FREQUENTLY ASKED QUESTIONS
Where have I heard of VCT before?
Founded in 1993 by Dr. Douglas Humphreys and Mr. Kenneth W. Watkinson, Vehicle Control Technologies, Inc. (VCT) is a valued member of vehicle design teams at Navy shipbuilders, weapon system prime contractors and Navy laboratories. The VCT team continues a commitment to excellence and service spanning more than 40 years – 30 years in the private industry (Titan Research & Technologies) and 10 in the Navy laboratory system. VCT is a small business with 8 employees, having started as a transition of personnel and technology from the ARAP group of Titan Research and Technologies.
What kinds of underwater vehicles do you specialize in?
You'll find AUVs, ROVs, and Towed Bodies throughout this website, and we've worked on all three types. We have a very long history with AUVs and other free-swimming bodies. Towed bodies turn out to be more complicated to design and control than AUVs, and we have a specialty in developing actively controlled tow bodies. ROVs are relatively new for us, but we can apply the same tools to their use when the situation warrants.
What's different about your products?
Our typical customer is a systems integrator that is pushing the edge of vehicle performance or who wants to come up to speed quickly and offer a new system to the marketplace. Our products are designed to a control specification for the performance required by your mission, and we do the right level of hydro modeling and simulation to make sure hydro issues never come up on your list of program risks.
What kind of modeling and simulation do you do?
VCT has a capability unique in the industry for predicting the hydrodynamic and aerodynamic coefficients of all types of undersea and airborne vehicles prior to scale-model testing. This capability is based on analytical, computational fluid dynamics (CFD) and semi-analytical predictive techniques developed over the past 30 years and applied successfully to hundreds of vehicles.
VCT utilizes a variety of codes for hydrodynamic and control system analysis. Linear design techniques allow a quick computational turn around, as well as the application of the wealth of linear system theory. These physics-based analyses couple with nonlinear six-degree-of-freedom (6-DoF) equations of motion, as well as models of the vehicle control hardware and software. These codes are implemented via a system of computer programs named VCT Tools™, which currently represents the state-of-the-art in vehicle modeling and simulation.
What is a semi-analytical model?
The semi-analytical techniques built into our model are the secret sauce that make it different. The term "semi-analytical" refers to the fact that physics-based models are modified using empirical data and have been validated across hundreds of vehicle designs over the years. Unlike CFD, semi-analytical techniques can be run very quickly. That means the model can be used to look at the entire design space, and not just a few point cases. With this capability, the model becomes a superb design tool and not just an analysis tool. VCT's insights come from using the model to analytically look at the entire solution space to find the best compromise, not just a few points that seem like the best.
Is your model validated?
Validation of the VCT prediction techniques has been a continuous process over the past 30 years. Because of this, the introduction of new methodologies can be added with confident, experimentally-validated steps. Hydrodynamic model predictions have been validated against tow tank, water tunnel, wind tunnel, planar motion mechanism (PMM), rotating arm (RA), radio-controlled model (RCM) and full-scale test data.
Test facilities used in these validations include David Taylor Model Basin (DTMB), Tracor Hydronautics, ARTEC, University of Maryland Glenn L. Martin Wind Tunnel and NASA Ames Wind Tunnel. Validation has been made for many types of Navy vehicles including UUVs, towed mine countermeasure vehicles, towed ASW vehicles, SEAL Delivery Vehicles (SDV) as well as Air Force aircraft and towed vehicles. Many of the hundreds of vehicle designs that used the VCT techniques were unusual shapes with large asymmetric components for which no hydrodynamic database existed prior to the design analysis. CFD methods have contributed significantly in these areas.
A sampling of our test experience includes:
- AQS-20 - Wind tunnel & full-scale in-water tests
- LSV 1 & LSV 2 - Tow tank, RCM & full-scale in-water tests
- Submarine Torpedo Defense (SMTD) - Tow tank, water tunnel & full-scale in-water tests
- SWCS and MK-8 SDV - Wind tunnel tests
- Lincoln Advanced Endbody - Wind tunnel & full-scale flight tests
- ASOS Towed Vehicle - Full-scale in-water tests
- Mk 30 Mod 2 Autonomous Target Vehicle - Wind tunnel & full-scale in-water tests
The key to obtaining models with a low level of uncertainty and accurate vehicle trajectory simulations for control system design is the development of a model that accurately predicts the complex linear and nonlinear hydrodynamic forces and moments acting on the vehicle. Vehicle hydrodynamic forces and moments in nonlinear (and many linear) maneuvers are dominated by the vorticity field about the vehicle. The dominant flowfield is created by vorticity shed from the hull and from the various lifting appendages.