Physical subspace identification for helicopters

Download

index.pdf

Date

2019

Author

Avcıoğlu, Sevil

Metadata

Show full item record

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

Item Usage Stats

283
views

152
downloads

Subspace identification is a powerful tool due to its well-understood techniques based on linear algebra (orthogonal projections and intersections of subspaces) and numerical methods like QR and singular value decomposition. However, the state space model matrices which are obtained from conventional subspace identification algorithms are not necessarily associated with the physical states. This can be an important deficiency when physical parameter estimation is essential. This holds for the area of helicopter flight dynamics where physical parameter estimation is mainly conducted for mathematical model improvement, aerodynamic parameter validation and flight controller tuning. The main objective of this study is to obtain helicopter physical parameters from subspace identification results. In order to achieve this objective, N4SID subspace identification algorithm is implemented for a multi-role helicopter using both FLIGHTLAB simulation and real flight test data. After obtaining state space matrices via subspace identification, constrained nonlinear optimization methodologies are utilized for extracting the physical parameters. The state space matrices are transformed into equivalent physical forms via both “Sequential Quadratic Programming” and “Interior Point” nonlinear optimization algorithms. The required objective function is generated by summing the square of similarity transformation equations. The constraints are selected with physical insight. Many runs are conducted for randomly selected initial conditions. It can be concluded that all of the parameters with high significance can be obtained with a high level of accuracy for the data obtained from the linear model. This strongly supports the idea behind this study. Results for the data obtained from the nonlinear model are also evaluated to be satisfactory in the light of statistical error analysis. Results for the real flight test data are also evaluated to be good for the helicopter modes that are properly excited in the flight tests.

Subject Keywords

Helicopters, Helicopters Aerodynamics., Subspace Identification, Parameter Estimation, Similarity Transformation, Optimization, Helicopter Dynamics.

URI

http://etd.lib.metu.edu.tr/upload/12623229/index.pdf
https://hdl.handle.net/11511/43399

Collections

Graduate School of Natural and Applied Sciences, Thesis

Suggestions

OpenMETU
Core

Identification of Physical Helicopter Models Using Subspace Identification Avcioglu, Sevil; Kutay, Ali Türker; Leblebicioğlu, Mehmet Kemal (2020-04-01) Subspace identification is a powerful tool due to its well-understood techniques based on linear algebra (orthogonal projections and intersections of subspaces) and numerical methods like singular value decomposition. However, the state space model matrices, which are obtained from conventional subspace identification algorithms, are not necessarily associated with the physical states. This can be an important deficiency when physical parameter estimation is essential. This holds for the area of helicopter ...
Similarity matrix framework for data from union of subspaces Aldroubi, Akram; Sekmen, Ali; Koku, Ahmet Buğra; Cakmak, Ahmet Faruk (2018-09-01) This paper presents a framework for finding similarity matrices for the segmentation of data W = [w(1)...w(N)] subset of R-D drawn from a union U = boolean OR(M)(i=1) S-i, of independent subspaces {S-i}(i=1)(M), of dimensions {d(i)}(i=1)(M). It is shown that any factorization of W = BP, where columns of B form a basis for data W and they also come from U, can be used to produce a similarity matrix Xi w. In other words, Xi w(i, j) not equal 0, when the columns w(i) and w(j) of W come from the same subspace, ...
Modeling Electromagnetic Scattering from Random Array of Objects by Form Invariance of Maxwell's Equations ÖZGÜN, ÖZLEM; Kuzuoğlu, Mustafa (2015-07-24) Electromagnetic scattering from a random array of objects is modeled by using special coordinate transformations that are based on the form invariance property of Maxwell's equations. The main motivation is to perform multiple realizations of Monte Carlo simulations corresponding to different positions of objects in an efficient way by using a single mesh. This is achieved by locating transformation media within the computational domain. The proposed approach is applied to finite element method and tested b...
Numerical Solution of Multi-scale Electromagnetic Boundary Value Problems by Utilizing Transformation-Based Metamaterials Ozgun, Ozlem; Kuzuoğlu, Mustafa (2011-06-23) We present numerical solution techniques for efficiently handling multi-scale electromagnetic boundary value problems having fine geometrical details or features, by utilizing spatial coordinate transformations. The principle idea is to modify the computational domain of the finite methods (such as the finite element or finite difference methods) by suitably placing anisotropic metamaterial structures whose material parameters are obtained by coordinate transformations, and hence, to devise easier and effic...
LCD codes from tridiagonal Toeplitz matrices Shi, Minjia; Özbudak, Ferruh; Xu, Li; Solé, Patrick (2021-10-01) Double Toeplitz (DT) codes are codes with a generator matrix of the form (I,T) with T a Toeplitz matrix, that is to say constant on the diagonals parallel to the main. When T is tridiagonal and symmetric we determine its spectrum explicitly by using Dickson polynomials, and deduce from there conditions for the code to be LCD. Using a special concatenation process, we construct optimal or quasi-optimal examples of binary and ternary LCD codes from DT codes over extension fields.

Citation Formats

S. Avcıoğlu, “Physical subspace identification for helicopters,” Thesis (Ph.D.) -- Graduate School of Natural and Applied Sciences. Aerospace Engineering., Middle East Technical University, 2019.