Extracting Interpretable Physical Parameters from Spatiotemporal Systems using Unsupervised Learning

Experimental data is often affected by uncontrolled variables that make analysis and interpretation difficult. For spatiotemporal systems, this problem is further exacerbated by their intricate dynamics. Modern machine learning methods are well-suited for modeling complex datasets, but to be effective in science, the result needs to be interpretable. We demonstrate an unsupervised learning technique for extracting interpretable physical parameters from noisy spatiotemporal data and for building a transferable model of the system. In particular, we implement a physics-informed architecture based on variational autoencoders that is designed for analyzing systems governed by partial differential equations (PDEs). The architecture is trained end-to-end and extracts latent parameters that parameterize the dynamics of a learned predictive model for the system. To test our method, we train the architecture on simulated data from a variety of PDEs with varying dynamical parameters that act as uncontrolled variables. Specifically, we examine the Kuramoto-Sivashinsky equation with varying viscosity damping parameter, the nonlinear Schr\"odinger equation with varying nonlinearity coefficient, and the convection-diffusion equation with varying diffusion constant and drift velocity. Numerical experiments show that our method can accurately identify relevant parameters and extract them from raw and even noisy spatiotemporal data (tested with roughly 10% added noise). These extracted parameters correlate well (linearly with $R^2>0.95$) with the ground truth physical parameters used to generate the datasets. Our method for discovering interpretable latent parameters in spatiotemporal systems will allow us to better analyze and understand real-world phenomena and datasets, which often have uncontrolled variables that alter the system dynamics and cause varying behaviors that are difficult to disentangle.