Sleep apnoea is a common sleep disorder during human sleep. It is usually diagnosed by a doctor after recording one nights' sleep signals. Patients have to go to the hospital to record sleep signals, which is time...
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Modular multilevel converters (MMCs) have the potential to improve the performance of high- and medium-power applications, such as renewable energy generation and fast charging stations. The functioning of MMCs relies...
Modular multilevel converters (MMCs) have the potential to improve the performance of high- and medium-power applications, such as renewable energy generation and fast charging stations. The functioning of MMCs relies on their ability to balance capacitor voltages across all modules. Motivated by the capacitor voltage balancing (CVB) problem, this paper studies consensus-based distributed model predictive control (DMPC) schemes. As a result, we propose an alternative cost function that enables output synchronization of linear systems and, consequently, solves the CVB problem. The advantages of the proposed method are demonstrated by proving its stability properties and comparing its computational time and performance with existing DMPCs. Simulation results for a benchmark multi-agent system example from the literature and an MMC AC/DC topology demonstrate the effectiveness of the developed consensus DMPC.
This paper deals with the design of a fast MPC algorithm for the current control of a power amplifier utilized for nanometer precision positioning systems within lithography machines. In order to achieve nanometer pre...
This paper deals with the design of a fast MPC algorithm for the current control of a power amplifier utilized for nanometer precision positioning systems within lithography machines. In order to achieve nanometer precision positioning, the internal power amplifier must accurately track a current reference in a very short time (tens of microseconds). Classical industrial control solutions based on transfer functions do not take duty-cycle limits into account and suffer from limited bandwidth, which in turn limits the achievable positioning precision. We design a fast gradient based MPC algorithm that can accurately track the dynamic current reference while satisfying constraints. Simulations show that the MPC-controlled amplifier results in at least 2x better nanometer positioning precision for specific metrics employed in the lithography industry, compared to an industrial loop-shaping controller and an LQR controller.
Cyber-physical power system (CPPS), with its bi-directional power and information flows, is considered as the next generation of widely distributed and automated electrical power network. However, CPPS is vulnerable t...
Cyber-physical power system (CPPS), with its bi-directional power and information flows, is considered as the next generation of widely distributed and automated electrical power network. However, CPPS is vulnerable to malicious cyberattacks that can cause significant operational risk and financial loss to stakeholders, such as electricity system operators. The complexity of vulnerabilities, which arises from the heterogeneity and interdependency of physical and cyber domains, will present substantial challenges for the detection and prevention of cyberattacks. This paper provides a comprehensive review of the defense mechanisms in CPPS against coordinated and widespread cyberattacks. The most prevalent cyberattacks in the CPPS are denial-of-service (DoS) and false data injection (FDI) attacks. This paper examines the state-of-the-art prevention, detection, and mitigation technologies for these major mainstreams and coordinated cyberattacks. In particular, the advantages and disadvantages of popular cyberattack prevention sciences such as Game Theory, Optimization, control Theory, and Data-driven method are discussed. It reveals that cyberattack detection techniques have evolved from traditional state estimation to artificial intelligence-based methods. Finally, the challenges and opportunities for future research on cybersecurity in CPPS are identified.
This paper focuses on formulating and solving the optimization of crude oil operations scheduling carried out in a system composed of a refinery and a marine terminal. The main challenge lies in coordinating the decis...
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This paper focuses on formulating and solving the optimization of crude oil operations scheduling carried out in a system composed of a refinery and a marine terminal. The main challenge lies in coordinating the decisions made at both facilities and, at the same time, dealing with the uncertainties inherent in this activity. To tackle this problem, we present a continuous-time mixed-integer non-linear programming (MINLP) formulation. Furthermore, uncertainty in the ship arrival times is considered through a two-stage stochastic programming approach. Finally, the Conditional Value-at-Risk (CVaR) risk measure is employed to weigh the risk of having high costs relative to the worst scenarios. In this way, the proposed model is capable of supporting the decision-making process under uncertainty in an integral way.
This study addresses the affine formation maneuver control of cooperative multi-agent systems (MAS) having periodic inter-agent communication for both static and dynamic leader cases. Here, we focus on the leader-foll...
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ISBN:
(数字)9798331531812
ISBN:
(纸本)9798331531829
This study addresses the affine formation maneuver control of cooperative multi-agent systems (MAS) having periodic inter-agent communication for both static and dynamic leader cases. Here, we focus on the leader-follower MASs. The primary aim of the control system is to steer the entire collection of agents to produce required patterns (geometric) along with any required maneuver through the direct control of only few a selected agents referred to as leaders. Most of the existing works are constrained to either the individual agents communicate with each other in continuous-time or the sample-data scenario where the leaders are stationary or have constant acceleration or velocities. Here, we consider the scenarios where the velocities of the leaders can be time-varying or constant. Here, different cases are addressed and some control laws are proposed. Conditions are established to help guarantee the overall stability of the systems. A simulation study is employed for the illustration of our proposed laws.
Saudi Arabia has embarked on a transformative journey, transitioning from an oil-centric to an environmentally-focused economy. A recent initiative involves empowering house-holds to generate electricity through small...
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Recently, Transformer has achieved great success in computer vision. However, it is constrained because the spatial and temporal complexity grows quadratically with the number of large points in 3D object detection ...
Recently, Transformer has achieved great success in computer vision. However, it is constrained because the spatial and temporal complexity grows quadratically with the number of large points in 3D object detection applications from point clouds. Previous point-wise methods are suffering from time consumption and limited receptive fields to capture information among points. To address these limitations, we propose the cosh-attention, which reduces the computation complexity of space and time from the quadratic order to linear order with respect to the number of points. In the cosh-attention, the traditional softmax operator is replaced by non-negative ReLU activation and hyperbolic-cosine-based operator with re-weighting mechanism. Then based on the key component, cosh-attention, we present a two-stage hyperbolic cosine transformer (ChTR3D) for 3D object detection from point clouds. It refines proposals by applying cosh-attention in linear computation complexity to encode rich contextual relationships among points. Extensive experiments on the widely used KITTI dataset and Waymo Open Dataset demonstrate that, compared with vanilla attention, the cosh-attention significantly improves the inference speed with competitive performance. Experiment results show that, among two-stage state-of-the-art methods using point-level features to refine proposals, the proposed ChTR3D is the fastest one.
We introduce a novel differentially private algorithm for online federated learning that employs temporally correlated noise to enhance utility while ensuring privacy of continuously released models. To address challe...
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ISBN:
(数字)9798350316339
ISBN:
(纸本)9798350316346
We introduce a novel differentially private algorithm for online federated learning that employs temporally correlated noise to enhance utility while ensuring privacy of continuously released models. To address challenges posed by DP noise and local updates with streaming non-iid data, we develop a perturbed iterate analysis to control the impact of the DP noise on the utility. Moreover, we demonstrate how the drift errors from local updates can be effectively managed under a quasi-strong convexity condition. Subject to an $(\epsilon, \delta)$ DP budget, we establish a dynamic regret bound over the entire time horizon, quantifying the impact of key parameters and the intensity of changes in dynamic environments. Numerical experiments confirm the efficacy of the proposed algorithm.
This paper proposes a new disturbance observer (DO)-based reinforcement learning (RL) control approach for nonlinear systems with unmatched (generalized) disturbances. While a nonlinear disturbance observer (NDO) is u...
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ISBN:
(数字)9798350340266
ISBN:
(纸本)9798350340273
This paper proposes a new disturbance observer (DO)-based reinforcement learning (RL) control approach for nonlinear systems with unmatched (generalized) disturbances. While a nonlinear disturbance observer (NDO) is utilized to measure the plant uncertainties, disturbances can exist in the plant via distinct channels from those of the control signals; so-called mismatched disturbances are theoretically difficult to attenuate within the channel of the system's states. A generalized disturbance observer-based compensator is implemented to address the uncertainty cancellation problem by removing the influence of uncertainties from the output channels. Con-currently, a composite actor-critic RL scheme is utilized for approximating the optimal control policy as well as the ideal value function pertaining to the compensated system by solving a Hamilton-Jacobi-Bellman (HJB) equation for both online and offline iterations simultaneously. Stability analysis verifies the convergence of the proposed framework. Simulation results are included to illustrate the effectiveness of the proposed scheme.
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