TECHNOLOGY AREAS: Electronics; Air Platform; Information Systems OBJECTIVE: The objective of this project is to develop a small unmanned aerial systems (sUAS) flight control system (FLCS) capable of supporting different dynamics through a model following algorithm (aka micro-VISTA), to support rate control input and output to control-surface actuators. The proposed effort is focused on developing the technology to provide an interface for lower-level commands (LLC) between autonomy algorithms and a sUAS simulating the dynamics of another aircraft. The UAS FLCS should permit the autonomy algorithms to use LLCs to fly the aircraft through the allowable flight envelope but should intercede to prevent loss of control in cases where the aircraft would exceed limits. Autonomy algorithms can be developed and testing using this capability with reduced risk and development time. DESCRIPTION: Given the complexity of autonomous systems and the environment we expect to use them, it is impossible to set up a complete set of necessary development and test scenarios in open air using target platforms. Therefore, including Live, Virtual, and Constructive (LVC) simulation into flight test will be mandatory for testing before fielding autonomies. Being able to test autonomies through a build-up of lower-to-higher fidelity simulation environments will be critical to evaluate autonomies, not just to support autonomy development, but also to enable testing future autonomous systems. Specifically, having a simulation architecture where autonomy software can move seamlessly between simulation environments before getting onto the objective platform is necessary, i.e., laboratory to software-in-loop/hardware-in-loop (SIL/HIL) simulations, to flight through in-air surrogates such as sUAS or VISTA/Venom platforms. So far, all autonomy test on surrogate platforms has used waypoint or Heading-Speed-Altitude (HSA) commands to an autopilot. Lower-level controls (e.g., roll, pitch, throttle) will be necessary to enable target platforms to perform complex intended behaviors that are either not easily performed or impossible to perform using waypoint or HSA commands, e.g., Beyond-Visual-Range (BVR), Basic Fighter Maneuvers (BFM). Although the 412TW VISTA platform is pioneering LLC interfacing that allows acceleration and roll-rate command inputs to F-16 flight controls there is currently no standard interface defined nor any option available for sUAS, thereby creating an expensive and sluggish gap between software testing and in-air testing. Being able to test complex intended behaviors on sUAS will reduce the overall cost to test autonomy as well as increase the tempo of flight test as sUAS are cheaper and easier to get up in the air. LLC systems enable executing roll, pitch, and throttle commands on the aircraft. A sUAS LLC system would effectively allow a sUAS to perform complex in-air maneuvers that require acceleration and roll-rate commands. Several efforts have demonstrated this LLC capability, but only on larger platforms (i.e., F-16) using platform-specific FLCS and none have demonstrated LLCs on sUAS using COTS autopilots. Model Following Algorithms (MFA) enable simulating the dynamics of another aircraft through a control augmentation process. An MFA on a sUAS would enable implementing multiple vehicle model types on that sUAS. Initial evaluations of overall accuracy will be performed with the FLCS integrated on a sUAS test aircraft. Air data captured using the FLCS would be evaluated and compared to the commanded inputs. On subsequent test efforts, the FLCS system would be integrated into a Renegade sUAS aircraft for evaluations of suitability and utility on faster sUAS systems. RESEARCH GOALS: Model Renegade sUAS for simulation and control law development Build FLCS to take various low-level commands inputs (e.g., rates, surface deflections) and generate servo commands MFA in FLCS to enable mimicking flight dynamics of other platforms with appropriate model Dynamic state control Auto-recovery from state-limit exceedance Interface control document (ICD) for FLCS interface PHASE I: This is a Direct-to-Phase-II (D2P2) topic, no Phase I awards will be made because of this topic. To qualify for this D2P2 topic, the Government expects the applicant to demonstrate feasibility by means of a prior Phase I-type effort that does not constitute work undertaken as part of a prior SBIR/STTR funding agreement. Applicants are expected to provide a white paper providing a comprehensive feasibility assessment that outlines the technical viability of developing an LLC and MFA enabled FLCS interface for sUAS. This assessment should address the suitability of the FLCS for sending LLCs to sUAS and their potential integration into different sUAS platforms, while allowing for model following. Furthermore, Data Analysis is essential, and it is anticipated that the Applicants conduct a thorough analysis and provide meaningful conclusions about the accuracy, suitability, and utility of the interface as sUAS aircraft equipment. Lastly, it is expected that an integration of the FLCS will be demonstrated on a sUAS using a COTS autopilot. Additional processing may be used in the platform. The Applicants should then demonstrate its performance in real-flight scenarios. PHASE II: The proposed effort is focused on maturing the technology to be able to provide roll, pitch, and throttle driven maneuvers to high performance aircraft in regimes near the upper speed limits of group 3 sUAS (Department of Defense, 2018). As a result, the Phase II Period of Performance objectives: 1) Create and verify aeromodel of Renegade sUAS. 2) Demonstrate a FLCS with simulated sUAS to include the Renegade sUAS. 3) Collect simulation test data to evaluate the FLCS against commanded inputs. 4) Integrate a FLCS into a Renegade sUAS with a COTS autopilot. 5) Collect flight test data using the Renegade aeromodel and sUAS model(s) used in #2 above. 6) Evaluate flight test data against commanded inputs. 7) Verify FLCS is permissive for agile maneuvers within the allowable flight envelope. 8) Verify FLCS can safely recover aircraft control during an envelope exceedance event. 9) Evaluate the suitability and utility of the FLCS for sUAS with a COTS autopilot. 10) Provide ICD of the FLCS. PHASE III DUAL USE APPLICATIONS: Phase III would transition this type of system to be the primary means of enabling LLC and MFA for sUAS. Autonomy test would be able to significantly reduce overall cost and risk by using LLC and MFA enabled sUAS. The 416th Emerging Technologies Integrated Test Force is expected to be the primary government group to sustain this capability. LLC and MFA enabled sUAS facilitate the integration and testing of autonomy algorithms and limits the risk, development time, and airworthiness approvals required for such assessments. These sUAS include the baseline autopilot capability and include interfaces to autonomy computers with a hardware architecture modeled after the 412 Test Wing X-62A VISTA. For both LLC and MFA enabled UAS and VISTA, the reliability and determinism of the baseline autopilot provides the foundation for airworthiness safety review assessments, airspace and range permissions, and risk assessments. Flight tests are no more dangerous than a routine operation since the experimental autonomy algorithm is prevented from exceeding the allowable flight envelope by the trusted and verified baseline autopilot recovery mechanism. Commercialization of LLC and MFA enabled sUAS can be extended to Phase III in which the system is integrated into the development cycle of novel autonomy algorithms with commercial and government teams. The system can be developed into a commercial product and retain government property rights for continued use and development. REFERENCES: 1. Air Force Materiel Command. (2023). 2023 AFMC Strategic Plan. 2. Department of Defense. (2018). Guidance for the Domestic Use of Unmanned Aircraft Systems in U.S. National Airspace. 3. Department of the Air Force. (2022). Seven Operational Imperatives. KEYWORDS: small unmanned aerial systems (sUAS); flight control system (FLCS); open air using target platforms; autonomous systems; simulation and control law development.
