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NEWS | Feb. 27, 2023

Carderock Inventors Patent New Modeling Software

By Benjamin Morley, NSWC Carderock Division Public Affairs

A team of engineers from Naval Surface Warfare Center, Carderock Division recently patented a new software modeling capability that digitally replicates the physics of underwater vehicles and towed bodies and tracks the movements of the tow cable when bodies attach or detach.

The patent, U.S. Patent 11,554,838 B1, titled “Maneuvering and Control Simulator for Underwater Vehicles," was filed in support of the Maneuvering and Control Simulator for Underwater Vehicles (MACSUV) program. The team responsible for developing the MACSUV program are team lead Alexander Tsarev and mechanical engineers Roger Kleinmann, Jennifer Nunes, and Jeeven Hugh, all with Carderock’s Maritime Systems Hydromechanics Branch.

Originally developed by Nunes, Hugh and Tsarev, MACSUV is a tool to simulate underwater vehicles and develop control systems for them. When Kleinmann came along in September 2018, Tsarev asked him to add a new capability to the program.

“I added cable interactions, which allows us to model towed bodies and vehicle-to-cable interactions beyond towed bodies,” Kleinmann said. “Through this design process, I was able to get what we call ‘discontinuous dynamics between cables and bodies,’ and that is the patentable feature of MACSUV. In other words, we can model for instance bodies detaching and deploying from tow cables or something attaching to a cable during a tow.”

Like all ships, a towing ship moves through waves and changes direction, all of which affects the cable and towed vessels. Other simulation tools model the cable to respond to continuous dynamics, which can handle most scenarios, such as towing in waves and performing maneuvers. However, these other tools cannot model cable response to sudden stimuli. For ships that recover unmanned vehicles, this was a major problem.

Towing vessels are subject to discontinuous cable contact, specifically how something attaches or detaches itself from a tow cable. The team researched the loads that cables and vehicles see during contact since these interactions were not a simple steady-state case.

In addition to being able to test for discontinuous dynamics in simulation, the program also creates a cost-savings measure by allowing naval architects to examine and modify towing designs in simulation and avoid the more expensive and time-consuming physical testing stage for dealing with design errors. Oftentimes, the design process, from conception to product, will start with basic calculations, general system design and model testing. While there are simulations in the process, it depends heavily on the program.

“By having this capability and invention as part of our tool suite now, we are able to do the numerical simulations, which allow us to look at it earlier in the design process compared to if we were doing it by test only,” Tsarev said.

MACSUV began as essentially a free-running model simulator where the designer could input a vehicle into the program, give it navigational commands and then see how it behaves untethered to a line. Designers also had a capability called Dynamic Cable and Body (DCAB) written by Carderock personnel decades ago. While DCAB could model tow bodies in various conditions in waves, currents, with various speeds and depth, MACSUV provided an easier way to build, model and tweak controllers and implement those changes on real-life systems.

The Maritime Systems Hydromechanics Branch wanted to add vehicle capabilities in MACSUV for control design, as well as the cable capabilities from DCAB. When Kleinmann joined the command four years ago, Tsarev asked if he could implement a cable component from DCAB into MACSUV. There were two ways to add the capability – the first was to port the code from DCAB and adjust it, the other was to build new code from the ground up. Kleinmann chose the latter, adding discontinuous cable contacts along the way.

The team plans on using MACSUV to work on various upcoming projects, as well as possibly improving the use of the software’s interface. Any future changes to MACSUV will be heavily project-driven and the team is excited to add capabilities as the opportunities arise.

“We’ve been using MACSUV for other projects and plan to use it for future projects, as well,” Tsarev said. “It wasn’t a one-time use kind of deal to maintain this kind of capability. It certainly seems like there is a lot of demand for its use going into the future especially with a renewed focus on multi-body interactions.”