The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Distributed process control systems, like those used in chemical, petroleum or other process plants, typically include one or more process controllers communicatively coupled to one or more field devices via analog, digital or combined analog/digital buses, or via a wireless communication link or network. The field devices, which may be, for example, valves, valve positioners, switches, and transmitters (e.g., temperature, pressure, level and flow rate sensors), are located within the process environment and generally perform physical or process control functions such as opening or closing valves, measuring process parameters, etc. to control one or more process executing within the process plant or system. Smart field devices, such as field devices conforming to the well-known Fieldbus protocol may also perform control calculations, alarming functions, and other control functions commonly implemented within the controller. The process controllers, which are also typically located within the plant environment, receive signals indicative of process measurements made by sensors and/or field devices and/or other information pertaining to the field devices and execute a controller application that runs, for example, different control modules that make process control decisions, generate control signals based on the received information and coordinate with the control modules or blocks being performed in the field devices, such as HART®, Wireless HART®, and FOUNDATION® Fieldbus field devices. The control modules in the controller send the control signals over the communication lines or links to the field devices to thereby control the operation of at least a portion of the process plant or system.
Information from the field devices and the controller is usually made available over a data highway to one or more other hardware devices, such as operator workstations, personal computers or computing devices, data historians, report generators, centralized databases, or other centralized administrative computing devices that are typically placed in control rooms or other locations away from the harsher plant environment. Each of these hardware devices typically is centralized across the process plant or across a portion of the process plant. These hardware devices run applications that may, for example, enable an operator to perform functions with respect to controlling a process and/or operating the process plant, such as changing settings of the process control routine, modifying the operation of the control modules within the controllers or the field devices, viewing the current state of the process, viewing alarms generated by field devices and controllers, simulating the operation of the process for the purpose of training personnel or testing the process control software, keeping and updating a configuration database, etc. The data highway utilized by the hardware devices, controllers and field devices may include a wired communication path, a wireless communication path, or a combination of wired and wireless communication paths.
A distributed process control system can include one or more remote terminal units (RTUs), which can be implemented as flow computers coupled to field devices. An RTU can include, for example, one or more I/O modules for connecting to wired Highway Addressable Remote Transducer (HART) field devices and one or more I/O modules for connecting to wireless HART field device. More generally, an RTU can support any suitable industrial automation protocol, including such suitable digital industrial automation protocols as HART, Fieldbus or Profibus.
An RTU can operate in a supervisory control and data acquisition (SCADA) network. The SCADA network can be a central or distributed supervisory network or system that connects one or multiple hosts executing software applications for monitoring processes, equipment, variables, etc. with special-purpose devices operating a process control system (or, more generally, an industrial control system). For example, a host that implements an asset management system (AMS) can communicate with one or more RTUs to collect information regarding field devices connected to the RTUs to construct an hierarchy of field devices and provide a description of the hierarchy to an operator via user interface of the AMS. The host also can implement, or be communicatively coupled to, a module that supports an industrial automation protocol for tunneling commands via an RTU to a field device. For example, the host can include a HART server module.
To assess the health of a field device, the host sends a message via the SCADA network and the RTU to the field device, receives the response or detects a timeout, and provides an appropriate indication to the operator via the user interface. In other words, the approach available today is based on directly accessing a field device from a remote host via a communication network. Collecting information in this manner can take several seconds per each field device, with operators experiencing a particularly long delay when a field device is not communicating and the host detects a timeout event. Moreover, this approach generates a large amount of traffic in the network, sometimes interfering with other communications, such as SCADA telemetry data collection.