Undersea Control Systems Design

Named after Greek god and Messenger of the Sea, theall-electric Triton silently glides among coral reefs, putting explorersface-to-face with denizens of the deep. Triton's designers pride themselves inthe craft's intuitive operation, savvy implementation of controls and a fewunexpected options befitting the $2-3 million acquisition price. These includedeveloped-for-marine science robotic grippers, fish feeder and laser-guidedspear gun.

Billed as the "world's first luxury deep submersiblesdesigned for yacht-based operation," Triton 1000/2 belongs to a family of four,ABS (American Bureau of Shipping)-classed, one-atmosphere civil submarines.Each turnkey vessel from the Triton 1000/2 (1,000 ft-rated, two-passengervessel) to the deep-sea Triton 3300/3 (3,300 ft-rated, three passengers)features such exclusives as direct launch and recovery from mega yachts andreal-time, Ethernet controller-to-iPhone monitoring.

Patrick Lahey, Triton Submarines LLC president and vicepresident of operations for U.S. Submarines, explains that the hand-builtTriton goes beyond one-upmanship among yacht owners. "Many yacht owners love being on the waterand they love diving," he says. "So it was hard to not imagine them wanting togo down deeper, for longer periods of times and do it safely."

Lahey added that most mega yachts feature helicopter pads- so outfitting a yacht with a crane for submersible launch and recovery is"not a big stretch."

Ethernet Goes Undersea

After two weeks of U.S. Submarine's training, virtuallyanybody can safely pilot Triton. The craft's ease of navigation is enabled byan intuitive graphical user interface (GUI) tied to Wago's programmablefieldbus couplers (PFCs), which enable real-time, controller-to-iPhonemonitoring. Per ABS regulations, all manned submersibles require mechanical analoginstrumentation. However, because Triton's spherical acrylic pressure hull(passenger compartment) emphasizes an outward and down view, analoginstrumentation is arranged behind the captain. This frees space for anF-16-style joystick (navigation/propulsion), GUI and unobstructed views.

Earlier Triton designs used large PLCs to communicate allmission-critical navigation, propulsion and HVAC information. However,packaging all the systems in the craft proved difficult and the existing HMI(human-machine interface) was considered "too industrial."

"Thebiggest challenges were making everything compact and aesthetically pleasing,as well as streamlined for maintenance," Lahey says. "For example, the panelcan't look like a squirrel cage of wiring, especially at a $2 million pricepoint."

At a tradeshow, Lahey saw a GUI from Vessel MonitoringInc. (VMI) and immediately wanted it for the Triton.

VMIreplaced the Triton's existing PLC and HMI with three Wago 750-842Ethernet TCP/IP PFCs and a Panasonic Toughbook-19 touch screen tablet PC. Datatransmission is Ethernet-based, with just four conductors among PFCs. A MoxaWi-Fi access point provides data transmission to above-surface equipment.

"Thanks to the PFC monitoring, you look at the GUIand know instantly what everything means," Lahey says. "VMI configured thegauges to feel similar to a car's."

TheGUI enables toggling between units of measurement for all displays, as well asmixing-and-matching of graphical, analog-style and purely digital outputs.

Tri-Zone Triton

Triton models are divided into three PFC-equipped zones:acrylic passenger hull, internal electrical junction box (IEJB) and externalelectrical junction box (EEJB). Within each zone, the PFC controls, monitorsand sends alarms for gases, environmental systems and machinery. Lahey says theWago PFC-based monitoring and controls system does not control any safetysystem, as all safety is mechanical-based. Instead the PFC controls funnel allpertinent data into the GUI.

Data from the PFCs are used for pre- and post-diveoperating reviews and to view battery current and digitally store all data.Remote-monitoring is also possible via PFC to streamline any troubleshooting,as well as enable software updates.

In Triton's Zone 1, the passenger hull, a Wago PFCreplaced what Lahey called the "lump under the passenger seat" to controldigital instrumentation and environmental gasses including temperature,humidity, high- and low-pressure oxygen, reserve oxygen and air, as well as theA/C set point. Zone 2's IEJB controls lighting, external HID (high-intensitydischarge) lamps and related 24V switching. The high-voltage EEJB in Zone 3houses contactors that activate thrusters and handle the main 120V and back-up24V batteries.

Forprotection from extreme thermal cycling, and 1468.5 psi resulting from cruisingat depths up to 3,300 ft, all control components were placed inpressure-resistant vessels. Each was outfitted with moisture sensors,backfilled with nitrogen, vacuumed and filled with dry nitrogen.

Compact size, modularity, marine approvals (such as ABS,GL, LR, DNV) and Cage Clamp spring pressure terminals are among the reasons whyMatt Youney, VMI president, specified Wago technologies for the Triton. Forhim, operating conditions for the Triton were a good demonstration of the needfor reliability. "If it works reliably at 1,000 ft below the surface of theocean, it'll work in a typical factory environment," he says. This comparisonto industrial systems is appropriate, considering that Triton's development wasapproached like the design for a typical decentralized, industrial controlproject replete with SCADA, PC software and multiple PFCs.

With the Triton "you have a very small footprint, yetfull-blown decentralized monitoring system," says Youney. "For instance, we use wireless sonar, whichis a serial device connected via a serial-to-Ethernet bridge. We also have awireless Doppler velocity log. Since the GPS in the Toughbook will not workafter submersion, the Doppler velocity log tracks the sub wirelessly andcommunicates the position via a serial-to-Ethernet bridge."

Lahey views the PFCs as "amazing tools" that enable datatracking within submarines roaming the globe.

PFC-to-iPhone Monitoring

Non-man-rated cranes launch/recover Triton, andpassengers wait while crane and crew guide Triton into the water. There itundulates with the waves while mission-critical and life-support systems activate.This includes moisture detectors to monitor propulsion battery pods for waterintrusion - crucial if an
O-ring was pinched or a vent was improperly sealed prior to launch.Environmental systems are also monitored, including humidity, percentage ofcarbon dioxide and oxygen, as well as absolute cabin pressure and even A/C setpoint.

Previously,the crane operator had to physically hold the PC to monitor all systems asTriton geared up. The PC was then handed to passengers after boarding. But oncethe craft is in the water, it's not the best idea to be handling a PCcontrolling mission critical systems over saltwater. "It's a dicey prospect,"Youney adds.

To address this issue, Lahey tethered his iPhone to thesystem during test dives, so that Youney could deliver a real-time iPhone appthat monitors all water alarms, as well as the status of electrical, mechanicaland environmental systems.

"I tied the iPhone's integrated Wi-Fi to Moxa," Youneyexplains. "I had already written the ModbusTCP stack in Cocoa (Apple'sdevelopment language) for another application."

Click here to watch a video of Triton on a dive in the Bahamas.