Asymmetric Stiffness Pitch Control - Transonic Pitch-Up Mitigation for the EF2000

Hanel, Martin; Osterhuber, Robert; Höfinger, Gerhard

doi:10.2514/6.2004-4752

Cited by 5 publications

(2 citation statements)

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“…Recently, Kim et al [21][22][23][24][25] has the proposed hybrid INDI control method which feedbacks the measured and calculated angular accelerations in highly unstable flight and transonic flight regime. In the flight conditions where wing flow separation occurs due to the unstable flow field, the symmetrical or asymmetrical flow separation may generate a sudden large imbalance in lift between wing panels [26,27]. These effects generate unexpected aircraft motions that degrade flying qualities and performance of the aircraft, threaten the pilot's health, overstress the aircraft structure and lead to instability of the structural load for a turning flight with high gravity.…”

Section: Introductionmentioning

confidence: 99%

Stability Margin and Structural Coupling Analysis of a Hybrid INDI Control for the Fighter Aircraft

Kim

Koh

et al. 2021

Int. J. Aeronaut. Space Sci.

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The sensor-based incremental nonlinear dynamic inversion (INDI) using angular acceleration measured by inertial measurement unit (IMU) sensor is a very robust control method on various model uncertainties when the aircraft maneuvers with moderate angle-of-attack (AoA) and high gravity in transonic speed flight conditions. However, the measured angular acceleration has time delay characteristics due to actuator and aircraft dynamics, IMU sensor dynamics, differential angular rate and structural coupling filter (SCF) and so on. These characteristics of angular acceleration feedback reduce dramatically the stability margin of the control system. In this paper, we propose the synchronization filter design method of the control surface feedback path for improving stability margin, based on the proposed hybrid INDI control method using error between the angular acceleration measured from IMU sensor and the angular acceleration calculated from on-board model (OBM) and control surface feedback. To evaluate the proposed control method, we perform the frequency-domain linear analysis and the time-domain simulation. As a result of the evaluation, synchronization method of control surface feedback not only improves the stability margin characteristics of the control system but also eliminates the structural coupling in low frequency range by designing the control surface command feedback using actuator command which is the output of flight control computer (FLCC).

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Section: Introductionmentioning

confidence: 99%

Stability Margin and Structural Coupling Analysis of a Hybrid INDI Control for the Fighter Aircraft

Kim

Koh

et al. 2021

Int. J. Aeronaut. Space Sci.

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“…To solve these problems, most of fighter aircraft such as F-18 15 and FA-50 16 adopt the Gbucket, which uses predefined scheduled control surface deflection to reduce the unexpected pitch motion in the specific transonic flight regime. Recently, "asymmetric stiffness" control, which uses additional AoA feedback loop, has been designed to more effectively reduce the unexpected pitch motion in case that the motion is imminent in the Eurofighter Typhoon 17 development program.…”

Section: Introductionmentioning

confidence: 99%

Control law design to improve the unexpected pitch motion in slow down turn maneuver

Kim¹,

Jin²,

Koh³

et al. 2021

Proceedings of the Institution of Mechanical Engineers, Part G:

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The highly maneuverable fighter aircraft is exposed to unexpected pitch motion such as over-Nz (normal acceleration) and Nz-drop characteristics in transonic and supersonic flight conditions with moderate angle of attack. These characteristics not only degrade flying qualities by destabilizing the aircraft but also threaten flight safety by increasing the structural load. This article proposes an additional augmentation control in the incremental nonlinear dynamic inversion structure, which feeds back the error of pitch angular acceleration to mitigate unexpected pitch motion in slow down turn maneuver. We evaluate the stability, flying qualities, and robustness of the proposed control system by performing the frequency-domain linear analysis and the time-domain numerical simulations based on the mathematical model of advanced trainer aircraft. As a result of the evaluation, the additional augmentation control further improves flying qualities and deceleration performance of the aircraft by decreasing over-Nz and Nz-drop characteristics in high-Nz maneuvering in the transonic flight condition as well as ensuring the stability and robustness of the control system against the major uncertainty factors of the aircraft system compared to the existing transonic pitching moment compensation (TPMC) control in which the predefined scheduling for Nz feedback is used.

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Backup Controller for Large Transport Aircraft with Insufficient Natural Stability

Wang¹,

Zhang²,

Holzapfel³

et al. 2017

Journal of Guidance, Control, and Dynamics

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Asymmetric Stiffness Pitch Control - Transonic Pitch-Up Mitigation for the EF2000

Cited by 5 publications

References 0 publications

Stability Margin and Structural Coupling Analysis of a Hybrid INDI Control for the Fighter Aircraft

Stability Margin and Structural Coupling Analysis of a Hybrid INDI Control for the Fighter Aircraft

Control law design to improve the unexpected pitch motion in slow down turn maneuver

Backup Controller for Large Transport Aircraft with Insufficient Natural Stability

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