupled with the Fieldbus control network 74. Each field device in the network 74 control includes a wireless transceiver.Each wireless transceiver implements a redundant wireless fieldbus connection with terminal 104, thereby allowing redundant wireless access to each field device from control room 60. A second embodiment of the invention of FIG. 2B it is illustrated by the devices connected to the Fieldbus control network 84. The transmitter 76, the valve setter 78, and the solenoid 80 each are ac opla with control network 84. The field module 82 is also coupled with the control network 84, which includes a wireless transceiver 122 energized by the Fieldbus control network Hl. The field module 82, in essence, forms a wireless bridge between the control network 84 and the terminal 104 in the control room 56, and allows the terminal 104 to provide access to each device coupled with the Fieldbus control network 84. . Accordingly, the field module 82 is ideally suited to provide redundant wireless access in an existing environment that has a variety of Fieldbus Hl devices, from different manufacturers. A third embodiment of the invention of Figure 2B is illustrated by DCS 58. In the DCS-58, the controller 88 is coupled with the bridge from H2 to Hl via the distribution network 94 Fieldubs H2. The bridge from H2 to Hl connects the Fieldbus distribution network 94 with the Fieldbus Hl control network 102. The bridge from H2 to Hl also includes a second Fieldbus port connected to the wireless transceiver 124, and communicates with a distant device such as the terminal 103. Accordingly, the terminal 103 in the control room 86 can give access to all the field devices that are serviced by the bridge from H2 to Hl, such as the transmitters 96 to 100 and the valve setter 98.

Figure 3 shows an embodiment of the present invention adapted for use in older distributed control systems that have been modified with newer Fieldbus field devices. The DCS 126 includes the control room 128, the controller 130, the collector bus 132, the discrete / analog I / O unit 134, the bridge / converter 136, the collector bus 137, the fieldbus control networks 138 and 140 Hl , the solenoids 142 and 152, the transmitters 144 and 148, the valve placers 146 and 150, the portable unit 154, and the terminal 156. The DCS 126 represents an older distruded control system designed for use with traditional field devices Discrete analog / discrete and hybrid. With the exception of terminal 156, everything above dotted line 158 represents components that are part of the oldest existing facility. All below dotted line 158 (and terminal 156) represents newer Fieldbus components that have been added to the installation. The bridge / converter 136 interfaces the oldest portion of the DCS 126 (line 158 dotted above) with the Fieldbus devices. The bridge / converter 136 includes a plurality of I / O processing channels (such as channel 160) which are coupled with the corresponding I / O processing channels of the discrete / analog I / O unit 134 (such as channel 162) by pairs of two twisted wires (such as pair 164 of two twisted wires). The bridge / converter 136 converts the analog, discrete, and / or hybrid information that is provided by the discrete / analog I / O unit 134 into the digital information that is transmitted to the devices and the Fieldbus networks HL 140 and 140, and converts the digital information received from the devices in the networks 138 and 140 into analog, discrete, and / or hybrid information that is required by the discrete / analog I / O unit 134. From the point of view of control room 128, Fieldbus field devices appear as traditional analog / discrete and hybrid field devices. Accordingly, the control room 128 can not give access to any of the secondary functions provided by Fieldbus field devices. To provide access to these functions, bridge / converter 136 is provided with a wired active Fieldbus port 166 and a wireless Fieldbus port 168. The wired Fieldbus port 166 connects to the Fieldbus network 170, which in turn connects to the terminal 156. In one embodiment, the terminal 156 is placed within the control room 128 and provides the operators within the room. control with access for all the functions that are provided by Fieldbus field devices, and that are not accessible through the components of the existing control room. Port 166 is not a redundant port, instead it is a secondary body that provides the control room with access to all the functions provided by Fieldbus-based devices. Accordingly, an operator of the control room can alternatively access a Fieldbus-based device through the discrete / analog I / O unit 134 or terminal 156. In contrast a redundant port is used as a backup or reinforcement if the first port fails. In the configuration shown in Figure 3, a redundant port will not be coupled to the control room. The Fieldbus port 168 is connected to a wireless transceiver 172, thereby forming a wireless Fieldbus network similar to the wireless Fieldbus networks shown in Figure 2. The portable unit 154 has a wireless transceiver 174 and communicates with devices 142 through 152 Fieldbus through the wireless transceiver 172 that connects to the bridge 168 wireless port / converter 136. In addition to the portable unit 154, a terminal having a wireless link (such as the terminal 104 and the wireless link 106 of the Figure 2) to communicate with field devices coupled with bridge / converter 136. The present invention provides an apparatus for providing secondary access to field devices in a distributed control system having a control room to provide primary access to the field devices. In a modern distributed control system that has Fieldbus devices coupled with a Fieldbus control room, the present invention provides a wireless link to a remote unit, such as a portable device or a terminal having a wireless link, thereby allowing a person to maintain access to each Fieldbus device in the field through the unit distant. Since a manufacturer's Fieldbus control room may not be able to provide access to the secondary functions of a Fieldbus device from another manufacturer, the portable unit may also provide a convenient way to give access to the secondary functions that are provided by the devices. different manufacturers of a single portable unit easily programmable or distant terminal. The present invention also provides an apparatus for providing wireless redundant access to field devices in a distributed control system having a control room that provides wired access to field devices. In a modern distributed control system having Fieldbus devices coupled with a Fieldbus control room, the present invention provides a redundant wireless means or a terminal having a wireless link. The apparatus of the present invention allows access to the field devices in the event of failure or other unavailability of the coupled means that couples the control room with the field devices, which is the primary way to give access to the control devices. In one embodiment, each Fieldbus-based device is provided with its own Fieldbus Hl or secondary wireless H2 port that is powered by the Fieldbus Hl control network. This modality provides maximum flexibility because no modification of the distributed control system is required and is ideally suited for new devices to be added to an existing Fieldbus installation. As soon as the Fieldbus Hl device is connected to the existing Fieldbus Hl control network, the device can be accessed through the wireless handheld unit or the wireless terminal. In another embodiment of the invention, a field module is connected to an existing Fieldbus control network. The field module has a wireless Fieldbus Hl or H2 port that is powered by the Fieldbus Hl control network, and provides access from the wireless handheld unit or the wireless terminal to all Fieldbus devices connected to the control network. This mode is ideally suited for distributed control systems that already have Fieldbus devices. In yet another embodiment of the present invention, the distributed control system is provided with a bridge from H 2 to H 1 having one or more H 1 control networks coupled with the Fieldbus devices. A wired H2 port coupled with a controller, and a wireless Fieldbus H2 or HL port. The Wireless Fieldbus port allows a wireless handheld unit or a wireless terminal to access all Fieldbus devices in all Hl control networks that are serviced by the H2 to Hl bridge. In a fourth embodiment of the present invention, a bridge / converter is connected with the pair of two twisted analog / discrete wires and the hybrid wires coming from an older control room and couples the older control salt with the Fieldbus devices newer. In this mode, the bridge / converter provides a Fieldbus port Hl or H2 to allow access to the functions of Fieldbus devices not accessible from the control room. In a «configuration, a terminal connects to the bridge / converter via a wired Fieldbus network. The terminal, which can be placed in the control room, provides the operators of the control system with access to all the functions of Fieldbus-based devices. In another configuration (which may complement the first configuration), the bridge / converter is provided with a wireless Fieldbus Hl or H2 port that allows Fieldbus field devices to access via a wireless terminal or wireless portable unit. Even though the present invention has been described with reference to preferred embodiments, the workers skilled in the art will recognize that changes can be made in the form and detail without deviating from the spirit and scope of the invention.

Claims (27)

1. R E I V I N D I C A C I O N E S: 1. A distributed control system comprising: a control room to provide primary control of the distributed control system; a plurality of network-based field devices with each network-based field device having a primary control network port; a control network coupled with each primary control network port of each network-based field device of the plurality of network-based field devices; a controller coupled with the control room, for controlling and providing primary access to the plurality of network-based field devices; a network connection means / controller for counting the control network with the controller; and a secondary access means for providing secondary and non-redundant access to the plurality of network-based field devices.
2. 2. The distributed control system according to claim 1, wherein the secondary access means comprises: a wireless transceiver coupled with a non-redundant secondary port of each of the plurality of network-based field devices.
3. 3. The distributed control system according to claim 2, wherein the wireless transceiver receives power from the control network through the primary control network port.
4. 4. The distributed control system according to claim 1, wherein the secondary access means comprises: a field module coupled to the control network, the field module comprises: a first network port coupled with the network of control; a secondary port that is not redundant; and a wireless transceiver coupled with the non-redundant secondary port.
5. 5. The distributed control system according to claim 4, wherein the field module receives power from the first network port. The distributed control system according to claim 1, wherein the controller is coupled to a distribution network, and the network / controller connection means comprises: a bridge for transmitting information from the distribution network to the network of control, the bridge comprises: a first port coupled with the distribution network; a second port coupled with the control network; a wireless transceiver; and a third non-redundant port coupled with the wireless transceiver. The distributed control system according to claim 1, wherein the network connection means / controller comprises: a discrete / analog I / O unit comprising: a collector bus coupled with the controller; and a plurality of discrete / analog I / O channels; and a bridge / converter comprising: a plurality of discrete / analog I / O channels coupled with the plurality of analog I / O channels of the discrete / analog I / O unit; a non-redundant network-based field device access port for providing access to the functions of the plurality of network-based field devices not accessible through the controller; and a control network port coupled with the control network. 8. The distributed control system according to claim 7, and further comprising: a terminal; and a wired connection between the terminal and the access port of the field device based on non-redundant network of the bridge / converter. 9. The distributed control system according to claim 7, and further comprising: a wireless transceiver coupled to the access port of the field device based on non-redundant network for the bridge / converter; and a remote access device having a wireless transceiver to give remote access to the plurality of network-based field devices. 10. A distributed control system comprising: a control room to provide primary control of the distributed control system through the wired means and having a terminal coupled with a wireless link to provide redundant wireless access; a plurality of network-based field devi with each network-based field device having a primary control network port; a control network coupled with each primary control network port of each network-based field device of the plurality of network-based field devi a controller coupled with the control room, for controlling and providing primary ac to the plurality of network-based field devi a network connection means / controller to connect the control network with the controller; and a secondary ac means for providing redundant wireless ac to the plurality of network-based field devifrom the wireless terminal in the control room. a first wireless transceiver configured to provide non-wireless access to the plurality of network-based devices; and a remote access device having a second wireless transceiver to provide remote access to the plurality of network-based field devices through the first wireless transceiver. The distributed control system according to claim 1, wherein the secondary access means comprises: a remote terminal configured to provide non-wireless access to the plurality of network-based devices. 13. A network-based field device comprising: a control means for implementing a control function; a primary control network port for providing primary control access to the network-based field device; and a non-redundant secondary port for providing non-redundant secondary access to the network-based field device. 14. The network-based field device according to claim 13, and further comprising: a wireless transceiver coupled with the non-redundant secondary port. 15. The network-based field device according to claim 14, wherein the wireless transceiver receives power from a connection to the primary control network port. The network-based field device according to claim 13, wherein the network-based field device implements a set of functions, with a subset of the set of functions accessible through the non-redundant secondary port and not accessible through the primary control network port. 17. A field module for providing secondary access not redundant to a plurality of network-based field devices coupled with a control network, the field module comprising: a first network port that connects to a control network; a secondary port that is not redundant; and a wireless transceiver coupled with the non-redundant secondary port. 18. The field module according to claim 17, wherein the field module receives power from a control network coupled with the first network port. The field module according to claim 17, wherein the field module facilitates access to a subset of functions implemented by the field devices connected to a control network, and the subset of functions can not gain access through a controller coupled with the control network. 20. A bridge to transmit information from a distribution network to a control network in a distributed control system, the bridge comprises: a first port that connects to the distribution network; a second port that connects to the control network; a wireless transceiver; and a third non-redundant port coupled with the wireless transceiver. The bridge according to claim 20, wherein the bridge provides access to a subset of functions implemented by the field devices connected to a control network, and the subset of functions can not be accessed by a controller coupled with the distribution network. 22. A bridge / converter comprising: a plurality of discrete / analog I / O channels that are connected to a discrete / analog I / O unit, which in turn is connected to a controller via a bus collector; a control network port that connects to a control network which in turn connects to a plurality of network-based field devices; a non-redundant network-based field device access port for providing access to functions of the plurality of network-based field devices not accessible through the controller coupled with the plurality of the discrete / analog I / O unit . 23. The bridge / converter according to claim 22, and further comprising: a wireless transceiver coupled with the field device access port based on non-redundant network. 24. A distributed control system comprising: a control room to provide primary control of the distributed control system; a plurality of network-based field devices that jointly implement a specific game with each network-based field device having a primary control network port; a control network coupled with each primary control network port of each network-based field device of the plurality of network-based field devices; a controller coupled with the control room, to control and provide primary access to the plurality of network-based field devices, the controller is not able to give access to a subset of specific game features; a network connection means / controller to connect the control network with the controller; and a sub-game feature access medium to provide access to the subset of the features. 25. The distributed control system according to claim 24, wherein the sub-game feature access means comprises: a wireless transceiver coupled with a secondary port of each of the plurality of network-based field devices. 26. The distributed control system according to claim 24, wherein the access means of the sub-game feature comprises: a field module coupled with the control network, the field module comprising: a first network port coupled with the control network; a secondary port; and a wireless transceiver coupled with the secondary port. 27. The distributed control system according to claim 24, wherein the controller is coupled to a distribution network and the network connection means / controller comprises: a bridge for transmitting information from the distribution network to the network of control, the bridge comprises: a first port coupled with the distribution network; a second port coupled with the control network; a wireless transceiver; and a third port coupled with the wireless transceiver. SUMMARY OF THE INVENTION An apparatus for providing access to field devices in a distributed control field system provides non-redundant secondary access to a plurality of field devices that are controlled by a control room. An apparatus that also provides redundant wireless access to the access field devices in a distributed control system having primary access to the field devices that is provided by a wired means that couples the field devices to the control room. The field devices are coupled with a Fieldbus control network. In a first embodiment, each field device is provided with a wireless Fieldbus port that is accessible via a portable wireless unit or a wireless terminal. The second mode, each Fieldbus control network, is provided with a field module that has a wireless Fieldbus port that allows all devices connected to the Fieldbus control network to access via a wireless handheld unit or a wireless terminal. In a third embodiment, a Filedbus bridge from H2 to Hl (which can service a plurality of Hl control networks) is provided with a wireless Filedbus port that allows all Fieldbus devices connected to the Hl control networks to receive service through the bridge from H2 to Hl to gain access through the wireless portable unit of a wireless terminal. In a fourth mode, a bridge / converter provides an interface between the components of the oldest analog control room and the newer Fieldbus field devices. In one configuration, the bridge / converter includes a wired Fieldbus port connected to a terminal that may be in the control room. In another configuration, the bridge / converter includes a wireless Fieldbus port that allows a wireless handheld unit or a wireless terminal to access Fieldbus devices that are serviced by the bridge / converter. The present invention allows a person to maintain access to Fieldbus field devices while servicing a device in the field, and allows the secondary functions of the field devices (which vary by the manufacturer) to have access from a single remote unit. The redundant wireless access that is provided by means of the present invention allows an operator of the control room to access the field devices in case of failure or unavailability of the wired medium that provides primary access to the field devices.