Stabilization of Networked Control Systems with Sparse Observer-Controller Networks

In this paper we provide a set of stability conditions for linear time-invariant networked control systems with arbitrary topology, using a Lyapunov direct approach. We then use these stability conditions to provide a novel low-complexity algorithm for the design of a sparse observer-based control network. We employ distributed observers by employing the output of other nodes to improve the stability of each observer dynamics. To avoid unbounded growth of controller and observer gains, we impose bounds on their norms. The effects of relaxation of these bounds is discussed when trying to find the complete decentralization conditions

Association of body mass index and physical activity with fatigue, depression, and anxiety among Iranian patients with multiple sclerosis

IntroductionDepression, fatigue, and anxiety are three common clinical comorbidities of multiple sclerosis (MS). We investigated the role of physical activity (PA) level and body mass index (BMI) as modifiable lifestyle factors in these three comorbidities.MethodsA cross-sectional study was conducted in the MS specialist clinic of Sina Hospital, Tehran, Iran. Demographic and clinical data were collected. BMI was categorized in accordance with the WHO’s standard classification. Physical activity (PA) level and sitting time per day were obtained using the short form of the International Physical Activity Questionnaire (IPAQ-SF). Fatigue, anxiety, and depression scores were measured using the Persian version of the Fatigue Severity Scale (FSS), Beck Anxiety Inventory (BAI), and Beck’s Depression Inventory II (BDI-II) questionnaires, respectively. The correlation between the metabolic equivalent of tasks (MET), BMI, and daily sitting hours with depression, anxiety, and fatigue were checked using the linear regression test. The normal BMI group was considered a reference, and the difference in quantitative variables between the reference and the other groups was assessed using an independent sample t-test. Physical activity was classified with tertiles, and the difference in depression, anxiety, and fatigue between the PA groups was evaluated by a one-way ANOVA test.ResultsIn total, 85 MS patients were recruited for the study. The mean ± SD age of the participants was 39.07 ± 8.84 years, and 72.9% (n: 62) of them were female. The fatigue score was directly correlated with BMI (P: 0.03; r: 0.23) and sitting hours per day (P: 0.01; r: 0.26) and indirectly correlated with PA level (P < 0.01; r: −0.33). Higher depression scores were significantly correlated with elevated daily sitting hours (P: 0.01; r: 0.27). However, the correlation between depression with PA and BMI was not meaningful (p > 0.05). Higher anxiety scores were correlated with BMI (P: 0.01; r: 0.27) and lower PA (P: 0.01; r: −0.26). The correlation between anxiety and sitting hours per day was not significant (p > 0.05). Patients in the type I obesity group had significantly higher depression scores than the normal weight group (23.67 ± 2.30 vs. 14.05 ± 9.12; P: 0.001). Fatigue (32.61 ± 14.18 vs. 52.40 ± 12.42; P: <0.01) and anxiety (14.66 ± 9.68 vs. 27.80 ± 15.48; P: 0.01) scores were significantly greater among participants in the type II obesity group in comparison with the normal weight group. Fatigue (P: 0.01) and anxiety (P: 0.03) scores were significantly different in the three levels of PA, but no significant difference was found in the depression score (P: 0.17).ConclusionOur data suggest that a physically active lifestyle and being in the normal weight category are possible factors that lead to lower depression, fatigue, and anxiety in patients with MS

Stabilization of uncertain distributed networked control systems with minimal communications network

We derive a network stability condition for linear time-invariant distributed networked systems as the system parameters are allowed to take values within a specified class of model uncertainties. We use the modified Lyapunov equation which provides a sufficient condition for robust stability of the entire networked control system. We then proceed to design a communications network which satisfies the derived network stability condition but has minimum number of links. Reducing the number of communication links implies minimization of the communication network\u27s cost and energy consumption. © 2012 IEEE

Stabilization Of Networked Control Systems With Sparse Observer-Controller Networks

In this technical note we provide a set of stability conditions for linear time-invariant networked control systems with arbitrary topology, using a Lyapunov direct approach. We then use these stability conditions to provide a novel low-complexity algorithm for the design of a sparse observer-based control network. We employ distributed observers by employing the output of other nodes to improve the stability of each observer dynamics. To avoid unbounded growth of controller and observer gains, we impose bounds on their norms. The effects of relaxation of these bounds is discussed when trying to find the complete decentralization conditions

Stabilization Of Distributed Networked Control Systems With Constant Feedback Delay

In this paper we study a delay-dependent stability condition for networked control systems with distributed control. We assume a constant processing and communication delay. We use an augmented Lyapunov-Krasovskii functional combined with the Leibniz-Newton formula to find a network stability condition that guarantees the global asymptotical stability of the entire networked control system under delayed feedback. To design the control network, we propose a method involving a constrained quadratic program (QP) and a convex feasibility problem. © 2013 IEEE

Stabilizing a random dynamics network with a random communications network

We study a networked control system with identical linear time-invariant subsystems and identical couplings. Using the Lyapunov method, we derive a sufficient network stability condition. Then, based on this condition we calculate bounds on the probability of stability of a random dynamics network with a random communications network. Finally, we investigate the stability trends of the random networks in the asymptotic regime. Numerical examples validate our analytical results. © 2012 IEEE

Stabilization of NCS with sparse controller networks

University of Rochester. Department of Electrical and Computer Engineering, 2016.We consider stabilization of networked control systems (NCS), consisting of N subsystems coupled via a directed network with topology using sparse control networks. Each subsystem comprises of a plant and a controller. The interaction of plants with each other forms the plant network. Control signals are exchanged using the control network, a.k.a. information, communications, or feedback network. For networks with arbitrary topology, the key question concerning the design of the control network is one of topological information requirements and can be framed as: Which nodes should be given the state and output information of a particular node, in order for the local controllers to be able to satisfy a global control objective? This question is critical in the design of massively distributed control systems, such as the Smart Grid. In addressing this key question, the goal is often to find the sparsest control network that satisfies the requirements. Considering various settings, we first develop stability conditions that guarantee global asymptotic stability, using the Lyapunov direct method. We then use these conditions to explore the problem of designing a sparse control network for a given plant network with arbitrary topology

Association of body mass index and physical activity with fatigue, depression, and anxiety among Iranian patients with multiple sclerosis

Introduction: Depression, fatigue, and anxiety are three common clinical comorbidities of multiple sclerosis (MS). We investigated the role of physical activity (PA) level and body mass index (BMI) as modifiable lifestyle factors in these three comorbidities. Methods: A cross-sectional study was conducted in the MS specialist clinic of Sina Hospital, Tehran, Iran. Demographic and clinical data were collected. BMI was categorized in accordance with the WHO’s standard classification. Physical activity (PA) level and sitting time per day were obtained using the short form of the International Physical Activity Questionnaire (IPAQ-SF). Fatigue, anxiety, and depression scores were measured using the Persian version of the Fatigue Severity Scale (FSS), Beck Anxiety Inventory (BAI), and Beck’s Depression Inventory II (BDI-II) questionnaires, respectively. The correlation between the metabolic equivalent of tasks (MET), BMI, and daily sitting hours with depression, anxiety, and fatigue were checked using the linear regression test. The normal BMI group was considered a reference, and the difference in quantitative variables between the reference and the other groups was assessed using an independent sample t-test. Physical activity was classified with tertiles, and the difference in depression, anxiety, and fatigue between the PA groups was evaluated by a one-way ANOVA test. Results: In total, 85 MS patients were recruited for the study. The mean ± SD age of the participants was 39.07 ± 8.84 years, and 72.9% (n: 62) of them were female. The fatigue score was directly correlated with BMI (P: 0.03; r: 0.23) and sitting hours per day (P: 0.01; r: 0.26) and indirectly correlated with PA level (P 0.05). Higher anxiety scores were correlated with BMI (P: 0.01; r: 0.27) and lower PA (P: 0.01; r: −0.26). The correlation between anxiety and sitting hours per day was not significant (p > 0.05). Patients in the type I obesity group had significantly higher depression scores than the normal weight group (23.67 ± 2.30 vs. 14.05 ± 9.12; P: 0.001). Fatigue (32.61 ± 14.18 vs. 52.40 ± 12.42; P