Model-based fault-tolerant control (FTC) often consists of two distinct steps: fault detection & isolation (FDI), and fault accommodation. In this work we investigate posing fault-tolerant control as a single Baye...
Model-based fault-tolerant control (FTC) often consists of two distinct steps: fault detection & isolation (FDI), and fault accommodation. In this work we investigate posing fault-tolerant control as a single Bayesian inference problem. Previous work showed that precision learning allows for stochastic FTC without an explicit fault detection step. While this leads to implicit fault recovery, information on sensor faults is not provided, which may be essential for triggering other impact-mitigation actions. In this paper, we introduce a precision-learning based Bayesian FTC approach and a novel beta residual for fault detection. Simulation results are presented, supporting the use of beta residual against competing approaches.
Neural architecture search (NAS) has low efficiency in evaluating a large number of candidate architectures. As an efficient evaluation method, accuracy predictor-based NAS algorithms have become popular because the p...
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Neural architecture search (NAS) has low efficiency in evaluating a large number of candidate architectures. As an efficient evaluation method, accuracy predictor-based NAS algorithms have become popular because the performance (accuracy) can be evaluated without training the candidate architectures. However, accuracy predictors still need some evaluated architectures that are difficult to train for achieving promising performance. In order to break this bottleneck, we investigate a semi-supervised accuracy predictor-based evolutionary NAS method (MSNAS) which requires only a small number of evaluated neural architectures. The accuracy predictor obtains high prediction performance by extracting the evaluated architectures, strong regressors and truncation mechanism. To find truly high-accuracy candidate architectures more easily, the multi-objective optimization method is presented to trade-off the prediction accuracy and confidence of candidate architectures. The MSNAS variants from different strong regressors are employed to validate the competitive performance of the MSNAS on NAS-Bench 201.
This paper studies a class of strongly monotone games involving non-cooperative agents that optimize their own time-varying cost functions. We assume that the agents can observe other agents' historical actions an...
This paper studies a class of strongly monotone games involving non-cooperative agents that optimize their own time-varying cost functions. We assume that the agents can observe other agents' historical actions and choose actions that best respond to other agents' previous actions; we call this a best response scheme. We start by analyzing the convergence rate of this best response scheme for standard time-invariant games. Specifically, we provide a sufficient condition on the strong monotonicity parameter of the time-invariant games under which the proposed best response algorithm achieves exponential convergence to the static Nash equilibrium. We further illustrate that this best response algorithm may oscillate when the proposed sufficient condition fails to hold, which indicates that this condition is tight. Next, we analyze this best response algorithm for time-varying games where the cost functions of each agent change over time. Under similar conditions as for time-invariant games, we show that the proposed best response algorithm stays asymptotically close to the evolving equilibrium. We do so by analyzing both the equilibrium tracking error and the dynamic regret. Numerical experiments on economic market problems are presented to validate our analysis.
In today’s interconnected world, securely sharing data between devices and systems is crucial. End-to-end big data sharing enables seamless communication and collaboration, but also presents data security and control...
In today’s interconnected world, securely sharing data between devices and systems is crucial. End-to-end big data sharing enables seamless communication and collaboration, but also presents data security and control challenges. To ensure data confidentiality and integrity, data usage control is important. We designed a control policy language to provide a unified way to describe data usage control policies. The language can embed common scripting languages for policy description and can describe policy rules for various access control models like ABAC and RBAC, as well as data usage obligations and conditions. By separating the policy description model rules and embedding them in the data, only a small set of rules needs to be transmitted for data using the same policy model, without retransmit data usage policies. We implemented a policy engine on Linux. Experiments show its transmission and storage overhead is reduced by 90% compared to directly attaching XACML to data.
This paper constructs a non-cooperative/cooperative stochasticdifferential game model to prove that the optimal strategies trajectory ofagents in a system with a topological configuration of a Multi-Local-Worldgraph w...
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This paper constructs a non-cooperative/cooperative stochasticdifferential game model to prove that the optimal strategies trajectory ofagents in a system with a topological configuration of a Multi-Local-Worldgraph would converge into a certain attractor if the system’s configuration isfixed. Due to the economics and management property, almost all systems aredivided into several independent Local-Worlds, and the interaction betweenagents in the system is more complex. The interaction between agents inthe same Local-World is defined as a stochastic differential cooperativegame;conversely, the interaction between agents in different Local-Worldsis defined as a stochastic differential non-cooperative game. We construct anon-cooperative/cooperative stochastic differential game model to describethe interaction between agents. The solutions of the cooperative and noncooperativegames are obtained by invoking corresponding theories, and thena nonlinear operator is constructed to couple these two solutions *** last, the optimal strategies trajectory of agents in the system is proven toconverge into a certain attractor, which means that strategies trajectory arecertainty as time tends to infinity or a large positive integer. It is concluded thatthe optimal strategy trajectory with a nonlinear operator of cooperative/noncooperativestochastic differential game between agents can make agentsin a certain Local-World coordinate and make the Local-World paymentmaximize, and can make the all Local-Worlds equilibrated;furthermore, theoptimal strategy of the coupled game can converge into a particular attractorthat decides the optimal property.
From the perspective of data stream, neural architecture search (NAS) can be formulated as a graph optimization problem. However, many state-of-the-art black-box optimization algorithms, such as Bayesian optimization ...
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From the perspective of data stream, neural architecture search (NAS) can be formulated as a graph optimization problem. However, many state-of-the-art black-box optimization algorithms, such as Bayesian optimization and simulated annealing, operate in continuous space primarily, which does not match the NAS optimization due to the discreteness of graph structures. To tackle this problem, the latent space Bayesian optimization NAS (LSBO-NAS) algorithm is developed in this paper. In LSBO-NAS, the neural architectures are represented as sequences, and a variational auto-encoder (VAE) is trained to convert the discrete search space of NAS into a continuous latent space by learning the continuous representation of neural architectures. Hereafter, a Bayesian optimization (BO) algorithm, i.e., the tree-structure parzen estimator (TPE) algorithm, is developed to obtain admirable neural architectures. The optimization loop of LSBO-NAS consists of two stages. In the first stage, the BO algorithm generates a preferable architecture representation according to its search strategy. In the second stage, the decoder of VAE decodes the representation into a discrete neural architecture, whose performance evaluation is regarded as the feedback signal for the BO algorithm. The effectiveness of the developed LSBO-NAS is demonstrated on the NAS-Bench-301 benchmark, where the LSBO-NAS achieves a better performance than several NAS baselines.
Humans have the ability to deviate from their natural behavior when necessary, which is a cognitive process called response inhibition. Similar approaches have independently received increasing attention in recent yea...
Humans have the ability to deviate from their natural behavior when necessary, which is a cognitive process called response inhibition. Similar approaches have independently received increasing attention in recent years for ensuring the safety of control. Realized using control barrier functions or predictive safety filters, these approaches can effectively ensure the satisfaction of state constraints through an online adaptation of nominal control laws, e.g., obtained through reinforcement learning. While the focus of these realizations of inhibitory control has been on risk-neutral formulations, human studies have shown a tight link between response inhibition and risk attitude. Inspired by this insight, we propose a flexible, risk-sensitive method for inhibitory control. Our method is based on a risk-aware condition for value functions, which guarantees the satisfaction of state constraints. We propose a method for learning these value functions using common techniques from reinforcement learning and derive sufficient conditions for its success. By enforcing the derived safety conditions online using the learned value function, risk-sensitive inhibitory control is effectively achieved. The effectiveness of the developed control scheme is demonstrated in simulations.
For reaction systems, the state variables (the number of moles) can be expressed using the concepts of extents of reaction and mass transfer for homogeneous and heterogeneous reaction systems. In this work, a general ...
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For reaction systems, the state variables (the number of moles) can be expressed using the concepts of extents of reaction and mass transfer for homogeneous and heterogeneous reaction systems. In this work, a general framework for designing asymptotic observers for homogeneous and gas-liquid reaction systems is presented using the concept of the extents. For gas-liquid reaction systems, it is shown that asymptotic observers can be designed using measurements in the gas-phase. The effect of noisy measurements on the estimation of unmeasured concentrations is also discussed. The proposed asymptotic observer approach is illustrated using an example of the chlorination of butanoic acid (gas-liquid reaction system).
We use interval reachability analysis to obtain robustness guarantees for implicit neural networks (INNs). INNs are a class of implicit learning models that use implicit equations as layers and have been shown to exhi...
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