Precision Sensing

Volume 1

Inertial Sensors –Applications and Integration

Meeting the demand for precise and accurate sensing technology

The defense procurement landscape has evolved, no longer does the military drive technology development. They are now a consumer of technology and subject to the whims of com-mercial markets such as component obsolescence. However, military mission requirements have only gotten tougher. Precision and accuracy are paramount whether the applica-tions are unmanned systems, laser targeting, or navigation.

The challenge for industry then is to provide capability that leverages commercial technology in packages that meet strin-gent mission requirements and meet the ever-growing demand for reduced size, weight, power, and cost (SWaP-C) in every application. They also must accomplish this within the current budget constraints of the U.S. Department of Defense (DOD).

Companies that answer this challenge, such as Sparton Navigation and Exploration (NavEx), not only have a legacy with the DOD of providing that capability, but they also have the manufacturing infrastructure to manage the total lifecycle cost of a product, which is crucial within today’s defense pro-curement environment.

In the following pages you will learn how Sparton delivers cost-effective capability to its customers through product lifecycle management. This is a huge issue in the defense world where platforms last decades but electronics technology can go obso-lete in as quickly as six months.

Also read how Sparton is not only enabling high performance in small packages with its MEMS technology, but also how the company helps educate government and industry users alike on whether to outsource a product or make it themselves.

We encourage you to dive into our content, learn about our inertial sys-tems, advanced acoustic sensors, and laser targeting technology. We continue to add capabilities and technology that allow us to offer more solutions than ever for your challenges. Our knowledgeable and highly experienced engineering team is always available to help you integrate our sensor solutions into your applications.

Learn More Airman 1st Class Mikal Mincer, a Radio Operator Maintenance and Driver (ROMAD), 5th Air Support Operations Squadron, Fort Lewis, Wash., uses a Special Operations Forces Laser Acquisition and Marker (SOFLAM) while supporting close-air-support missions in support of Pacific Thunder, Joint Base Lewis-McChord, Wash., July 27, 2010. The SOFLAM is used by ROMADS and Joint Terminal Attack Controllers (JTACs) for laser target acquisition and range finding. (U. S. Air Force Photo/Master Sgt. Greg Steele)

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4 SWaP-C and why your component partner matters

6 Integration and operational guidelines for MEMS-based inertial systems

11 Solving the make vs. buy decision in defense electronics procurement

13 Due diligence: questions to ask a potential CM partner

14 Suffering from obsolescence headaches in defense procurement?

16 Who’s doing product lifecycle management?

17 Videos

18 Common issues with magnetic compasses By Richard Wheatley, Sparton Engineer

20 What is an Attitude Heading and Reference System?

22 Design considerations in the presence of magnetic fields

24 Solutions

26 Products

Precision Sensing | Volume 1 | 3

Leveraging optimized SWaP-C navigation components for military applications

Precision Sensing

Volume 1

CONTENTS

INTEGRATING TECHNOLOGY OF THE SMALLThe 21st century military is operating on a new battle-field, one on which soldiers are working with both legacy vehicles and aircraft and new devices with advanced capabilities. Keeping soldiers connected to real-time logistical information and keeping devices powered up is critical, yet the need to provide device and system portability is greater than ever.

Recent advances in micro-electromechanical systems (MEMS) are delivering critical performance capabilities with significant reductions in size, weight, power, and cost helping manufacturers meet the SWaP-C challenge. Now, it’s possible for up to two or three power-hungry components to be replaced by a single component that is smaller and lighter and provides the same functionality. By working with a component partner that keeps their eyes on the big picture with out-of-the-box thinking, com-bining functions and sharing components, manufacturers and their military customers can reduce the number of sensors needed in a communications system.

SWaP-C challenges Many of today’s military applications require signifi-cantly advanced functionality and greater processing

SWaP-C and why your component partner matters

For many years, the U.S. Department of

Defense (DOD) has had strict requirements

about the size, weight and power (SWaP)

of components and systems developed for

military applications. A challenging budget

environment led to a new acronym including

“c” for cost, or SWaP-C. In 2012, the DOD

presented a budget that was designed to

“conform to the 2011 Budget Control Act’s

requirement to reduce Defense Department

future expenditures…[even though] we still

have significant gaps in modernization that will

need to be filled in coming years.”

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SWAP-C

performance. Smaller, less costly navigation systems aren’t always as accurate as legacy systems and compromises and tradeoffs may be required along the way. As technology advances, soldiers carry more batteries to keep devices pow-ered, creating a need to keep the devices themselves as small as possible. Because legacy vehicles and systems are limited as to how much power they can provide, there is a need to integrate new technology into these systems for more power and perfor-mance with the additional challenge of limiting added weight.

All of these demands pose a challenge when the goal is to provide the smallest and lightest device possible with the longest possible field life. As a result, product designers must often choose between power and performance at critical points in their design process. With the many challenges involved in meeting DOD demands for reductions in size, weight, power and cost, a high level of collabora-tion with manufacturing partners is needed.

Choosing the right partnerFollowing are some important characteristics to

seek out when evaluating a potential component

manufacturing partner.

1 FLEXIBILITYYour partner should work with you to develop a truly collaborative relationship and be willing to go beyond simply delivering the device; they should also collaborate

every step of the way to help reduce the SWaP-C of the finished product. A good partner understands the criticality of each com-ponent of SWaP-C reduction guidelines and will work diligently to help make adjustments in the overall device or system. Even if the partner cannot make direct reductions in the size or weight of the specific component, their software engineers may be able to make firmware adjustments or make tradeoffs between com-ponents that will result in significant cost savings down the line.

2 OUT-OF-THE BOX THINKING The ideal partner will bring a combination of engineering experience and innovative thinking to the end product. It will be important to seek out a partner that sees the

“big picture” to find creative solutions that can not only reduce the size and weight of the finished product, but also incorporate technologies that can actually multitask and replace more than one component.

It is also important to keep an eye out for innovations that the partner is developing that may benefit future designs. Many com-ponent manufacturers are working on new technologies that are potential game changers. Watch and listen for hints at designs in development that could make a difference in the future.

3 ONGOING SUPPORT It is important to work with a partner that plays a consulta-tive role throughout the design and development process. By engaging a partner early in the process, they are better

able to collaborate on adjustments that can be made to the device when needed and help get the end product back on course.

4 MILITARY KNOW-HOW New components or designs for aerospace and defense must undergo a rigorous qualification process and require a significant amount of internal testing and review. A

partner that has an understanding about how the military works can provide technical support and adjustments quickly at critical points in the process. As a result, it is important to work with a company that has a history of working with the military and is familiar with how the military does business.

5 FORWARD THINKING Chances are, when the time comes for the next genera-tion of a device, the military will set new requirements for lighter weight, better performance and more capabilities —

at the same cost or less. That is why a partner should always be looking for ways to decrease the weight and cost — and increase the performance — of the component so that the next product upgrade can quickly meet new requirements.

CONCLUSIONWhile recent technological advances are helping the military and their manufacturing partners meet the demand for reductions in size, weight, power, and cost will continue to be a daunting chal-lenge, and it will continue to be important to work with a partner that goes beyond the product to provide a complete package of solutions, service, and support.

Rugged, mission-critical military and aerospace applications need the design and manufacturing sophistication of a partner such as Sparton. As both a defense contractor and a supplier to recognized leaders in the market, we have expertise in your demanding and highly regulated environment.

We create devices that include a variety of highly specialized tech-nologies such as embedded systems, RF, lasers, optics, sensors and robotics for uses as varied as undersea warfare to cockpit controls and satellite communications. Every project we take on benefits from the Sparton Production System, as well as our expe-rience and commitment to building strong partnerships.

Technologies in embedded systems, RF, lasers, optics, sensors, and robotics

Learn More

Precision Sensing | Volume 1 | 5

Integration and operational guidelines for MEMS-based inertial systems

A high performance inertial system that includes magnetometers can provide accurate platform heading

information in a variety of applications and operational aaaenvironments. The key components of these

systems include: magnetometers to measure the Earth’s local magnetic field, accelerometers to determine

tilt, and gyroscopes to determine rotation of the system. Together, these sensors provide data that can be

processed to accurately calculate platform attitude and heading. However, magnetometers are susceptible to

measurement distortion in the presence of any magnetic material. There are techniques available to mitigate

distortion — the following will describe the product integration guidelines and the operational considerations

and available on-board calibration procedures that will optimize the overall product performance.

“A hard magnetic distortion is easier to compensate for, but is usually a much larger

contributor to the overall magnitude of distortion than the

soft magnetic components…”

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MEMS-BASED INERTIAL SYSTEMS

Integration guidelines for inertial systems Magnetic field distortions Since magnetic material close to the system could distort the intensity or direction of the measured Earth’s magnetic field, performance depends greatly on where the inertial system is installed within the application. Onboard calibration procedures can correct for magnetic disturbances, however the larger the disturbance, the harder it is to compensate accurately. To maxi-mize system performance, great care must be taken in the place-ment and orientation of the inertial system. There are two types of magnetic distortion: hard and soft.

Soft magnetic materials can easily become magnetized and demagnetized when exposed to even weak magnetic fields. They will attract and distort the local field and will vary with ori-entation. Since they cause a non-uniform distortion, it is harder to compensate. Examples of soft magnetic materials would be iron, steel, nickel, or other ferrous materials.

When identifying the ferrous material that may affect your system, be sure to consider mounting brackets, mounting hardware, wires, printed circuit boards, as well as your application specific compo-nents. On printed circuit boards, watch out for nickel-plating leads and iron or other steel on nearby components.

Hard magnetic materials are those that retain their magnetism and are difficult to demagnetize even after the removal of the magnetic field, such as a permanent magnet or magnetized iron or steel. Since the distortion remains constant and in a fixed location, hard magnetic distortions are easier to compensate for but larger contributors to overall distortion than the soft magnetic components. The most common sources of hard magnetic dis-tortion in a system include permanent magnets and batteries.

Permanent magnets are often found in speakers, generators, electrical motors, microphones, engines, fan motors, electrical currents carried in wires, and batteries. Also, electrical cur-rents passing through wires will create magnetic fields even if the wire is non-magnetic (e.g., copper), and if the current is not consistent, the magnetic field strength will have a time-varying effect.

Since batteries are magnetic they must be kept as far away from the inertial system as possible. Batteries are of particular con-cern because their magnetic fields distortion may vary over their life and can even vary from battery to battery. Lithium batteries typically have the least magnetic distortion, followed by Alkaline and Nickel-Cadmium.

When integrating the inertial system into any application, the soft and hard magnetic materials should be identified, evaluated, and placed as far away from the inertial system as possible.

Inertial systems can also be affected by time-varying magnetic fields generated by the motion of magnetic materials or unpre-dictable electrical currents. Examples would include magnetic distortion due to motion of magnetic materials (i.e., magnetic switches, Hall Effect sensors, etc.), and time-varying electrical currents. Special care should be taken to ensure any time-varying magnetic disturbances are placed far away from the inertial system.

Inertial system mounting hardware It is critical to follow mounting guidelines for the inertial system, and mount it permanently so compensation procedures can be effective. The mounting hardware bracket and screws must be non-magnetic material, and only austenitic (non-magnetic) stainless steel can be used closer than 25mm to the inertial system. Austenitic stainless steel includes type 302, 303, 304, 316 and 316L. There also may be variations in the magnetic properties of each batch of hardware. Depending on accuracy requirements of the system and the proximity of the stainless steel, sampling may be required. Sweeping a moderately strong magnet over the parts can easily test stainless steel compo-nents; any hardware attracted to the magnet is not suitable for use near the inertial system.

Avoid shielding the inertial system Never enclose the inertial system in a magnetically shielded housing — that will further distort the Earth’s magnetic field. Adding shielding to hard and soft magnetic disturbances in the system is also not recommended, because that will just add to the overall magnetic distortion and make the system more sus-ceptible to fluctuations if exposed to strong external magnetic fields or environmental changes.

Precision Sensing | Volume 1 | 7

Judicial use of shielding could be considered if there is a strong time-varying magnetic disturbance that could not be calibrated out, but should be the last resort. The best way to mitigate the distortion of time-varying effects is distance from the inertial system and operational timing.

Platform considerations When integrating the inertial system within the larger applica-tion platform, consider the external magnetic influences of the platform since the inertial system cannot compensate for time-varying magnetic field distortions or magnetic material that is not fixed relative to the inertial system.

There are also several design considerations for integrating into an aircraft or UAV application, including acceleration, which can affect the accurate determination of the attitude of the inertial system. Some vendors will provide adaptive sensor fusion algo-rithms to correlate the accelerometers and gyroscopes.

EVALUATION OF MAGNETIC DISTURBANCES Performance optimization Integration guidelines are unique for each application, as it is difficult to calculate or predict the magnetic profile of each. Also, application packaging and weight constraints make it impossible to create an ideal magnetic environment for the inertial system. To optimize performance, there must be trade-offs between the system requirements, packaging limitations, and the application components. The performance of the inertial system should be evaluated as well in the presence of the known magnetic mate-rial at the component and system level.

Inertial system performance evaluation Most inertial systems suppliers have a development kit that can be used to evaluate performance at the application level. When using the development kit, it is important to consider how the test environment will contribute to the magnetic environment. Operate the inertial system away from equipment that may have a time-varying magnetic effect and keep it in a fixed location. Magnetic field strength drops off over distance, but distance is not the only contribution to magnetic disturbance. The amount, shape and uni-formity of the material as well as the location and orientation to the inertial system will impact overall magnetic distortion.

System performance evaluation Depending on the packaging constraints and tolerance of inertial system accuracy, a system breadboard can be used to evaluate the inertial system operation in the application configuration prior to testing the final assembly. A system breadboard will allow designers to evaluate component locations and orientations rela-tive to the inertial system in various modes of operations. This breadboard can also be used to evaluate the effectiveness of the inertial system onboard compensation in the presence of the system’s fixed and time-varying magnetic disturbances.

COMPENSATION FOR MAGNETIC DISTURBANCES Compensation procedures While magnetic interferences can be minimized by careful mate-rial selection and component placement, platform size and weight limitations will limit how magnetically quiet the device can be. On-board calibration and adaptive compensation can be used to minimize the impact of magnetic disturbances, and operational

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scenarios will allow optimization of the inertial system perfor-mance through monitoring, timing, and operational guidelines.

If the magnetic characteristics of the platform are spatially fixed and relatively permanent, then local magnetic distortions can be corrected through compensation. Distortions that move rela-tive to the inertial system cannot be completely compensated for using traditional inertial system compensation procedures.

All high accuracy inertial systems will have an onboard magnetic com-pensation procedure to correct for hard and soft magnetic disturbances, usually device-specific 2-D and 3-D calibration involving azimuth and ele-vation measurement sampling. This generates compensation coefficients that are electronically stored and applied to the device. Some systems store multiple compensation coef-ficients to support multiple system operating configurations.

Calibration schemes for a device usually involve system factory cali-bration, in-field calibration, and periodic recalibration as defined by the application’s operational requirements. Recalibration is rec-ommended after changing sensor modules, battery packs, or other platform accessories.

Factory calibration Factory calibration compensates for magnetic disturbances due to the inertial system itself, and adjusts offsets and axial mis-alignments in the full 3-dimensions. These coefficients are elec-tronically stored as the default values.

Then once the inertial system is integrated into the product, application factory calibration compensates for magnetic distor-tions specifically inherit to the product configuration.

To be accurate, the calibration must be performed after final assembly in an environment free from magnetic disturbances. The coefficients can then be electronically stored in the inertial system.

Finally, the inertial system needs to be calibrated in use. The end-use application must provide techniques to rotate the overall platform in order to support inertial system calibration at the application level or limit calibration to two dimensions if 3-dimen-sional calibration is impractical.

Operational compensation considerations Operational environments present a wide variety of natural and manmade magnetic anomalies for which traditional compensa-tion procedures cannot predict or correct. Natural magnetic dis-turbances include celestial events and ore deposits. Manmade interferences include power lines, buildings, bridges, passing vehicles, underground power lines, pipes, tanks, or equipment carried by the user such as a watch, weapon, or other nearby equipment. If the inertial system is integrated into a larger system such as a naval vessel or a UAV, the entire environment will have a unique magnetic profile.

Some of these local environmental distortions can be identified and mitigated by user equipment restrictions. In other cases, such as in an urban environment, the effects are unpredictable and the inertial system alone cannot identify and compensate for these. To optimize performance in a magnetically dynamic and unpredictable environment, the following items must be considered:

› In-field calibration requirements › True north accuracy/World Magnetic updates › IS measurements time-varying magnetic disturbances › Adaptive compensation with integrated gyroscopes

In-Field Calibration is needed if the magnetic environment changes or the calibration was performed in a poor magnetic environment. It involves orienting the system in various positions over 360 degrees of heading, making magnetic field measure-ments at each of up to 12 positions. The inertial system will cal-culate and save the compensation coefficients that will correct for changes in application’s magnetic distortions. The inertial system should be recalibrated if the following occurs:

› Device relocation › Changes to user equipment › Changes position of equipment relative to device › Large change in operational temperature › Battery pack replacement › Addition/removal of ancillary equipment on/near device

To evaluate inertial system performance

in the vicinity of other system components the relative change

in the inertial system readings can then be

used as opposed to absolute accuracy.

Precision Sensing | Volume 1 | 9

World Magnetic Models (WMM) are included in many iner-tial systems to provide accurate true north heading anywhere. The inertial system determines the magnetic heading, while the WMM provides the magnetic declination or difference between the magnetic north and true north. The heading is then adjusted to report the true north heading. To maintain true north heading accuracy the sensor systems should include an in-field method to upgrade the WMM when updates are released.

System Time-Varying Magnetic Disturbances are found in most sophisticated systems, despite the best efforts to eliminate them. Each application must have a defined operational profile to minimize any effect, such as system warm-up to ensure the magnetic distortion has reached steady state. Also, electrical current surges or use of mechanical or magnetic switches during operation should be considered, and prevented if possible. An example includes electrical current surge due to the firing of a laser range finder (LRF).

Gyroscope-Enhanced Adaptive Compensation maximizes system performance in dynamic environments, such as handheld applications in urban environments or unmanned vehicles that encounter unpredictable magnetic material or large magnetic fields.

The gyroscopes measure angular rotation rates around three orthogonal axes to provide information about movement of the inertial system. The inertial systems with adaptive sensor fusion algorithms will monitor the magnetometers, accelerometers, and gyroscopes to weigh the measurements in order to provide a more

stable heading, pitch, and roll output. These adaptive sensor fusion algorithms can outperform the traditional and extended Kalman Filtering approaches by providing real-time environmental noise characterization used to optimize the inertial system performance in dynamic environments. The traditional and extended Kalman Filter approach uses fixed, hard coded parameters or requires the user to accurately predict and input the operational environment of the application. These traditional approaches work best when the error sources are easily modeled and predictable.

In dynamic environments, it is best to use an inertial system with an adaptive sensor fusion algorithm that can provide real time characterization and compensation to heading, pitch, and roll as it operates in the varying magnetic and mechanically noisy environ-ments. The adaptive algorithms can compensate for the presence of hard and short iron magnetic effects in the application platform with their innovative in-field calibration that optimizes the magne-tometer sensitivity and offset in the full three-dimensions.

CONCLUSIONInertial systems performance can be greatly enhanced through careful design and oper-ational considerations designed to limit distortion from challenging magnetic envi-ronments. Material selection and placement guidelines can minimize soft and hard mag-netic disturbances, while system measure-ment timing and operational guidelines can address most residual platform time-varying magnetic distortion.

Packaging constrains often make it impos-sible to eliminate all internal magnetic distortions from the system, though on-board calibration can compensate for any remaining internal magnetic distortions. Using these product integration guidelines, operational considerations, and available onboard calibration procedures, the inertial system can operate at its specified perfor-mance in a wide range of applications and dynamic operational environments.

To enhance performance further, use of inertial systems with adaptive sensor fusion algorithms, such as those produced by Sparton Navigation & Exploration, make it now possible to operate an inertial system in the most challenging of magnetic environ-ments. These systems provide a fusion of accelerometers, mag-netometers, and gyroscopes, along with the adaptive algorithms that outperform traditional and extended Kalman Filter based approaches by providing real-time optimization of the sensor per-formance resulting in exceptional heading accuracy in a variety of magnetically dynamic applications and environments.

Inertial systems can perform in a wide rage of applications and dynamic operational environments

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MEMS-BASED INERTIAL SYSTEMS

Solving the make vs. buy decision in defense electronics procurement

The decision about whether to manufacture your product in-house or to outsource it to a contract manufacturer

(CM) is one that will have short and long-term strategic implications for your company. While there are a

number of factors that go into that decision, some are more easily quantified than others — like projected

time to market, production capacity, and the overhead costs for capital equipment and personnel. Other

factors are more difficult to quantify with a high degree of confidence, especially for those businesses that

traditionally focus on design instead of manufacturing.

In today’s complex, highly competitive marketplace, businesses face new pressures. They must contain

costs with leaner manufacturing processes and improved asset utilization, maintain high levels of customer

service, and keep pace with rapid technological developments. As a result, many businesses — for which

manufacturing is not a core competency — are looking to develop strong partnerships with CMs who can

help them contend with today’s new challenges.

Here’s the good news: The world of CMs has evolved to such an extent that there is a viable CM option for

nearly every product in nearly every industry — including aerospace, defense, energy, medical, automation,

and precision motion control.

SIX FACTORS TO CONSIDER IN THE MAKE OR BUY DECISIONNo two make or buy decisions are alike. Some companies may choose to out-source the entire manufacturing pro-cess for a product, while others may outsource only some subassemblies that are not core components of the manufacturing process. In any case, the decision should not be made lightly. Many factors should be taken into con-sideration when weighing the relative merits of each strategy.

The decision should be considered at both the strategic and operational level. At the strategic level, factors that will impact the decision include government regulations, market trends and compet-itive activity. Factors at the operational level include cost considerations, plant capacity and control. Here we explore some key factors that may make or break your make or buy decision.

Precision Sensing | Volume 1 | 11

MAKE VS. BUY

1 CORE COMPETENCYIf the manufacturing process that you are considering is a critical component of your company’s business or dependent on highly valuable intellectual property, it is

probably not a candidate for outsourcing. After all, if the manu-facturing process itself is your key differentiator, you’ll want to maintain control of that proprietary information.

On the other hand, if the manufacturing process is not a signifi-cant component of your business model today, there is probably no benefit to keeping manufacturing in-house. If your strengths are product marketing and commercialization, for example, you’ll want to find a CM that can take over the manufacturing so that you can focus on what you do best — ideally, helping you save production time and costs in the process.

2 SKILL SETS When you’re ready to consider the make vs. buy decision, it will be important for you to anticipate the skills that will be needed — and to assess whether your internal capa-

bilities include those skills. If not, it will be costly and difficult to add those capabilities and manage them effectively. If the manu-facturing process demands specialized expertise or a new tech-nology that does not currently exist within your organization, you may want to seek out an outside resource that has the skills and experience needed to make your product successful.

If yours is a medical device, for example, you’ll want to look for a source with experience in developing products that meet FDA regulations and standards. It will be important for you to visit their facilities in order to get a better understanding about whether their techniques would be transferable to your project.

3 CAPACITYOften, the lack of sufficient production capacity is the single driver of the decision to outsource manufacturing. In those cases, making the move to contract with a partner

that has the needed physical space is a no-brainer.

If you are considering making the capital investment in space and equipment to perform manufacturing at your own facility, however, it will be important to look beyond the initial phases of the project and forecast what your future needs will be. Start with an assump-tion about the capacity demands and impact on your facility at the outset and, when the space is no longer needed, think about what you might use that space for in the future. Will there be some-thing else in the future that you could use that space for? Or will it become a financial burden?

4 RAMPING UPThere is a potentially dramatic difference between in-house manufacturing and outsourcing when it comes to ramping up people and processes. If your staff does not

currently possess the capabilities needed to manufacture the component or product, you’ll need to consider the cost and time involved in integrating a new team into your organization. Some

estimate that interviewing, training, and incorporating new skill-sets and processes into your organization — plus getting it all up and running — can take up to a year.

By contrast, when you make the decision to work with a CM with the relevant capacity and skills in place to manufacture your product, you can potentially be up and running in a much shorter time.

5 HIDDEN COSTS In the midst of a make vs. buy decision, there can be many so-called “hidden costs” that businesses tend to ignore.

These include: › Certifications that are required for personnel that will

perform certain processes › Retraining that may be needed in the event of changes in

technology › Administrative costs — including process setup and

inventory management › Software costs — the majority of which are incurred after

product launch and the potentially significant cost of ongoing maintenance by developers

› Shipping costs of materials for production › Material management › Working capital management

There are many startup costs that businesses don’t consider upfront when making the make or buy decision. These include setting up databases for document and revision control, setting up the line and establishing the manufacturing footprint, opti-mizing line flow with lean/Six Sigma processes, getting up to speed with ISO certifications, purchasing new software (from database storage to MRP and ERP), and much more.

6 CHANGESWhen inevitable technology advances happen, a part becomes obsolete or feedback from the field necessitates a change in a product or component, the company that

developed the original design will be able to turn around changes more quickly. In this case, working with a CM with design and manufacturing capabilities offers real benefits. It reduces risks when you transfer from design to manufacturing, and the time and costs involved when the need for updates arises. A CM will also be well equipped to advise about aftermarket issues, including how parts obsolescence will impact the serviceability and repair of products into the future.

THE DECISIONWhen you have completed the complex make vs. buy evaluation process and you’ve concluded that you’ll need to outsource your manufacturing function, it will be important to carefully evaluate potential CM partners. At Sparton, we encourage potential manu-facturing partners to evaluate our production methodology, tour our facilities, and talk with our key personnel. Ask us anything — we’re an open book. Learn More

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MAKE VS. BUY

Due diligence: questions to ask a potential CM partnerWhen you outsource the production of your product or component to a CM, you can focus on your core capabilities. That’s the idea, but not all CMs are alike. Here are a few questions that may help you determine whether the potential partner is right for you.

QUESTIONS TO ASK AND WHY IT’S IMPORTANT

Q: Do you have best-in-class production systems in place?

› A simple “yes” is not a sufficient answer. You want assurances that the CM will deliver the quality you expect, so make sure the CM has adopted quality standards and can provide documentation and test data.

› Best-in-class is not simply that you ARE measuring, but HOW you are measuring yourself to a high standard.

Q: Do you have quality management systems in place?

› There is a wide range of quality management systems that demonstrate how a CM stacks up, including: › ISO 9001 certification requires a CM to focus on continuous improvement in customer service and satisfaction › SO 13485 is a specific quality management system for the design and manufacture of medical devices › AS 9100 is a specific quality management system for the aerospace industry › Simply having these certifications is not enough. The CM must have a strong record with no certification disruptions or black

marks for performance.

Q: Can you help with compliance issues?

› The CM should not only understand the regulations and standards that your product needs to meet, but also be willing to provide labeling guidance and manage regulatory filings that may be necessary.

Q: Do you operate with an open book?

› The CM should provide information about their production processes and costs (material, labor, and overhead) so there are no surprises later.

Q: What’s your inventory management process?

› You want to be sure that the CM can ensure that components are available when needed and that they are willing to inventory parts that may not be needed immediately.

Q: How will you protect my intellectual property?

› Your CM should have the systems in place that can ensure that your sensitive proprietary information is 100 percent secure.

Q: Can you demonstrate expertise in manufacturing specifically to the technology in my device?

› You should understand the specifics about the experience the CM has in working with various technologies, applications, and platforms. This means getting out on the production floor in addition to case study demonstrations and examples.

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MAKE VS. BUY: QUESTIONS TO ASK

Suffering from obsolescence headaches in defense procurement?The one constant in defense procurement is that platforms last decades while commercial electronic

components will often go obsolete in six months, causing major headaches for suppliers all along the

defense electronics supply chain. Combine this with increasing global competition and the need for greater

efficiencies and speed to market and these headaches become migraines.

However, businesses of all sizes have found a way to alleviate much of that pain by using product lifecycle

management (PLM) as a way to boost productivity. Now widely used in the aerospace and automotive

industries, PLM can provide a holistic view of product management for highly complex manufactured

products and can deliver significant productivity benefits.

Providing your contract manufacturing (CM) partner with well-defined lifecycle requirements that include

information about your product and your processes is a first step toward streamlining and improving all

stages of product development and manufacturing. In this way, you provide your CM with a roadmap of your

expectations at every stage of your product’s lifecycle, which arms them with the tools they need to work

closely with you every step of the way.

As a business strategy, PLM enables you and your CM partner to work in unison as you collaborate at every

phase of the product lifecycle — as you innovate, design and develop, support and retire your products.

Following are some of the benefits

of — and best practices for —

collaborating with your CM at

every stage.

SETTING THE STAGE FOR PRODUCT LIFECYCLE MANAGEMENTA product lifecycle encompasses a series of stages through which a product pro-gresses — a process that usually pro-ceeds from concept and design through end of life (EOL) or discontinuation and unavailability. However, the speed at which a product progresses through each stage can vary widely, depending on the industry.

Some trajectories are more compressed than others because of frequent shifts in consumer requirements or other devel-opments. Others may be more extended Proactive CM partner looking ahead to your product’s future

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PRODUCT LIFECYCLE MANAGEMENT

because the product is mature and customers do not require many changes. For example, defense contractors work with much longer product lifecycles because their customers, after making significant capital investments in their products, tend to resist any updates or introductions of new products.

Industries also vary widely in the types and degrees of external forces with which they need to contend along the way. Medical device manufac-turers, for example, must deal with an alphabet soup of FDA requirements that include premarket approval (PMA), investigational device exemp-tion (IDE), and good manufac-turing practice (GMP).

Let’s take a look at what hap-pens at each stage of a typ-ical product lifecycle and how a partnership with a CM can streamline the process.

1 CONCEPT DEVELOPMENT AND DESIGN This is the very earliest

stage in a product’s lifecycle, when critical decisions are made that will have a sig-nificant impact on the supply chain. This is when the bill of materials (BOM) is built and com-ponents are identified. It is also the ideal time in which manu-facturing processes should be developed rather than at a later stage in the process as can frequently be the case. In today’s extremely competitive marketplace, design and process must be coordinated carefully to produce a best “first-time” solution.

Ideally, you will engage a CM partner you can trust with your design concepts and intellectual property early in the process. The CM should also practice the art of design for manufacturability (DFM), design for test (DFT) and design for service (DFS) early in the process — at the concept development and design stage — to provide you with valuable information about ways in which you can facilitate the manufacturing process and reduce costs.

An effective CM partner will have a high level of expertise and experience working with organizations like yours, enabling them to provide valuable insights at the design stage about materials, component availability and obsolescence potential, and manufac-turing practices that can save you time and money down the line.

2 PRODUCT LAUNCH Once your product is introduced to the marketplace, it will be met with consumer acceptance at varying levels — sometimes with little competition at the outset, and with

greater competition at the growth stage.

The supply chain should continue to be a priority at this stage. An effective CM partner will be proactive, looking ahead to determine whether there are potential pitfalls in your product’s future and researching the availability of components to ensure that they are available from a reliable source. They will also consider the risk of a part becoming obsolete during the manu-facturing phase.

3 GROWTH The growth stage is the point at which a product expands market share and experiences a period of increased sales and profitability, so it will be important to be able

to meet growing consumer demand. By having engaged the supply chain early in the product lifecycle, you will be better able to meet customer demands for on-time delivery and to provide high levels of customer service. Careful planning will help you keep pace with rising costs and take actions to prevent excessive shipping and inventory costs.

4 MATURITY At the maturity stage, competition for your product is on the rise while profit growth may be on the decline. This is often the stage at which your focus shifts to improve-

ments in design or the addition of features and benefits that can help expand your market share and your product’s lifecycle. Your CM partner can help you develop change processes and supply chain recommendations that will enable the most cost-effective redesign.

When your product reaches the stage at which the need for cus-tomer support decreases dramatically, you may also continue to need to provide services to existing customers. A proactive CM partner will have planned early in the process for maintaining the right levels of inventory for specific components and the level of support you will need at that stage.

Sale

s an

d Pr

ofit

Life (time)

Concept development & design

Concept development & design

GrowthGrowth MaturityMaturity End-of-lifeEnd-of-life

Contract Manufacturer EngagementContract Manufacturer Engagement

= Generation 1= Generation 2

Product launch

Product launch

Precision Sensing | Volume 1 | 15

The CM can also help you prepare for your prod-uct’s end of life by closely monitoring reductions in consumer demand in order to prevent having excess inventory on hand.

5 END OF LIFE Inevitably, a product reaches the decline stage — the point at which demand erodes and ends completely — often

due to replacement by a new version or intro-duction of a new and improved product. At this point, the remaining inventory of component parts must be managed carefully, with an ade-quate amount kept in reserve for sales support. The CM can work with you to make sure that all supply chain partners are informed about the product’s status in order to prevent unnecessary costs and waste.

CONCLUSION One of the best ways to ensure that you have done the best possible job of defining your product lifecycle requirements is to work closely with your CM partner at the outset of your product design through its entire lifecycle. An experienced CM will have knowledge about your industry that can help refine your product design and requirements, and they may even be in touch with trends and changes in other industries that could have an impact on your product and processes.

In addition, an effective CM partner will be an invaluable source of knowledge about the components and materials called for in your design and your supply chain. By working together from an early point in the design stage, you and your CM partner can develop requirements that will best support your prod-ucts and your customers.

At Sparton Corp., we provide end-to-end ser-vices for every stage of your product’s lifecycle — from inspiration to implementation. We offer holistic and flexible product design and devel-opment for breakthrough solutions, the Sparton Production System, logistics services from the production floor to the end customer and sup-port for aftermarket needs — from repair and spare parts to managed obsolescence.

Who’s doing product lifecycle management?

The list of industries that are adding value to their manufacturing processes by leveraging the benefits of product lifecycle management is growing:

❏ Aerospace & Defense

❏ Automotive

❏ Consumer Goods

❏ Education

❏ Energy

❏ Financial

❏ Food & Beverage

❏ Government

❏ Healthcare

❏ High Tech Electronics

❏ Industrial

❏ Medical Devices

❏ Pharmaceutical

Learn More

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PRODUCT LIFECYCLE MANAGEMENT

Precision Sensing | Volume 1 | 17

VIDEOS

SPARTON NAVEX PRODUCT OVERVIEW This short introduction video to see the precision inertial sensors offered by Sparton NavEx and some of their many potential applications.

AHRS-8 QUADCOPTER DEMONSTRATION The Sparton AHRS-8 inertial sensor system compensates for magnetic interference in a magnetically challenged environment.

IMU-10 INERTIAL MEASUREMENT UNIT In this video we discuss our Inertial Measurement Unit, the Sparton IMU-10. The IMU-10 is our ultimate sensing system, featuring 10 Degrees of Freedom and High Speed Synchronous sampling. For more information visit us at www.SpartonNavEx.com. Music by Mike Bagley & Harry Newhook, “Avarice”

GEDC-6E ROVER DEMONSTRATION The Sparton GEDC-6E inertial sensor system compen-sates for magnetic interference in a magnetically challenged environment.

Common issues with magnetic compasses By Richard Wheatley, Sparton Engineer

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COMMON ISSUES/PROBLEMS

MOST COMMON ISSUES WHEN USING A MAGNETIC COMPASSCalibration has long been a source of error in the eventual heading readings of a magnetic compass. With many sys-tems, the calibration is tedious and is often referred to as the “Chicken Dance” due to its complexity requiring the user to rotate to multiple positions while tilting the device upside-down. Most of the difficulty of these procedures lies in the fact that the user does not know which points are needed and which are not. In this case, there is the belief that a true and perfect calibration that will work best with all points if only these procedures are followed exactly. This is definitely not the case.

During the in-field calibration process, typically a system is required to rotate 360° in each of the three perpendicular planes: X/Y, Y/Z, and Z/X. A large number of devices will not actually be used in these specific pitch and roll orienta-tions, but they are required to reach the best solution for the spherical accuracy of the system. Some host devices can only move in limited pitch and roll ranges and therefore cannot afford a compass calibration that requires flipping the device upside down. Some devices are too heavy to be moved a great deal only to have the system remain relatively stationary during usage.

Sparton systems have been reliably tested to be accurate at >45° pitch and roll after only being calibrated at +/- 15° during the in-field calibration process. This limited pitch and roll sce-nario means that the user only has to calibrate our system in an environment that matches their system as close as possible.

INTEGRATION AND ALIGNMENTWhen integrating a magnetic compass into a product it can be difficult to find the ‘correct’ spot to minimize the magnetic distor-tions that can impact the sensors. There are many passive and active electronic components in most systems these days. Even in the systems where only passive components are used, not all of them will be utilized or turned on during the usage of the device. It is these time-varying fields that cause the most issues when the system is integrated.

Once the least magnetically disturbing location has been found, it can still be difficult to place the compass in an orientation that aligns with the host device’s X-Y-Z axes. If the system is not aligned properly, the heading/pitch/roll during static and dynamic situations will be compromised.

Sparton currently has three methods to align the systems: a simple boresight matrix, InvokeTare, and the azimuth/pitch/roll (APR) tare procedure.

› The boresight matrix is a simple rotation matrix held inside the compass that is only used on heading, pitch, and roll. This can be figured out mechanically ahead of time by the systems integrator.

› The InvokeTare procedure has the user align the system with a known magnetic North and has the end device placed flat and level. It is important to realize not to use the compass data to measure north and level during this

procedure since this procedure is used to align the compass with the host device.

› The APR tare procedure allows a user to point to any known heading, pitch, and roll with the host device to calibrate t he alignment.

These last two are typically used only when the true mechanical alignment may be too difficult to figure out.

KNOWING WHEN THINGS ARE OFFDuring and after in-field calibrationSelecting the magnetic calibration points is usually left to the compass manufacturer and requires a 4 to12-point calibration that includes flipping the device in odd orientations (the Chicken Dance) and usually gives a calibration score that is not readable by an end user. A typical calibration point selection procedure has the user point at 0°, 90°, 180°, 270° heading and -45°, 0°, 45° pitch during these procedures all while giving the unit from -30° to 30° of roll. Sometimes users are required to do three rotations implying the order of points taken matters in the data collection process.

Sparton systems outline a near-infinite number of calibrations: the standard 4-point North, South, East, West calibration, the 6-point maximum magnetic field on each axis calibration using the possible magnetic point quality factor, the icosahedron 12-point calibration, and the ability to perform limited pitch and roll calibrations and still achieve the desired accuracy.

After calibration and alignmentOnce the compass is aligned and calibrated inside the host device, everything is perfect right? Not really! Once the system is fielded, there will still be chances for external magnetic influ-ences to affect and distort heading. If there isn’t any information that the system is off, then the user has no idea that the heading will be incorrect.

Sparton sensors have the ability to tell the user when the system sees a magnetic anomaly and also when that environ-ment returns to normal. One can also use this data with external procedures to allow the user to find whether or not the com-pass needs to be recalibrated or when the device is near to an external magnetic anomaly that needs to be avoided.

CONCLUSIONMagnetic compasses provide accurate platform heading and attitude information in a variety of applications and in many operational environments. However, these devices are sus-ceptible to distortion with the presence of magnetic material. There are, however, techniques and best practices to minimize this risk to performance. The proper calibration of a device is critical in its performance capability. Where a device is imple-mented and how it is aligned into a system can further impact its performance. Continued monitoring of the environment and performance once in operation ensures the magnetic compass provides the best results possible. Manufacturers and users who adhere to these practices can better expect their magnetic compass to perform in otherwise challenging magnetic envi-ronments and applications.

Precision Sensing | Volume 1 | 19

An Attitude Heading and Reference System,

better known as an AHRS, is a 3-axis sensor

system that provides real-time 3-D attitude

position – pitch, roll, and heading. The primary

function then of an AHRS is to provide orientation

data. AHRS are designed to replace traditional

gyro-based instruments and to provide superior

reliability and accuracy.

Some of the many applications for AHRS include control and stabilization, measurement and correction, and navigation. An example of control and stabilization could be where a camera or antenna mounted on a system such as a plane or ship needs to be stable. Measurement and correction best applies to imaging systems where an AHRS is used to ensure the direction the imager is pointed. And in navigation, an AHRS can be used to provide orientation and direction.

AHRS consist of magnetometers, micro-electromechanical systems (MEMS) accelerometers, and MEMS gyroscopes on all three axes. In other words, a MEMS-based AHRS includes

What is an Attitude Heading and Reference System?

20 | Volume 1 | spar tonnavex.com

ATTITUDE HEADING AND REFERENCE SYSTEM

sensors for 3-axis magnetic, 3-axis acceleration, and 3-axis gyro. These sensors, combined with a built-in processor, create an inertial sensor system fully capable of measuring the atti-tude of objects in 3-D space.

The sensors in AHRS use algorithms to estimate this attitude in 3-D space. Some AHRS units will use traditional Kalman filter algorithms that use magnetic and acceleration measure-ments to estimate the time-varying gyro bias in real-time. Other AHRS systems utilize modified non-Kalman filters that compute an estimation of orientation in real-time. A potential advantage

of these modified algorithms is that they can outperform tra-ditional Kalman filter-based sensors by providing real-time optimization of performance for varying magnetic or dynamic operating environments.

Magnetometers are used in AHRS to measure the direction of the magnetic field at a point in space. A more traditional mag-netometer would be a fluxgate system. Though this technology provides good accuracy and reliability, it is not conducive to a MEMS-based AHRS due to its larger form size and greater power requirements. An alternative to fluxgate technology is a magneto-inductive (MI) sensing technology. Not only does this technology provide the desired smaller form factor and low power requirement, MI also provides very high resolution – higher than what competing technologies such as anisotropic magneto resistive (AMR) sensors can provide at similar cost.

Accelerometers measure proper acceleration – the rate at which the velocity of an object is changing. They measure the static (gravity) or dynamic (motion or vibration) acceleration forces of a given object. The ideal accelerometer in an AHRS provides long-term stability, low vibration error, and reliability.

AHRS demand very precise gyroscopes as the quality of these devices greatly impacts the overall performance of the inertial sensor system. An example of a very high-end gyroscope is a fiber optic gyroscope, commonly known as a FOG. FOGs pro-vide extremely precise rotational rate information due to their lack of moving parts. However, FOGs have a great deal of inherent development and manufacture costs as well as a larger form factor and higher power demands. As technology improves, MEMS-based gyroscopes have closed the performance gap on some FOGs. When factoring in lower cost and power require-ments, MEMS-based devices provide an excellent answer for the need of precision in a gyroscope.

MEMS-based Attitude and Heading Reference Systems (AHRS) continue to develop and improve in both technology and applica-tion. As the requirements of both military and commercial systems evolve, there is increasing demand for continuous improvement. Both existing systems and those in development must incorpo-rate size, weight, power, and cost (SWaP-C) standards. Simply put, demand will increasingly require systems and their compo-nents to be smaller, lighter, use less power, and all at a lower cost. AHRS are no different in this initiative. Manufacturers must adhere to these principles, all while improving the performance of AHRS. Manufacturers who fail to adjust to these demands will find themselves left behind.

THE SPARTON NAVEX AHRS-8Sparton Navigation and Exploration (Sparton NavEx) offers the AHRS-8 as a fully temperature compensated Attitude Heading and Reference System (AHRS), individually cali-brated over the -40 °C to +70 °C operating range. It delivers heading accuracy in a broad range of challenging dynamic and magnetic environments.

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Precision Sensing | Volume 1 | 21

Design considerations in the presence of magnetic fields

Greater processing power and the demand for

operator safety has driven a dramatic increase in

unmanned vehicle use.

Unmanned vehicles generally require some form of naviga-tion system that provides a heading reference. Traditional navigation heading solutions included magnetic compasses with mechanical gyroscopes, Global Positioning Systems (GPS), and inertial navigation systems. With the advent of Micro-Electro-Mechanical Systems (MEMS) sensor technology, the digital compass emerged as a leader in price-performance, offering a number of advantages to the designer as a method of providing and maintaining accurate heading. The benefits of a digital compass to a designer are many:

› Low cost — depending upon the application and heading accuracy required, digital compasses start as low as a few hundred dollars

› Small form factor and low mass — oday’s digital compasses can be well under two square inches and weigh as little as 25 grams.

› Low power requirement — depending on the application and heading accuracy requirements, digital compasses can operate at less than 50 mw of power

› Highly accurate — today’s digital compasses can provide heading accuracy in a static application environment after calibration to as low as 0.3 degrees RMS error

› No reliance on GPS to maintain heading — a digital compass relies on magnetometers to passively detect the Earth’s magnetic field to derive heading and does not rely on the presence of an active

› GPS signal — adaptable calibration for a variety of applications and environments. The digital compass is very versatile in that it can provide accurate heading in a large number of applications and environments.

Today’s digital compasses provide a practical solution to the chal-lenging needs of many unmanned applications. Digital compasses utilize magnetometers to measure the Earth’s magnetic field to pro-vide heading reference relative to magnetic north. As such, their accuracy is subject to degradation in the presence of magnetic interference. Therefore, magnetic materials should be kept away from a digital compass for best performance. In practice this may not always be possible, particularly if the unmanned vehicle passes through stray magnetic fields as part of its course of navigation.

UNMANNED VEHICLE DIGITAL COMPASS DESIGN CONSIDERATIONSDigital compasses should be mounted away from strong mag-netic fields or highly magnetic material. This includes close prox-imity to batteries, electric motors, and electric currents. Batteries typically contain a magnetic signature and electric motors gen-erate magnetic fields that will affect compass performance. It is recommended that these items be placed as far away as prac-tical from the digital compass.

Digital compasses should be calibrated in-house by the supplier to remove any magnetic anomalies associated with the compass itself and to ensure the product’s accuracy. Typically, the mag-netometers are calibrated at the factory in a Dycome and the gyroscopes are calibrated via a Rate Table.

The computer-controlled precision factory calibration corrects:

› Sensor offset and sensitivity › Sensor linearity › Axial misalignment in 3-Dimensions

The digital compass should also be calibrated in its environment of end use in the unmanned vehicle itself. Optimally, digital com-passes should come equipped with in-field calibration functions to help compensate for nearby magnetic material.

Digital compasses should compensate for both soft and hard iron interference. Hard iron anomalies are generated by ferrous (magnetized) materials and soft iron anomalies are produced by materials that while not magnetized, could still affect the mag-netometer’s ability to obtain an accurate heading reference by measurement of the Earth’s magnetic fields.

MAGNETIC INTERFERENCE COMPENSATION IN THE FIELDCorrecting the impact of magnetic field distortions on heading in unmanned vehicles in service is more challenging. The nature and strength of the magnetic anomalies that may be experienced as an unmanned vehicle passes in close proximity to magnetic mate-rial is unpredictable. These magnetic effects may momentarily degrade heading accuracy. The degree of degradation will vary depending on the distance to and quantity of the ferrous material:

› Amount and shape of the magnetic material › Location and orientation relative to compass › The degree of magnetization (which can change over time) › Uniformity of the magnetization across the material

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MAGNETIC FIELDS

Digital compass designs must compensate for these magnetic disturbances. This is accomplished by in-field calibration and the utilization of gyroscopes to augment the traditional digital com-pass design.

IN-FIELD CALIBRATIONIn-field calibration algorithms enable unmanned vehicles to maintain heading accuracy. When the compass is mounted in the user’s application, any magnetic material (screws, brackets, components, etc) will affect the compass accuracy if not com-pensated. In-field calibration is required to remove many of these interferences. The digital compass should provide calibration capability in full 3-dimensions.

Ideally, digital compasses should constantly monitor the mag-netic field conditions and automatically calibrate for hard and soft magnetic distortions as the product is used. Since the magnetic environment in which the compass is used is typically unpre-dictable in many situations, it can make continuous calibrations unreliable. It is therefore more desirable to have the end-user control the calibration process to insure that the environment has minimal impact to the calibration process. During a typical in-field calibration, the end-user will orient their product, which contains a digital compass, in different positions and then command the compass to sample the magnetic field conditions at each orien-tation. Up to twelve magnetic measurements are taken to allow the compass to learn the distortions within the product and com-pensate for them. The in-field calibration algorithm will adjust the magnetic offsets and scaling so that all of the magnetic mea-surements are spherical under all rotations. These offsets and scaling parameters are saved and used in normal operation. Any significant modifications to the vehicle after the compass has been calibrated like installation of new hardware, batteries changed, etc., may require the compass to be recalibrated.

GYROSCOPE DIGITAL COMPASS ENHANCEMENTThe magnetometers utilized in the digital compass design are prone to error when exposed to magnetic interference. Forms of magnetic interference include stray magnetic fields in the path of the unmanned vehicle or from internal transient mag-netic effects from power cables or electric motors under varying operating conditions.

Errors from the presence of these stray magnetic fields expe-rienced during the operation of unmanned vehicles can be improved by adding gyroscopes to the digital compass design. Typical gyroscopes used in this application are MEMS devices. Tri-axial angular rate sensors measure rotation rates around three orthogonal axes (X, Y, and Z). These gyroscopes give more information about how the compass is moving so it can properly compensate and provide a more stable heading, pitch, and roll in the presence of spurious magnetic interference. A smart sensor fusion algorithm is typically used to combine the magnetometer, accelerometer, and gyro measurements into an accurate orientation output. Disturbances in the magnetometer measurements are not typically reflected in the accelerometer and gyro measurements. The sensor fusion algorithm looks for these differences and weights the sensors accordingly to ensure that the compass, and vehicle, stays on course.

Accelerometers used as tilt sensors are included in digital com-pass designs to compensate for the relative orientation of the magnetometers that measure the Earth’s magnetic fields to pro-vide heading. The accelerometers are affected by acceleration due to motion, especially linear motion. An added benefit of the gyroscopes is that since they measure angular rates in X, Y, and Z, they can also be used to overcome the disturbances of motion in the accelerometers. Gyroscopes only provide a relative measure-ment in that if the compass is not rotating, the gyroscopes out-puts are zero. Therefore, the compass relies more heavily on the gyroscopes and magnetometers during periods of motion and the accelerometers and magnetometers during periods of rest. Similar to magnetic disturbances, disturbances in linear acceleration are not typically reflected in the magnetometer and gyro measure-ments. The sensor fusion algorithm can therefore detect these disturbances and adapt to them to keep the compass orientation output from being affected.

CONCLUSIONIn summary, operating environments can adversely affect magnetic compasses. Time- varying magnetic fields may degrade compass performance. Integration of a digital compass requires a degree of application specific engineering to ensure the best possible accuracy is gained from the digital compass.

The Dycome

The Rate Rable

Precision Sensing | Volume 1 | 23

Laser Targeting

In situations where precision is an absolute must, Sparton delivers the inertial sensor systems that can be trusted time and time again. Our products have been built to improve on today’s product standards with even greater performance than is required for tomorrow’s laser targeting systems.

Targeting systems require maximum accuracy at all times and under all conditions. Whether hand-held or mounted on tri-pods, vehicles, or weapons the system must perform reliably and con-sistently to meet the needs of today’s warfighter.

Heading and azimuth angle are vital components for accurate targeting. The complex nature of targeting systems presents significant challenges to obtaining maximum accuracy reliably, quickly, and repeatedly. Magnetic disturbances, whether pro-duced by external sources or internal components of the system, cause errors in the output of conventional digital magnetic com-passes (DMCs).

A complete system integrating MEMS inertial sensors, magne-tometers, and algorithms to process and manage sensor data is required to overcome the difficulties of this complex application. All this must be accomplished in a small, lightweight package with minimum power consumption.

Unmanned Systems

Unmanned vehicles continue to impress with rapid advances in technology that make these vehicles suitable for military and commercial use. The inertial sensor is a critical component for unmanned operation success and Sparton is lock step in the rapid development of sensor systems technologies for air, sea, and ground.

Whether it swims, crawls, or flies navigation systems are critical for performance of unmanned vehicles. These systems sup-port complex functions such as surveillance, reconnaissance, vehicle tracking, hazardous material disposal, and many military/defense applications. In harsh environments or when GPS is not available (denied or comprised) it is vital to maintain accurate heading and orientation of the unmanned vehicle.

Conventional navigation solutions take up large amounts of space, are costly, heavy, and have high power consumption. Transient magnetic disturbances can induce heading errors compromising performance.

Applications requiring the highest degree of precision trust Sparton as their go-to solution for inertial

sensor systems. The entire product family, from inertial measurement units (IMU) to attitude heading

reference systems (AHRS), performs to task for the toughest, most ruggedized solutions. Stemming from

our roots in government contracting, the Sparton suite of products are unmatched for critical solutions

such as laser targeting, satellite communications, unmanned vehicles, and oil and gas exploration.

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24 | Volume 1 | spar tonnavex.com

SOLUTIONS

Communications Positioning

Panning the sky in search for satellite signals takes on a whole new meaning in urgent conditions when time is of the essence. Getting your connections established in short order requires absolute accuracy — accuracy that can only be delivered by Sparton’s inertial sensor systems.

Whether your product is intended to be used in defense or civilian applications, the performance of today’s leading edge communication systems are demanding efficient, reliable and accurate antenna positioning. In either portable or permanent system installations, RF and SATCOM systems require high antenna pointing accuracy at all times and under extreme envi-ronmental conditions.

Azimuth and elevation angles are vital components for accu-rate antenna positioning and optimum system performance. The complex nature of communication systems presents significant challenges to obtaining maximum accuracy- reliably, quickly, and repeatedly. Manual antenna pointing and alignment can be cum-bersome and time consuming for your customer. Since most sys-tems measure the Earth’s horizontal magnetic field to determine heading, unwanted magnetic disturbances, whether intrinsically produced by hard and soft iron components on the antenna plat-form, or from transient external sources cause errors in the heading output of conventional analog or digital magnetic compasses.

A complete system integrating MEMS inertial sensors, mag-netometers, and algorithms to process and manage sensor data is required to overcome the difficulties of this challenging application. For many applications this must be accomplished cost effectively within a small, lightweight package with minimal power demands on the system.

Exploration and Surveying

Exploring the vast ocean floor for oil and gas opportunities is a daunting task. Sparton’s inertial sensor product offerings help produce the critical accuracy needed to survey, collect, and ana-lyze the sea floor to mine these natural resources.

The performance of today’s leading edge towed seismic streamer systems and bottom mounted arrays are demanding more efficient, reliable, and accurate cable navigation and posi-tioning. In seismic system installations, these systems require high heading and attitude accuracy real-time and under extreme ocean conditions.

Precise and real-time measurements of heading, pitch, and roll angles along the array cables are valuable output data for accurate seismic streamer navigation, positioning and survey performance. The complex nature of dynamic seismic sub-bottom profiling and imaging systems presents significant technical challenges, requiring maximum sensor accuracy - reliably, quickly, and repeatedly. Seismic data collection is costly and time consuming. Oil and gas geophysical explo-ration customers are increasing demands for better survey data quality.

A complete system integrating MEMS inertial sensors, mag-netometers, and algorithms to process and manage sensor data is required to overcome this challenging application. More accurate streamer positioning and navigation results in enhanced, higher resolution image processing from the ship’s survey. For seismic streamers and in-water ancillary equip-ment this must be accomplished cost effectively within a small, lightweight package with minimal power demands on the data acquisition system.

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Precision Sensing | Volume 1 | 25

Fully temperature compensated, the AHRS-8 is individually calibrated for industry-leading heading accuracy. Our AdaptNav II™ algorithm provides accurate in-field calibration, while the NorthTek™ Development System makes it the world’s only fully programmable inertial system.

› Integrated AdaptNav II™ provides real-time noise characterization and active gyro drift compensation for superior heading, pitch and roll performance in electrically and mechanically noisy environments

› Fully temperature compensated over the entire operating range, individually calibrated from -40° to +70° C

› Powerful user programmable sensor customization apps via NorthTek™ Forth interpreter

› 2-D and 3-D adaptive in-field cal providing hard and soft magnetic interference compensation

› Advanced sensing technology (3-axis magnetic, 3-axis MEMS acceleration, and 3-axis MEMS gyro)

› Selectable 4g or 8g accelerometer ranges, suitable for highly dynamic application environments

› Magnetic and True North heading (yaw), pitch, and roll measurement

› Full 360° rollover capability › Low power consumption and power management (Sleep

Mode) functionality › Supports multiple communication protocols › In-field calibration point selection and distribution indicator › Quality of in-field calibration indicator › Centripetal acceleration correction

Harsh environmental conditions, extreme magnetic interference, mechanical shock and transient platform vibrations all contribute to the challenge of high accuracy inertial sensing and platform attitude reporting. Sparton’s IMU-10 inertial sensing system thrives in such environments and provides end-users with a reli-able high-performance, high-accuracy 10DOF inertial sensing package in a ruggedized enclosure.

› 10DOF High Performance Inertial Measurement Unit (IMU) › Advanced Micro Electro-Mechanical (MEMS) sensing

technology (3-axis magnetic, 3-axis acceleration, 3-axis gyro and Barometer)

› 40 kHz accel/gyro (all simultaneous) data sampling filtered to 2 kHz

› Coning/sculling compensation of 2 kHz data down to customer defined rate

› Customizable on-board high speed digital filtering › High Speed UART interface (user selectable up to 1MBaud) › High speed data logging capability to off-board µSD card › Ruggedized, shockproof design with proprietary seals that

allow barometric pressure sensing combined with IP67 performance

› Low latency and consistent latency between data collection and data output

› Powerful user programmable customizations via NorthTek™ Forth interpreter

› Supports multiple communication protocols › Full 360° rollover capability

AHRS-8 IMU-10

26 | Volume 1 | spar tonnavex.com

PRODUCTS

By eliminating nearly all external magnetic disturbances that affect heading accuracy, the Sparton GEDC-6E AHRS provides highly dynamic response features combined with long-term sta-bility and accuracy. An enhanced version of our GEDC-6, it has a faster start-up time and in-field calibration convergence.

› Integrated AdaptNav II™ adaptive algorithms provide realtime optimization of sensor performance when used in environments prone to mechanical vibrations and gyro saturation

› 2-D and 3-D adaptive in-field cal providing hard and soft magnetic interference compensation

› High dynamic heading accuracy enhanced by use of gyroscopes and fast sampling rate

› Simple 2-wire serial (UART) interface (3.3V logic level) with user-selectable baud rate

› Advanced sensing technology (3-axis magnetic, 3-axis MEMS acceleration, and 3-axis MEMS gyro)

› Built-in World Magnetic Model for accurate True North › Rugged (epoxy encapsulated) construction and small

physical size › Magnetic and True North heading (yaw), pitch, and roll

measurement › Low power consumption and power management (Sleep

mode) functionality › NorthTek™ enabled › Full 360° rollover capability › In-field calibration point selection and distribution indicator › Quality of in-field calibration indicator

Incorporating next generation software to enable optimized performance, the DC-4E with 6 DOF offers improved in-field calibration and reduced start-up time. Its best-in-class reliability and accuracy provides 3-D absolute magnetic field measure-ment and full 360° tilt-compensated heading, pitch, and roll data.10DOF High Performance Inertial Measurement Unit (IMU)

› 2-D and 3-D adaptive in-field calibration providing hard and soft magnetic interference compensation

› Simple 2-wire serial (UART) interface (3.3V logic level) with user-selectable baud rate

› Built-in World Magnetic Model for accurate True North › Advanced sensing technology (3-axis magnetic, 3-axis

MEMS acceleration) › Magnetic and True North heading (yaw), pitch, and roll

measurement › Low power consumption and power management (Sleep

Mode) functionality › Powerful user programmable customizations via NorthTek™

Forth interpreter › Industry leading static accuracy and resolution › Rugged (epoxy encapsulated) construction › Supports multiple communication protocols › Full 360° roll-over capability › Small physical size › In-field calibration point selection and distribution indicator › Quality of in-field calibration indicator

GEDC-6E DC-4E

Precision Sensing | Volume 1 | 27

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