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Schilling Robotics Introduces the Digital Telemetry System(TM)

Posted on: Tuesday, 14 February 2006, 03:03 CST

By Stanley, Jason

In 1998, Schilling Robotics launched an extensive research and development program to create a modular subsea control system that could be applied to virtually any type of underwater application. The result of that program, the Remote Systems Engine(TM), has gained over five years of field experience in the subsea industry in virtually every oil and gas region of the world, in water depths exceeding 4,000 meters.

Philosophy

The Remote Systems Engine(TM) was developed so that the subsea industry could provide users with a basic set of building blocks with which to form the core of their subsea machines. The system was designed to be modular, easily expandable, and extremely capable. All system components were designed to offer as much capability as possible, so that a small number of core parts could be used in a wide variety of applications, allowing for smaller spares kits and less training for users.

The Next Generation

Continuing innovation with the RSE(TM) control system family of modules led to the development of the second-generation control system, the Digital Telemetry System(TM) (DTS(TM)). The DTS(TM) is fundamentally a digital system, based on a gigabit Ethernet backbone.

Ethernet, characterized by the IEEE 802.3 standards, was originally developed in the 1970s and has grown into the most pervasive networking technology in the world. Many large industrial manufacturing facilities use Ethernet for real-time control of factory automation systems because Ethernet technology in its current state is highly reliable, and an ever-increasing number of sensors and peripherals are moving from serial communications to the Ethernet standard.

The DTS(TM) leverages the Ethernet technology developed for a wide variety of industries that demand reliability and performance. The fundamental components used in the DTS(TM) are manufactured by the millions, virtually guaranteeing high reliability, high performance, and significant longevity, all of which are important requirements for the subsea marketplace.

The DTS(TM) Node

The DTS(TM) system is extremely flexible and can be configured to meet a range of subsea networking needs. The fundamental components of the system can be used to form various network structures, depending on redundancy requirements, the size of the network, and the number of sensors to be interfaced.

The DTS(TM) node is the core building-block of the control system. DTS(TM) nodes act as signal distribution points on the network, providing connection points for sensors, actuators, vision systems, and even other networks. The node has two versions: the subsea node and the rack node. The subsea DTS(TM) node is a hybrid design with most of the board housed in a pressure-compensated, oil- filled composite housing, and the fiber transmission system housed at atmospheric pressure in a titanium housing. All penetrations between pressurized and non-pressurized regions of the housing are accomplished within the PCB layers, using a technique patented by Schilling Robotics and used in the original RSE(TM) control system. The resulting assembly is significantly smaller and lighter than traditional subsea electronics housings, and the node is constructed of materials that are completely corrosion resistant.

Side view

The subsea DTS(TM) node

Each subsea DTS(TM) node includes two gigabit Ethernet ports, and supports up to 16 separate connections using the DTS(TM) port modules. The node can be configured to support several types of interfaces by installing the appropriate port module. 10/100 Mbps Ethernet devices are supported using the network interface module (NIM), video sources are supported using the video interface module (VIM), and serial devices (RS-232 or RS-485) are supported using serial interface modules (SIM). USB 2.0 devices are also supported. Using this "plug and play" configuration, users can quickly configure and reconfigure the system to support devices without performing tedious, unreliable, manual wiring. With this capability, spare parts also become useful. Spare VIMs, for example, could be used to replace SIMs to allow connection of additional video cameras to the node for a specific task. Each port module includes electronic fuses (which can be reset from the surface), individual current monitoring, power switching, and line isolation. The standard port module connector type is the Schilling Robotics SeaNet connector, but other connector types can be fitted to the port modules if required.

DTS(TM) serial interface module

The DTS(TM) node supports digital and analog video. All video channels on the network are accessible at any point on the network. (For example, users can elect to view one or all video streams on a network on one PC monitor with only an Ethernet connection.) Alternatively, composite video signals (NTSC or PAL format) can be accessed at the rack node to allow connection to standard video displays.

Devices with high bandwidth communication requirements, such as multi-beam sonars, can be interfaced to the DTS(TM) node using the integrated, two-channel coarse wave-division multiplexer (CWDM) module. Real time HDTV video and Firewire (IEEE 1394) devices are also supported using this CWDM module. Additional channels can be added to the network in increments of four or eight channels, using an external CWDM module.

The DTS(TM) node connects to the surface network via singlemode fiber. Signal multiplexing takes place within the node. Nodes can be "stacked" or connected together in a daisy-chain configuration using the onboard fiber connection points. With this capability, users can increase system capacity simply by connecting additional nodes to the network. In an ROV application, for example, an additional DTS(TM) node could be located on a tool skid to support additional sensors for a specific task. In an application requiring greater network separation, such as a seafloor observation network, nodes can be connected by fiber and separated by up to 120 kilometers between each node or node cluster.

Since nodes can be so easily added, system capacity can be quickly increased without significant weight, space, or cost effects. Traditional pressure vessel control canister systems are severely limited in expansion capability. Even if additional user channels are available within the canister, the canister end bell physically limits the number of penetrations that can be made to access the available channel. To expand such a system typically requires adding a completely separate canister, with significant weight, space, and cost effects to the subsea system.

If a problem develops with a DTS(TM) node, the user is required only to troubleshoot to the module level. Users are assisted in root cause detection by the topside control software, and once the issue is isolated to a known module, the module can quickly be replaced with minimal system downtime. Module replacement can take place in typical offshore environments with little concern for water or debris intrusion. The user is no longer faced with the question "which board is it??" when tracing system problems.

DTS(TM) simple troubleshooting

The fundamental design of the subsea DTS(TM) node also allows the system to be operated in air for unlimited periods. The nodes and associated equipment are powered by humansafe 24 VDC. All systems can be operated using only 24 VDC from an on-deck power supply, without requiring high-voltage AC power to operate instruments.

The DTS(TM) rack node acts as the surface network connection and signal distribution point. The same node PCB used in the subsea node is used in the rack node. The rack node is mounted in a standard 19- inch rack (as the name suggests). The unit provides 16 connection points for Ethernet, video, serial, or USB devices. Users can configure the output of the rack node using port modules in the same way that subsea nodes are configured.

The DTS(TM) rack node provides surface network connections

Additional DTS(TM) rack nodes can be connected to the surface network to provide further network interface points as required.

Architecture Flexibility & Redundancy

Using the Ethernet standard provides the DTS(TM) with unparalleled ability to be configured and expanded beyond traditional subsea control system capabilities. Subsea networks can be configured with up to 255 subsea DTS(TM) nodes, which equates to the system having no practical capacity limit. Bandwidth is the only limiting factor, and this can be expanded by using additional fibers.

The DTS(TM) network can be configured to provide various levels of redundancy, depending on the application requirements. Physical configuration options, along with network protocols, provide significant redundancy options. The DTS(TM) nodes support spanning tree protocol (STP), a link management protocol that provides path redundancy while preventing undesirable network loops. To provide path redundancy, STP defines a tree that spans all switches in an extended network. STP forces certain redundant data paths into a standby state, or blocks these paths once a more favorable connection has been established. If one DTS(TM) node becomes unreachable, or if STP reliability changes, the spanning-tree algorithm reconfigures the spanning-tree topology and reestablishes the link by activating the standby path. For example, if a spare fiber is available at the subsea node, both the primary and secondary fibe\rs can be connected to the node at all times. If the primary fiber fails or telemetry degrades, the STP will force all network communication to seamlessly and automatically switch to the secondary fiber path. No user intervention is required.

Physical redundancy can be added in the form of subsea DTS(TM) GigE switches. Each switch assembly provides up to 16 separate fiber- switching modules, allowing users to configure a massively redundant system with seamless fiber switching built in-without software modifications.

Further network expansion can be supported using the DTS(TM) general-purpose input/output (GPIO) modules, which support several low-latency devices and use only one port on the DTS(TM) node.

Software

The Schilling Robotics controls team developed the system software as part of the original Remote Systems Engine(TM) program. The software architecture is also modular, providing integrated support for DTS(TM) hardware. Users are provided with intuitive touchscreen user interfaces that display feedback, provide control, and offer detailed diagnostics functionality. Device drivers, where necessary, are provided with the system as part of a growing library. As devices are connected to the DTS(TM) system, the software automatically detects the device connected, as well as detecting device revision in some cases.

The RSE(TM) software supports the direct interface of visualization systems, survey computers, and other topside systems.

Leveraging the Ethernet networking technology, users can also connect to the RSE(TM) control software and DTS(TM) network from remote locations, providing an Ethernet network link.

Applications

The DTS(TM) is fundamentally designed to support an extensive range of subsea applications. For users capable of creating or using existing software to communicate and drive sensors, actuators, and vision systems subsea, the DTS(TM) can act as a flexible conduit. For users requiring complete turnkey systems, the DTS(TM) can be pre- configured and easily reconfigured to meet changing requirements. The technology lends itself to everything from ultra deepwater subsea networks, to upgrades of control systems nearing, or at the point of obsolescence.

Touchscreen interface provides feedback and control of DTS(TM) nodes

By Jason Stanley, V.P. & Regional Manager, Schilling Robotics Gulf Coast

Copyright Technology Systems Corporation Jan/Feb 2006

Source: Ocean News & Technology

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