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Product Distribution (PO) theory was recently developed as a broad framework for analyzing and optimizing distributed systems. Here we demonstrate its use for adaptive distributed control of Multi-Agent Systems (MASS), i.e., for distributed stochastic optimization using MAS s. First we review one motivation of PD theory, as the information-theoretic extension of conventional full-rationality game theory to the case of bounded rational agents. In this extension the equilibrium of the game is the optimizer of a Lagrangian of the (Probability dist&&on on the joint state of the agents. When the game in question is a team game with constraints, that equilibrium optimizes the expected value of the team game utility, subject to those constraints. One common way to find that equilibrium is to have each agent run a Reinforcement Learning (E) algorithm. PD theory reveals this to be a particular type of search algorithm for minimizing the Lagrangian. Typically that algorithm i s quite inefficient. A more principled alternative is to use a variant of Newton's method to minimize the Lagrangian. Here we compare this alternative to RL-based search in three sets of computer experiments. These are the N Queen s problem and bin-packing problem from the optimization literature, and the Bar problem from the distributed RL literature. Our results confirm that the PD-theory-based approach outperforms the RL-based scheme in all three domains.

The Objective of this study is to address the critical need for automation in the domestic food processing sector and to study its impact. This study investigates the challenges arising out due to the dependency of the modern human for processing of food. Through the medium of this study a pressing need for the development of an automatic cooking machine is proposed. The impact of the development of this product has also been profoundly discussed. By E. Sankaran. ME "Distributed Control Systems in Food Processing" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-3 | Issue-1 , December 2018, URL: http://www.ijtsrd.com/papers/ijtsrd18921.pdf Direct URL: http://www.ijtsrd.com/engineering/other/18921/distributed-control-systems-in-food-processing/e-sankaran-me

This paper is concerned with the analysis and design of secure Distributed Control Systems in the face of integrity attacks on sensors and controllers by external attackers or insiders. In general a DCS consists of many heterogenous components and agents including sensors, actuators, controllers. Due to its distributed nature, some agents may start misbehaving to disrupt the system. This paper first reviews necessary and sufficient conditions for deterministic detection of integrity attacks carried out by any number of malicious agents, based on the concept of left invertibility of structural control systems. It then develops a notion equivalent to structural left invertibility in terms of vertex separators of a graph. This tool is then leveraged to design minimal communication networks for DCSs, which ensure that an adversary cannot generate undetectable attacks. Numerical examples are included to illustrate these results.

Finite dimensional approximation schemes that work well for distributed parameter systems are often not suitable for the analysis and implementation of feedback control systems. The relationship between approximation schemes for distributed parameter systems and their application to optimal control problems is discussed. A numerical example is given.

Standard model predictive control strategies imply the online computation of control inputs at each sampling instance, which traditionally limits this type of control scheme to systems with slow dynamics. This paper focuses on distributed model predictive control for large-scale systems comprised of interacting linear subsystems, where the online computations required for the control input can be distributed amongst them. A model predictive controller based on a distributed interior point method is derived, for which every subsystem in the network can compute stabilizing control inputs using distributed computations. We introduce local terminal sets and cost functions, which together satisfy distributed invariance conditions for the whole system, that guarantees stability of the closed-loop interconnected system. We show that the synthesis of both terminal sets and terminal cost functions can be done in a distributed framework.

In this paper, we present distributed controllers for sharing primary and secondary frequency control reserves for asynchronous AC transmission systems, which are connected through a multi-terminal HVDC grid. By using Lyapunov arguments, the equilibria of the closed-loop system are shown to be globally asymptotically stable. We quantify the static errors of the voltages and frequencies, and give upper bounds for these errors. It is also shown that the controllers have the property of power sharing, i.e., primary and secondary frequency control reserves are shared fairly amongst the AC systems. The proposed controllers are applied to a high-order dynamic model of of a power system consisting of asynchronous AC grids connected through a six-terminal HVDC grid.

Dynamic Adaptive Streaming over HTTP (DASH) is a recently proposed standard that offers different versions of the same media content to adapt the delivery process over the Internet to dynamic bandwidth fluctuations and different user device capabilities. The peer-to-peer (P2P) paradigm for video streaming allows to leverage the cooperation among peers, guaranteeing to serve every video request with increased scalability and reduced cost. We propose to combine these two approaches in a P2P-DASH architecture, exploiting the potentiality of both. The new platform is made of several swarms, and a different DASH representation is streamed within each of them; unlike client-server DASH architectures, where each client autonomously selects which version to download according to current network conditions and to its device resources, we put forth a new rate control strategy implemented at peer site to maintain a good viewing quality to the local user and to simultaneously guarantee the successful operation of the P2P swarms. The effectiveness of the solution is demonstrated through simulation and it indicates that the P2P-DASH platform is able to warrant its users a very good performance, much more satisfying than in a conventional P2P environment where DASH is not employed. Through a comparison with a reference DASH system modeled via the Integer Linear Programming (ILP) approach, the new system is shown to outperform such reference architecture. To further validate the proposal, both in terms of robustness and scalability, system behavior is investigated in the critical condition of a flash crowd, showing that the strong upsurge of new users can be successfully revealed and gradually accommodated.

This project is to study the estimation and control of elastic systems composed of beams and plates in order to develop efficient and accurate estimation and control algorithms. Results have been obtained for the estimation in static beams and plates, control and location of actuators for static beams and plates, and identifiability for discrete approximations of second order elliptic boundary value problems. Currently testing codes are being developed for numerical experimentation for estimation of damping and elastic coefficients in dynamic linear plate models, estimation of boundary parameters for second order elliptic problems, estimation of elastic coefficients in cantilevered beams using perturbed boundary conditions, optimal location of actuators for the control of beams, and control of plates through forces at points and forces distributed over sets of small measure and curves. The plan is to next investigate boundary control and estimation, estimation and control in structures, use of friction as an active control, and parallelization of estimation and control algorithms.

Distributed averaging-based integral (DAI) controllers are becoming increasingly popular in power system applications. The literature has thus far primarily focused on disturbance rejection, steady-state optimality and adaption to complex physical system models without considering uncertainties on the cyber and communication layer nor their effect on robustness and performance. In this paper, we derive sufficient delay-dependent conditions for robust stability of a secondary-frequency-DAI-controlled power system with respect to heterogeneous communication delays, link failures and packet losses. Our analysis takes into account both constant as well as fast-varying delays, and it is based on a common strictly decreasing Lyapunov-Krasovskii functional. The conditions illustrate an inherent trade-off between robustness and performance of DAI controllers. The effectiveness and tightness of our stability certificates are illustrated via a numerical example based on Kundur's four-machine-two-area test system.

Efforts to develop computational methods for the identification and optimal control of linear and nonlinear systems governed by distributed parameter systems are reported on. Specifically, approximation methods for determining Optimal LOG compensators (feedback control and estimator gains) and functional parameters in linear and nonlinear partial differential equations and hereditary systems were developed, analyzed and tested. The study included theoretical, experimental and numerical components. Covergence theories for spline-based and modal finite element schemes were established and extensive numerical studies on both conventional (serial) and vector supercomputers were carried out. A parameter estimation scheme was tested using experimental data taken from the RPL structure, a laboratory experiment designed to test control algorithms for the large angle slewing of spacecraft with flexible appendages, and other projects involving the identification of flexible structures based upon experimental data were initiated.

Traditionally, power system scheduling and control are separately implemented. To bridge the gap between these two activities, online adjustment of the optimal schedule is necessary. Because such adjustment degrades energy efficiency and dynamic response, it is desirable to integrate the two functions seamlessly. One possible solution is to optimize the control references directly. In this paper, a fully-distributed, multi-agent based control solution is presented to reduce the fuel consumption of shipboard power systems. Every generator has an associated agent that only communicates with its neighboring agents. With a properly-designed communication network, the solution can guarantee convergence, even during losses of the communication channel. This fully-distributed design can significantly improve the reliability and survivability of the system, especially during battle conditions. The improved subgradient based optimization solution can address both equality and inequality constraints and can provide performance comparable to that of centralized solutions. Simulation studies demonstrate the effectiveness of the proposed solution.

This report describes research on the effects of computer-mediated communications on distributed command and control. The study extends the investigation of computer-mediated communication with shared graphics in distributed C2 to a three-person group (triad) to examine the effects of computer-mediation on the ability of a supervisor to interact with staff members and to exercise control over task accomplishment. An experiment was conducted that required two team members, under the supervision of a third individual, to collaborate on a military tactical movement order task. The three people were also required to perform other work to simulate conditions typical for command staffs. Work was performed face-to-face (FTF) and with the group separated using various modes of computer-mediated communications. The experimental modes evaluated were (1) face-to-face, (2) synchronous with voice communications (SYNCH+V), and (3) voiceless asynchronous electronic-mail communications (ASYNCH). Results indicate that little is lost in performance quality or speed when moving from face-to-face to computer-mediated communications with an auxiliary voice channel.

Research on optimal and adaptive control and adaptive identification of distributed systems has been performed. Most of the research has focused on digital control and identification methods, to allow for real-time implementation. The main applications have been to identification and control of flexible structures. Both new mathematical theory and new numerical methods have been primary objectives and results of the research. Experimental application of the new methods for adaptive identification and disturbance rejection has been carried out.

Here an original idea is suggested to prove the existence of optimal control for some types of non- linear problems. The obtained results can be considered as individual existence theorems (in some sense).

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The reduced order model problem in distributed parameter systems adaptive identification and control is investigated. A comprehensive examination of real-time centralized adaptive control options for flexible spacecraft is provided.

Progress toward the implementation of distributed engine control in an aerospace application may be accelerated through the development of a hardware-in-the-loop (HIL) system for testing new control architectures and hardware outside of a physical test cell environment. One component required in an HIL simulation system is a high-fidelity model of the control platform: sensors, actuators, and the control law. The control system developed for the Commercial Modular Aero-Propulsion System Simulation 40k (C-MAPSS40k) provides a verifiable baseline for development of a model for simulating a distributed control architecture. This distributed controller model will contain enhanced hardware models, capturing the dynamics of the transducer and the effects of data processing, and a model of the controller network. A multilevel framework is presented that establishes three sets of interfaces in the control platform: communication with the engine (through sensors and actuators), communication between hardware and controller (over a network), and the physical connections within individual pieces of hardware. This introduces modularity at each level of the model, encouraging collaboration in the development and testing of various control schemes or hardware designs. At the hardware level, this modularity is leveraged through the creation of a Simulink(R) library containing blocks for constructing smart transducer models complying with the IEEE 1451 specification. These hardware models were incorporated in a distributed version of the baseline C-MAPSS40k controller and simulations were run to compare the performance of the two models. The overall tracking ability differed only due to quantization effects in the feedback measurements in the distributed controller. Additionally, it was also found that the added complexity of the smart transducer models did not prevent real-time operation of the distributed controller model, a requirement of an HIL system.

This paper proposes a new gradient-based optimization approach for designing optimal feedback kernels for parabolic distributed parameter systems with boundary control. Unlike traditional kernel optimization methods for parabolic systems, our new method does not require solving non-standard Riccati-type or Klein-Gorden-type partial differential equations (PDEs). Instead, the feedback kernel is parameterized as a second-order polynomial whose coefficients are decision variables to be tuned via gradient-based dynamic optimization, where the gradient of the system cost functional (which penalizes both kernel and output magnitude) is computed by solving a so-called costate PDE instandard form. Special constraints are imposed on the kernel coefficients to ensure that, under mild conditions, the optimized kernel yields closed-loop stability. Numerical simulations demonstrate the effectiveness of the proposed approach.

Unexpected increases in demand and most of all flash crowds are considered the bane of every web application as they may cause intolerable delays or even service unavailability. Proper quality of service policies must guarantee rapid reactivity and responsiveness even in such critical situations. Previous solutions fail to meet common performance requirements when the system has to face sudden and unpredictable surges of traffic. Indeed they often rely on a proper setting of key parameters which requires laborious manual tuning, preventing a fast adaptation of the control policies. We contribute an original Self-* Overload Control (SOC) policy. This allows the system to self-configure a dynamic constraint on the rate of admitted sessions in order to respect service level agreements and maximize the resource utilization at the same time. Our policy does not require any prior information on the incoming traffic or manual configuration of key parameters. We ran extensive simulations under a wide range of operating conditions, showing that SOC rapidly adapts to time varying traffic and self-optimizes the resource utilization. It admits as many new sessions as possible in observance of the agreements, even under intense workload variations. We compared our algorithm to previously proposed approaches highlighting a more stable behavior and a better performance.

Progress toward the implementation of distributed engine control in an aerospace application may be accelerated through the development of a hardware-in-the-loop (HIL) system for testing new control architectures and hardware outside of a physical test cell environment. One component required in an HIL simulation system is a high-fidelity model of the control platform: sensors, actuators, and the control law. The control system developed for the Commercial Modular Aero-Propulsion System Simulation 40k (40,000 pound force thrust) (C-MAPSS40k) provides a verifiable baseline for development of a model for simulating a distributed control architecture. This distributed controller model will contain enhanced hardware models, capturing the dynamics of the transducer and the effects of data processing, and a model of the controller network. A multilevel framework is presented that establishes three sets of interfaces in the control platform: communication with the engine (through sensors and actuators), communication between hardware and controller (over a network), and the physical connections within individual pieces of hardware. This introduces modularity at each level of the model, encouraging collaboration in the development and testing of various control schemes or hardware designs. At the hardware level, this modularity is leveraged through the creation of a Simulink (R) library containing blocks for constructing smart transducer models complying with the IEEE 1451 specification. These hardware models were incorporated in a distributed version of the baseline C-MAPSS40k controller and simulations were run to compare the performance of the two models. The overall tracking ability differed only due to quantization effects in the feedback measurements in the distributed controller. Additionally, it was also found that the added complexity of the smart transducer models did not prevent real-time operation of the distributed controller model, a requirement of an HIL system.

The results are presented of a detailed study of the discrete control of linear distributed systems with specific application to the design of a practical controller for a plant representative of a telescope primary mirror for an orbiting astronomical observatory. The problem of controlling the distributed plant is treated by employing modal techniques to represent variations in the optical figure. Distortion of the mirror surface, which arises primarily from thermal gradients, is countered by actuators working against a backing structure to apply a corrective force distribution to the controlled surface. Each displacement actuator is in series with a spring attached to the mirror by means of a pad intentionally introduced to restrict the excitation of high-order modes. Control is exerted over a finite number of the most significant modes.

Large scale distributed systems consists of workstations, mainframe computers, supercomputers and other types of servers, all connected by a computer network. These systems are being used in a variety of applications including the support of collaborative scientific research. In such an environment, issues of access control and privacy arise. Access control is required for several reasons, including the protection of sensitive resources and cost control. Privacy is also required for similar reasons, including the protection of a researcher's proprietary results. A possible architecture for integrating available computer and communications security technologies into a system that meet these requirements is described. This architecture is meant as a starting point for discussion, rather that the final answer.

In this project questions related to stabilization of vibrating system by feedback were studied. A vibrating system is uniformly stabilized by a feedback if there is a uniform rate of decay for all vibrational modes of the closed-loop system, which is the system with feedback. Necessary conditions were found for certain kinds of feedback to uniformly stabilize a system which is originally undamped and has the feedback applied at the boundary. Sufficient conditions were found for the feedback to lead to a closed-loop system which is mathematically well-posed. It was also shown that in a large class of systems which are stabilized by feedback, if a small delay is introduced in the computation of the feedback, then the stability of the closed-loop system is destroyed. Keywords: Robust stabilization.

In this paper, we consider a diffusion process pertaining to a chain of distributed control systems with small random perturbation. The distributed control system is formed by n subsystems that satisfy an appropriate Hormander condition, i.e., the second subsystem assumes the random perturbation entered into the first subsystem, the third subsystem assumes the random perturbation entered into the first subsystem then was transmitted to the second subsystem and so on, such that the random perturbation propagates through the entire distributed control system. Note that the random perturbation enters only in one of the subsystems and, hence, the diffusion process is degenerate, in the sense that the backward operator associated with it is a degenerate parabolic equation. Our interest is to estimate the exit probability with which a diffusion process (corresponding to a particular subsystem) exits from a given bounded open domain during a certain time interval. The method for such an estimate basically relies on the interpretation of the exit probability function as a value function for a family of stochastic control problems that are associated with the underlying chain of distributed control systems.

In this tutorial paper, a comprehensive survey is given on several major systematic approaches in dealing with delay-aware control problems, namely the equivalent rate constraint approach, the Lyapunov stability drift approach and the approximate Markov Decision Process (MDP) approach using stochastic learning. These approaches essentially embrace most of the existing literature regarding delay-aware resource control in wireless systems. They have their relative pros and cons in terms of performance, complexity and implementation issues. For each of the approaches, the problem setup, the general solution and the design methodology are discussed. Applications of these approaches to delay-aware resource allocation are illustrated with examples in single-hop wireless networks. Furthermore, recent results regarding delay-aware multi-hop routing designs in general multi-hop networks are elaborated. Finally, the delay performance of the various approaches are compared through simulations using an example of the uplink OFDMA systems.

In this tutorial paper, a comprehensive survey is given on several major systematic approaches in dealing with delay-aware control problems, namely the equivalent rate constraint approach, the Lyapunov stability drift approach and the approximate Markov Decision Process (MDP) approach using stochastic learning. These approaches essentially embrace most of the existing literature regarding delay-aware resource control in wireless systems. They have their relative pros and cons in terms of performance, complexity and implementation issues. For each of the approaches, the problem setup, the general solution and the design methodology are discussed. Applications of these approaches to delay-aware resource allocation are illustrated with examples in single-hop wireless networks. Furthermore, recent results regarding delay-aware multi-hop routing designs in general multi-hop networks are elaborated. Finally, the delay performance of the various approaches are compared through simulations using an example of the uplink OFDMA systems.

Modern authorization systems span domains of administration, rely on many different authentication sources, and manage complex attributes as part of the authorization process. This . paper presents Cardea, a distributed system that facilitates dynamic access control, as a valuable piece of an inter-operable authorization framework. First, the authorization model employed in Cardea and its functionality goals are examined. Next, critical features of the system architecture and its handling of the authorization process are then examined. Then the S A M L and XACML standards, as incorporated into the system, are analyzed. Finally, the future directions of this project are outlined and connection points with general components of an authorization system are highlighted.

Much of the work to date to apply Role-Based Access Control (RBAC) to database management systems has focused on single database systems or an integrated distributed database system. For situations where the need exists to consolidate multiple independent databases, and where the direct integration of the databases is neither practical nor desirable, the application of RBAC requires that policy be enforced via a method that is distinct from the databases. The method must provide for the verification of the RBAC policy, while allowing for the independence of the various databases on which the policy is enforced. This paper proposes a model for an application that provides for a web-based interface for users to be granted access to data held in various independent databases. The application enforces a strict RBAC policy on a well-defined set of accesses, while alleviating the need for users to have a separate account on each of the databases.

In this final technical report, we outline a number of problems in robust and nonlinear control theory which we have studied using an operator theoretic methodology. In particular, we discuss an approach to the structured singular value and mu-synthesis procedure in robust control which is based on a new type of interpolation method. We consider nonlinear extension of H-infinity optimization theory and investigate corresponding question in causality which arise in this area. Moreover, we discuss a saddle-point, game-theoretic approach to such problems. Further. we sketch the application of our skew Toeplitz methods to distributed (infinite dimensional) H-infinity control. We also consider and h-infinity of approach to sampled data systems based on a lifting method, as well as consider problem using h-infinity - H2 combined suboptimal controller. Finally we list some of our results in image processing and computer vision as applied to visual tracking.

The work in this quarter concentrated on three areas: scheduling algorithms based on bidding, scheduling algorithms for systems with hard real-time constraints and on scheduling based on stochastic learning automata. Section 2 of this report describes the progress made in these areas.

The aim of this paper is to present the results of a CNES research project on distributed computing systems. The purpose of this research was to study the impact of the use of new computer technologies in the design and development of future space applications. The first part of this study was a state-of-the-art review of distributed computing systems. One of the interesting ideas arising from this review is the concept of a 'virtual computer' allowing the distributed hardware architecture to be hidden from a software application. The 'virtual computer' can improve system performance by adapting the best architecture (addition of computers) to the software application without having to modify its source code. This concept can also decrease the cost and obsolescence of the hardware architecture. In order to verify the feasibility of the 'virtual computer' concept, a prototype representative of a distributed space application is being developed independently of the hardware architecture.

The maintenance of consistency in a distributed database system environment presents a number of vexing problems to the database system designer. This is more so the case when the database system contains replicated data and is also designed to provide a high degree of availability under conditions of network partitioning. This thesis investigates the use of a proposed adaptive concurrency control algorithm as a possible alternative solution for a number of the problems facing the database system designer in the areas of concurrency control, partitioned networks, and long-lived transactions. (Author)

This final report describes the purpose and details of the equipment purchased under a University Research Instrumentation Program (URIP) grant. Equipment includes instruments for remote sensing of vibrations, for modal analysis of vibrating structures, and for active vibration suppression of viscoelastic beams.

This final report describes the purpose and details of the equipment purchased under a University Research Instrumentation Program (URIP) grant. Equipment includes instruments for remote sensing of vibrations, for modal analysis of vibrating structures, and for active vibration suppression of viscoelastic beams.

In this paper, we consider the stability analysis of large-scale distributed networked control systems with random communication delays between linearly interconnected subsystems. The stability analysis is performed in the Markov jump linear system framework. There have been considerable researches on stability analysis of Markov jump systems, however, these methods are not applicable to large-scale systems because large numbers of subsystems result in an extremely large number of the switching modes. To avoid this scalability issue, we propose a new reduced mode model for stability analysis, which is computationally efficient. We also consider the case in which the transition probabilities for the Markov jump process contain uncertainties. We provide a new method that estimates bounds for uncertain Markov transition probability matrix to guarantee the system stability. The efficiency and the usefulness of the proposed methods are verified through examples.

The goal of this project was to put the intuitive idea of gain-scheduling on a rigorous foundation for a class of nonlinear, distributed-parameter systems. This involved a study of the existence and characterization of the ideal, infinite-dimensional, feedback control. Since in most applications the feedback function cannot be computed in closed form it was necessary to study the convergence of approximate feedback functions, based on increasingly higher order finite-dimensional approximations of the system, to the ideal function. Finally, the results were applied to Burgers' Equation, which can be viewed as a low-order approximation to a wide variety of physical phenomena, including viscous compressible flow.

Research has been conducted in the following general areas; Optimal Control of Distributed Parameter System, Adaptive Identification and Control, and Robust Control. Work includes research in approximation theory and numerical methods for the design of finite dimensional compensators for optimal control of systems represented by partial differential equations, and adaptive control and tracking problems for flexible structures and manipulators with flexible links and joints. (Author)

This report summarizes the work and results produced during this contract over the past year. A summary of our results on the use of Bayesian Decision theory is reported. Two master's thesis were completed: one on bidding and one on stochastic learning automata. We have also been working on an analytical model but little new progress over that reported in the last quarterly report has been made in this area. Progress was made on a decentrailized scheduling approach for systems with tasks having real-time constraints. This report also briefly states our overall conclusions and makes several recommendations for the work to be done in the final year of this contract. Section 5 lists the papers, thesis, and presentations produced this year. Section 6 contains the required budget information, and finally the report ends with a copy of the distribution list. (Author)

Sensor-actuator network components tend to be unreliable, especially when they are low cost or deployed in unpredictable environments. These components may even exhibit byzantine behavior in which case their effect on the underlying systems can be severe. In this paper, we focus our attention on applications of sensor networks in control of linear systems and show how to deal with byzantine faults of components. Based on the well known Lyapunov formulation of stability, we identify two types of fault-tolerant control schemes for linear systems: masking and self-stabilizing.

The main purpose of this research is to develop a rigorous mathematical framework for the design of control laws for feedback stabilization and for controllability of the transient behavior of flexible structures based on distributed parameter models of such structures. This work has entailed deriving accurate distributed parameter models for elastic structures and understanding the implications of the various models for the controllability and stabilizability of structures. Substantial progress has been made for models of multiple-link constructions that are composed of elastic beams, plates., shells or combinations of such elastic elements. Such structures are representative of trusses, frames, robot arms, solar panels, antennae, deformable mirrors, etc., currently in use.

A distributed processing system is defined as a collection of processor-memory pairs (hosts) that are physically and logically interconnected, with decentralized system-wide control of all resources, for the cooperative execution of application programs. Such systems may be dedicated to a single application or may implement a general purpose computing facility. By decentralized system-wide control is meant that there exists distributed resources in the system, that there is decentralized control of these resources (i.e., there is no single, central host in charge, nor is there a central state table), that there is system-wide cooperation between independent hosts which results in a single unified system. By system-wide cooperation is meant that the algorithms of the system operate for the good of the whole and not for a particular host. For systems meeting this restrictive definition of distributed processing, it is hypothesized that their reliability, extensibility, and performance will be better than a what is generally available today. In this report the term distributed processing refers to this very specific type of highly integrated distributed system. The major objective of this research project was to develop and compare decentralized scheduling algorithms for distributed processing systems.

This report summarizes the work performed during the tenth quarter of this contract, from March 15, 1984 to June 14, 1984. The work in this quarter concentrated in three areas: simulations of our real-time bidding algorithms, non-traditional architectures studies for real-time systems, and scheduling tasks with resource requirements in hard real-time systems. Section 2 of this report describes the progress made in each of these areas. Significant results have been obtained which provides insight into the effectiveness of the algorithm. An improvement over the basic algorithm has been found. The improvement uses the prediction of future surplus time instead of the current surplus time in modifying bids. This report describes the basic algorithm and then describes the simulation results.

This report describes research and findings on the effects of computer-mediated communications on distributed command and control. To support collaboration among distributed remote command staffs, computer-mediated communications may be needed to share information, provide supervision, coordinate operations, perform analyses, and provide recommendations. This may require computer aiding, shared graphics, shared data bases, and two-way graphic communication. To test the potential of computer-mediated communication, an experiment was conducted that required two people to collaborate on a tactical movement order task. Both people were also required to perform other work to simulate conditions typical for command staffs. Measures were taken on the performance of primary and other work and of features on the communication transcripts. Work was performed face-to-face (FTF) and with the two people separated using various modes of computer-mediated communications. Of interest were voice or voiceless communications and synchronous or asynchronous communications. The following experimental modes were selected: 1) face-to-face (FTF), 2) synchronous with voice communications (SYNCH+V), 3) synchronous without voice communications but with the exchange of typed computer messages (SYNCH-V), 4) voiceless asynchronous electronic-mail communications (ASYNCH).

The performance of concurrency control algorithms is explored in the context of pessimistic distributed mutual exclusion algorithms. A detailed model of the underlying asynchronous distributed system and its parameters are defined for fail-free systems and systems where processes may fail. New performance metrics are proposed as a means to measure the efficiency of distributed mutual exclusion algorithms. A model of distributed mutual exclusion algorithms and analytical approximations of their performance are developed. Simulation results of five selected distributed mutual exclusion algorithms on fully-connected, star and ring topologies are cataloged. Finally, simulation results of four selected distributed mutual exclusion algorithms on a fully-connected topology where processes may fail are cataloged. Conclusions are drawn as to which algorithm is most appropriate for particular environments.

The research was directed to initiate a study of large-scale hereditary/non-hereditary control and distributed systems under randomly varying structural perturbations. The areas of research, namely, (1) Error estimates between the stochastic and corresponding deterministic systems, (2) Numerical methods, and (3) Diagonalization and stability are investigated.

This paper considers the distributed robust control problems of uncertain linear multi-agent systems with undirected communication topologies. It is assumed that the agents have identical nominal dynamics while subject to different norm-bounded parameter uncertainties, leading to weakly heterogeneous multi-agent systems. Distributed controllers are designed for both continuous- and discrete-time multi-agent systems, based on the relative states of neighboring agents and a subset of absolute states of the agents. It is shown for both the continuous- and discrete-time cases that the distributed robust control problems under such controllers in the sense of quadratic stability are equivalent to the $H_\infty$ control problems of a set of decoupled linear systems having the same dimensions as a single agent. A two-step algorithm is presented to construct the distributed controller for the continuous-time case, which does not involve any conservatism and meanwhile decouples the feedback gain design from the communication topology. Furthermore, a sufficient existence condition in terms of linear matrix inequalities is derived for the distributed discrete-time controller. Finally, the distributed robust $H_\infty$ control problems of uncertain linear multi-agent systems subject to external disturbances are discussed.

This project studied emergent behavior in distributed cyber-physical systems (DCPS). Emergent behavior does not a priori appear in the descriptions of such systems. The approach undertaken is to characterize this perspective as invalid: any behavior not a prior specified by the requirements and specifications of a system is emergent. With this perspective and using formal methods, formal verification with reachability analysis and inductive invariance, as well as architectural runtime monitoring and runtime assurance, this project developed and demonstrated novel ways to specify, verify, monitor, and control behavior in DCPS, such as groups of unmanned autonomous systems (UASs).

The goal of this research is the development of new fundamental insights and methodologies to exploit structural properties of large-scale dynamical networks in order to quantify their inherent fundamental limits on sparsity, performance, and robustness and characterize their resulting fundamental tradeoffs