Online Monitoring of Aircraft Modal Parameters during Flight Test based on permanent Output-Only Modal Analysis

Jelicic, Goran; Schwochow, Jan; Govers, Yves; Sinske, Julian; Buchbach, Ralf; Springer, Julian

doi:10.2514/6.2017-1825

Cited by 17 publications

(8 citation statements)

References 3 publications

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“…The largest mismatch is visible in the channel from the blended inputs (flap deflections) to the blended outputs (acceleration measurements), where it is assumed that free play in the pitch excitation system yields smaller amplitudes than expected. During the experiments, the aeroelastic modes of interest are directly identified by means of a real-time capable output-only modal analysis, see [20] and [21] for more details. For the first wing bending mode, the natural frequency remains almost constant while its damping increases with airspeed.…”

Section: A Model Validationmentioning

confidence: 99%

Aeroelastic Modeling and Control of an Experimental Flexible Wing

Pusch

Ossmann

Kier

et al. 2019

AIAA Scitech 2019 Forum

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Structural weight reduction and high aspect ratio wings play a key role in improving the performance of modern transport aircraft. This leads to a highly flexible aircraft structure which is sensitive to external disturbances like gusts. To counteract this undesired effect, active control is a promising technology. In this paper, a gust load alleviation controller is designed for a wind tunnel model of a flexible wing with various trailing edge flaps and acceleration sensors. For a sophisticated model-based controller design, a detailed aeroelastic model is derived describing the coupling of structural dynamics and aerodynamics. Additionally, actuator dynamics and structural modes are identified and used to improve model accuracy. Subsequently, the weakly damped first wing bending mode, which causes high structural loads, is isolated via H 2-optimal blending of control inputs and measurement outputs. In this way, a gain-scheduled single-input single-output controller can be designed to control the desired aeroelastic mode. Eventually, the great potential of the proposed control approach is verified by a wind tunnel test including different gust excitations and varying airspeeds.

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Section: A Model Validationmentioning

confidence: 99%

Aeroelastic Modeling and Control of an Experimental Flexible Wing

Pusch

Ossmann

Kier

et al. 2019

AIAA Scitech 2019 Forum

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show abstract

“…The aeroelastic modes of the model are slightly different and vary with wind speed. To verify the aeroelastic modes of the model, on-line estimation techniques described in References [27,28] have been performed during the wind tunnel experiments. For example, the first wing bending mode has a damping of 0.1 when considering aerodynamic forces at a wind speed of 40 m/s compared to 0.004 without them.…”

Section: Modelingmentioning

confidence: 99%

Fault Tolerant Control of an Experimental Flexible Wing

Ossmann

Pusch

2019

Aerospace

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Active control techniques are a key factor in today’s aircraft developments to reduce structural loads and thereby enable highly efficient aircraft designs. Likewise, increasing the autonomy of aircraft systems aims to maintain the highest degree of operational performance also in fault scenarios. Motivated by these two aspects, this article describes the design and validation of a fault tolerant gust load alleviation control system on a flexible wing in a wind tunnel. The baseline gust load alleviation controller isolates and damps the weakly damped first wing bending mode. The mode isolation is performed via an H 2 -optimal blending of control inputs and measurement outputs, which allows for the design of a simple single-input single-output controller to actively damp the mode. To handle actuator faults, a control allocation scheme based on quadratic programming is implemented, which distributes the required control energy to the remaining available control surfaces. The control allocation is triggered in fault scenarios by a fault detection scheme developed to monitor the actuators using nullspace based filter design techniques. Finally, the fault tolerant control scheme is verified by wind tunnel experiments.

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“…Table 1 summarizes the measurement points acquired during flight vibration testing that are presented in this document. Modal analysis performed on these datasets is presented in [8].…”

Section: Comparison Of Various Excitation Techniques In Flightmentioning

confidence: 99%

“…It is based on the assumption that only stochastic excitation forces are applied to a structure. During DLR's internal ALLEGRA project (2012)(2013)(2014)(2015)(2016)) the DLR Institute of Aeroelasticity optimised the computational highly demanding methods to such an extent that they reached nearly real-time capability [6][7][8]. The developed system has already shown real-time aeroelastic identification capability within several wind tunnel testing campaigns in the transonic wind tunnel Göttingen (TWG) and the cryogenic wind tunnel in cologne (KKK) from German Dutch Wind Tunnels (DNW) [6,9,10].…”

Section: Introductionmentioning

confidence: 99%

HALO flight test with instrumented under-wing stores for aeroelastic and load measurements in the DLR project iLOADS

et al. 2018

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HALO (High Altitude and Long Range Research Aircraft), the atmospheric research aircraft of the German Aerospace Center (DLR), can be equipped with under-wing stores at different wing positions to transport scientific instruments for atmospheric research. The particle measurement system (PMS) carrier is such an external store which can carry three instruments at the same time per wing. Any modifications on an aircraft must be tested numerically and experimentally to ensure the structural integrity of the aircraft for all flight conditions. Load and flutter analyses can be validated with flight test data. For flight test, the aircraft and the under-wing stores of HALO must be equipped with acceleration and strain sensors. To reduce flight test time it is necessary to make quick decisions during the flight test. Therefore the DLR Institute of Aeroelasticity in Göttingen has developed a real-time analysis procedure for online identification of modal parameters like eigenfrequencies, damping ratios and mode shapes. These parameters vary with flight conditions and are necessary to analyse the aeroelastic stability of the system. The department of loads analysis and aeroelastic design and the department of structural dynamics and system identification have tested the newly developed procedure in 14 flight hours on the HALO. A network of three distributed data acquisition modules enabled the recording of the flight test instrumentation with 51 accelerometers and 16 strain gauge bridges. The measured data were distributed online on several computers where the newly developed software was implemented, allowing an instantaneous analysis of the structural dynamics behaviour and loads in flight. This paper provides an overview of the conducted flight vibration tests with HALO. It also shows the capability of the newly developed online monitoring system for aeroelastic identification.

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Online Monitoring of Aircraft Modal Parameters during Flight Test based on permanent Output-Only Modal Analysis

Cited by 17 publications

References 3 publications

Aeroelastic Modeling and Control of an Experimental Flexible Wing

Aeroelastic Modeling and Control of an Experimental Flexible Wing

Fault Tolerant Control of an Experimental Flexible Wing

HALO flight test with instrumented under-wing stores for aeroelastic and load measurements in the DLR project iLOADS

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