rasmussen
Identification of Gaussian Process State Space Models
Stefanos Eleftheriadis, Tom Nicholson, Marc Deisenroth, James Hensman
The Gaussian process state space model (GPSSM) is a non-linear dynamical system, where unknown transition and/or measurement mappings are described by GPs. Most research in GPSSMs has focussed on the state estimation problem, i.e., computing a posterior of the latent state given the model. However, the key challenge in GPSSMs has not been satisfactorily addressed yet: system identification, i.e., learning the model. To address this challenge, we impose a structured Gaussian variational posterior distribution over the latent states, which is parameterised by a recognition model in the form of a bi-directional recurrent neural network. Inference with this structure allows us to recover a posterior smoothed over sequences of data. We provide a practical algorithm for efficiently computing a lower bound on the marginal likelihood using the reparameterisation trick. This further allows for the use of arbitrary kernels within the GPSSM. We demonstrate that the learnt GPSSM can efficiently generate plausible future trajectories of the identified system after only observing a small number of episodes from the true system.
Scientists suggest modifying cars to hit fewer hedgehogs
Placing ultrasound repellants on cars could protect the spiny mammals. Up to one in three hedgehogs in local populations die on roads. Breakthroughs, discoveries, and DIY tips sent six days a week. When it comes to how animals use ultrasound, chances are you immediately think of bats and their amazing echolocation ability. However, researchers have discovered another--arguably much cuter--animal that can also hear ultrasound, with significant implications for its conservation.