On Board Vehicle Power (OBVP): Mobile power for tomorrow's battlefield

Story

December 23, 2009

Doug B. Mays

Diversified Technologies

Current threats on our military forces have created a tremendous requirement for mobility as it relates to mission specifications.

The development of On Board Vehicle Power (OBVP) systems not only increases warfighter mobility but also enables more effective power supply to current and emerging battlefield electronic systems by providing improved physical characteristics, in addition to more effective power disbursement than traditional Tactical Quiet Generators, thanks to new OBVP inverter technology.

The deployed U.S. soldier is given every technological advantage possible on the battlefield. U.S. warfighters have become more than rifle carriers, now utilizing a vast array of military systems active in any number of methods: From on-site radar and threat evaluation systems to UAV patrols to fighter-mounted thermographic and spectral imaging, these systems have provided the ability to not only outgun but completely control an occupied space.

A push is underway to make the U.S. military more agile, mobile, and lethal. To do so requires new weapons systems and next-generation computational systems. Many of these services and applications fall under the Army Brigade Combat Team (BCT) modernization strategy (formerly Future Combat Systems). Some of these most advantageous next-generation military applications involve high-density computational systems that can perform functions such as RF/spectrum scanning and analysis, dispersion analysis, locational detection, cryptanalysis, horizon bogey detection and threat prediction (as opposed to simple evaluation), and probability analysis directly on the battlefield, providing real-time information to on- and off-battlefield commanders. These applications are invaluable to the warfighter in the modern theater and are critical to maintaining situational awareness for the battlefield commander and dominance of active war space.

When talking of these next-generation battlefield systems, an often overlooked but critical question must be addressed: How does one power them? It is not possible to simply plug into an outlet in the middle of a desert. The move to these sophisticated battlefield applications will raise the demand for power exponentially.

Consequently, the rise in demand of power for these advanced deployed systems means an increase in the output of power required from generator systems. With traditional skid-mounted or trailer-towed fuel power technologies, the end result is reduced to nothing more than larger, heavier, and more fuel-hungry generators. This is in direct opposition to the nearly decade-old emphasis to create a faster, lighter, and more agile deployed force. However, new On Board Vehicle Power (OBVP) systems are providing a viable remedy with an improved physical design and new inverter technology for more effective power disbursement.

Traditionally deployed power systems: Designs no longer sufficient

As mentioned, traditionally, theater-deployed systems are powered by trailer-towed or skid-mounted generators. Hitched directly to an HMMWV, these towed generators require ample diesel (fuel) to operate, reduce troop mobility and response times, and, when in operation at a site, are frequently giveaways to the adversary as to the intentions and location of the camped troops. These “Tactical Quiet Generators” have been in use since the late 1980s and require the carrying of additional fuel to generate power. Skid-mounted units also drastically reduce the cargo capacity of the HMMWV, as they are typically carried in the rear cargo area of the vehicle.

In the past, commanders were dealing with defined combat lines and specific operational theaters and occupation directives. In the modern theater this is no longer the case, and power generators and techniques of the past cannot power the military and its systems of the future. While technology has improved, certain characteristics such as noise, lack of mobility, serviceability constraints, the need for extra vehicles to carry fuel and generators, and other logistical issues that are inherent to the design and use of these Tactical Quiet Generators have created battlefield nightmares for the operators (not to mention increased costs and the swelling of budgets for commanders to accommodate these logistical shortcomings). And all of these issues are in direct opposition to the current military push of “lighter, faster, stronger, smarter.” They must be overcome to maintain Armed Forces dominance of an active theater.

To mitigate the shortcomings of present power technologies, a spur of developments in onboard vehicle power mechanisms is occurring. The result: power systems that are compact, lightweight, and provide the military with the mobility desired while providing the robust power needed by next-generational computational systems.

Advances in the inverter technology used in OBVP systems, such as the increasing use of Insulated-Gate Bipolar Transistors (IGBTs) to create high-powered inverters, have spurred key developments in these modern power units. No longer is a simple conversion from the 28 VDC source to single-phase, 120 VAC/60 Hz enough. Mobility, serviceability, and space constraints must be considered as well. OBVP units do not require an external fuel source and can be mounted directly (in various mounting configurations – including wheel well, behind a seat, and so forth) to the HMMWV without decreasing needed cargo space, and can provide a wide range of output power to the end application.

OBVP systems: It’s all in the inverter

These modern OBVP units are single- or three-phase AC power units for ruggedized environments that require mobility, portability, and durability. Power envelopes for these OBVP modules range from 2 kW to 30 kW. These units receive input voltages of 24-28 VDC from the vehicle’s alternator. The OBVP unit contains control, pre-charge, and protection circuitry, phase power modules, and feedback monitoring and control. The OBVP inverter itself can be paired with other controllers and interfaces, allowing ease of operation by the user. In a nutshell, the unit takes DC power from the vehicle and inverts that to three-phase AC. Figure 1 contains a basic diagram of an OBVP unit and speed control interface.

Figure 1: Basic diagram of an OBVP unit and speed control interface

(Click graphic to zoom by 1.4x)

There is typically a speed control mechanism connected via relays to the integrated OBVP unit and the alternator and engine complex of the HMMWV. These speed controllers can monitor and control throttle and RPMs as needed, and relay the information via a communications bus to an Interface and Indicator Unit (IIU). The IIU is where the operator controls the function of the OBVP inverter, either producing more or less power and monitoring states and so on. IIU can also have a Graphical User Interface (GUI) and easily understandable controls.

The speed control mechanism and IIU allow the operator to control the output of the OBVP unit. While the unit receives 28 VDC input current from the HMMWV, the operator may select any of a range of output currents. If the system or application required the basic single-phase, 120 VAC/60 Hz output discussed earlier, three-phase 208 VAC, or 50 Hz or even 400 Hz frequencies, modern OBVP systems allow the operator to set the output of choice for the intended application with a variety of output waveform options.

As mentioned, the OBVP inverter is mounted onto the HMMWV in an area that does not affect cargo capacity or function of the vehicle and allows instant availability to power in any area to which the HMMWV can maneuver. The modular methodology of not only the components but of the installation mechanisms means that the OBVP system can easily be removed from one HMMWV – returning the vehicle to its original configuration – and quickly and readily installed on other vehicle platforms as needed. (Figure 2 shows a side-mounted OBVP unit.) This provides the ability to provide critical power to areas of the battlefield including those facing harsh environmental conditions, ensuring that critical systems are operational at all times.

Figure 2: Example of a side-mounted OBVP unit

Realizing tactical goals with OBVP systems

As advances in battlefield technology force the requirements of higher power levels and more mobile power technologies, On Board Vehicle Power units will find their way into many deployments, providing an innovative physical design and improved power disbursement via advanced inverter technology. The military’s focus on “faster, lighter, stronger” requires the use of new technology and next-generation computational and communication systems, and these systems and their deployments will all require newer mobile, rugged power solutions. Trailer-towed and skid-mounted power generators fail in these regards, as they add bulk, reduce mobility, and require external fuel (diesel) to operate, which further reduces the cargo of a military vehicle. Mobile vehicle power systems, like Diversified Technology’s VPS10K, that draw power directly from the alternator and do not impede much-needed cargo space will be the go-to solution for the deployment of on-battlefield systems in the 21st century military.

Doug B. Mays is a field application engineer for Diversified Technology, Inc. He can be contacted at [email protected].

Diversified Technology 800-443-2667 www.dtiruggedpower.com www.dtims.com