67 research outputs found
Episodic Gaussian Process-Based Learning Control with Vanishing Tracking Errors
Due to the increasing complexity of technical systems, accurate first
principle models can often not be obtained. Supervised machine learning can
mitigate this issue by inferring models from measurement data. Gaussian process
regression is particularly well suited for this purpose due to its high
data-efficiency and its explicit uncertainty representation, which allows the
derivation of prediction error bounds. These error bounds have been exploited
to show tracking accuracy guarantees for a variety of control approaches, but
their direct dependency on the training data is generally unclear. We address
this issue by deriving a Bayesian prediction error bound for GP regression,
which we show to decay with the growth of a novel, kernel-based measure of data
density. Based on the prediction error bound, we prove time-varying tracking
accuracy guarantees for learned GP models used as feedback compensation of
unknown nonlinearities, and show to achieve vanishing tracking error with
increasing data density. This enables us to develop an episodic approach for
learning Gaussian process models, such that an arbitrary tracking accuracy can
be guaranteed. The effectiveness of the derived theory is demonstrated in
several simulations
Real-time Uncertainty Decomposition for Online Learning Control
Safety-critical decisions based on machine learning models require a clear
understanding of the involved uncertainties to avoid hazardous or risky
situations. While aleatoric uncertainty can be explicitly modeled given a
parametric description, epistemic uncertainty rather describes the presence or
absence of training data. This paper proposes a novel generic method for
modeling epistemic uncertainty and shows its advantages over existing
approaches for neural networks on various data sets. It can be directly
combined with aleatoric uncertainty estimates and allows for prediction in
real-time as the inference is sample-free. We exploit this property in a
model-based quadcopter control setting and demonstrate how the controller
benefits from a differentiation between aleatoric and epistemic uncertainty in
online learning of thermal disturbances.Comment: Submitted to ICRL 2021, updated after rebuttal perio
Single-Model Attribution of Generative Models Through Final-Layer Inversion
Recent groundbreaking developments on generative modeling have sparked
interest in practical single-model attribution. Such methods predict whether a
sample was generated by a specific generator or not, for instance, to prove
intellectual property theft. However, previous works are either limited to the
closed-world setting or require undesirable changes of the generative model. We
address these shortcomings by proposing FLIPAD, a new approach for single-model
attribution in the open-world setting based on final-layer inversion and
anomaly detection. We show that the utilized final-layer inversion can be
reduced to a convex lasso optimization problem, making our approach
theoretically sound and computationally efficient. The theoretical findings are
accompanied by an experimental study demonstrating the effectiveness of our
approach, outperforming the existing methods
Strategyproofness and Proportionality in Party-Approval Multiwinner Elections
In party-approval multiwinner elections the goal is to allocate the seats of
a fixed-size committee to parties based on the approval ballots of the voters
over the parties. In particular, each voter can approve multiple parties and
each party can be assigned multiple seats. Two central requirements in this
setting are proportional representation and strategyproofness. Intuitively,
proportional representation requires that every sufficiently large group of
voters with similar preferences is represented in the committee.
Strategyproofness demands that no voter can benefit by misreporting her true
preferences. We show that these two axioms are incompatible for anonymous
party-approval multiwinner voting rules, thus proving a far-reaching
impossibility theorem. The proof of this result is obtained by formulating the
problem in propositional logic and then letting a SAT solver show that the
formula is unsatisfiable. Additionally, we demonstrate how to circumvent this
impossibility by considering a weakening of strategy\-proofness which requires
that only voters who do not approve any elected party cannot manipulate. While
most common voting rules fail even this weak notion of strategyproofness, we
characterize Chamberlin--Courant approval voting within the class of Thiele
rules based on this strategyproofness notion.Comment: Appears in the 37th AAAI Conference on Artificial Intelligence
(AAAI), 202
Uncertainty evaluation for velocity–area methods
Velocity–area methods are used for flow rate calculation in various industries. Applied within a fully turbulent flow regime, modest uncertainties can be expected. If the flow profile cannot be described as “log-like”, the recommended measurement positions and integration techniques exhibit larger errors. To reduce these errors, an adapted measurement scheme is proposed. The velocity field inside a Venturi contour is simulated using computational fluid dynamics and validated using laser Doppler anemometry. An analytical formulation for the Reynolds number dependence of the profile is derived. By assuming an analytical velocity profile, an uncertainty evaluation for the flow rate calculation is performed according to the “Guide to the expression of uncertainty in measurement”. The overall uncertainty of the flow rate inside the Venturi contour is determined to be 0.5 % compared to 0.67 % for a fully developed turbulent flow
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