Flight Control Design using Incremental Nonlinear Dynamic Inversion with Fixed-lag Smoothing Estimation
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ORIGINAL PAPER
Flight Control Design using Incremental Nonlinear Dynamic Inversion with Fixed-lag Smoothing Estimation Tito J. Ludeña Cervantes1 · Seong H. Choi1 · Byoung S. Kim1 Received: 15 June 2019 / Revised: 22 January 2020 / Accepted: 18 March 2020 © The Korean Society for Aeronautical & Space Sciences 2020
Abstract In this study, a flight control design strategy based on incremental nonlinear dynamic inversion (INDI) and smoothing algorithm is presented. The INDI is an enhanced version of the nonlinear dynamic inversion technique with a better robust performance. It reduces the aircraft model dependence via the feedback information of the state derivative, that is, angular acceleration for the aircraft attitude motion (or angular velocity related to the wind axis parameters). However, the state derivatives cannot always be obtained by direct measurement, thus they need to be estimated on-line. Moreover, taking into account that INDI requires one-step delay of state derivative and the fact that the inertial measurement unit (IMU) operates faster than the flight control computer (FCC), there will be additional information that can be used to improve the estimation. Therefore, a fixed-lag smoothing algorithm based on a discrete Kalman filter is proposed for angular velocity and angular acceleration estimation. The smoother utilizes the state variable from the sensor measurement and thus dealing with noise and delay. Keywords Incremental nonlinear dynamic inversion · Smoothing algorithm · Control augmentation system
Abbreviation
Subscripts
ρ V b S c m J p, q, r
k cmd 0 ˆ, ~
α, β θ, φ δe, δr, δa L, M, N Da , Y a , L a X T, Y T, Z T vin vout C l , C m , C n,
B 1
Air density (kg/m3 ) Airspeed (m/s) Wingspan (m) Wing surface area (m2 ) Mean aerodynamic chord (m) Mass of the aircraft (kg) Moment of inertia matrix of the aircraft (kg m2 ) Roll, pitch and yaw rates around x, y, z body axis (rad/s) Angle of attack and sideslip angle (rad) Pitch and roll angle (rad) Elevator, rudder and aileron deflection (rad) Moments around x, y, z body axis (N m) Total aerodynamic drag, total aerodynamic sideslip force, and lift force (N) Thrust force along x, y, z body axis (N) Inner loop virtual control (rad/s2 ) Outer loop virtual control (rad/s) Aerodynamic moment coefficients
Tito J. Ludeña Cervantes [email protected] Aerospace Department, Gyeongsang National University, Gyeongsangnam-do, Jinju 52828, South Korea
Discrete index Commanded Point at the current solution of the system Estimation, augmentation of a vector or matrix
1 Introduction Flight control design for super maneuverable aircraft requires the use of nonlinear control approaches to overcome the limitations of linear control techniques. There exist a variety of nonlinear control techniques such as backstepping, nonlinear dynamic inversion (NDI), and sliding mode control. Among them, NDI has proved to be a suitable controller design approach for fighter aircrafts and has been applied for high angle of attack flight [1] and super maneuverable aircrafts [
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