Abstract:
A communication system that enables an operator to remotely query and control the process sections in an industrial plant by exchanging data with a central computer that controls the process sections. The operator communicates with the process sections through a mobile wireless device remotely connected with one of the multiple wireless access points on a data network. This data network is, in turn, connected to the central computer that controls these process sections. The central computer stores the location of the process sections and the operator profiles. When requested, it collates and processes this data and presents it to the operator. Further, if the need arises, the central computer tracks and interacts with the operator.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to industrial control systems. More specifically, this invention relates to providing an operator with an interactive mobile wireless unit in order to communicate remotely with the industrial control system. 
   2. Description of Related Art 
   Manufacturing and process industries have become quite complex during the last few decades. Today, even a small manufacturing plant can easily contain several hundreds to several thousands of manufacturing and processing machines. These machines are usually connected to each other intricately to form sub-systems, which in turn, are connected to form larger systems, and so on, until together they form the entire plant. Since these individual machines are connected so intricately, a small variation in the output of one machine (or of an equipment) can easily result in malfunction of another machine or can even result in the final product being unacceptable. Hence, in all such industries today, there is a need to continuously monitor and control various chemical, mechanical and related processes. 
   In a typical industrial plant, which could, for instance, be a power plant, a refinery, a paper mill, or a petrochemical plant, a Distributed Control System (DCS) is used to monitor and control various processes. The Distributed Control System of the plant would usually have a centralised control room, and multiple controller and operator stations. The control room has a process controller and a process I/O subsystem. These are connected to the controller and operator stations through a communication bus. Since this communication bus is absolutely vital for the smooth operation of the plant, the bus is usually designed so that it has a high degree of fault tolerance and built-in redundancy. In addition to being connected to the controller and operator stations, the process  110  subsystem is also connected to various analog and digital field devices. Field devices are well known in the prior art related to control systems. The field devices include various types of analytical and monitoring equipment such as pressure sensors, temperature detectors, thermocouples, strain gauges, limit switches, on/off switches, flow transmitters, pressure transmitters, capacitance level switches, valve controllers and solenoids. The monitoring of various processes by the distributed control system usually involves collecting periodic data from these systems and controlling the parameters that govern these systems. 
   In rudimentary distributed control systems, any qualified user such as an operator, a technician or an engineer would periodically visit various machines and equipment and gather data from the associated measuring instruments. The same or a different operator would then collate and interpret this data, and, if required, prescribe a corrective action depending upon the results. Clearly such distributed control systems require a lot of human effort and are costly. Also, since it takes substantial time for the operator to gather, collate and interpret the data, such systems are not able to handle emergency situations. Hence, it is not surprising that most distributed control systems in manufacturing and processing industries have moved onto higher levels of automation and integration. 
   In contemporary automated distributed control systems, the monitoring and the control of various systems and sub-systems are done by a central process control system. In such systems, an operator would usually reside in the central process controlling area and would monitor and control different parameters of various machines and systems (from this central process controlling area). However, even in these automated systems, situations arise when an operator would have to physically visit a site and inspect a machine, a sub-system or an entire system, change set points or make other adjustments during times of ordinary production or process flow. Most production inspections are fairly routine and pre-scheduled. There can also arise inspections that are scheduled for regular or anticipated maintenance purposes. In addition, inspections may also be un-scheduled and some may even arise because of emergencies. One frequent example of such an un-scheduled inspection is when the operator suspects that certain monitoring equipment—such as a pressure sensor—is malfunctioning. In such a case, the operator is likely to physically visit the machine (or the system) and use his/her domain knowledge so as to identify and possibly rectify the problem. Indeed, when an operator visits the site, he/she would usually require real-time status information regarding the system (and/or other interconnected systems) so that the problem can be identified and rectified. Hence, proper co-ordination is required between the operator and the central process control system. There are several methods known in the prior art that provide status information of a system (or systems) to an operator when he/she visits a particular site; these are briefly discussed below. 
   In a simple implementation, each system is provided with a display terminal. The terminal collates the status information of the machine and equipment from the various sensors and measuring instruments. If required, the status information of this machine, or of the sub-system or the entire system, may be further collated by the central process control system and sent to this terminal. In some cases, the maintenance of a particular machine, sub-system or an entire system may require information to be gathered from connected systems. In such a case, this terminal may query other terminals (and/or the central process control system). After all the information has been retrieved and collated by the terminal, it is presented to the operator. The operator uses the information to identify the problem with the machine or the system. In some cases, the terminal may also provide the ability to control the machine or the entire system, by setting appropriate parameters, so that the operator can rectify the problem. This implementation suffers from two major drawbacks. The first drawback is that one terminal has to be provided for each machine to be monitored; hence, thousands of such terminals are required and this may render the entire solution economically infeasible (especially, if these terminals are being used only for infrequent inspections). The second major drawback is that in order to retrieve the information from other machines or from connected systems, the terminal may have to query the central process control system many times; consequently, a large number of such queries may result in over-loading of the central process control system. 
   An alternate solution provides a computer system and a terminal placed in each process section of the plant. This terminal would collate the information from various related systems in the process section, and provide a comprehensive report to the operator. This value added information would enable quicker inspection runs and faster identification of various faults in the systems. A modification of this solution is also proposed wherein these terminals may be provided with multiple profiles, i.e., different ways of presenting the status information. The status information is customised either locally on the terminal itself or centrally on the central process control system and then sent to the terminal. An important advantage of this modification is that operators with different expertise are presented different views of the same information. For example, the service technician may be provided a more detailed and exhaustive view of the status information compared to a more collated view for a process engineer. Clearly, since this information is suitably refined for the operator, this solution will improve the efficiency of the inspection process. Furthermore, since a computer system has been provided in each process section and since the terminal may collate and customise the status information, the load on the communication bus and on the central process control system is reduced. In today&#39;s automated industries, and unmanned process sections, it may not be feasible to provide each process section with a computer system and terminal, since these would not be utilized frequently. 
   A third solution known in prior art proposes equipping every technician with a mobile device. This mobile device communicates with a centralized computer system over a communication network. The communication network may be wired or wireless. In a wired implementation, the mobile device would be connected to the wired network, called a Local Area Network (LAN), at one of a finite number of LAN access points. In a wireless network, a wireless link (which may be formed using Radio Frequency (RF) waves, infrared waves, ultrasound waves, etc.) could be used to establish communication between the mobile device and the central process control system. The prior art proposes that the central process control system provides the mobile device with the status information of systems in the vicinity of the mobile device. In order to determine the systems in the vicinity of the mobile device, in both the wired and the wireless case, the physical location of the mobile device needs to be determined first. In the wired case, the location of the mobile device can be determined by its proximity to a particular wired access point, whereas, in the wireless case, several location-determining means that are already known in the prior art, may be used to locate the mobile device. (These means include placing a number of sources of electromagnetic waves in the field, and determining the location of the mobile device relative to these sources.) In this implementation, once the location of the mobile device has been determined, a means is required to identify the machine or the system for which the status information is required. In some implementations, the mobile device may itself point and identify the physical system for which the status information is required. Four patents given below disclose various kinds of mobile devices known in prior art. 
   WO Patent 9319414, which is titled “Portable exploitation and control system”, discloses a portable device for controlling one or more remote systems. This portable device communicates with the remote system over an unspecified wired or wireless communication link. It is envisaged that this portable device is provided with multiple application software for controlling multiple remote systems, wherein each remote system has a corresponding application software. The portable device is intended primarily for use with remote military devices, such as unmanned vehicles and electronic weapon systems. Accordingly, a rugged design of the device to facilitate use in the field is proposed. The invention does not elaborate on the nature of the communication link or the nature of information transmitted. Further, the invention is designed as a push system, wherein information or a control signal flows from the portable device to the remote system. In other words, it is the operator who can get information from the central process control system, and never vice versa. 
   WO Patent 9612993, which is titled “Apparatus for providing access to field devices in a distributed control system”, discloses an apparatus for providing wireless access to multiple field devices in a Distributed Control System. Field devices refer to devices that are typically found in various industries. These devices are generally remote from the central process control system. They include pumps, valves, pressure transmitters, temperature transmitters, flow transmitters and other such devices. All these devices are connected to a fieldbus control network. The fieldbus is a communication bus that forms the connection between the field devices and the central process control system. The invention contemplates that each field device is equipped with a wireless access port so that a wireless handheld device has access to the field device. In an alternative embodiment, the wireless access port can be located on a fieldbus module that provides access to a plurality of field devices. Thus a wireless handheld device can access these devices through this module. 
   U.S. Pat. No. 5,598,572, which is titled “Information terminal system getting information based on a location and a direction of a portable terminal device”, discloses a mobile device that points to and identifies the system to be inspected. The central process control system maintains a database of unique characteristics of each machine, sub-system and of each system. The invention suggests using the location, the physical appearance, the characteristic sound and/or the temperature profile of the system, to uniquely identify the system. Once the mobile device identifies a system, it conveys the observed characteristics to the central process control system, and the two together can distinguish the system based on its unique characteristics. Alternatively, the machine or the system may bear a unique identification code, such as a bar code, and the mobile device can be equipped with an identifying means, such as a bar code reader, to identify the system. Alternatively, the system may be equipped with a code-transmitting unit. This transmitting unit would then identify the system to a mobile device in its vicinity and the mobile device would identify the system appropriately. In either case, once the machine or the system has been uniquely identified, the unique identifier is used to query the central process control system to extract the status information of this machine, system and of other connected systems. 
   U.S. Pat. No. 6,167,464, which is titled “Mobile human/machine interface for use with industrial control systems for controlling the operation of process executed on spatially separate machines”, discloses a mobile device, called a Human-Machine Interface (HMI) that interacts with a wired LAN. The wired LAN connects various systems in an industrial plant and a central computer; this central process control system controls the processes occurring on these systems. Each local part of the system in the manufacturing or processing plant has status information and a control program. An operator uses the mobile device to query the state of a system. The mobile device communicates with the central process control system using a Radio Frequency (RF) link. The mobile device identifies the machine or the system by means as mentioned above and by other means that are well known in prior art. In one embodiment of this invention, the wired LAN is only used for process control and is not employed by the mobile device. In yet another embodiment of the same invention, the mobile device communicates with the local part of the system in the manufacturing or processing plant directly rather than with the central process control system. Further, the mobile device now broadcasts its identification over a short range RF link to a detector provided on each system. The detector uses the wired LAN to extract information and programs from the central process control system, and provides these to the mobile device. This invention also contemplates providing only the appropriate status information to various users operating on the mobile device. 
   The processes and systems in manufacturing and processing industries are becoming increasingly more complex. For these systems, the status information is often very complicated and still has to be interpreted in a short period of time. Thus, the need for a mobile device that can analyse and present this information in a suitable manner is imperative. The technologies are evolving at great pace and new and better functionalities are being added to these mobile devices. It would be beneficial if the mobile device may be able to interact with the central process control system and obtain the relevant information immediately. The mobile devices mentioned in the prior art extracted information primarily from a central repository. 
   The inventors envision that in order to quickly complete normal production, maintenance and inspection routines, the real-time information should be available at all levels and a more interactive and responsive mobile device is required. And, of course, such a mobile device has to be tailor-made for different users (with different profiles). Further, if there were a means of tracking these mobile devices, then a particular user, operator or engineer could be quickly located in an emergency. In addition to tracking the operator, information regarding the nature of the emergency could be quickly communicated. Further, the operator could then use the mobile device to check the status of other systems that may be affected (by such an emergency), and issue control instructions. The central process control system could then carry out these control instructions. 
   In addition to all the above-mentioned salient features in addition to normal production use (that are critical for handling emergencies and disruptions in real-time), there is a need for the mobile devices to be used by the operators in an interactive manner in order to effectively and efficiently schedule maintenance programs. Thus, enhancing the mobile computing device by incorporating a tracking means, will lead to significant productivity improvements. 
   The above-mentioned desirable characteristics of the mobile device can be implemented by the use of Radio Frequency (RF) devices. Short range wireless standards including HomeRF, 802.11, Bluetooth, and several others are being developed and deployed so that various mobile devices can be connected to wired LANs that already exist in buildings, plants, manufacturing companies, and warehouses. One standard known as Bluetooth protocol offers short-range communication between Bluetooth enabled devices by using wireless access points. Bluetooth technology uses radio waves at a frequency of 2.45 Giga Hertz and currently permits data transfer rates of up to 1 Megabit per second. The high data transfer rate enables Bluetooth devices to carry up to three simultaneous synchronous voice channels. Hence, these high data transfer rates permit increased interactivity. Further, Bluetooth uses spread-spectrum frequency hopping technology, wherein the frequency at which communication occurs, is switched periodically. This feature enables the mobile devices to remain networked even in noisy environments. Another important feature of Bluetooth enabled device is that it remains passively connected to the network, once a connection has been established. There is low energy consumption of the Bluetooth enabled device while it is not actively communicating with the network. 
   SUMMARY OF THE INVENTION 
   It is an aim of the invention to provide a communication system that enables an operator to remotely query and control process sections in an industrial plant by exchanging information with a central control system that controls the process sections. 
   To attain the above-mentioned aim, the communication system comprises plurality of wireless access points spread throughout the plant on a data network, a mobile wireless device that provides access to the operator to exchange data with the central control system, and a control system interface that connects the mobile wireless device with the central control system using the wireless access points on the data network. 
   The mobile wireless device preferably includes an input means, such as a touch screen, a voice interface, a keyboard or a mouse, for inputting information; an output means, such as a graphical display screen or a headset, for outputting the information obtained from the central control system, and a wireless communication means, including but not limiting to a Radio Frequency (RF) antenna, an Infrared (IR) antenna, an Ultrasonic antenna, or an antenna based on similar wireless technologies known in prior art. 
   Further, the mobile wireless device has a means to enable the operator to login to the central control system or the mobile wireless device. 
   In an alternative embodiment of the invention, an interactive industrial control system is provided that can be remotely accessed by an operator equipped with a mobile wireless device. 
   In another alternative embodiment, the invention provides status information from a process section, which may be customized according to the profile of the operator equipped with a mobile wireless device. 
   In yet another alternative embodiment, the invention is used to locate and track an operator equipped with a mobile wireless device in an industrial plant using a plurality of wireless access points. 
   Preferably, the industrial control system maintains a database of the profiles for each operator and dynamically updates a table containing the information about the mobile wireless device into which each operator has been, or can be, logged on to. The industrial control system also maintains information about the process sections located in a vicinity of each wireless access point. The industrial control system may also use software objects to represent the process sections, has a list of pre-defined characteristics of these objects, and structures these objects in an object-hierarchy or some other object classification. 
   Therefore, the use of above-mentioned communication system provides the operator the ability to remotely interact with the central control system. The invention also allows this interaction to be tailored for a particular operator and process section. This invention also provides a higher degree of interactivity, such as voice-enabled communication, between the operator and the central control system. The invention thus leads to significant reductions in the time required to carry out normal production operations as well as to gather, analyse and troubleshoot processes in the industrial plant. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The preferred embodiments of the invention will hereinafter be described in conjunction with the appended drawings provided to illustrate and not to limit the invention, where like designations denote like elements, and in which: 
       FIG. 1  is a block diagram showing an operator remotely accessing process sections in an industrial plant according to an embodiment of the present invention. 
       FIG. 2  is a flowchart of a method of interacting with a central control system according to an embodiment of the present invention. 
       FIG. 3  is a block diagram showing process sections modelled as objects in an industrial plant according to an embodiment of the present invention. 
       FIG. 4  is a flowchart of a method of browsing an industrial plant using a hierarchy of objects in an industrial plant according to another embodiment of the present invention. 
       FIG. 5  illustrates the Bluetooth communication protocol used according to a preferred embodiment of the present invention. 
       FIG. 6  is a flowchart of a method of locating an operator in an industrial plant according to another further embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1  is a block diagram showing an operator remotely accessing process sections in an industrial plant. A manufacturing or process industry contains many process sections and one such process section  120  is shown in  FIG. 1 . A process section may be a large section such as a production line, a bleaching plant or a paper machine or a small section of a process such as a single apparatus. There are many machines and/or sub-systems in a process section  120  that are interconnected to execute a specific process. In most industries, there is a central control system  118  to control and monitor process sections  120 . The central control system  118  co-ordinates and controls various process sections  120  over a data network. The data network is usually a wired LAN connecting the process sections  120  to the central control system  118 . The central control system  118  receives status information  116  from the process sections  120  and sends control instructions for the process section over the data network. The flow of status information and the control instructions allow the central control system to monitor and control each machine and/or subsystem in each process section  120 . The central control system  118  refers to a centralized system for monitoring and controlling individual machines, subsystems or process sections  120  in the industrial plant. There are multiple commercial implementations of centralized control systems. 
   The present invention allows an operator  100  to remotely query and control a process section  120  in the industrial plant. During normal production operations, the operator  100  may physically visit the site of the process section  120  to physically inspect or to gain access to the information about the process section  120 . The present invention provides the operator  100  with a mobile wireless device  102  to interact with the process section  120 . The mobile wireless device  102  is connected over a communication link  104  to a wireless access point  106 . The wireless access point  106  is connected to a control system interface  110  through a data network  108 . The control system interface  110  provides the ability to send and receive information from the central control system  118 , thereby connecting the mobile device  102  to the central control system  118 . The control system interface  110  sends query and control instructions  114  to the central control system  118 . The central control system  118  accordingly returns the status information  115  of the process section  120 . 
   The present invention may be used by an operator  100  in the normal course of a production run in the industrial plant. The mobile wireless device  102  enables the operator  100  to elegantly control the process section  120  by issuing appropriate control instructions. The operator  100  may also use the present invention during scheduled maintenance runs. The ability to remotely access the information regarding the process section  120  enables the maintenance runs to be quickly completed. Further, the present invention may also be used in an emergency in a process section  120 . The operator  100  is then located using the present invention by the method shown in  FIG. 6 . 
   In the preferred embodiment, the mobile wireless device  102  is a thin client, i.e., a hardware device running a software that uses fewer and smaller amount of resources, including but not limiting to low processing power, low memory requirements, less weight, and low battery usage. The status information is processed by the control system interface  110 . This mobile wireless device  102  is readily portable and the minimal requirements keep costs low. The mobile wireless device  102  may thus be equipped with a simple input means such as a touch screen. 
   Further, the mobile wireless device  102  may have either a simple text-based display or a graphical display. It will be appreciated by those skilled in the art that the mobile wireless device  102  may equivalently be a powerful computing device, and that such mobile wireless devices  102  may become economically feasible in the near future. There are many handheld computing devices available that are configured or may easily be configured for communication and wireless communication. A Personal Digital Assistant (PDA) product or similar devices such as a Palm Piloff™, a HP Jomada™, a Compaq Ipaq™ or a Psion™ PDA can be used as the mobile wireless device  102 . A computerised mobile telephone such as the Ericsson R380™ and the Nokia Communicator™ can also be used as the mobile wireless device  102 . 
   The present invention enables an operator to query and control a process section  120  remotely. In the preferred embodiment, the operator  100  carrying the mobile wireless device  102  approaches one of many wireless access points  106 . The wireless access points  106  may be distributed over a relatively large area in the industrial plant. The mobile device  102  (or a wireless access point that is in the vicinity of the mobile device) sets up a communication link  104  with a wireless access point  106  in its vicinity (with the mobile device, respectively) by methods known in prior art. The communication link  104  permits the operator  100  to communicate with the control system interface  110 . The process section  120  in the vicinity of the mobile wireless device  102  is then determined, using information regarding placement of the wireless access points  106  in the industrial plant. 
   The control system interface  110  provides the necessary interface between an operator  100  in a process section  120  and the central control system  118 . The information about a particular process section  120  may be further customized for the operator  100  by the control system interface  110 . An operator  100  visiting a process section  120  would preferably be offered access only to relevant information about the process section  120 . Thus, of all the information available in the central control system  118  about a process section  120 , only a selected “view” is preferably provided to the operator  100 . The information may be selected by the control system interface  110  according to the job function of the operator  100 . The job function of the operator  100  and other information relevant to selecting information from a process section  120  are stored in an operator profile. Accordingly the control system interface  110  maintains one or more databases  112 . Firstly, the databases would contain the authorized list of operators  100 . This database  112  would enable establishing access rights for an operator  100 . Further, the databases  112  would contain information regarding the process sections  120  in the vicinity of each wireless access point  106 . Thus, once a communication link  104  is established by the mobile wireless device  102  with any one of the access points  106 , the location of the mobile wireless device  102  is determined by the control system interface  110 . Further, the databases  112  would contain the operator profiles. These operator profiles are used by the control system interface  110  to select information from a process section  120  to be sent to a particular operator  100 . While a single database is illustrated and described in  FIG. 2 , it will be obvious that this information may alternatively be distributed among more than one database. 
     FIG. 2  illustrates the method by which the operator  100  interacts with the central control system  118  to query and control a process section  120 . In step  200  the operator  100  of the mobile wireless device  102  is identified by the control system interface  110  by means of login information of the operator  100  provided by the mobile wireless device  102 . In step  202 , the location of the operator  100  is determined to be in one of the process sections  120  by using the location information of each wireless access point stored in the database  112 . The wireless access point  106  may detect the mobile wireless device  100  by methods known in the prior art. In the preferred embodiment, the mobile wireless device  102  broadcasts a request signal and waits for an acknowledgment signal from a wireless access point  106  in the vicinity. Once a wireless access point  106  establishes a communication with the mobile wireless device  102 , the process section  120  is identified as the one in which the wireless access point  106  is present. In step  204 , the control system interface  110  reads the profile of the identified operator  100  from the database  110  in the control system interface  110 . In step  206 , the information of the determined process section  120  is then obtained by sending one or more queries  114  to the central control system  118 . In step  208 , this information from the process section  120  is customized according to the profile of the operator  100 . In step  210 , the interaction with the operator  100  commences. Thus, the operator  100  studies the information about the process section  120  and issues certain control instructions, if required. Alternatively, the operator  100  may need to investigate further, possibly in other process sections  120 . In this case, the operator  100  may either physically visit another process section  120 , or may use the established communication link  104  with the control system interface  110  to navigate through information from other process sections of the plant. The method for navigating to obtain information regarding other process sections is depicted in  FIG. 4 . In step  212 , the communication link  104  is terminated when the operator  116  moves out of range of a wireless access point. The operator  100  may also wilfully terminate the communication link  104 . 
   The present invention provides a means for enabling the operator  100  to navigate in the control system to remotely control any process section  120  in the industrial plant. The present invention permits this navigation function once the operator  100  has established a communication link with any wireless access point  106 . This navigation is preferably customized based on the profile of the operator or any other user. In order to enable easy navigation through the industrial plant, various process sections in the industrial plant are represented using abstract objects. The abstraction concept is further elaborated in  FIG. 3 . A real object  300 , such as a machine, a sub-system or a process section is represented using a software object  302 . Different facets of a real world object  300 , such as its physical location, the current stage in a process, a control function, an operator interaction, a simulation model, some documentation about the object and other features, may each be described as different aspects  304  of the software object  302 . Thus, in the preferred embodiment, each software object  302  contains a list of aspects  304 , a selection of which are presented to the operator  100 , when the corresponding real object  300  is accessed. 
     FIG. 4  illustrates the method by which an operator  100  of a mobile wireless device  102  browses the industrial plant. This method is best carried out when the industrial plant is represented within the control system as a hierarchy of software objects  302 . In step  400 , the operator presses a button or activates other input means to request a menu of a list of software objects  302 , to be displayed on the mobile wireless device  102 . In step  402 , the list of objects is determined according to the profile of the operator and the location of the operator as determined in steps  200  to  208 , and the list of objects is displayed on the mobile wireless device  102 . In step  404 , the operator  100  selects an object  302  from the displayed menu. In step  406 , the control system interface  110  selects a sub-list of aspects  304  of all aspects of the selected software object  302 , by using the operator&#39;s profile. In step  408 , the operator  100  obtains information, shown as aspects  304 , regarding the software objects  302 , corresponding to a process section  120 . Thus, the operator  100  is able to interact with the aspects  304  of a particular selected object  302 , thereby being able to query and control the real object  300 , for example, the process section  120 . 
   Further, the operator  100  may wish to obtain information regarding a specific object in the object-hierarchy using the mobile wireless device  102 . In step  410 , the operator  100  may choose to continue this process of browsing for specific objects in the object-hierarchy. Thus, the operator  100  is able to browse through all the objects  302  in the object-hierarchy of the plant and obtain customised information regarding a real object  300  in the plant. 
   In the present invention, a hierarchy of software objects  302  is envisioned to model the industrial plant. It will be appreciated by those skilled in the art that for the purpose of enabling an operator to browse in the industrial plant, any well-defined categorization of these software objects  302  is adequate, and a strict hierarchy is not necessary. Thus, the present invention covers various well-known taxonomies for these software objects  302 , including but not limiting to, those based on physical similarity and functional similarity of the real objects  300 . These categories, generated from the above mentioned classification scheme, could be suitably linked together, not necessarily in an hierarchy, to permit the operator  100  to browse through the industrial plant. 
   The attainment of the above-mentioned functionalities requires a control system that monitors and controls the individual process sections in a plant. The present invention is best carried out in conjunction with a Control IT™ control system manufactured by ABB. 
   The wireless communication protocol used to establish and maintain the communication link  104  may be one of many known in prior art. Popular wireless protocols include IEEE 802.11 and Bluetooth. In an alternative embodiment of the present invention, Bluetooth communication protocol is used in the communication link  104 . In this embodiment, the mobile wireless device  102  may have voice input and output capabilities, to permit an operator  100  hands-free access to information regarding process sections  120 . A few particular features of Bluetooth communication protocol, mentioned below, highlight the advantages of this alternate embodiment of the present invention. 
     FIG. 5  illustrates an industrial control system that uses the Bluetooth protocol over the wireless communication link  104  between a Bluetooth enabled mobile wireless device  500  and a Bluetooth access point  502 . One example of a commercial Bluetooth access points is the Bluetooth local infotainment point (Blip) manufactured by Ericsson. Another example is the AXIS 9010 access point from Axis Corporation (of Lund, Sweden) that is also a Bluetooth access point. Also, the Bluetooth protocol is based on spread-spectrum frequency hopping technology. The Bluetooth enabled devices remain networked with each other at 79 different frequencies and the frequencies can change as rapidly as 1600 times per second. Thus, the Bluetooth access point  502  and the Bluetooth enabled mobile wireless device  500  can remain connected in very noisy environments. This might prove particularly beneficial in noisy process sections, where there may be high interference in the communication link  104  due to existing electromagnetic waves. Unlike a Bluetooth communication link, a normal static link might be repeatedly interrupted, and hence rendered ineffective, in such a process section. 
   Another important characteristic of Bluetooth is that the Bluetooth enabled devices remain passively networked with each other, once a connection has been established. This characteristic can be used to locate the Bluetooth enabled mobile wireless device, as it remains passively networked with the Bluetooth access points. Yet another key feature of Bluetooth is the high data transfer rates that can be achieved. Up to 1 Megabit per second of data transfer is currently possible using Bluetooth. Hence, the Bluetooth enabled mobile wireless units can receive high-resolution graphical content. The high data transfer rate also enables Bluetooth devices to carry up to three simultaneous synchronous voice channels. Thus, the Bluetooth enabled device can also be a headset that receives voice data. This headset implementation may be of great importance in cases where carrying the hand-held graphical display unit might be a problem. In addition, Bluetooth protocol is designed to operate with minimal energy consumption, thus permitting longer periods of uninterrupted connectivity. 
   The present invention also provides a means to track and locate an operator  100  in the industrial plant. This feature is particularly useful in case of an emergency in a process section  120 . In order to handle the emergency, a particular operator may need to be quickly located. The industrial control system of  FIG. 5 , which uses the Bluetooth protocol in an alternative embodiment, may be used to track and locate a particular operator  100 . An advantage of using the Bluetooth protocol is that the Bluetooth devices remain passively connected when in the operating range. A method of locating a particular operator is illustrated in  FIG. 6 . In step  600 , the control system interface  110  receives a demand to locate a particular operator  100 . In step  602 , the control system interface  110  searches a table containing the login information of each operator using a Bluetooth device  500 . The table would be updated whenever a Bluetooth device  500  connects or disconnects from a Bluetooth access point  502 . In step  604 , if the searched operator&#39;s login information is not found in the table, the search is stopped. However, if in step  604 , the search operator&#39;s login information is found, then in step  606 , the relevant data is sent to the corresponding Bluetooth device  500  by the Bluetooth access point  502 . The relevant data can be in the form of an alarm signal or in form of a graphical display on the Bluetooth device  500 . The operator  100  would then be notified of the emergency in a process section  120 , and provided with the relevant information to troubleshoot the problem. 
   It will be appreciated by those skilled in the art of wireless technology and control systems that the Bluetooth technology and Bluetooth devices can be easily replaced by 802.11 or HomeRF or other new wireless technologies that have either been developed or are in the process of being developed. For example, instead of using a Bluetooth access point, an Aironet  340  access point from Cisco (of San Jose, Calif., USA), which is an 802.11 access point, can be used. 
   In another alternative embodiment, the functions of the control system interface  110  can be carried out by the central control system  118 . Thus, the central control system  118  maintains and updates the databases  112 . Further, the central control system  118  customises the information and provides it to the mobile wireless device  102  through the data network  108  and the wireless access points  106 . 
   While the preferred embodiments of the invention have been illustrated and described, it will be clear that the invention is not limited to these embodiments only. Numerous modifications, changes, variations, substitutions and equivalents will be apparent to those skilled in the art without departing from the spirit and scope of the invention as described in the claims.