A Robust Roll Stabilization Controller with Aerodynamic Disturbance and Actuator Failure Consideration

Combining adaptive theory with an advanced second-order sliding mode control algorithm,a roll stabilization controller with aerodynamic disturbance and actuator failure consideration for spinning flight vehicles is proposed in this paper.The presented controller is summarized as an“observer-controller”system.More specifically,an adaptive secondorder sliding mode observer is presented to select the proper design parameters and estimate the knowledge of aerodynamic disturbance and actuator failure,while the proposed roll stabilization control scheme can drive both roll angle and rotation rate smoothly converge to the desired value.Theoretical analysis and numerical simulation results demonstrate the effectiveness of the proposed controller.

Non-synchronous blade vibration analysis of a transonic fan

This study numerically investigates the aeromechanic behavior of a transonic fan model with a flat tip-leading-edge on the NASA rotor 67 test case.Single-passage unsteady calculations at a near stall operating point of 82%design speed show that the dominant frequencies of mass flow were not the harmonics of the rotor rotational frequency.A full-annulus fluid–structure interaction analysis was subsequently carried out to examine the unsteady flows and their interactions with blade vibrations.The results show that the modal displacement of the backward traveling seventh nodal diameter of the second torsion mode grew exponentially,which reveals that the blade vibration was non-synchronous.The vibration pattern indicates that the aerodynamic mode was resonant with the structural vibration mode.Around the rotor tip,the circumferential vortical propagation induced by interactions among the main flow,tip leakage flow,and tip clearance vortex was the source of aerodynamic excitation.To clarify the mechanism of the non-synchronous vibration,the coupling between aerodynamic disturbance and structural response,i.e.,aliasing,was summarized.The frequency spectra of the fluctuating pressure show that an aerodynamic Back-ward Traveling Wave(BTW)was co-aliased to a structural BTW due to the propagation of the cir-cumferential vortex.The correlation between the frequency and free convective speed of the aerodynamic disturbance determined the directions of aliasing.