Bayesian Logical Data Analysis for the Physical Sciences: References

In this paper, the problem of active fault tolerant control for a reusable launch vehicle (RLV) with actuator fault using both adaptive and sliding mode techniques is investigated. Firstly, the kinematic equations and dynamic equations of RLV are given, which represent the characteristics of RLV in reentry flight phase. For the dynamic model of RLV in faulty case, a fault detection scheme is proposed by designing a nonlinear fault detection observer. Then, an active fault tolerant tracking strategy for RLV attitude control systems is presented by making use of both adaptive control and sliding mode control techniques, which can guarantee the asymptotic output tracking of the closed-loop attitude control systems in spite of actuator fault. Finally, simulation results are given to demonstrate the effectiveness of the developed fault tolerant control scheme.

Active fault tolerant control design for reusable launch vehicle using adaptive sliding mode technique

Flight Vehicle System Identification: A Time-Domain MethodologyJategaonkarR. V., Progress in Aeronautics and Astronautics, 2nd ed., AIAA, Reston, VA, 2015, 648 pp., $119.95.

This paper presents a combined feedback and feedforward active load alleviation system and its associated design and tuning methodology The feedback part is strongly structured and its robust performance across the flight envelope is ensured by the use of a multi-model and multi-objective controller design approach The feedforward function is based on a Doppler LIDAR sensor and the processing of the measurements as well as their physical interpretation combines various ideas from the system identification, the signal processing, and the control design domains The proposed solution remains very easy to use and tune, thanks to a limited number of parameters that can easily be interpreted physically and that exhibit only very little and very predictable couplings The performance and behavior of the active load alleviation functions is shown extensively based on a representative flexible long range aircraft model (based on the Airbus XRF1 configuration)

/pdf/combined-feedback-and-lidar-based-feedforward-active-load-3uz7ffib43.pdf

Combined Feedback and LIDAR-Based Feedforward Active Load Alleviation

The low-biased, fast, airborne, short-range, and range-resolved determination of atmospheric wind speeds plays a key role in wake vortex and turbulence mitigation strategies and would improve flight safety, comfort, and economy. In this work, a concept for an airborne, UV, direct-detection Doppler wind lidar receiver is presented. A monolithic, tilted, field-widened, fringe-imaging Michelson interferometer (FWFIMI) combines the advantages of low angular sensitivity, high thermo-mechanical stability, independence of the specific atmospheric conditions, and potential for fast data evaluation. Design and integration of the FWFIMI into a lidar receiver concept are described. Simulations help to evaluate the receiver design and prospect sufficient performance under different atmospheric conditions.

/pdf/design-of-a-monolithic-michelson-interferometer-for-fringe-2v6i6pgyki.pdf

Design of a monolithic Michelson interferometer for fringe imaging in a near-field, UV, direct-detection Doppler wind lidar.

In this paper, in-flight remote sensing technologies are considered for two applications: active load alleviation of gust and turbulence and wake impact alleviation. The paper outlines the strong commonalities in terms of sensors and measurement post-processing algorithms and presents also the few differences and their consequences in terms of post-processing. The way the post-processing is being made is detailed before showing results for both applications based on a complete and coupled simulation (aircraft reaction due to disturbances and control inputs during the simulation is influencing the sensor measurements). The performances in terms of wind reconstruction quality for the gust/turbulence case and in terms of wake impact alleviation performance for the wake vortex case are shown based on simulations and are very promising.

/pdf/in-flight-remote-sensing-and-identification-of-gusts-21g55g3nz4.pdf

In-flight Remote Sensing and Identification of Gusts, Turbulence, and Wake Vortices Using a Doppler LIDAR

This paper presents an overview of the DLR activities on active load alleviation in the CleanSky Smart Fixed Wing Aircraft project. The investigations followed two main research directions: the multi-objective, multi-model, structured controller design for the feedback load alleviation part and the use of Doppler LIDAR technologies for gust/turbulence anticipation. On this latter topic, the prior work made in the AWIATOR European FP6 project constituted a reference in terms of demonstrations and the objective was not to repeat these previous investigations with a real sensor in flight test but to develop new ideas for the exploitation of the Doppler LIDAR measurements for gust alleviation purposes. Very fruitful exchanges between industry partners and research organizations took place during this project and all the work presented in this paper has been made using a generic long-range benchmark provided by Airbus on the basis of the XRF-1 model.

/pdf/gust-load-alleviation-for-a-long-range-aircraft-with-and-z8kw3xv6ov.pdf

Gust load alleviation for a long-range aircraft with and without anticipation

This paper presents a sensitivity study of a wake vortex impact alleviation system based on an airborne forward-looking Doppler LiDAR sensor. The basic principle of the system is to use this sensor to measure the wind remotely ahead of the aircraft. On the basis of these measurements the system estimates whether a wake vortex is located in front of the aircraft. If this is the case, the wake vortex characteristics are identified and the control deflections countervailing the wake-induced aircraft response are computed and applied. An integrated simulation environment comprising a full nonlinear 6-DoF A320 model (with control laws), wake vortex models, and the wake impact alleviation algorithms was developed. The LiDAR sensor subsystem has many design parameters that influence the overall performance in a complex way, which makes it difficult to derive adequate requirements. The presented parameter study provides first insights into the role of each parameter as well as some adequate parameter combinations.

Airborne Doppler LiDAR Sensor Parameter Analysis for Wake Vortex Impact Alleviation Purposes

This article presents an Hinfin control design method based on the acceleration sensitivity (AS) function. This approach can be applied to any fully actuated generalized second order system. In this framework, classical modal specifications (pulsations / damping ratios) are expressed in terms of Hinfin templates allowing other frequency domain specifications to be taken into account. Finally, a comparison between AS with a more classical Hinfin approach and with the cross standard form (CSF) is presented. A 2 degrees of freedom spring-damper-mass academic example is used to illustrate the properties of the AS, though this method was developed and is used for atmospheric reentry control design.

Nicolas Fezans

Papers

Combined Feedback and LIDAR-Based Feedforward Active Load Alleviation

In-flight Remote Sensing and Identification of Gusts, Turbulence, and Wake Vortices Using a Doppler LIDAR

Gust load alleviation for a long-range aircraft with and without anticipation

Airborne Doppler LiDAR Sensor Parameter Analysis for Wake Vortex Impact Alleviation Purposes

H ∞ control design for generalized second order systems based on acceleration sensitivity function