Simultaneous actuator and inertial measurement unit faults pose a significant challenge for flight safety. This study analytically demonstrates the impact of such faults on incremental nonlinear dynamic inversion (INDI)-based controllers and proposes an active fault-tolerant control method that concurrently mitigates these faults and accounts for in-flight turbulence. The method employs an optimal two-stage extended Kalman filter with a higher-order sliding mode differentiator (OTSEKF-HOSM) for inertial measurement unit fault identification, together with a variable forgetting factor recursive least squares (VFF-RLS) algorithm for online on-board model estimation, collectively forming the Active-Adaptive (AA) INDI framework. Numerical simulation results show that AA-INDI outperforms conventional and Adaptive INDI in terms of tracking performance under time-varying inertial measurement faults and sudden actuator failures.

Sustainability is a key commitment for future innovation and improvement of the aerospace industry and to realise active research is invested towards advanced and new aircraft designs such as the Flying V. The Flying V is a flying wing design for commercial aviation, promising higher efficiency against conventional tube-and-wing aircraft. The Flight Control System (FCS) has to be designed to prove the airworthiness of the aircraft. In this work, a fault-tolerant FCS is designed that includes an adaptive incremental dynamic inversion inner loop rate control law with an outer loop that consists of longitudinal C* control law and Rate Control Attitude Hold roll control laws for lateral control. Research and activities has led to an updated geometry design with aerodynamic data from RANS simulation, which requires tuning of its outer loop flight controls to be within level 1 handling quality. To investigate the fault tolerance of the aircraft with a structural fault case that results in a loss of effectiveness. It is shown that the adaptation allows the aircraft to cope with the faults and maintain satisfactory tracking performance.

The Flying-V aircraft could revolutionize commercial aviation, boasting a potential 25% increase in aerodynamic efficiency. Due to inherent design limitations regarding static stability, a proper Flight Control System (FCS) is essential for the development of the aircraft. The concept of Hybrid Incremental Nonlinear Dynamic Inversion (INDI) was introduced to mitigate the insufficient stability margin encountered in existing sensor-based INDI systems due to sensor time delays to achieve Level 1 Handling Qualities (HQ). Furthermore, the research introduces an exponential potential function-based command limiting Flight Envelope Protection (FEP) to enhance safety compared to the currently implemented linear-based FEP. The study compares and evaluates the effectiveness of the updated system under various flight conditions and parametric uncertainties. Results show improved stability margins and a safer FEP. However, additional research is required into actuator saturation and control allocation issues during the approach condition and to enhance robustness.

Commercial applications of flying wing aircraft present a unique opportunity to improve fuel efficiency in aviation, but also pose significant challenges in stability and control. This paper improves the existing flight control laws of a commercial flying wing concept called the Flying-V. The paper designs and evaluates normal law flight controls through piloted flight simulations on a moving base flight simulator, assessing handling qualities, certification compliance, and flight envelope protection capabilities. Industry-inspired outer guidance loops include envelope protections for angle of attack, bank, pitch, and load factor, using command limiting exponential potential functions to smoothly enforce limits and prevent longitudinal instability. The inner loop employs incremental nonlinear dynamic inversion. Results demonstrate that the Flying-V model, augmented with the proposed controller, achieves Level 1 handling qualities and meets nearly all certification requirements. Flight envelope protection maneuvers confirm that exponential potential functions deliver protection performance comparable to commercial aircraft and successfully prevent unstable behavior.

Commercial applications of flying wing aircraft, as the Flying-V here considered, can contribute to reducing carbon and nitrogen emissions produced by the aviation sector. However, because of the lack of a tail, all flying wing aircraft have reduced controllability. For this reason, the placement and sizing of the control surfaces along the wing is a non-trivial problem. The paper focuses on solving this problem using offline handling quality simulations based on certification requirements. In different flight conditions, the aircraft must be able to perform a certain set of maneuvers as defined by the certifying authorities. First, offline simulations calculate the minimum control authority required from the elevator, aileron, and rudder to perform each maneuver. Then, based on the global minimum for all maneuvers, the control surfaces are sized and placed along the wings. The aerodynamic model employed uses a combination of Reynolds-averaged Navier-Stokes (RANS) and vortex lattice method (VLM) simulations. The control authority of the control surfaces is estimated with VLM and VLM calibrated with RANS simulations, showing significant differences between the two.

The Flying-V is a novel flying wing aircraft design that aims to improve aerodynamic efficiency and fuel consumption. In recent years, there has been an increased effort to evaluate the handling qualities (HQs) of the Flying-V, and to develop new flight control strategies. One of the latest flight control designs for the Flying-V uses Incremental Nonlinear Dynamic Inversion (INDI) with a Flight Envelope Protection system. The purpose of this research is to validate this FCS design and its conclusions on handling qualities by conducting piloted experiments. To facilitate a sound comparison, the aerodynamic model, flight control structure, and airframe characteristics are taken as is from the existing study. For the experiment, numerous maneuvers are designed and carried out. The experiment is performed on the SIMONA Research Simulator of the Delft University of Technology, with three real-life test pilots as participants. The results show a significant correlation with offline findings and demonstrate the improvement in HQs provided by the flight control system.

Commercial applications of flying wing aircraft, such as the Flying-V considered herein, can contribute to reducing carbon and nitrogen emissions produced by the aviation sector. However, because of the lack of a tail, all flying wing aircraft have reduced controllability. For this reason, the placement and sizing of the control surfaces along the wing is a nontrivial problem. The paper focuses on solving this problem using offline handling quality simulations based on certification requirements. In different flight conditions, the aircraft must be able to perform a set of maneuvers as defined by the certification specifications. First, offline simulations calculate the minimum control authority required from the elevator, aileron, and rudder to perform each maneuver. Then, based on the global minimum for all maneuvers, the control surfaces are sized and placed along the wings. The aerodynamic model employed uses a combination of Reynolds-averaged Navier–Stokes (RANS) and vortex lattice method (VLM) simulations. The control authority of the control surfaces is estimated with VLM and VLM calibrated with RANS simulations, showing significant differences between the two.

The Flying-V emerges as a unique flying wing type commercial aircraft design, distinguished by its V-shaped configuration. For such unconventional airframes, flight control systems are vital for ensuring safety and enhancing flight performance. Current Flying-V control systems primarily use incremental nonlinear dynamic inversion (INDI), a sensor-based feedback linearization method requiring an onboard control effectiveness model. Although INDI handles model uncertainties, significant mismatches between actual and onboard models caused by damages or faults degrade performance and compromise flight safety. This study proposes an adaptive strategy for incremental nonlinear dynamic inversion, employing an online two-step method to estimate changes in the aircraft’s control effectiveness. Estimates are used to update the onboard control effectiveness model to minimize the mismatch between the actual and onboard representation of control effectiveness.

This research describes a near-optimal feedback guidance, based on nonlinear orbit control, for low-thrust Earth orbit transfers. Lyapunov stability theory leads to proving that although several equilibria exist, only the desired operational conditions are associated with a stable equilibrium. This ensures quasi-global asymptotic convergence toward the desired final orbit. The dynamical model includes the effect of eclipsing on the available thrust, as well as all the relevant orbit perturbations, such as several harmonics of the geopotential, solar radiation pressure, aerodynamic drag, and gravitational attraction due to the Sun and the Moon. Near-optimality of the feedback guidance comes from careful selection of the control gains. They are identified in two steps. Step (a) is an extensive table search in which the gains are changed in a large interval. Step (b) uses a numerical optimization algorithm that refines the gains found in (a), while minimizing the time of flight. For the numerical simulations, two scenarios are defined: (i) nominal conditions and (ii) nonnominal conditions, which arise from orbit injection errors and stochastic failures of the propulsion system. For case (i), gain optimization leads to obtaining numerical results very close to those corresponding to a known optimal orbit transfer with eclipse arcs. Moreover, for case (ii), extensive Monte Carlo simulations demonstrate that the nonlinear feedback guidance at hand is effective in driving a spacecraft from a low Earth orbit to a geostationary orbit, also in the presence of nonnominal flight conditions.

This research proposes a near-optimal feedback guidance based on nonlinear control for low-thrust Earth orbit transfers. For the numerical simulations, two flight conditions are defined: (i) nominal conditions and (ii) nonnominal conditions that account for the orbit injection errors and the stochastic failures of the propulsion system. Condition (ii) is studied through an extensive Monte Carlo Analysis, to demonstrate the nonlinear feedback guidance’s numerical stability andconvergence properties. To illustrate the performance under both conditions, an orbit transfer from low Earth orbit to geostationary orbit is considered. Near-optimality of the feedback guidance comes from carefully selecting the nonlinear control gains. Comparison of the transfer with an existing study that uses optimal control reveals that orbit transfers based on feedback orbit control are very close to the optimal solution.