The present disclosure relates to an industrial control system and an industrial field device in an industrial control system for monitoring and/or controlling an industrial process. The disclosure provides for wireless communication of second signals to/from the industrial field devices.
In an industrial plant the control system is used to control many of the industrial processes performed at the plant. Typically, the plant has a centralized control room having a computer system with user I/O, disc I/O, and other peripherals as are known in the computing art. Coupled to the computing system are a controller and a process I/O subsystem.
The process I/O subsystem includes a plurality of I/O ports which are connected to various field devices throughout the plant. Field devices known in the control art include various types of analytical equipment, pressure sensors, capacitive pressure sensors, resistive temperature detectors, power switches, thermocouples, strain gauges, limit switches, on/off switches, flow transmitters, pressure transmitters, capacitance level switches, weigh scales, transducers, valve positioners, 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 control art.
Traditionally, analog field devices have been connected to the control room by current loops and the field devices are capable of responding to or transmitting an electrical signal within a specified range, typically a current of 4-20 milliamps. Recently, hybrid systems that superimpose digital data on the current loop have been used in distributed control systems and one hybrid system is known in the control art as the Highway Addressable Remote Transducer (HART). The HART protocol uses the magnitude of the current in the current loop to sense a process variable and also superimposes a digital carrier signal upon the current loop signal. HART is an industry standard nonproprietary system.
U.S. Pat. No. 5,682,476 entitled “Distributed control system having central control providing operating power to wireless transceiver connected to industrial process control field device which providing redundant wireless access” describes an apparatus for providing redundant wireless access to field devices in a distributed control system. The abstract states: The redundant wireless access provided by the present disclosure allows a control room operator to access field devices in the event of failure or unavailability of the hard-wired media that provides primary access to the field devices.
However, the field device wireless ports, as shown in
Another aspect of power supply arrangements is that the available power in the control data network is low and it might not be possible to continuously run the wireless port of a plurality of field devices on this power. Even if the available power in the control data network would be enough to continuously run one wireless port, the number of wireless ports that can continuously be operated at the same time on the same control data network line is strongly restricted.
Another aspect of using field devices in distributed control systems is that in order to configure field devices today, it is necessary for the operator to approach each device and program it using the Human-Machine Interface (HMI) placed on the instrument. This method to program field devices is time consuming
Exemplary embodiments disclosed herein can provide a second communication link with the field devices in an industrial control system over wireless transceivers. The second wireless transceiver connected to the industrial field device is powered by energy storage means which stores energy collected from the data network.
An industrial control system is disclosed, comprising: a plurality of industrial field devices for controlling and monitoring an industrial process, each industrial field device having first control functions and at least one industrial field device having second control functions; first control means connected via a first respective signal path to each industrial field device to communicate first signals between the first control means and each industrial field device, for controlling the first control function; and second control means connected via a second respective wireless signal path to at least one industrial field device to communicate second signals between the second control means via a first wireless transceiver and at least one industrial field device via a second wireless transceiver for controlling the second control function of at least one industrial field device, wherein a plurality of said industrial field devices are arranged with an energy storage means for storing energy drawn from said first respective signal path and said energy storage means supplies operating power for the second wireless transceiver.
An industrial field device is disclosed, in an industrial control system comprising: first control functions and second control functions, and first control means connected via a first respective signal path to said industrial field device to communicate first signals between the first control means and said industrial field device, for controlling said first control function; and second control means connected via a second respective wireless signal path to said industrial field device to communicate second signals between the second control means via a first wireless transceiver and said industrial field device via a second wireless transceiver for controlling said second control function of said industrial field device, wherein said industrial field device is arranged with an energy storage means for storing energy drawn from said first respective signal path and said energy storage means supplies operating power for said second wireless transceiver.
A method for wireless communication with one or more industrial field devices in a distributed industrial control system is disclosed. Such a method comprises controlling and monitoring an industrial process by a plurality of industrial field device, each industrial field device having first control functions and at least one industrial field device having second control functions; communicating first signals between first control means and each industrial field device for controlling the first control function, said first control means being connected via a first respective signal path to each industrial field device; and communicating second signals between second control means via a first wireless transceiver and at least one industrial field device via a second wireless transceiver for controlling the second control function of at least one industrial field device, said second control means being connected via a second respective wireless signal path to at least one industrial field device, wherein an energy storage means is supplying the operating power for said second wireless transceivers on said industrial field devices and said energy storage means draws energy from said first respective signal path.
The disclosure will be elucidated by reference to an exemplary embodiment partially illustrated in the drawings.
The energy needs of the second wireless transceivers connected to the industrial field devices are further reduced by operating the transceivers non-continuous mode. This non-continuous mode of operation or transceiver duty cycling is a method to achieve low average energy consumption of the second wireless transceivers. The idea is that the transceivers are put in a low power mode for large portions of the time and powered up intermittently to communicate. This reduces the overall energy drain, whilst keeping the system open for communication and processing.
To program field devices using a handheld data device (for example a PDA) or directly from a terminal in the central control means over a wireless connection is more efficient than programming each field device on the Human-Machine Interface (HMI) placed on the field device.
According to an exemplary embodiment, an industrial control system is disclosed wherein the second data signals comprises any form of non-control signal such as: configuration data, set-points, diagnostic data, identity, clock synchronisation.
According to an exemplary embodiment, an industrial control system is disclosed wherein the second control means is a handheld device, for example, a mobile telephone or a PDA, which may be used for communicating with the field device.
According to an exemplary embodiment, an industrial control system is disclosed wherein the second wireless transceivers arranged with the industrial field devices comprise means for communicating with each other and relaying information to first wireless transceiver.
According to an exemplary embodiment, an industrial control system is disclosed wherein different types of networks (star, meshed or cluster-tree) are formed by inter-communicating transceivers.
According to an exemplary embodiment, an industrial control system is disclosed wherein the first signal comprises, at least in part, compatible with any from the group of: Hart, FF, Ethernet, fieldbus (SP50), ISA SP100, ZigBee, WLAN.
According to an exemplary embodiment, an industrial control system is disclosed wherein the energy storage means comprises any of rechargeable battery, accumulator, compulsator, storage capacitor.
According to an exemplary embodiment, an industrial control system is disclosed wherein the energy storage means comprises a capacitor.
According to an exemplary embodiment, an industrial control system is disclosed wherein part of the first respective signal path is arranged for transmission of analog signals only and the wireless signal path is adapted to communicate additional digital information sent to and received from modern field devices (as in communication protocol Highway Addressable Remote Transducer, HART or similar).
According to an exemplary embodiment, an industrial control system is disclosed wherein the industrial field device, on failure or break-down of first signal path, is arranged for backup communication of first signal over wireless signal path.
The physical interface 2 connects to the fieldbus, receives and sends control data, and also draws off energy from the fieldbus. The energy is stored in a power storage means 3, which may be a capacitor, battery etc. The sensing module 4 performs one or more functions of the field device on the industrial process. Examples of field device functions are measuring of process variables, controlling processes and process flows. The wireless module 5 takes power from the power storage means and sends out wireless signals. The signals are sent out in a non-continuous mode with cyclic power-ups and power-downs of the wireless module 5.
A sensing module 50 communicates with a field device transceiver 51 which communicates over a wireless network with another transceiver 52 which in turn can communicate with a control means 53 which may be a central control means or a handheld data device for example a PDA.
In this exemplary embodiment the message passed is “read_switches( )” which is a call requesting the press state of the human-machine-interface (HMI) buttons on the control means 53. The call is passed from the sensing module 50 to the field device transceiver and stored in a message buffer until the wake up (after×ms time of inactivity) of the field device transceiver 51. When the field device transceiver 51 wakes up it associates with the control means transceiver 52 and the message is passed.
To make sure that the latest press state of the HMI of the control means 53 is available to the control means transceiver 52, it polls the control means 53 for status at a higher frequency than the frequency with which the field device transceiver is powered up and down. The last buffered state is thus sent to the field device transceiver 51 so that this may get a reply while it is still awake. The reply is then passed on to the sensing module 50 before the timeout of the field device transceiver occurs.
A star network 60 is one where the control means connects to each field device directly. This network type is characterized by low power consumption. A mesh network 61 is one where each field device may connect to the control means and several other field devices. This network type is characterized by high level of reliability and scalability. A cluster-tree network 62 is a hybrid of the star/mesh topology. The cluster-tree network combines the benefits of the star network and the mesh network with low power consumption and a high level of reliability.
Block 70 where the transceiver is idle and an internal device or microprocessor in the field device keeps track of the time. When a preset time has elapsed, the method continues to block 71, which is a check on the power level in the field device energy storage means. If the power level is not sufficient for operating the transceiver, the transceiver remains idle (return to block 70) or if the power level is sufficient for operating the transceiver the method continues to block 72 and the transceiver is powered up.
In block 73 the transceiver searches for a network coordinator or another network connection. When a network connection is established the method continues to block 74 where the transceiver starts to transmit and/or receive. After a predetermined time of communication, the method continues to block 75 where the transceiver is powered down and the method returns to the wait state in block 70.
It will be appreciated by those skilled in the art that the present invention can be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The presently disclosed embodiments are therefore considered in all respects to be illustrative and not restricted. The scope of the invention is indicated by the appended claims rather than the foregoing description and all changes that come within the meaning and range and equivalence thereof are intended to be embraced therein.
Number | Date | Country | Kind |
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06011197.8 | May 2006 | EP | regional |
This application claims priority under 35 U.S.C. §119 to EP Application 06011197.8 filed in Europe on May 31, 2006, and as a continuation application under 35 U.S.C. §120 to PCT/EP2007/055254 filed as an International Application on May 30, 2007 designating the U.S., the entire contents of which are hereby incorporated by reference in their entireties.
Number | Date | Country | |
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Parent | PCT/EP2007/055254 | May 2007 | US |
Child | 12323613 | US |