Electric aircraft and the promise of autonomous air taxis are advancing quickly. Aerospace original equipment manufacturers (OEMs) and their supply chain partners face intense pressure to be first to market with a safe and reliable product. Many practices that worked 20 years ago no longer suffice due to today’s complexities and challenges. Therefore, OEMs are rethinking their approach to product development, which begins with systems engineering. As companies explore the tradeoffs between hundreds of design configurations and prepare for the challenges of certifying electric aircraft, systems engineering is critical to their success.

Companies often struggle with the complexity of autonomous systems, flight controls, and system integration when relying on document-centric processes for systems engineering. Requirements might be in one database, spreadsheet, or document while system modeling might be in Microsoft Visio or SysML. System safety analysis might be spread across a variety of tools. Verification and test data often end up in yet another spreadsheet. Everything is disconnected, often occurring in isolated work silos. In the rapidly evolving area of future-forward aircraft, as new requirements and system architectures are established, these document-centric approaches don’t scale, and it’s nearly impossible to manage traceability when trying to address thousands of systems interactions.

A digitalized approach that connects all aspects of concept, design, manufacturing, and maintenance is the answer.

MBSE in electric aircraft

Companies leading the way in developing electric aircraft realize the importance of model-based systems engineering (MBSE), which is growing in popularity because of its disciplined approach to systems engineering. It brings a new level of integration and efficiency to complex systems and processes across many multi-domain challenges future-forward aircraft manufacturers confront. When companies move to MBSE they collaborate more easily across domains and throughout the entire supply chain.

The MBSE approach is more than functional or logical modeling. It serves as the digital backbone that unites engineering, manufacturing, supply chain, and program management activities to create a comprehensive digital thread – a composite of interwoven and interconnected digital strands, creating an ecosystem for program execution excellence.

MBSE can satisfy electric aircraft manufacturers with:

Support for the entire lifecycle of product development – MBSE allows teams to troubleshoot, explore, and pinpoint the ideal outcome. Because of the MBSE digital thread, what happens in one domain gets shared throughout the entire product lifecycle. For example, the electric motor is different from the traditional turbine engine. The center of gravity is in a different location and has a different weight. Before the engine is installed on an aircraft, engineers must consider the weight and balance trade-offs, and how they will impact downstream activities.

Another challenge is to determine where to place the batteries as they add significant weight to an all-electric aircraft. Using MBSE allows teams to purposefully design and build around a structure that includes increased electrification. Batteries, and more importantly power density, are key design challenges in an electric aircraft (Figure 1, below). As these challenges are met, product risk is lowered and certification becomes easier.

Certification – Increasingly, MBSE is gaining widespread use as companies seek to certify more complex and highly integrated systems. The Federal Aviation Agency (FAA), the European Union Aviation Safety Agency (EASA), along with other regulatory agencies are requiring more organized systems engineering for OEMs and their partners. The U.S. Department of Defense (DOD) also recognizes the need for MBSE to communicate requirements more effectively to the OEMs and have a process in place to check that all requirements have been satisfied. A robust MBSE digital thread enables companies to accelerate their product development and certification processes, while improving communications with various regulatory agencies.

And it’s not just an electric aircraft’s propulsion system that’s different, it’s the entire vehicle configuration. There are FAA rules for fixed-wing aircraft, rotorcraft, and tilt-rotors – all adding another layer of complexity to the certification requirements – which makes MBSE critical in aircraft certification.

Managing the product architecture – Product architecture needs to ensure OEMs are managing all product interfaces, including the electrical system, flight control system, and propulsion system. All these functions represent interfaces that must be managed. With MBSE, teams have a good process for managing requirements and tying together the project’s models. This also gives the OEM a good verification plan. Engineers can verify at the component level, the subsystem level, and at the aircraft level knowing all requirements have been satisfied. An MBSE digital thread connects requirements to model, design, analysis, and ultimately, to verification processes and artifacts. Automating these data hand-offs with a digital thread provides full traceability. Other key areas include thermal management and addressing electromagnetic interference.

Embracing digital transformation

An MBSE digital thread connects multiple domains within the digital enterprise. In addition to an MBSE digital thread, there are digital threads from each essential domain. Through the tight integration of an MBSE digital thread, teams from all domains can test and push the boundaries without jeopardizing downstream work or timelines. When companies transition from system modeling to using a digital thread, they can use any system modeling tool and connect to the entire data and information lifecycle to certify, deliver, and maintain new products. From the conceptual design through to service, all pertinent data needs to be easily accessible by a comprehensive digital thread, and it should be built on a flexible and open ecosystem that can accommodate various tools for requirements and system modeling while ensuring customers can carry their architecture and legacy tools forward as they develop their MBSE capability.

Making the move

Many in the industry believe requirements engineering or system modeling is MBSE. To some extent this is true, but MBSE is also system safety, software engineering, verification – all linked closely to product design, optimization, manufacturing, and product support. Aerospace companies involved in electric aircraft are implementing the Siemens MBSE digital thread to accelerate product development and be first to market. They are moving faster than the competition and are meeting program budget guidelines. They are reducing the risk of design changes. When there is a change, they have a better understanding of how to make that change and how to deal with the ripple effects that could follow. MBSE is the right choice to lead our industry forward.

Siemens Digital Industries Software

About the author: Dale Tutt is the vice president of aerospace and defense industry for Siemens Digital Industries Software. He can be reached at dale.tutt@siemens.com.

The 2018 strategic summary of U.S. defense priorities highlighted elements of defense planning that must adapt to cope with changing global realities. One of the key aspects is a shift from large, centralized infrastructure to “smaller, dispersed, resilient, adaptive basing” with the capability to “deploy, survive, operate, maneuver, and regenerate.” Maintaining force readiness under these distributed operational conditions is a logistical challenge, particularly the task of supplying spare parts for diversified forces. A comparable task presents itself in commercial aviation.

Additive manufacturing (AM) addresses that challenge by providing flexibility: a Supply Chain to the Edge™. AM that can produce a significant range of spare parts would replace the logistical challenge of maintaining a large inventory of unique parts with the relatively straightforward task of ensuring an adequate supply of raw materials. To date, AM has been too limited to fulfill that role, but the high-power blue industrial laser is pushing AM to fulfill its promise at the edge of the supply chain.

The new power of blue

When introduced, AM was primarily valued for its ability to produce plastic parts to check form, fit, and function. The technology rapidly matured with various techniques demonstrating the capability to fabricate metal parts, and laser-based methods are prized for the ease and accuracy with which they deliver energy to a target material. Unfortunately, traditional industrial lasers are absorbed poorly by industrially important metals. For 3D printing, that translates to limited speed, small production volumes, low part density, and high part cost – blue laser fixes all of that.

Copper, aluminum, stainless steel, nickel, titanium, and other metals absorb blue light better than other wavelengths, and not by a slim margin: copper absorbs blue 13x better than it absorbs infrared (IR) wavelengths. The first high-power blue industrial laser was released in 2017, and it leveraged that fundamental physical advantage to quickly make its mark in materials processing applications.

For example, the absorption advantage leads to performance benefits for copper welding. Blue welds copper 10x faster than IR. Poor IR absorption also leads to quality problems – material spatter and residual holes that degrade the mechanical and electrical integrity of the finished parts. Blue isn’t just faster than IR, it also eliminates those defects. Because other metals also absorb blue light well, the blue laser addresses the difficulty of joining dissimilar metals with quality and speed.

The same features that lead to blue’s welding performance also led to improved performance in AM, which is fundamentally the same fusing process. Blue fabricates parts faster, its low spattering leads to high-density parts, and it produces parts from dissimilar metals – a problem for alternative fabrication methods.

After initial successes welding stacks of thin copper foils, blue laser welding rapidly progressed to applications such as joining stainless steel battery casings, connecting hairpin windings in efficient electric motors, and high-volume production of components essential for cooling the electronics of 5G smartphones. That rapid progression was the result of two parallel developments: refinement of process parameters by applications engineers and continued technological advances in the capabilities of blue lasers. The technology continues to improve (see sidebar) and its impact on AM is poised to follow that same rapid trajectory.

Independent laboratory tests demonstrate that a moderate power blue laser is faster than a much higher power IR laser for metal deposition. Tests have also shown how blue can produce dense structures of copper, steel, and other metals larger than those previously produced by AM. Those early demonstrations all hinge on higher absorption at blue wavelengths.

Although laser-based AM methods vary in their details, they all require heating metals to the point where they fuse. As in welding, the key is to transfer energy from the beam to the metal. The more efficiently that can be done, the faster the process will be and the higher the quality of the finished parts. With copper, for example, reflecting more than 90% of the incident IR radiation, the efficiency is low, and the reflected light can damage the optics in the AM apparatus. Early investigations with blue have demonstrated that its productivity has greater magnitude than IR.

The latest advances in blue laser technology will enhance performance even more. If equivalent blue and IR beams each transmit through an identical lens, the blue spot will be less than half the size of the IR. That also means that a blue laser can produce the same size spot as an IR laser nearly 2.5x further away from the lens. For AM, that translates to a fabrication volume 10x larger than possible with IR.

Supply chain implications

Although blue laser is in its infancy, experience with welding and early investigations demonstrate the scope of the future evolution. The high-power blue laser enables:

• 10x faster speed
• 10x larger build volume
• Greater part density
• Accessibility to additional metals
• Ability to produce bimetallic parts

These all lead to low-cost, volume manufacturing of customized parts.

Blue laser AM will simplify the logistics of supporting deployed military forces and civil aviation fleets, while simultaneously lowering costs, bringing maximum value and flexibility, and pushing the supply chain to the edge.

Nuburu Inc.

About the authors: Jean-Michel Pelaprat is co-founder and chief marketing & sales officer and Mark Zediker is co-founder and chairman of the board at Nuburu. Reach them at jmp@nuburu.net.

Recent advancements in test and measurement capability and related architecture have allowed oscilloscopes to expand into the radio frequency (RF) domain and RF analysis.

The Keysight UXR oscilloscope can simultaneously sample up to 256 Giga-samples per second (GSa/s) on 4 channels, allowing for a functional RF frequency range/bandwidth up to 110GHz. This capability, combined with the performance of a 10-bit analog to digital converter (ADC), allows the UXR to be considered for RF measurements across the spectrum.

However, with such high sample rates, one must pay attention to the memory usage since most oscilloscopes have limited on-board memory. Segmented memory and digital down conversion techniques play an important role in memory efficiency by making meaningful measurements.

Memory efficiency techniques

Segmented memory – Real-time oscilloscopes make repetitive measurements via an external trigger signal to define an event of interest. Triggering makes meaningful visual measurements that allow the user to see an event of interest based on the trigger criteria.

While this visualization technique doesn’t provide enough memory efficiency for radar pulse analysis, the use of an external trigger for a segmented capture does. Segmented capture allows the user to define the length of a capture interval in terms of samples or seconds along with the number of segments. This enables the user to capture short events of interest of similar length, using the onboard capture memory for meaningful information that meets the user’s criteria.

Real-time digital down conversion – The ultra-high sampling rate of modern real-time oscilloscopes is a strength and weakness. On the one hand, ultra-high sampling rates directly capture signals with very high carrier frequencies and wide modulation bandwidths. However, exceptionally high sample rates also consume the onboard memory blazingly fast, reducing the amount of time for capture.

Digital down conversion (DDC) is a relatively common technique used in digitizers that’s made its way into modern digital oscilloscopes. Within the field-programmable gate arrays (FPGAs) and application-specific integrated circuits (ASICs) of the UXR oscilloscope, users can selectively define a center frequency and bandwidth for a measurement, instead of having to directly sample at 2.5x, the highest frequency component of a signal of interest to satisfy the Nyquist frequency (or folding frequency). DDC allows the functional reduction of sample rate from tens to hundreds of GSa/s to hundreds to thousands of MSa/s, enabling the user to capture a longer signal of interest.

Combining segmented capture with DDC allows users to go from capturing a pulsed RF signal over milliseconds, in hope there’s enough information to determine the correct operation of a device, to acquiring pulses over tens to hundreds of seconds to show operation of a system under test.

Measuring challenging signals

Modern radar/electronic warfare (EW) signals are more diverse than past signals. Frequency agility, low probability of intercept (LPI), wider bandwidth, and staggered pulse repetition intervals (PRIs) present measurement challenges because one must now capture pulses over a longer time to see a radar mode or electronic attack (EA) system under test technique to ensure they’re operating correctly. With signals from a technique lasting 30 seconds or more, combined with wider bandwidths, the challenge to effectively capture, analyze, and report results is even more critical.

Theory in practice

Using the Keysight UXR0334A oscilloscope and the 89600 PathWave Vector Signal Analysis (VSA) software, we can visualize the efficiency gains from segmented memory and digital down conversion. In the case below, we will capture and analyze a pulse radar signal of interest with the following parameters:

• Center frequency (CF)= 20GHz
• Pulse repetition interval (PRI) = 1ms
• Pulse width (PW) = 1µs
• Duty cycle = 0.1%
• Calculated with N7660C multiple emitter scenario generation (MESG) application scenario

Measurement setup 1 – Direct full sample rate We start the test by running the scope at a full 128GSa/s sample rate and under control by the VSA software. This sample rate satisfies Nyquist given the center frequency of 20GHz (i.e. 20e9 *2 = 40 e9 Samples/second). At this sample rate, we can use 800MSa of onboard memory to capture seven pulses of our signal or a 6.25ms acquisition as shown in Figure 1 (see page 24).

This length of capture provides some insight to our example signal; however, it would be difficult to provide insights into long-term pulse stability or proper operation throughout part or all of a scenario. By reducing the sample rate to 64GSa/s, the 20GHz signals can still be captured, but with twice the number of pulses. However, 14 captured pulses are still not enough to verify a pulse radar signal scenario.

Measurement setup 2: Introducing segmented capture – With a 64GSa/s user setup sample rate, we can now attempt to become more efficient with the oscilloscope memory by using the segmented UXR’s capture feature. In this case, we choose a 1.2µs segment length since our pulses of interest are 1µs long. Given the known PRI of 1ms and the pulse width of 1µs, by capturing a segment length of 1.2µs and not saving samples during the off time of the pulsed RF signal, we can greatly increase memory efficiency.

The segmented capture capability allows for acquisition of up to 6,722 segments/pulses, which results in RF pulse capture >6.7s of target activity time. Compared to the initial 6.25ms, the 6.7s capture has more than a 1,000x increase in capture length, as shown in Figure 2 (see page 24).

Measurement setup 3: Segmented capture + digital down conversion – Finally, we can incorporate real-time DDC combined with segmented capture to achieve pulse capture across the longest target activity time. Instead of requiring a sample rate based on the center frequency of the signal, we only need to account for the desired capture bandwidth, which in this case would be about 400MHz to capture the signal modulation on the carrier. This allows us to set a sample rate of 800MSa/s on the UXR, capturing more than 70,000 segments/pulses for a total logical capture length of more than 70 seconds (see Figure 3, page 26). Now we can view RF pulses across the course of a typical scenario.

EA, RGPO jamming example

One fundamental technique of jamming against a radar to prevent it from successfully tracking a target is called range gate pull off (RGPO). Consider a situation where an electronic attack (EA) system aboard an aircraft needs to jam a surface-to-air missile radar to prevent the missile from launching or being guided to the aircraft. In this example, we’ll say the distance from the missile launch point to the aircraft is 10km. It would be reasonable to assume that it’ll take approximately 20 seconds for the missile to reach that distance – an important time frame to capture pulses.

With the RGPO, the aircraft EA system listens to the missile radar, and then exploits the range gates in the radar tracking system by creating false radar return signals. The jammer signals received at the radar receiver are larger than the real radar RF pulse reflections, possibly 10dB to 20dB larger, and slowly move away from the location of the real reflections (see Figure 4, page 26). This causes the range gates in the radar receiver to get pulled off from tracking the real reflections and fooled into tracking the false echo jamming signals. Then the jammer pulses vanish causing the radar to break its track.

There is a cycle of:

• RGPO, radar breaks track
• Radar back to search mode
• Radar re-acquires
• Radar tracks again, then the cycle repeats

RGPO example

A reasonable scenario example would include 1µsec wide radar pulses and a jammer that creates 1µsec wide false echo RF pulses, which pull from real radar echo signals by around 10µsec across a 10 second period (see Figure 5, page 27). To increase range resolution, pulses have a 400MHz wide chirp. The carrier frequency is 30GHz and PRI is 1msec.

RF pulse capture requirements

To effectively evaluate the jammer RGPO operation, the goal is to capture every radar reflection pulse and jammer pulse over multiple RGPO 10-second cycles. Using full, 128GSa/s sampling, with or without segmented capture, isn’t adequate to capture pulses over one RGPO cycle. Plus, a 5µsec trigger rearm time complicates the use of fixed segments due to missed pulses during the rearm dead time.

Variable width segmented capture

A better approach is to use variable width segmented capture with real-time digital down conversion, where an IF trigger senses when a signal is present and only stores samples into segments when it’s present. This eliminates dead time in between pulses and maximizes memory use. Now 800MSa/s in-phase and quadrature-phase (I and Q) data for 640MHz bandwidth to capture the modulation riding on the carrier can be used, extending the oscilloscope memory.

Total scenario time, including potential missile flying time where RF pulses can be captured, has increased significantly. VSA software, with the BHQ radar pulse option, can capture 83,000 pulses in record mode which equates to around 50 seconds of scenario time, more than enough to analyze the 20-second missile flying time as well as multiple 10-second-long cycles of the RGPO engagement including interaction prior to launch. This capture and analysis, shown in Figure 6 (see pages 28-29), includes RGPO process verification by displaying PRI in Trace D.

Conclusion

Modern day real-time oscilloscopes such as the Keysight UXR, allow for exceptional performance with the direct sampling of signals up to 110GHz. The combination of this raw performance with segmented capture and digital down conversion allow for greater insights into signals of interest and long-term trends.

Keysight Technologies (Aerospace & Defense)

About the authors: Brad Frieden, factory application engineer for Keysight’s Aerospace and Defense group, focuses on calibration and use of UXG signal generators in multi-port electronic warfare threat emulation systems. Philip Gresock, solution planner for Keysight’s Aerospace and Defense group, focuses on high performance radar and EW signal analysis platforms and measurement techniques.

Family-owned gear cutting shop Boulevard Machine & Gear was founded in 1954 to serve the Pioneer Valley, a hub for the paper industry in Massachusetts. Throughout the years, with various family members in charge, the company transitioned to primarily serving the aerospace and defense industries. In 2006, Susan Kasa acquired the company and transformed it into the versatile manufacturing facility it is today.

While Susan’s focus was to grow the company and have it become more efficient, Boulevard Machine’s staff started to notice they’d have some issues completing certain jobs with their conventional side-lock-and-collet tool holders. They immediately reached out to Lindco Springfield Sales Engineer Jim Roberts to see if he could guide them to a solution.

“Boulevard wanted to run more accurately with tooling and extend tool life,” Roberts explains. “I immediately recommended they take a look at the Haimer product offering.”

After seeing some of the benefits firsthand, Boulevard Machine decided to take the plunge and invest in Haimer products – a Power Clamp Special Edition shrink-fit machine, Standard Shrink chucks, and Power Shrink chucks and extensions, with the help of Haimer USA Regional Sales Manager Mike O’Connor.

Based on its high gripping torque and 360° clamping around the cutting tool, Haimer shrink-fit technology provides superior gripping torque and allows for excellent runout accuracy, balance repeatability, and consistent clamping. Boulevard Machine now has a wide assortment of CAT40 and HSK-63 holders in Power and Standard shrink, along with the extensions.

Since switching to the heat-shrink holders, machinists noticed they were able to pick up their feeds and speeds as well. They cut 750ipm with the 3/4" Haimer Ultra Short Power Shrink HSK-63 holder. Before, they could only cut 300ipm in the same material.

“We have more than doubled our feeds with the Haimer Ultra Short Power Shrink,” CNC Programmer Kristian Kasa explains. “It’s our go-to holder for roughing. It keeps our projection length short, which gives us much more rigidity than a conventional side lock or milling chuck.”

Boulevard Machine is now doing as many 5-axis jobs as they do 3- or 4-axis jobs, whether it’s 3+2 or 5-axis simultaneously. The Haimer Power Mini shrink-fit holders and shrink-fit extensions help access all the hard-to-reach areas easily.

“We’ve had extensions stacked into Haimer basic holders with more than 10" of projection with as little as 0.0002" runout,” Kristian says. “Without these holders, we wouldn’t be able to machine a large amount of the jobs through the shop.”

For Boulevard Machine, it was an easy decision to purchase and invest in Haimer technology. When Susan acquired the company, she decided to modernize it by reinvesting between 20% and 30% of its yearly revenue into capital equipment. The reason for this was to innovate for the current workforce and for the next generation of machinists joining the team.

“We work closely with our programmers and engineers to make sure that what we’re implementing and using is making their jobs as easy and efficient as possible,” Susan explains. “Having the Haimer technology and staying up to date with everything else, our team is no longer hesitant about quoting or taking jobs, and they have the confidence to do any task because of the sophisticated technology.”

Like Haimer, Boulevard Machine keeps employees at the center of their company and strives to produce high-quality products every time.

After successfully implementing Haimer and other technologies, Boulevard Machine quickly outgrew their footprint and decided to move to a larger, state-of-the-art facility in Westfield, Massachusetts.

“It really has increased productivity and energized the employees to be in this bright, new building,” Susan relates. “We’ve even hosted visits for people interested in the Haimer technology. Honestly, a lot of our success has come from collaboration, especially between us, Lindco Springfield, and Haimer.”

Kristian adds, “I would recommend Haimer to anybody who might not even be struggling. Just test it and see how much more you can push your machine and increase productivity.”

Boulevard Machine & Gear

Haimer USA

Lindco Springfield