Data-driven system identification using quadratic embeddings of nonlinear dynamics
This work addresses the challenge of system identification for researchers in dynamical systems and control, offering a novel approach that is incremental over existing methods like SINDy.
The paper tackles the problem of identifying governing equations for nonlinear dynamical systems by proposing QENDy, a method that embeds systems into a higher-dimensional space to achieve quadratic dynamics, and demonstrates its efficacy and accuracy on benchmark problems with comparisons to SINDy and deep learning methods.
We propose a novel data-driven method called QENDy (Quadratic Embedding of Nonlinear Dynamics) that not only allows us to learn quadratic representations of highly nonlinear dynamical systems, but also to identify the governing equations. The approach is based on an embedding of the system into a higher-dimensional feature space in which the dynamics become quadratic. Just like SINDy (Sparse Identification of Nonlinear Dynamics), our method requires trajectory data, time derivatives for the training data points, which can also be estimated using finite difference approximations, and a set of preselected basis functions, called dictionary. We illustrate the efficacy and accuracy of QENDy with the aid of various benchmark problems and compare its performance with SINDy and a deep learning method for identifying quadratic embeddings. Furthermore, we analyze the convergence of QENDy and SINDy in the infinite data limit, highlight their similarities and main differences, and compare the quadratic embedding with linearization techniques based on the Koopman operator.