2010 First IEEE International Conference on Smart Grid Communications
In this paper, we consider two abstract market models for designing demand response to match powe... more In this paper, we consider two abstract market models for designing demand response to match power supply and shape power demand, respectively. We characterize the resulting equilibria in competitive as well as oligopolistic markets, and propose distributed demand response algorithms to achieve the equilibria. The models serve as a starting point to include the appliance-level details and constraints for designing practical demand response schemes for smart power grids.
Proceedings.Twenty-First Annual Joint Conference of the IEEE Computer and Communications Societies
We demonstrate that the dynamic behavior of queue and average window is determined predominantly ... more We demonstrate that the dynamic behavior of queue and average window is determined predominantly by the stability of TCP/RED, not by AIMD probing nor noise traffic. We develop a general multi-link multi-source model for TCP/RED and derive a local stability condition in the case of a single link with heterogeneous sources. We validate our model with simulations and illustrate the stability region of TCP/RED. These results suggest that TCP/RED becomes unstable when delay increases, or more strikingly, when link capacity increases. The analysis illustrates the difficulty of setting RED parameters to stabilize TCP: they can be tuned to improve stability, but only at the cost of large queues even when they are dynamically adjusted. Finally, we present a simple distributed congestion control algorithm that maintains stability for arbitrary network delay, capacity, load and topology.
The paper consde the problem of titing, from expem a data, real Parameters for amodd with unceint... more The paper consde the problem of titing, from expem a data, real Parameters for amodd with unceinty in the foim of both additive noe and mrm bouded peturbation. Suh mdelsfreuetly arise in robus control thery, and a framewor is introduced for the consideration of experimeal dat in robst cotrl analyn prob_l i the analysis took applied inude robust stabiliy tess for real parameter variations (real i), then the fraewwork can be used to addri the problem of ruobns parameter identificatwn. Wile the di dhere can qukckly become computainay overwheming whe applied to physical system and real data, the approach introduce a new way of looking at the idetificaon problem and may be helpfiu in ariving a more tractable method
Mixed H2 and H∞ norm analysis and synthesis problems are considered in this paper. It is shown th... more Mixed H2 and H∞ norm analysis and synthesis problems are considered in this paper. It is shown that the mixed norm analysis combined with structured uncertainty can be used to give bounds on robust H2 and H∞ performance. It is also shown that the mixed norm controller shares a separation property similar to those of pure H2 or H∞ controllers.
Future space structures have many closely spaced, lightly damped natural frequencies throughout t... more Future space structures have many closely spaced, lightly damped natural frequencies throughout the frequency domain. To achieve desired performance objectives, a number of these modes must actively be controlled. For control, a combination of collocated and noncollocated sensors and actuators will be employed. The control designs will be formulated based on models which have inaccuracies due to unmodeled dynamics, and variations in damping levels, natural frequencies and mode shapes. Therefore, along with achieving the performance objectives, the control design must be robust to a variety of uncertainty. This paper focuses on the benefits and linmitations associated with multivariable control design using noncoUocated versus collocated sensors and actuators. We address the question of whether performance is restricted due to the noncollocation of the sensors and actuators or the uncertainty associated with modeling of the flexible structures. Control laws are formulated based on models of the system and evaluated analytically and experimentally. Results of implementation of these control laws on the Caltech flexible structure are presented.
This paper considers the analysis and synthesis of control systems subject to two types of distrb... more This paper considers the analysis and synthesis of control systems subject to two types of distrbance signals: signals with bonded power spectral density and sinals with bounded power. The reslting control problem involves min-iiZing miXed X2 andX. norm ofthe system. Ltis shown that the controller share a separtion property similr to those of pure 72 or 74. controller It is also shown that the mized problem reduces naturally to X2 and 7X. problem in specal cas Some necesary Lad sufficient conditions are obtained for the existence of a solution to the mixed problem. Exicit sate space formulae are given for the optimal controllers.
The general distance problem which arises in the general H∞ optimal control problem is considered... more The general distance problem which arises in the general H∞ optimal control problem is considered. The existence of an optimal solution is proved and the expression of the optimal norm γo is obtained from a somewhat abstract operator point of view. An iterative scheme, called γ-iteration, is introduced which reduces the general distance problem to a standard best approximation problem.
The robustness analysis of system performance is one of the key issues in control theory, and one... more The robustness analysis of system performance is one of the key issues in control theory, and one approach is to reduce this problem to that of computing the structured singular value, μ. When real parametric uncertainty is included, then μ must be computed with respect to a block structure containing both real and complex uncertainties. It is shown that μ
his article reviews the current transmission control protocol (TCP) congestion control protocols ... more his article reviews the current transmission control protocol (TCP) congestion control protocols and overviews recent advances that have brought analytical tools to this problem. We describe an optimization-based framework that provides an interpretation of various flow control mechanisms, in particular, the utility being optimized by the protocol's equilibrium structure. We also look at the dynamics of TCP and employ linear models to exhibit stability limitations in the predominant TCP versions, despite certain built-in compensations for delay. Finally, we present a new protocol that overcomes these limitations and provides stability in a way that is scalable to arbitrary networks, link capacities, and delays.
The success of targeted cancer therapy is limited by drug resistance that can result from tumor g... more The success of targeted cancer therapy is limited by drug resistance that can result from tumor genetic heterogeneity. The current approach to address resistance typically involves initiating a new treatment after clinical/radiographic disease progression, ultimately resulting in futility in most patients. Towards a potential alternative solution, we developed a novel computational framework that uses human cancer profiling data to systematically identify dynamic, pre-emptive, and sometimes non-intuitive treatment strategies that can better control tumors in real-time. By studying lung adenocarcinoma clinical specimens and preclinical models, our computational analyses revealed that the best anti-cancer strategies addressed existing resistant subpopulations as they emerged dynamically during treatment. In some cases, the best computed treatment strategy used unconventional therapy switching while the bulk tumor was responding, a prediction we confirmed in vitro. The new framework pr...
We describe a variant of TCP, called FAST, that can sustain high throughput and utilization at mu... more We describe a variant of TCP, called FAST, that can sustain high throughput and utilization at multigigabits per second over large distances. We present the motiva- tion, review the background theory, summarize key features of FAST TCP, and report our first experimental results.
Given a linear system, all stabilizing controllers such that a specified closed-loop transfer fun... more Given a linear system, all stabilizing controllers such that a specified closed-loop transfer function has H~ norm less than a given scalar, are parametrizedo This characterization involves the solution to two algebraic Riccati equations, each with the same order as the system, and further gives feasible controllers also with this order. The relationship to the risksensitive LQG stochastic control problem is estabfished, giving an equivalence between robust and stochastic control.
Integral feedback for perfect adaptation is a ubiquitous strategy in engineering and biology. Lon... more Integral feedback for perfect adaptation is a ubiquitous strategy in engineering and biology. Long studied in deterministic settings, it can now be understood in the context of the fully stochastic systems that are prevalent in biology.
In this article, we consider the dual scheduling algorithm for a generalized switch. For a satura... more In this article, we consider the dual scheduling algorithm for a generalized switch. For a saturated system, we prove the asymptotic optimality of the dual scheduling algorithm and thus establish its fairness properties. For a system with exogenous arrivals, we propose a modified dual scheduling algorithm, which is throughput-optimal while providing some weighted fairness among the users at the level of flows. The dual scheduling algorithm motivates a new architecture for scheduling, in which an additional queue is introduced to interface the user data queue and the time-varying server and to modulate the scheduling process, so as to achieve different performance objectives. Further research stemming out of this article includes scheduling with Quality of Service guarantees with the dual scheduler, and its application and implementation in various versions of the generalized switch model.
2010 First IEEE International Conference on Smart Grid Communications
In this paper, we consider two abstract market models for designing demand response to match powe... more In this paper, we consider two abstract market models for designing demand response to match power supply and shape power demand, respectively. We characterize the resulting equilibria in competitive as well as oligopolistic markets, and propose distributed demand response algorithms to achieve the equilibria. The models serve as a starting point to include the appliance-level details and constraints for designing practical demand response schemes for smart power grids.
Proceedings.Twenty-First Annual Joint Conference of the IEEE Computer and Communications Societies
We demonstrate that the dynamic behavior of queue and average window is determined predominantly ... more We demonstrate that the dynamic behavior of queue and average window is determined predominantly by the stability of TCP/RED, not by AIMD probing nor noise traffic. We develop a general multi-link multi-source model for TCP/RED and derive a local stability condition in the case of a single link with heterogeneous sources. We validate our model with simulations and illustrate the stability region of TCP/RED. These results suggest that TCP/RED becomes unstable when delay increases, or more strikingly, when link capacity increases. The analysis illustrates the difficulty of setting RED parameters to stabilize TCP: they can be tuned to improve stability, but only at the cost of large queues even when they are dynamically adjusted. Finally, we present a simple distributed congestion control algorithm that maintains stability for arbitrary network delay, capacity, load and topology.
The paper consde the problem of titing, from expem a data, real Parameters for amodd with unceint... more The paper consde the problem of titing, from expem a data, real Parameters for amodd with unceinty in the foim of both additive noe and mrm bouded peturbation. Suh mdelsfreuetly arise in robus control thery, and a framewor is introduced for the consideration of experimeal dat in robst cotrl analyn prob_l i the analysis took applied inude robust stabiliy tess for real parameter variations (real i), then the fraewwork can be used to addri the problem of ruobns parameter identificatwn. Wile the di dhere can qukckly become computainay overwheming whe applied to physical system and real data, the approach introduce a new way of looking at the idetificaon problem and may be helpfiu in ariving a more tractable method
Mixed H2 and H∞ norm analysis and synthesis problems are considered in this paper. It is shown th... more Mixed H2 and H∞ norm analysis and synthesis problems are considered in this paper. It is shown that the mixed norm analysis combined with structured uncertainty can be used to give bounds on robust H2 and H∞ performance. It is also shown that the mixed norm controller shares a separation property similar to those of pure H2 or H∞ controllers.
Future space structures have many closely spaced, lightly damped natural frequencies throughout t... more Future space structures have many closely spaced, lightly damped natural frequencies throughout the frequency domain. To achieve desired performance objectives, a number of these modes must actively be controlled. For control, a combination of collocated and noncollocated sensors and actuators will be employed. The control designs will be formulated based on models which have inaccuracies due to unmodeled dynamics, and variations in damping levels, natural frequencies and mode shapes. Therefore, along with achieving the performance objectives, the control design must be robust to a variety of uncertainty. This paper focuses on the benefits and linmitations associated with multivariable control design using noncoUocated versus collocated sensors and actuators. We address the question of whether performance is restricted due to the noncollocation of the sensors and actuators or the uncertainty associated with modeling of the flexible structures. Control laws are formulated based on models of the system and evaluated analytically and experimentally. Results of implementation of these control laws on the Caltech flexible structure are presented.
This paper considers the analysis and synthesis of control systems subject to two types of distrb... more This paper considers the analysis and synthesis of control systems subject to two types of distrbance signals: signals with bonded power spectral density and sinals with bounded power. The reslting control problem involves min-iiZing miXed X2 andX. norm ofthe system. Ltis shown that the controller share a separtion property similr to those of pure 72 or 74. controller It is also shown that the mized problem reduces naturally to X2 and 7X. problem in specal cas Some necesary Lad sufficient conditions are obtained for the existence of a solution to the mixed problem. Exicit sate space formulae are given for the optimal controllers.
The general distance problem which arises in the general H∞ optimal control problem is considered... more The general distance problem which arises in the general H∞ optimal control problem is considered. The existence of an optimal solution is proved and the expression of the optimal norm γo is obtained from a somewhat abstract operator point of view. An iterative scheme, called γ-iteration, is introduced which reduces the general distance problem to a standard best approximation problem.
The robustness analysis of system performance is one of the key issues in control theory, and one... more The robustness analysis of system performance is one of the key issues in control theory, and one approach is to reduce this problem to that of computing the structured singular value, μ. When real parametric uncertainty is included, then μ must be computed with respect to a block structure containing both real and complex uncertainties. It is shown that μ
his article reviews the current transmission control protocol (TCP) congestion control protocols ... more his article reviews the current transmission control protocol (TCP) congestion control protocols and overviews recent advances that have brought analytical tools to this problem. We describe an optimization-based framework that provides an interpretation of various flow control mechanisms, in particular, the utility being optimized by the protocol's equilibrium structure. We also look at the dynamics of TCP and employ linear models to exhibit stability limitations in the predominant TCP versions, despite certain built-in compensations for delay. Finally, we present a new protocol that overcomes these limitations and provides stability in a way that is scalable to arbitrary networks, link capacities, and delays.
The success of targeted cancer therapy is limited by drug resistance that can result from tumor g... more The success of targeted cancer therapy is limited by drug resistance that can result from tumor genetic heterogeneity. The current approach to address resistance typically involves initiating a new treatment after clinical/radiographic disease progression, ultimately resulting in futility in most patients. Towards a potential alternative solution, we developed a novel computational framework that uses human cancer profiling data to systematically identify dynamic, pre-emptive, and sometimes non-intuitive treatment strategies that can better control tumors in real-time. By studying lung adenocarcinoma clinical specimens and preclinical models, our computational analyses revealed that the best anti-cancer strategies addressed existing resistant subpopulations as they emerged dynamically during treatment. In some cases, the best computed treatment strategy used unconventional therapy switching while the bulk tumor was responding, a prediction we confirmed in vitro. The new framework pr...
We describe a variant of TCP, called FAST, that can sustain high throughput and utilization at mu... more We describe a variant of TCP, called FAST, that can sustain high throughput and utilization at multigigabits per second over large distances. We present the motiva- tion, review the background theory, summarize key features of FAST TCP, and report our first experimental results.
Given a linear system, all stabilizing controllers such that a specified closed-loop transfer fun... more Given a linear system, all stabilizing controllers such that a specified closed-loop transfer function has H~ norm less than a given scalar, are parametrizedo This characterization involves the solution to two algebraic Riccati equations, each with the same order as the system, and further gives feasible controllers also with this order. The relationship to the risksensitive LQG stochastic control problem is estabfished, giving an equivalence between robust and stochastic control.
Integral feedback for perfect adaptation is a ubiquitous strategy in engineering and biology. Lon... more Integral feedback for perfect adaptation is a ubiquitous strategy in engineering and biology. Long studied in deterministic settings, it can now be understood in the context of the fully stochastic systems that are prevalent in biology.
In this article, we consider the dual scheduling algorithm for a generalized switch. For a satura... more In this article, we consider the dual scheduling algorithm for a generalized switch. For a saturated system, we prove the asymptotic optimality of the dual scheduling algorithm and thus establish its fairness properties. For a system with exogenous arrivals, we propose a modified dual scheduling algorithm, which is throughput-optimal while providing some weighted fairness among the users at the level of flows. The dual scheduling algorithm motivates a new architecture for scheduling, in which an additional queue is introduced to interface the user data queue and the time-varying server and to modulate the scheduling process, so as to achieve different performance objectives. Further research stemming out of this article includes scheduling with Quality of Service guarantees with the dual scheduler, and its application and implementation in various versions of the generalized switch model.
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