Sparse and Constrained Stochastic Predictive Control for Networked Systems

This article presents a novel class of control policies for networked control of Lyapunov-stable linear systems with bounded inputs. The control channel is assumed to have i.i.d. Bernoulli packet dropouts and the system is assumed to be affected by additive stochastic noise. Our proposed class of policies is affine in the past dropouts and saturated values of the past disturbances. We further consider a regularization term in a quadratic performance index to promote sparsity in control. We demonstrate how to augment the underlying optimization problem with a constant negative drift constraint to ensure mean-square boundedness of the closed-loop states, yielding a convex quadratic program to be solved periodically online. The states of the closed-loop plant under the receding horizon implementation of the proposed class of policies are mean square bounded for any positive bound on the control and any non-zero probability of successful transmission

Packetized MPC with dynamic scheduling constraints and bounded packet dropouts

We study a Networked Control System architecture which uses a communication network in the controller-actuator links. The network is affected by packet dropouts and allows access to only one plant input node at each time instant. This limits control performance significantly. To mitigate these limitations we propose a control and network protocol co- design method. Succinctly, the underlying features of the proposed method are as follows: a sequence of predicted optimal control values over a finite horizon, for an optimally chosen input node, is obtained using Model Predictive Control ideas; the entire resulting sequence is sent to the chosen input node; a smart actuator is used to store the predictions received and apply them accordingly. We show that if the number of consecutive packet dropouts is uniformly bounded, then partial nonlinear gain l2 stability and also a more traditional linear gain l2 stability can be ensured via appropriate choice of design parameters and the right assumptions. Whilst our results apply to general nonlinear discrete-time multiple input plants affected by exogenous disturbances, for a disturbance-free case we prove that Global Asymptotic Stability follows from our main result. Moreover, we show that by imposing stronger assumptions, Input-to-State Stability is achievable as well. Finally we demonstrate the potential of the proposed method via simulations.<br/

The Digitalization Revolution in Dental Health Care and the Application of VR and AR

The digital revolution has radically changed the world of dentistry, so the digital transformation in dental medicine is based on electronic health information, also known as one of the major changes of the 21st-century digital world which is addressing the current challenges of the future in dental as well as oral health care. This progress has been exponentially supported by the Internet of medical things (IoMT), big data and analytical algorithms, internet and communication technologies (ICT) including digital social media, augmented and virtual reality, and artificial intelligence (AI). The interplay between these sophisticated digital aspects has dramatically changed healthcare, and especially that of dental care. These received applications of technology will not only be able to direct dental (oral) health care but will facilitate the workflow, increase oral health at a fraction of the actual cost, facilitate the work of the dentist and dental support staff from their routine tasks which are also tedious. As a narrative summary of this paper, we can emphasize that the latest digitalization of dentistry that includes technological advances, limitations, challenges, and modern theoretical conceptual approaches to oral health prevention and care, especially in quality assurance, efficiency, and strategic dental care in the modern era of dentistry

Robustness of networked control systems with multiple actuator-links and bounded packet dropouts

This paper presents an MPC based controller and network protocol co-design strategy for networked control systems with multiple controller-actuator links. These links are closed via unreliable data-like network which allows access to only one actuator node at each time instant. The concept of nonlinear gains is used to show that in the case of uniform boundedness of the number of consecutive packet dropouts, nonlinear gain ℓ2 stability can be ensured via appropriate choice of design parameters. Numerical simulations illustrate the potential of the proposed strategy.</p

Packetized MPC with dynamic scheduling constraints and bounded packet dropouts

We study a Networked Control System architecture which uses a communication network in the controller-actuator links. The network is affected by packet dropouts and allows access to only one plant input node at each time instant. This limits control performance significantly. To mitigate these limitations we propose a control and network protocol co-design method. Succinctly, the underlying features of the proposed method are as follows: a sequence of predicted optimal control values over a finite horizon, for an optimally chosen input node, is obtained using Model Predictive Control ideas; the <i>entire</i> resulting sequence is sent to the chosen input node; a smart actuator is used to store the predictions received and apply them accordingly. We show that if the number of consecutive packet dropouts is uniformly bounded, then partial nonlinear gain ℓ₂ stability and also a more traditional linear gain ℓ₂ stability can be ensured via appropriate choice of design parameters and the right assumptions. Whilst our results apply to general nonlinear discrete-time multiple input plants affected by exogenous disturbances, for a disturbance-free case we prove that Global Asymptotic Stability follows from our main result. Moreover, we show that by imposing stronger assumptions, Input-to-State Stability is achievable as well. Finally we demonstrate the potential of the proposed method via simulations

Robust stability of a class of Networked Control Systems

Networked Control Systems (NCSs) affected with packet dropouts and scheduling are considered. The undesirable effects of packet dropouts and scheduling, such as instability or deteriorated performance, are addressed by application of a protocol and controller co-design method. The used method exploits Model Predictive Control (MPC) framework and the flexible NCS architecture which allows for distributed computation. Uniform Global Asymptotic Stability (UGAS) is established by assuming a finite bound on the number of consecutive packet dropouts and appropriate modifications to often adopted MPC stability-related assumptions. Two approaches that demonstrate UGAS are provided. The proof of one approach consists of finding an appropriate Lyapunov candidate function, while the other uses a cascade stability idea

Communication scheduling in robust self-triggered MPC for linear discrete-time systems

We consider a networked control system consisting of a physical plant, an actuator, a sensor, and a controller that is connected to the actuator and sensor via a communication network. The plant is described by a linear discrete-time system subject to additive disturbances. In order to reduce the required number of communications in the system, we propose a robust self-triggered model predictive controller based on rollout techniques that robustly asymptotically stabilizes a certain periodic sequence of sets in the state space while guaranteeing robust satisfaction of hard state and input constraints. At periodically occurring scheduling times, the self-triggered model predictive control algorithm determines the times at which the control input and plant measurement are updated in the time span until the next scheduling time. We establish a certain upper bound on the average sampling rate in the closed-loop system. Moreover, we show how increasing the asymptotic bound on the system state, which is a design parameter in the control scheme, can be used to further reduce the average number of communications in the system