NASA Generic Transport Model Research Articles

Adaptive Actuator Failure and Structural Damage Compensation of NASA Generic Transport Model

This paper studies design and evaluation of a multivariable model reference adaptive control (MRAC) scheme for aircraft systems under simultaneous actuator failures and structural damage. A key design condition–system infinite zero structure is investigated for nominal and posthazard aircraft systems and the invariance of this essential condition is concluded under realistic failure and damage conditions. The multivariable model reference adaptive control scheme is developed to ensure stability and asymptotic output tracking for the aircraft in the presence of uncertain actuator failures and structural damage. The developed fault-tolerant control design is evaluated by a high-fidelity nonlinear aircraft model–the NASA generic transport model.

Upset Dynamics of an Airliner Model: A Nonlinear Bifurcation Analysis

Despite the significant improvement in safety linked to the fourth generation of airliners, the risk of encountering upset conditions remains an important consideration. Upset, which may arise from faults, external events, or inappropriate pilot inputs, can induce a loss-of-control incident if the pilot does not respond in the correct manner. Any initiative aimed at preventing such events requires an understanding of the fundamental aircraft behavior. This paper presents the use of bifurcation analysis, complemented by time-history simulations, to understand the flight dynamics of the open-loop NASA generic transport model by identifying the attractors of the dynamical system that govern upset behavior. A number of drivers for potential upset conditions have been identified, including nonoscillatory spirals and oscillatory spins. The analysis shows that these spirals and spins are connected in two-parameter space and that, by an inappropriate pilot reaction to the spiral, it is possible to enter the oscillatory spin.

Recent results in robust adaptive flight control systems

SUMMARYAdaptive control has been increasingly used in flight control of late, with notable technology transitions to autonomous flight platforms such as Joint Direct Attack Munition (JDAM), X–36 Tailless Fighter Agility Research Aircraft, NASA Generic Transport Model (GTM), and Boeing Phantom Ray. Given the need to make these flight systems autonomous, the spotlight, more than ever, is firmly on adaptive control and in particular, robust adaptive control systems. In this paper, we present a few recent results in robust Adaptive Flight Control Systems (AFCS) that showcase the advantages, properties, and performance of AFCS, whose foundations were laid more than 50 years ago. Copyright © 2012 John Wiley & Sons, Ltd.

Design of an Adaptive Controller for a RemotelyOperated Air Vehicle

This paper presents an augmented control architecture for safe flight. This architecture consists of a nominal controller that provides satisfactory performance under nominal flying conditions and a direct model reference adaptive controller that provides robustness to parametric uncertainty. The design, implementation, tuning, and robustness analysis procedures of both the nominal and augmented controllers are presented. The aim of these procedures, which encompass both theoretical and practical considerations, is to develop a controller suitable for flight. The architecture proposed is applied to the NASA generic transport model. This is a model of a transport aircraft for which both a dynamically scaled flight-test article and a high-fidelity simulation are available. A robustness analysis framework, which bounds the set of adverse flying conditions for which all closed-loop requirements are met, indicates some advantages and drawbacks of adaptation. The adverse conditions considered are grouped into four categories: aerodynamic uncertainties, structural damage, unknown time delays, and actuator failures. These failures include partial and total loss of control effectiveness, locked-in-place control surface deflections, and engine-out conditions. The requirements are fast pilot-command tracking, bounded structural loading, satisfactory transient response, bounded flight envelope, and satisfactory handling/riding qualities. A computational approach that integrates this robustness analysis framework and a design-optimization technique is proposed. This approach enables the systematic search for the controller’s parameters that yield the best robustness characteristics allowed by the control structure.

Adaptive Fault Detection and Fault-Tolerant Control of NASA Generic Transport Aircraft Model

In this paper, adaptive fault detection and fault-tolerant control schemes for aircraft flight systems are investigated and evaluated on a high-fidelity aircraft model–the nonlinear NASA generic transport model. State feedback for output tracking and output feedback for output tracking multivariable model reference adaptive control schemes are developed, where plant-model matching conditions are much less restrictive than that of the state feedback for state tracking design, to ensure stability and asymptotic output tracking for the aircraft in the presence of uncertain actuator failures and structural damage. Based on an aircraft system dynamic coupling feature and different actuator failure patterns, adaptive detectors are constructed to detect damage and actuator failures. Our adaptive detection schemes are equipped with feedback fault-tolerant control to ensure signal boundedness requirement. Desired performance of the developed schemes is demonstrated by extensive simulation studies on the nonlinear NASA generic transport model.

Closed‐loop performance metrics for fault detection and isolation filter and controller interaction

SUMMARYFault detection and isolation (FDI) filters are typically synthesized for open‐loop or closed‐loop systems. The controller affects the FDI filter performance in the closed‐loop system. FDI filter performance and closed‐loop controller–filter interaction in the presence of uncertain dynamics were investigated as was the role of controller robustness on the FDI filter performance. The NASA Generic Transport Model aircraft was considered as a motivating application. Multiple example scenarios were presented to highlight the utility of FDI filter performance metrics. For example, comparing fault detection performance of different filters under identical uncertain plant dynamics and controller, the effect of different controllers on the FDI filter performance, and the effect of model uncertainty on filter performance. The Generic Transport Model aircraft FDI filter results are validated using worst‐case analysis and linear simulations. Copyright © 2011 John Wiley & Sons, Ltd.

Multivariable Adaptive Control of NASA Generic Transport Aircraft Model with Damage

DOI: 10.2514/1.53258 This paper develops a linearization-based adaptive control technique for control of the nonlinear NASA Generic Transport Model with large parametric and structural uncertainties caused by damage. It presents new studies of linearization of the nonlinear aircraft dynamics in the presence of damage. A state-feedback multivariable model reference adaptive control scheme is developed for the linearized aircraft modelwith damageto ensure stability and asymptotic output tracking for aircraft in the presence of damage. The invariance characteristic of system infinityzerostructuresofthenonlinearandlinearsystemmodelsisinvestigated.Thisworkshowshowalinearization-based modelreference adaptivecontrol schemeusingstate feedbackcan beapplied to anonlinearaircraft dynamicsystem with damage, and the control system simulation of the Generic Transport Model demonstrates some desired performance of such a control system in the neighborhood of the chosen operating point.

Nonlinear region of attraction analysis for flight control verification and validation

Current practice for flight control validation relies heavily on linear analyses and nonlinear, high-fidelity simulations. This process would be enhanced by the addition of nonlinear analyses of the flight control system. This paper demonstrates the use of region of attraction estimation for studying nonlinear effects. A nonlinear polynomial model is constructed for the longitudinal dynamics of NASA's Generic Transport Model aircraft. A polynomial model for the short period dynamics is obtained by decoupling this mode from the nonlinear longitudinal model. Polynomial optimization techniques are applied to estimate region of attractions around trim conditions.

Robust Fault Detection for Commercial Transport Air Data Probes

AbstractAir data probes provide essential sensing capabilities to aircraft. The loss or corruption of air data measurements due to sensor faults jeopardizes an aircraft and its passengers. To address such faults, sensor hardware redundancy is typically combined with a voting system to detect and discard erroneous measurements. This approach relies on redundancy, which may lead to unacceptable increases in system weight and cost. This paper presents an alternative, model-based approach to fault detection for a non-redundant air data system. The model-based fault detection strategy uses robust linear filtering methods to reject exogenous disturbances, e.g. wind, and provide robustness to model errors. The proposed algorithm is applied to NASA's Generic Transport Model aircraft with an air data system modeled based on manufacturer data provided by Goodrich Corporation. The fault detection filters are designed using linearized models at one flight condition. The detection performance is evaluated at a particular reference flight condition using linear analysis and nonlinear simulations.