Browse Topic: Avionics
Modern space exploration relies more and more on vehicles that carry expansive antenna arrays, a trend driven by steady progress in the field of space engineering. The study centers on constructing a coupled model that accounts for structural rigidity, flexibility, and thermal effects in a sizable orbital unfurling parabolic antenna, along with designing its orientation regulation system. A blended coordinate formulation and a heat-based discretization approach are employed to derive the motion and temperature-governing equations of the assembly. A unified pointing control method is then developed by merging classical feedback control principles with torque compensation control. Computational experiments involving a spacecraft fitted with such a dish antenna are executed. The findings reveal that sudden heat fluctuations, exemplified by the transition out of Earth’s umbra, trigger oscillatory behavior in the antenna framework and disrupt the satellite’s angular position. The designed orientation regulator successfully counteracts these thermally driven perturbations, even when the system representation contains inaccuracies.
In response of the stringent requirements of high-resolution optical remote sensing satellites for attitude control stability and micro-vibration environment, this study focuses on the friction dynamics modeling and simulation analysis of large-angular-momentum flywheels across a wide speed range. To quantify the impact of flywheel friction disturbances on satellite attitude pointing accuracy, friction torque characteristic data were first acquired through ground testing over the full speed range, and a high-fidelity static fitting mathematical model was constructed using the least squares method. To further elucidate the nonlinear friction mechanisms in the low-speed regime—particularly during speed zero-crossings—the LuGre dynamic friction model was introduced, and its core parameters were identified and optimized. Comparative results demonstrate that the model exhibits high-precision characterization capabilities, with a deviation of less than 0.0015 Nm from measured data within the critical low-speed range of ±50 rpm. Subsequently, the established friction model was integrated into a satellite attitude control closed-loop system for digital simulation to quantitatively evaluate the disturbance of friction torque on system steady-state accuracy. The results indicate that under the closed-loop control compensation mechanism, the impact of flywheel friction on satellite attitude pointing accuracy is effectively suppressed, with the attitude angle deviation maintained within 0.002°, thereby meeting the engineering requirements for high-precision remote sensing imaging. This research provides a theoretical basis and data support for the optimization design of flywheel systems and the refined design of satellite attitude controllers.
This SAE Aerospace Standard (AS) establishes guidelines for enhancement to IEEE 1394-2008 Beta (formerly IEEE 1394b) PHYsical (PHY) layer. It encompasses enhancements to the IEEE 1394-2008 Beta PHY to reduce port connection times and increase port connection reliability. Therefore, this document contains extensions/restrictions to “off-the-shelf” IEEE 1394 standards and assumes that the reader already has a working knowledge of IEEE 1394. The enhancements covered in this document include: Detect loss of descrambler synchronization Fast-ReTrain (FRT) Fast Power-on Re-connect (FPR) Fast Connection Tone Debounce (FTD) Programmable invalidCount Bus Reset Cause This document does not identify specific environmental requirements (electromagnetic compatibility, temperature, vibration, etc.); such requirements will be vehicle-specific and even LRU-specific. One should refer to the appropriate sections of MIL-STD-461E for their particular LRU and utilize handbooks such as MIL-HDBK-454A and MIL-HDBK-5400 for guidance. This document is referred to as a “slash sheet” and accompanies the AS5643B base standard.
This paper addresses the determinacy issue of multi-task execution in the Remote Data Conversion Unit of an integrated modular avionics (IMA) system in a non - operating system environment. A three - level hierarchical static scheduling table architecture for the Remote Data Conversion Unit is proposed. In this architecture, the maximum execution cycle of functional parameters is used as the device scheduling table cycle, the minimum execution cycle is used as the scheduling block cycle, and the worst - case execution time is used as the functional execution time. Through hierarchical design, the orderly connection of functions, scheduling blocks, and devices is achieved. A periodic interrupt mechanism is adopted between scheduling blocks to ensure time alignment at the scheduling block cycle level. Inside the scheduling block, a polling mechanism is used to perform static sorting according to the worst - case execution time of functions, and a wait function is introduced to achieve time alignment and fault isolation. For fault - tolerant faults, a delayed response strategy is adopted to avoid violating atomicity. For non - fault - tolerant faults, rapid detection and restart processing are achieved relying on periodic interrupts. A Simulink model is used to conduct a comparative simulation of the Remote Data Conversion Unit using a competition mechanism and the scheduling table mechanism. The results show that under normal and fault conditions, this architecture significantly reduces data transmission jitter, improves system determinacy and fault - tolerance ability, meets the requirements of the DO - 297 standard for functional independence and safety, and provides an effective solution for improving the determinacy of the civil aviation Remote Data Conversion Unit.
To solve a problem that ignition anomaly can’t be detected in time, based on the thermal equilibrium equation, the space heat flow, heater heating, propellant combustion, and thermal radiation to cryogenic space are considered to build an accurate ignition temperature method for the 10 N thruster by using on-orbit true temperature. Further, considering the error of measuring the thermistor, an envelope model for the 10 N thruster ignition temperature is established. Based on the above, a detection method for the 10 N thruster ignition anomaly of on-orbit satellites is proposed. The accuracy of the method is relatively high, and the absolute error is less than 3 degrees Celsius. An anomaly can be quickly detected when the 10N thruster ignition temperature deviates from the normal trend by 3–5 degrees celsius. The method is applied to a DFH-3 satellite, and the maximum difference of 10 N thruster ignition temperature between the theoretical values calculated by the proposed method and the measured values is only 2.72 degrees celsius. It has been proven that the prediction accuracy of the proposed method is high. It plays an important role in discovering the 10N thruster ignition anomaly in time and ensuring the success of satellite orbit or attitude control.
This document presents criteria for flight deck controls and displays for Airborne Collision Avoidance Systems.
The proliferation of Autonomous Aerial Vehicles (AAVs) necessitates robust solutions for dynamic obstacle avoidance, particularly against non-cooperative intruders whose trajectories are unpredictable. While traditional path-planning algorithms excel in static environments, they struggle with dynamic obstacles due to the inherent difficulty in accurately estimating and registering their real-time depth and velocity into a world model. This paper presents a novel two-stage vision-based framework that leverages deep learning for reactive avoidance of non-cooperative dynamic intruders. Our approach decouples the perception and decision-making processes: an object detection deep neural network first processes monocular camera images to detect and track the 2D pixel coordinates of intruders. This perceptual output is then fed into a deep reinforcement learning agent, which learns a mapping from the intruder's image-space location to a high-level avoidance maneuver. This leads to more efficient learning, as the RL agent focuses solely on the policy without the burden of learning visual features. The advantage of using RL lies in its ability to handle partially observable situations—because reliable depth or full 3-D position information is not always readily available from monocular imagery, the RL agent learns to act based on the observable visual cues. Simulation results confirm that our proposed framework provides an effective solution for vision-based, non-cooperative intruder avoidance.
This paper presents the development, optimization, and flight test validation of a Trajectory Control System (TCS)-based flight control system for a tiltwing unmanned aerial vehicle. The TCS is a configuration-independent middle-loop longitudinal controller for vertical takeoff and landing aircraft and is integrated here with explicit model following inner-loop controllers, inverse propulsor models, and a tiltwing-specific control allocation scheme. The resulting flight control system provides coordinated control across vertical flight mode, hybrid flight mode, transition flight mode, and forward flight mode while relying on a concise feedback set and requiring only airspeed from the air data system. The control laws are obtained using a formal constrained optimization framework and transferred directly from simulation to flight without additional on-site retuning. Flight test results from piloted, semi-autonomous, and fully autonomous operations demonstrate stable and predictable behavior throughout the flight envelope, including tight hover performance, simultaneous climb rate and speed tracking in hybrid flight, and successful departure and arrival transitions at multiple speeds. Selected simulation-versus-flight comparisons further show that the nonlinear model captures the dominant trends in the measured response while also identifying specific aerodynamic and transition regime effects that warrant further refinement. Overall, the results demonstrate that the TCS + EMF architecture provides a practical and effective control solution for tiltwing VTOL aircraft.
When surveying the current landscape of Deterministic Ethernet avionics solutions in the aerospace industry, the three main technologies in the market are ARINC 664 part 7 rate-constrained Ethernet (commonly known by its trademark name "AFDX®"), TTEthernet (which combines ARINC 664 part 7 with Best-Effort Ethernet, while adding a new class of synchronous determinism defined in SAE AS6802 [Time-Triggered Ethernet]), and IEEE 802.1 Time-Sensitive Networking (TSN). No single deterministic Ethernet technology optimally satisfies certification, MOSA, and lifecycle goals across all avionics domains. Instead, successful digital backbones require intentional partitioning of responsibilities across technologies. This paper will seek to identify a number of those considerations and provide guidance on which technologies offer the best fit. After first opening with an explanation of the market forces driving the trends towards these technologies, this paper will delve into a short outline of each of these Ethernet standards. Following that, this paper will compare a variety of characteristics of each of the above Ethernet technologies pertaining to certifiability, MOSA conformance for DoD use cases, and supply chain considerations. Finally, the paper will synthesize those comparisons into a number of recommendations regarding the most appropriate uses for each Ethernet technology.
This paper presents the development flight test campaign of autopilot Upper Modes for T-625 Gökbey helicopter. The primary objective of the test campaign is to evaluate the newly developed Upper Modes in the frequency and time domain across the operational flight envelope. For quantification of performance and stability, various metrics are selected from the literature. Flight tests are designed to extract the metrics from time domain data and tests are conducted. Initial flight tests revealed discrepancies between theoretical design models and actual aircraft dynamics, requiring iterative control law gain optimizations. Furthermore, combined mode engagements required targeted simultaneous tuning of different modes to maintain stability margins in combined engagement. By integrating quantitative data analysis with qualitative pilot feedback, engagement logic and control parameters were successfully refined.
Given the necessity of performing System Certification according to SAE ARP4754, accepted as guideline by aeronautics certification authorities for development of aircrafts and complex systems, the need to define a robust and adaptable system requirements Validation and Verification (V&V) process has become a priority. SAE ARP4754 compliant processes shall be applied for certification of new complex systems, as well as to existing ones. Defining suitable and compliant processes for projects that were already in an advanced development stage when compliance to ARP4754 became mandatory is even more challenging with respect to the application to new projects, as the need of rearranging existing certification documentation naturally arises. This paper illustrates a process compliant with ARP4754 guidelines to achieve the System level requirement V&V. The presented process – based on the Function-Based Systems Engineering (FuSE) – has been applied to the civil certification of the Fly-By-Wire Flight Control System (FCS) of the AW609 tiltrotor by Leonardo Helicopters and has been reviewed by the Federal Aviation Administration (FAA).
The certification of highly integrated electric Vertical Take-Off and Landing (eVTOL) aircraft requires a rigorous bridge between simulation and flight reality. This paper presents the Joby Disturbance Generator, a high-integrity software framework natively integrated into the aircraft flight control system. The system utilizes a deterministic state machine to inject a library of signals, ranging from standard doublets and chirps to complex waveforms, directly into internal control loops. Applications include frequency sweeps for stability margin extraction and structural mode identification, time-domain inputs for handling qualities assessment, synthetic fault injection for redundancy management verification, and precise loads model validation. The system continuously monitors vehicle health, automatically aborting test points upon detecting genuine failures. For loads validation, it coordinates temporary relaxation of flight envelope protections with precise disturbance injection. This methodology accelerates development by shifting risk from flight execution to software verification, providing deterministic, data-driven evidence for certification. Flight test results demonstrating these capabilities are presented.
An automatic clear area takeoff mode is developed and initial flight tested for the Airbus Helicopters 5-bladed H145, certification name BK117 D-3, equipped with the Helionix® avionic system and a 4-axis automatic flight control system. While the automatic rearward and vertical takeoff modes are already certified up to the maximum Cat A weight, the clear area procedure - often providing the highest performance in terms of gross weight - currently requires manual execution. The introduction of an automatic clear area takeoff mode ensures a repeatable, procedure conform clear area takeoff profile while respecting engine limits and reducing overall pilot workload. The paper details the integration of the automatic clear area takeoff mode into the existing automatic flight control system, covering automatic clear area normal, continued, and rejected takeoff procedures. Initial flight test results are presented to demonstrate the consistency of the automated flight path and the ability to provide timely and correct responses to simulated engine failures, thereby enhancing overall operational safety.
Developing high-integrity software is a complex process that involves meeting strict standards across various industries. For instance, in the avionics sector, the DO-178C Design Assurance Level A (DAL-A) sets the highest level of rigor, requiring comprehensive evidence that the software will perform its intended safety functions. Modern avionics systems are made up of hardware and software from different vendors, all integrated by prime contractors. By achieving modularity in these systems, we can reduce interface complexity, manage version control, address supply chain vulnerabilities, and significantly lower recertification costs. To support a high degree of integration and software reuse in avionics systems, certain architectural elements are necessary. These include a certified Real-Time Operating System (RTOS), open standards consortia like FACE® and MOSA, multicore partitioning strategies, deterministic networking, and hypervisor-based virtualization. The role of a certified RTOS, for example, is crucial in ensuring the reliable and efficient operation of safety-critical software components. Open standards consortia, on the other hand, facilitate the development of interoperable systems, while multicore partitioning strategies enable the efficient use of system resources. The use of deterministic networking and hypervisor-based virtualization also plays a key role in enabling the integration of multiple systems and reducing the complexity of system design. By leveraging these technologies, we can create a 'certify once, deploy anywhere' paradigm, which reduces development timelines, lowers lifecycle costs, and positions safety-critical software components for reuse across heterogeneous platforms. This approach not only improves the efficiency of system development but also enhances the reliability and safety of the resulting systems. In essence, the development of high-integrity software for avionics systems requires a comprehensive approach that considers the complex interactions between hardware and software components. By adopting modular architectures and leveraging open standards, certified RTOS, and advanced networking and virtualization technologies, we can create systems that are not only safe and reliable but also efficient and cost-effective. This, in turn, can help reduce the risks associated with system development and deployment, while also improving the overall performance and safety of the resulting systems.
This paper presents enhancements to the supervisory controller developed for the National Research Council Canada's Bell 412 autonomous helicopter. Building on a Discrete Event System Specification (DEVS)-based framework, the updated Supervisor introduces two new operational modes-Knobs Mode and Sticks Mode-and a structured approach for managing transitions between them and the existing modes. Drawing inspiration from NASA's Flight Guidance System philosophy, the proposed design emphasizes consistency, scalability, and flexibility in handling multiple autonomy modes. Implementation results demonstrate the effectiveness of the updated architecture in supporting future expansion of autonomous mission operations in complex and dynamic environments.
Developing a comprehensive autonomy solution for the Army's current and future aircraft fleet requires a robust computational and perception capability for decision-making across the entire flight envelope without a pilot. This also requires a flight control system and infrastructure capable of executing autonomous decisions in complex mission environments. Ongoing development of automation and autonomy, utilizing a wide range of perception sensors, has been conducted on platforms such as Sikorsky's S-70 and the Army's UH-60Mx aircraft. This work builds upon previous efforts and leverages ongoing collaborations with industry, the Department of War (DoW), and the Defense Advanced Research Projects Agency (DARPA) to advance autonomous capabilities for both optionally piloted and uncrewed aircraft.
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