Deploying Ruggedized Systems in Unmanned Military Vehicles for
Advanced Air-Sea-Land Applications - download pdf
Part 2
Implementation Methods & Key Factors for Success: Designing, Integrating and Deploying COTS/Custom Computing Platforms
Overview
Part 1 in this series of whitepapers described the escalating trend toward the use of advanced unmanned vehicle platforms as key tactical elements within overall military reconnaissance and war-fighting strategies.
In the following sections, Part 2 of this series provides a more detailed exploration of the specific implementation methodologies and issues that must be addressed in the creation of high-performance, ruggedized systems to meet the needs of these ultra-demanding deployment environments.
Designing the Optimal Platform
As previously described, the optimal approach is to leverage both COTS and custom design capabilities that build upon pre-qualified platform building blocks, while offering the feature flexibility and configurability to meet the needs of specific programs.
This approach can give project engineers and program managers a wide range of latitude to consider different cooling methods, power supply loads/designs, backplane architectures, I/O configurations and EMI/RFI specs. The result is a cost-effective platform tailored to fit the overall design requirements, rather than either a rigid platform that forces compromises or a full-custom approach that forces both high-cost and extended development timeframes.
SWaP – Size, Weight and Power
With any military electronics application, balancing size, weight and power (SWaP) presents the biggest challenges to designers. This is especially true for unmanned aerial vehicle applications, where the airframe design and payload parameters place the most stringent constraints on the electronics system design. As these constraints have gotten tighter, electronics systems are often being designed to perform multiple tasks, rather than having multiple systems dedicated to separate tasks. While this can help to conserve overall space in the vehicle, it does place even more demands on the primary system thereby further driving up performance, storage, cooling and reliability requirements.
Advanced Cooling Methodologies
There are five principal types of cooling methodologies:
1) Forced convection
2) Conduction, with forced air through hollow side walls
3) Conduction, using passive convection across external fins
4) Cold Plate cooling (active or passive cold plate)
5) Liquid cooled
Forced Convection Cooling essentially involves moving air across the system boards, power supplies and other components, with the moving air absorbing heat that is then exhausted out of the enclosure. In many ground-based systems, convection cooling is handled via the brute force method of adding more and bigger fans to drive air through the system (assuming that space, cost and noise are not an issue). However, with unmanned aerial systems, the brute force approach runs counter to SWaP constraints.
In contrast, Conduction Cooling solutions typically have the system boards, power supplies, and other components sealed inside an air tight enclosure, with the edges of all system elements mechanically clamped to the sides of the enclosure. Forced air moving through the structure of the enclosure then conducts heat away and exhausts it out of the system. With conduction solutions, the moving air never actually touches the system components. Movement of air through the system can be active or passive.
For example, the FS-5985 chassis (shown at right) uses conduction cooling via forced air through hollow side walls. It is a five slot, 200 watt chassis for either cPCI or VPX. Designed to operate with either an integrated rear fan or with the aircraft plenum, this type of cooling approach provides a high degree of configuration flexibility while assuring a consistent level of cooling for the internal electronics.
For airborne applications, the use of conduction cooling solutions is on the increase; while active convection cooled solutions are shrinking. (Liquid cooled or cold plate methods can be considered but typically run counter to SWaP objectives.)
Backplane & Bus Fundamentals: High-speed Signaling
High-performance is critical to the success of modern unmanned vehicle electronics applications and high-speed backplanes & bus architectures form the foundation for delivering the required performance. Depending on the specific application, this can require cPCI, VPX, or other semi-custom backplane configurations. From a chassis design standpoint, it is critical to provide support for a variety of bus architectures while assuring ruggedized dependability and minimizing both idle state and operational state noise. In addition, configuration requirements may need custom backplane designs with options for custom I/O routing.
Storage Subsystems: High-Capacity & Quick-swap Options
As previously mentioned the extended mission cycles and advanced vision/sensor systems used in UAS vehicles can generate huge amounts of data that must be stored by the on-board platform. It’s not uncommon for today’s UAS systems to require solid-state drives that provide local storage of a half terabyte or more; plus these demands are destined to keep increasing.
In addition, data from UAS missions is almost always time-critical and the aerial vehicles often must be turned around quickly for deployment in a subsequent duty cycle. Most embedded storage subsystems are therefore designed for quick-swap of the solid-state drives, rather than waiting to download the data through the I/O connection. From a chassis design perspective, meeting these requirements can mean mounting the drives on the front panel for easy access, with quick-connect SATA interfaces.
Leveraging Standards-Based Communications
Standards-based communications is another element that has become critical in the design and operation of remote unmanned vehicle applications. The on-board electronics systems provide the vital link between the acquisition of data and the analysis/actions that follow – often in real-time response to emerging on-the-ground situations where reliable communications can literally make a life-or-death difference. Compliance with standards such as MIL STD 1553B, ruggedization of key I/O connections and the ability to integrate I/O structures directly into the backplane can be important factors in meeting the overall communications and mission objectives.
Key Factors for Success
“COTS-to-Custom” Optimizing Performance, Reliability and Cost
The design approach of leveraging proven platforms from “COTS-to-Custom” yields a number of advantages including 1) faster development, 2) higher reliability, 3) lower cost, and 4) greater flexibility. For example, as shown below, a COTS FS-5975 catalog chassis provided the solid foundation for designing the MTS/Predator, MTS/MH60 and MH60 2nd generation systems, as well as others.
This reuse of proven technology not only makes each new development process faster and results in more reliable designs; it also continuously feeds the improvement and innovation cycles for enhancing the underlying COTS chassis designs.
Design for Field Maintainability
In addition to resulting in superior designs, the COTS-to-Custom approach also can allow for more efficient support logistics and improved field maintainability. The combination of proven, reusable design elements and leveraging of some manufacturing processes across multiple programs can provide lower costs and improve logistics synergies. Also, having empirical data from a larger number of related COTS systems deployed to multiple programs can help to drive ongoing quality improvement and maintainability objectives.
Real-world Configuration Examples
The following are just a few examples of COTS systems in the FS-59xx family that have already been adapted for deployment into a variety of demanding applications, including unmanned vehicle electronics.
The Bottom Line
The unprecedented advances in UAV/UAS capabilities over the past few years, coupled with their proven success in thousands of deployment scenarios, has resulted in a series of game-changing shifts in both strategic and tactical combat methodologies.
Tightly intertwined with the evolution of these new war-fighting platforms has been a dramatic evolution of COTS-to-Custom systems solutions that provide proven reliability along with the adaptability to support each new generation of application requirements.
The general fields of vehicle-embedded electronics and mission computing will continue to evolve into an ever-expanding range of land, sea and air vehicles for military applications; as well as into other non-military applications such as homeland security, law enforcement, fire & rescue and commercial exploration arenas.
As these new application areas unfold, many of the same challenges that have been addressed and resolved in UAV/UAS systems will be effectively handled through new adaptations of these already-proven COTS-to-Custom design methodologies.
Over the past decade, military platforms of all types and sizes have seen a dramatic increase in the use of sophisticated on-board electronic systems. This growing reliance on small embedded, rugged computers and complex high-speed I/O requirements for “mission computing” provides a wide range of real-time applications to support both reconnaissance and war-fighting activities on land, in the air and at sea. These high performance mobile systems offer significant advantages to protect troops on the battlefield and enhance their combat capabilities, as well as improving inter-unit communication and coordination at both tactical and strategic levels.
One of the key arenas in which advanced on-board electronics have proven to be a fundamentally game-changing factor is the evolution of Unmanned Vehicles that can operate remotely to provide critical intelligence and/or attack capabilities. In addition to providing some of the greatest opportunities, these unmanned vehicles also present some of the most difficult design challenges. This is because of the need to package a high level of computing power and data collection/distribution elements within minimal size, weight and power constraints, while assuring the ruggedized capabilities to survive and perform in very demanding operational environments.
This first whitepaper provides an overview of the factors that are driving unmanned vehicle applications and the key design requirements for successful deployments. While most of the discussion will focus on unmanned aerial platforms, many of the same concepts are being incorporated into advanced ground vehicles that support warfighting and defensive functions for all the armed services. Part 2 in this series of whitepapers will provide a discussion of the specific issues that must be addressed to optimize ruggedized system platforms to handle these requirements. The follow-on paper will also describe a number of real-world COTS solutions that can be readily adapted and customized to address the demanding challenges of remote platforms operating in unmanned vehicles.
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