Army 18. 1 Small Business Innovation Research (sbir) Proposal Submission Instructions

Increased versatility of AM in the RF design space requires high dielectric substrates. AM filaments with dielectric constants greater than 4 are not commercially available. However, techniques exist to extrude AM filaments [3] from polymer/ceramic composites with high dielectric constants [4-6]. The process disperses high dielectric ceramic particles into a polymer substrate where the volume fraction of ceramic particles to polymer matrix determines the dielectric constant of the filament [5,7]. These filaments are generally not characterized below X-band frequencies, and the dielectric constant of the printed substrate can deviate from that of the filament. Characterization of complex permittivity of printed dielectric substrates is paramount to this SBIR effort.

AM of RF and multi-material structures have hurdles to overcome. One area will be controlling interfaces and bonding between printed layers [8,9]. Another issue is the anisotropic nature due to the orientation of the printed material deposited in each layer which can lead to changes in mechanical properties [10]. Other concerns of AM technologies relate to surface roughness, repetitiveness, and porosity [11-13]. These concerns are being addressed by many research activities [14-17] and should not derail the progression of research in printing multi-material RF structures.

A final need for AM of RF components is research into the areas of conductive inks. Conductive inks can achieve conductivity of five to ten times less than bulk copper, but require sintering at temperatures above 175 degrees Celsius [18]. AM substrates printed from polymer based filaments will melt at these temperatures making these methods not viable for AM antennas or other RF components. Alternative methods such as localized laser sintering or flash annealing should be researched to achieve high conductivity in the presence of 3D printed dielectric substrates.

PHASE I: Phase I shall explore processes for the loading polymers with high dielectric constant particles and the extrusion process for producing high dielectric constant additive manufacturing (AM) filaments that are compatible with an nScrypt 3D printer. Prototype filaments of differing dielectric constants should be produced and a maximum relative permittivity of 15 should be demonstrated. The loss tangent of these filaments should be less than 0.002. Filament diameter should be either 1.75mm (+/- 0.05mm) or 2.85mm (+/- 0.05mm). At the end of Phase I, 3D printed substrates of 8”x8”x0.25” using these filaments will be fabricated and complex permittivity will be measured from 1 GHz to 20 GHz. Differences between the measured permittivity and filaments should be quantified and explained. Furthermore, research into methods for increasing the conductivity of conductive inks printed on composite polymer substrates to 10X less than bulk copper (i.e. 5.8x10^6 S/m) should identify a technique to be demonstrated in Phase II.

PHASE II: Phase II will demonstrate measured conductivity of sintered conductive ink printed on a polymer substrate reaching 5.8x10^6 S/m or better. Any major deviations identified in Phase I between the complex permittivity of the filament and that of the printed substrate should be accounted for. At the end of Phase II a fully fabricated additively manufactured (AM) antenna structure should be realized (including ground plane, connectors, feed, multiple dielectric substrates, and aperture) in a fully automated process and in a single print utilizing the same machine.

Laboratory antenna measurements such as return loss, radiation pattern, and antenna efficiency will be made. A comparison of the AM antenna to the same antenna manufactured by traditional means will be made as well as a comparison to an antenna model utilizing electromagnetic (EM) modeling software such as HFSS or CST. The radiation efficiency of the AM antenna should be within 10% of the same antenna produced by traditional fabrication techniques. The center of the resonance frequency of the AM antenna should vary less than 5% compared to the same antenna produced by traditional fabrication techniques. The AM antenna should also vary less than 5% in resonance frequency and less than 1.0 dB in realized gain across the operational bandwidth of the antenna model.

PHASE III DUAL USE APPLICATIONS: Phase III will focus on the commercialization of additive manufacturing (AM) technology for antennas and RF devices. The final AM process should demonstrate the repetitiveness of AM for both military and commercial applications. Commercialization would be of great interest to the radar and wireless sensing community while also providing an innovative technology solution to assist the military reduce logistical burdens for the storing and transporting of antennas and radio frequency (RF) components in the field. Similarly, lightweight AM antennas would be of great interest to the space and satellite communications industry.

REFERENCES:

1. R. K. Luneburg & M. Herzberger. Mathematical Theory of Optics. Providence, Rhode Island: Brown University, pp. 189–213, 1944.

2. D. Roper, B. Good, S. Yarlagadda, & M. Mirotznik, “Fabrication of a Flat Luneburg Lens using Functional Additive Manufacturing”, USNC-URSI Radio Science Meeting (Joint AP-S Symposium), 2014.

3. A. Moulart, C. Marrett & J. Colton, “Polymeric composites for use in electronic and microwave devices”, Polymer Engineerung and Science, vol. 44, pgs. 588–597, 2004.

4. Agarwala M. K. et al., “Structural ceramics by fused deposition of ceramics”, Proceedings of Solid Freeform Fabrication Symposium, pgs. 1–8, 1995.

5. B. Duncan, et al., “3D Printing of Millimeter Wave RF Devices”, Workshop on Additive Manufacturing of Antennas and Electromagnetic Structures, MITRE, 2017.

6. F. Castles, et al., “Microwave Dielectric Characterization of 3D-printed BaTiO3/ABS Polymer Composities”, US National Library of Medicine, PMC4778131, 2016. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4778131/#b20

7. Y. Rao, et al., “Novel polymer-ceramic nanocomposite based on high dielectric constant epoxy formula for embedded capacitor application”, Journal of Applied Polymer Science, 2001.

8. C. Bellehumeur, et al., “Modeling of bond formation between polymer filaments in the fused deposition modeling process”, Journal of Manufacturing Processes, vol. 6, iss. 2, pgs. 170-178, 2004.

9. M. Odell, et al., “Material characterization of fused deposition modeling (FDM) process”, Proceedings, Rapid Prototyping and Manufacturing Conference, Society of Manufacturing Engineers, Cincinnati, OH, 2001.

10. S-H. Ahn, et al., “Anisotropic material properties of fused deposition modeling ABS”, Rapid Prototyping Journal, vol. 8, iss 4, pgs. 248-257, 2002.

11. D. Ahn, et al., “Representation of surface roughness in fused deposition modeling”, Journal of Materials Processing Technology, vol. 209, iss. 15-16, pgs. 5593-5600, 2009.

12. A Sood, et al., “Improved dimensional accuracy of fused deposition modeling processed part using grey Taguchi method”, Journal of Material and Design, vol. 30, iss. 10, pgs. 4243-4252, 2009.

13. K. Ang, et al., “Investigation of the mechanical properties and porosity relationships in fused deposition modeling-fabricated porous structures”, Rapid Prototyping Journal, vol. 12, iss. 2, pgs. 100-105, 2006.

14. K. Thrimurthula, et al., “Optimum part deposition orientation in fused deposition modeling”, International Journal of Machine Tools and Manufacturing, vol. 66, iss. 6, pgs. 585-594, 2003.

15. M. Hossain, et al., “Improved mechanical properties of fused deposition modeling-manufactured parts through build parameter modifications”, Journal of Manufacturing Science, vol. 136, iss. 6, 2014.

16. A. Boschetto, L. Bottini, “Accuracy prediction in fused deposition modeling”, International Journal of Advanced Manufacturing Technology, vol. 73, iss. 5, pgs. 913-928, 2014.

17. K. Tong, et al., “Error compensation for fused deposition modeling (FDM) machine by correcting slice files”, Rapid Prototyping Journal, vol. 14, iss. 1, 2008.

18. [D. Roberson, R. Wicker, E. MacDonald, “Ohmic curing of printed silver conductive traces”, Journal of Electronic Materials, vol. 41, iss. 9, pgs. 2553-2566, 2012.

KEYWORDS: additive manufacturing, electromagnetic materials, material characterization, antennas, RF devices, manufacturing materials, manufacturing processes

A18-021

TITLE: Electric machines and hybrid drives for vertical takeoff and landing (VTOL) tactical air vehicles

TECHNOLOGY AREA(S): Air Platform

OBJECTIVE: Develop and demonstrate lightweight hybrid or electric-enhanced drive system technologies for novel vertical take-off and landing (VTOL) tactical aircraft with powerplant output in the range of 50-250 kW class.

DESCRIPTION: Aircraft capable of vertical takeoff and landing are a critical enabler for many US Army operations. A large fleet of several thousand crewed helicopters provide much of this capability today, while future Army operations will increasingly employ uninhabited aerial systems.

The smallest uninhabited VTOL aerial systems rely on fully electric propulsion and batteries, while large crewed rotorcraft are primarily powered by liquid-fueled turbine engines coupled to mechanical drive systems. In the intermediate Group III unmanned aerial systems (max. gross takeoff weight <1320 lbs), with equivalents up to crewed light helicopters and small personal aerial vehicles, the design range from “light” hybridization or electrical assistance through to full electric propulsion may enable new military-relevant vehicles for expeditionary maneuver and sustainment of theater operations.

Recent rapid improvements in the specific power of aviation electric motors and electrical energy storage are enabling revolutionary VTOL aircraft configurations in this intermediate size class. However, conversion of energy stored in readily available and transportable liquid fuels remains an important capability for the Army for aerial maneuver where electrical infrastructure is inadequate for all-electric aircraft. This, coupled with a desire for long range and versatility, is likely to differentiate propulsion architectures from those envisioned for domestic logistics markets and urban aerial transportation.

This topic seeks development of high power density drivetrain technologies needed for efficient and flexible distribution and transfer of propulsive energy in lightweight aerial vehicles capable of vertical takeoff and landing. These technologies will reduce mechanical interfaces and components through hybridization or electrification of VTOL conventional mechanical drive systems. While it is desirable that chosen technologies be relevant to more than a single vehicle architecture, proposers are encouraged to choose a general vehicle configuration such as lightweight helicopter, ducted fan personal vehicle, tiltwing/tiltrotor, etc. to allow engineering analysis and trade studies to quantify the impacts of the technology. The focus of the proposal should remain on the drivetrain technology offered; the overall vehicle configuration need not be treated in depth provided reasonable engineering assumptions are made.

Aviation electric machines with high specific power (>5 kW/kg) and low inertia feature prominently in many current designs in this type of vehicle. Technologies specifically related to the propulsive devices (rotors, fans, propellers, etc.) are considered outside the scope and not sought within this topic. Powerplants such as heat engines and energy storage devices such as batteries are also not sought within this topic, but reasonable assumptions about technology improvements or advancements in those areas may be made by offerors if required to support the proposed power distribution technology. Any assumed technology improvements or advancements should be likely within 5-10 years with little additional investment given current technology trends and the state-of-the-art.

Proposals should address any increases in weight relative to traditional technologies such as mechanical drive systems, and these weight penalties must be reasonable and offset by other improvements in performance, endurance, durability, flexibility or mission capability afforded by the new configuration.

PHASE I: Establish feasibility of the proposed energy distribution/transfer technology. Develop a specific detailed design for this technology within the 50-250 kW class, and a concept of the propulsion distribution system in sufficient detail to support feasibility assessment. Clearly identify the vehicle configuration and flight profiles for which the propulsion system will be analyzed and provide a comparison to a conventional mechanical drivetrain in terms of propulsion system mass, propulsive efficiency, specific power, range and endurance. A minimum endurance of sixty minutes should be achievable by the proposed architecture/technology. Conduct simulation and/or breadboard evaluation of the technology for demonstration. Provide a detailed technical and commercialization plan demonstrating a credible path toward a commercial product. Identify technical risks in further development as well as requirements and assumptions about companion technologies needed to achieve system level performance.

PHASE II: Further develop the technology concept including performing a detailed design and construction of an engineering prototype to validate performance through some form of physical test. This phase may also include screening tests required in advance of the prototype design, modeling and simulation efforts, or other supporting tasks required to demonstrate the proposed concept. Establish scale tolerance of the design, minimally across the 50-250 kW range described by this topic. Evaluate performance across the designed envelope of static conditions as well as transient and dynamic flight conditions. Refine estimates of propulsion system mass, propulsive efficiency, specific power, vehicle range and endurance. Specific power of individual electric machines should exceed a minimum of 5 kW/kg and overall propulsion system dry weight should be minimized.

PHASE III DUAL USE APPLICATIONS: Transition the Phase II effort into commercial use. Proposals to this topic must articulate a feasible strategy to transition the successful Phase II effort into commercialization. This strategy should address whether technology will be patented and licensed, produced internally or through partnering, etc. Barriers to adoption in an aviation application should be identified and mitigations offered. Initial markets in the transition effort may be civil or military, and may be non-aviation, provided the offeror demonstrates a feasible path to a future Army-relevant aircraft. Technology developed herein has considerable potential to be integrated in a broad range of both military and civilian aircraft or personal vehicles where flexible adaptable and distributed propulsion may be employed. Military logistics represents a large and obvious future market to which this topic is targeted. An emerging market of civil personal and logistical air vehicles is also developing rapidly, enabled by advancements in vehicle autonomy.

REFERENCES:

1. https://vtol.org/what-we-do/transformative-vtol-initiative/the-electric-vtol-news/the-electric-vtol-news

2. Proceedings of the 3rd Joint Workshop on Enabling New Flight Concepts Through Novel Propulsion and Energy Architectures, https://vtol.org/what-we-do/transformative-vtol-initiative/transformative-proceedings/3rd-transformative-workshop-briefings

3. Siemens, “Siemens develops world-record electric motor for aircraft,” Press Release. March 24, 2015

4. Fredericks, W. J., Moore, M. D., & Busan, R. C. (2013). Benefits of Hybrid-Electric Propulsion to Achieve 4x Cruise Efficiency for a VTOL UAV. In 2013 International Powered Lift Conference (p. 4324).

5. Warwick, G. (2014). Electrifying Aviation: Light aircraft are early targets for the efficiency and safety benefits touted for electric propulsion. Aviation Week & Space Technology, 176(23).

6. Brown, G. V., Kascak, A. F., Ebihara, B., Johnson, D., Choi, B., Siebert, M., & Buccieri, C. (2005). NASA Glenn Research Center program in high power density motors for aeropropulsion. NASA/TM—2005-213800

KEYWORDS: VTOL aircraft, drive system, motors, power transmission, propulsion

TECHNOLOGY AREA(S): Information Systems

OBJECTIVE: Develop extremely efficient, capable small form-factor autonomous, UAS lift and maneuver technologies in support of relocatable unattended ground sensors.

DESCRIPTION: The mobility of imaging ground sensors on the battlefield is a major challenge for the next generation of Intelligence, Surveillance, and Reconnaissance (ISR) sensors. Ground sensors restricted to operation from a fixed position do not support the mobile, expeditionary nature of Army combat operations. In addition, relocatable sensors need to be packaged into remote delivery systems that transport the sensor to staging positions tens of kilometers (km) forward of controlled spaces [1].

Key functional characteristics, of the relocatable sensor include autonomous launch and landing in denied spaces, autonomous recharging, navigation, obstacle avoidance, small size, and attitude control for ISR operations. To realize future Army capabilities, suggested mission parameters for such a platform includes 1) flight hovering durations of at least 20 minutes; 2) flight distances up to 8 km between charging; 3) an autonomy capable of launch and landing in denied spaces, navigation, obstacle avoidance, small size, and attitude control to support imaging operations without human intervention; 4) an ISR sensor payload consisting of a stabilized, multi-axis gimbal with multi-spectral imaging (e.g., visible 1080p and IR) and processing capable of onboard, real-time processing of the imagery; and, 5) multiband communications capable of supporting HD video. The autonomy, sensing and communications payloads should not exceed 500 grams. When packaged in a delivery system, the body of the proposed solution should be capable of fitting within a 100mm x 100mm cylindrical container with a total wingspan, when unpackaged, of 200mm or less so that it may be integrated with a future Army air delivery-transport system.

The system must be able to operate without human intervention for more than 10 flight-return-recharge cycles. State-of-the-art commercial and experimental micro UAS platforms are not able to meet our objective requirements [2, 4, 5]. While many of these component technologies have been commercially developed or demonstrated in research endeavors, developing a fully integrated, autonomous system capable of all of the behaviors indicted while maintaining sufficient engine power for lift and overcoming ground effects with a 500 gram payload; integrated battery and aerodynamic design capable of flying 8 km, hovering for 20 minutes without recharging while performing obstacle avoidance while performing visual scene processing.

Major research challenges in this topic are not the component technologies (lift and flight, flight control and navigation, imagers, computer vision algorithms etc.) but rather 1) the integration of the behaviors, components and systems and implementation of those technologies into the prepackaged/collapsible, small form-factor identified above, and 2) the ability of the system to work autonomously without human intervention.

The research conducted in this SBIR should enable a UAS with a 500 gram, 50 cubic centimeter payload which can be packaged in a 100 x 100 mm cylindrical container to fly at least 8 kilometers at an altitude greater than 300 meters, hover for 20 minutes at 150 meters while using no more than 80% of its power source (the balance is assumed to the payload).

PHASE I: The research effort shall explore autonomous unmanned platform technologies for mobility of micro UAS for sensor relocation. Investigate and determine the design characteristics of the solution that meets the requirements. Research for this phase will focus on developing an integrated system design including engineering designs necessary to meet the system requirements including lift systems, materials, power sources, and packaging strategies; the research will develop integrated flight control and navigation hardware, software and algorithms capable of meeting the system requirements; and, specifying an onboard intelligence package to include sensor systems and algorithms to meet the system requirements. Using modeling and simulation software, demonstrate a solution that meets the performance requirements: With a 500 gram, 50 cubic centimeter payload, 1) lift off the ground on its own power; 2) hover for at least 20 minutes, fly at least 8 kilometers, and land in a position/orientation suitable for another launch without human intervention. In addition, the research must substantiate through detailed aerodynamic, materials, power, and environmental analysis, a design capable of meeting the objective performance and form-factor requirements. Develop documentation for a proposal for the solution for phase 2 consideration.

Additionally, research should identify lightweight materials, miniaturization and dual use of critical component technologies, high-energy power sources, multifunctional hardware, and high efficiency aerodynamics that are critical enabling technology. The research to adapt these critical enabling technologies can be the focus off the Phase I option period.

PHASE II: Based on the simulation results from Phase I, perform the research to design, develop, and integrate a hardware platform with performance capable of meeting the required capabilities within a 125x 125 mm cylindrical container with a 250 mm maximum wingspan form-factor. Deliver 1 system to ARL for testing to validate that the system is capable of meeting the specified performance. The system must be able to meet all system performance specifications, except those specified in Phase III deliverables.

Additionally, Phase II research should identify lightweight materials, miniaturization and dual use of critical component technologies, high-energy power sources, multifunctional hardware, and high efficiency aerodynamics that are critical enabling technology to achieve the 100mm by 100mm form factor. The research to adapt these critical enabling technologies can be the focus off the Phase II option period.

PHASE III DUAL USE APPLICATIONS: Vision: The final product should be able to rapidly deploy itself and then autonomously identify and move to an optimum location, where it performs ISR tasks, and then redeploys and recharges.

The End State of the program, building on the results from Phase II, and the simulation and modeling from Phase I, will meet or exceed the required capabilities within a 100 x 100 mm cylindrical container with a 200 mm maximum wingspan form-factor. Deliver 2 systems to ARL for testing to validate that the system is capable of meeting the specified performance.

Potential Transition and Military Transition Path and Application: Eventual military applications could include Intelligence, Surveillance, and Reconnaissance (ISR) for a maneuver group or fixed location with a dynamic surrounding landscape. Expeditionary forces responding to a humanitarian disaster would use these rapidly deployable, mobile agents to establish a perimeter and provide ISR for locating people, infrastructure and safety concerns. The CLARK Kit as well as PM Soldier's Soldier Borne Sensor, PM Ammo and PM UAS would have a need for this class of technology.