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Relay-based identification of Aerodynamic and Delay Sensor Dynamics with applications for Unmanned Aerial Vehicles

Anees Peringal, Mohamad Chehadeh, Igor Boiko, Yahya Zweiri

Abstract

In this paper, we present a real-time system identification method based on relay feedback testing with applications to multirotor unmanned aerial vehicles. The proposed identification method provides an alternative to the expensive lab testing of certain UAV dynamic parameters. Moreover, it has the advantage of identifying the parameters that get changed throughout the operation of the UAV, which requires onboard identification methods. The modified relay feedback test (MRFT) is used to generate stable limit cycles at frequency points that reveal the underlying UAV dynamics. The locus of the perturbed relay system (LPRS) is used to predict the exact amplitude and frequency of these limit cycles. Real-time identification is achieved by using the homogeneity properties of the MRFT and the LPRS which are proven in this paper. The proposed identification method was tested experimentally to estimate the aerodynamic parameters as well as the onboard sensor's time delay parameters. The MRFT testing takes a few seconds to perform, and the identification computations take an average of 0.2 seconds to complete in modern embedded computers. The proposed identification method is compared against state-of-the-art alternatives. Advantages in identification accuracy and quantification of uncertainty in estimated parameters are shown.

Relay-based identification of Aerodynamic and Delay Sensor Dynamics with applications for Unmanned Aerial Vehicles

Abstract

In this paper, we present a real-time system identification method based on relay feedback testing with applications to multirotor unmanned aerial vehicles. The proposed identification method provides an alternative to the expensive lab testing of certain UAV dynamic parameters. Moreover, it has the advantage of identifying the parameters that get changed throughout the operation of the UAV, which requires onboard identification methods. The modified relay feedback test (MRFT) is used to generate stable limit cycles at frequency points that reveal the underlying UAV dynamics. The locus of the perturbed relay system (LPRS) is used to predict the exact amplitude and frequency of these limit cycles. Real-time identification is achieved by using the homogeneity properties of the MRFT and the LPRS which are proven in this paper. The proposed identification method was tested experimentally to estimate the aerodynamic parameters as well as the onboard sensor's time delay parameters. The MRFT testing takes a few seconds to perform, and the identification computations take an average of 0.2 seconds to complete in modern embedded computers. The proposed identification method is compared against state-of-the-art alternatives. Advantages in identification accuracy and quantification of uncertainty in estimated parameters are shown.
Paper Structure (21 sections, 30 equations, 5 figures, 3 tables)

This paper contains 21 sections, 30 equations, 5 figures, 3 tables.

Table of Contents

  1. Introduction
  2. Literature Review
  3. Motivation
  4. Contribution
  5. Problem Statement
  6. Identification on the Normalized Subspace
  7. The modified relay feedback test
  8. Proof of homogeneity properties using the LPRS
  9. Unit frequency manifold
  10. UAV Model
  11. Reference Frames and Conventions
  12. Nonlinear Time Delay UAV Model
  13. Dynamics decoupling
  14. Results
  15. Simulation results
  16. ...and 6 more sections

Figures (5)

  • Figure 1: Effect of time and gain scaling of process parameters on MRFT excited oscillations frequency and amplitude. We prove the homogeneity of arbitrary closed-loop linear dynamics with MRFT using the LPRS.
  • Figure 2: A slice of the UFM which corresponds to the known $T_p$ is shown in red in Fig. \ref{['fig:UFM']}. The amplitude of oscillations for this set of processes is shown in Fig. \ref{['fig:UGM']}.
  • Figure 3: The experimental hexarotor UAV Design II.
  • Figure 4: The identified propulsion dynamics are compared to the step test of the actual propulsion system
  • Figure 5: The parameters for the altitude dynamics as well as the attitude dynamics is obtained from the intersection point of the two manifolds