Flight Performance Evaluation of a Conceptual eVTOL System using Nonlinear Simulations

Surmann, Denis; Zrenner, Maria; Myschik, Stephan

doi:10.2514/6.2022-2220

Cited by 5 publications

(1 citation statement)

References 10 publications

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“…Incremental Nonlinear Dynamic Inversion (INDI) is a control method that uses a local linearization of the model to derive a control law to control the defined output and its derivatives, by computation of an increment in the control input, neglecting any state-dependent terms [6]. Through the feedback of derivatives of the system output, such as angular acceleration in the case of inner loop control of an aircraft, unmodeled effects and disturbances are directly measured, and compensated for in the next control increment, which led to an increased popularity of the concept in flight control applications [7][8][9][10][11][12][13]. The controller responds under specific simplifications to the system to disturbances or unmodeled dynamics with the combined dynamics of the actuators and any filtering that is done on the output, and this has been observed in practical experiments as well [14].…”

Section: Introductionmentioning

confidence: 99%

Non-Linear Dynamic Inversion with Actuator Dynamics: an Incremental Control Perspective

Steffensen¹,

Steinert²,

Smeur³

2022

Preprint

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In this paper, we derive a Nonlinear Dynamic Inversion (NDI) control law for a non-linear system with first order linear actuators, and compare it to Incremental Nonlinear Dynamic Inversion (INDI), which has gained popularity in recent years. It is shown that for first order actuator dynamics, INDI approximates the corresponding NDI control law arbitrarily well under the condition of sufficiently fast actuators. If the actuator bandwidth is low compared to changes in the states, the derived NDI control law has the following advantages compared to INDI: 1) compensation of state derivative terms 2) well defined error dynamics and 3) exact tracking of a reference model, independent of error controller gains in nominal conditions. The comparison of the INDI control law with the well established control design method NDI adds to the understanding of incremental control. It is additionally shown how to quantify the deficiency of the INDI control law with respect to the exact NDI law for actuators with finite bandwidth. The results are confirmed through simulation results of the rolling motion of a fixed wing aircraft.

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