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Near Optimal Rate Selection for Wireless Control Systems
"... Abstract—With the advent of industrial standards such as WirelessHART, process industries are now gravitating towards wireless control systems. Due to limited bandwidth in a wireless network shared by multiple control loops, it is critical to optimize the overall control performance. In this paper, ..."
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Abstract—With the advent of industrial standards such as WirelessHART, process industries are now gravitating towards wireless control systems. Due to limited bandwidth in a wireless network shared by multiple control loops, it is critical to optimize the overall control performance. In this paper, we address the scheduling-control co-design problem of determining the optimal sampling rates of feedback control loops sharing a WirelessHART network. The objective is to minimize the overall control cost while ensuring that all data flows meet their end-toend deadlines. The resulting constrained optimization based on existing delay bounds for WirelessHART networks is challenging since it is non-differentiable, non-linear, and not in closed-form. We propose four methods to solve this problem. First, we present a subgradient method for rate selection. Second, we propose a greedy heuristic that usually achieves low control cost while significantly reducing the execution time. Third, we propose a global constrained optimization algorithm using a simulated annealing (SA) based penalty method. Finally, we formulate rate selection as a differentiable convex optimization problem that provides a closed-form solution through a gradient descent method. This is based on a new delay bound that is convex and differentiable, and hence simplifies the optimization problem. We evaluate all methods through simulations based on topologies of a 74-node wireless sensor network testbed. Surprisingly, the subgradient method is disposed to incur the longest execution time as well as the highest control cost among all methods. SA and the greedy heuristic represent the opposite ends of the tradeoff between control cost and execution time, while the gradient descent method hits the balance between the two. I.
Three Aspects of Real-Time Multiprocessor Scheduling: Timeliness, Fault Tolerance, Mixed Criticality
, 2012
"... The design of real-time systems faces two important challenges: incorporating more functions/services on existing hardware to make the system more attractive to the mar-ket, and deploying existing software on multiprocessors (e.g., multicore) to utilize more processing power. Adding more services on ..."
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Cited by 1 (0 self)
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The design of real-time systems faces two important challenges: incorporating more functions/services on existing hardware to make the system more attractive to the mar-ket, and deploying existing software on multiprocessors (e.g., multicore) to utilize more processing power. Adding more services on the same hardware needs efficient resource utilization. In addition, satisfying the real-time constraints, while at the same time effi-ciently utilizing the multiprocessor platform, is a challenging problem. This thesis deals with global multiprocessor scheduling for real-time systems, that is, the fixed-priority scheduling of sporadic tasks, where each task is allowed to run on any processor. More specifically, this thesis considers three aspects of the design and analysis of global scheduling algorithms: timeliness, fault tolerance, and mixed criticality. Timeli-ness is about meeting the deadlines of the tasks; fault tolerance is about producing the correct output within the deadline even in the presence of faults; and mixed criticality is about facilitating the certification of systems when tasks having different criticality (or importance) are hosted on a common computing platform.
xx Near Optimal Rate Selection for Wireless Control Systems
"... With the advent of industrial standards such as WirelessHART, process industries are now gravitating towards wireless control systems. Due to limited bandwidth in a wireless network shared by multiple control loops, it is critical to optimize the overall control performance. In this paper, we addres ..."
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With the advent of industrial standards such as WirelessHART, process industries are now gravitating towards wireless control systems. Due to limited bandwidth in a wireless network shared by multiple control loops, it is critical to optimize the overall control performance. In this paper, we address the schedulingcontrol co-design problem of determining the optimal sampling rates of feedback control loops sharing a WirelessHART network. The objective is to minimize the overall control cost while ensuring that all data flows meet their end-to-end deadlines. The resulting constrained optimization based on existing delay bounds for WirelessHART networks is challenging since it is non-differentiable, non-linear, and not in closed-form. We propose four methods to solve this problem. First, we present a subgradient method for rate selection. Second, we propose a greedy heuristic that usually achieves low control cost while significantly reducing the execution time. Third, we propose a global constrained optimization algorithm using a simulated annealing (SA) based penalty method. We study SA method under both constant factor penalty and adaptive penalty. Finally, we formulate rate selection as a differentiable convex optimization problem that provides a quick solution through a convex optimization technique. This is based on a new delay bound that is convex and differentiable, and hence simplifies the optimization problem. We study both the gradient descent method and the interior point method to solve it. We evaluate all methods through simulations
Publication Cyber-Physical Systems Wireless Sensor Networks Embedded Systems Real-Time Systems Parallel and Multi-core Computing
, 2008
"... (RTAS ’11); pp. 13–22 ..."
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Dear Members of the Search Committee:
, 2013
"... In response to your advertisement on your department website, I am offering myself as a candidate for the position of a tenure-track assistant professor. I am completing my PhD by May of 2013 under the supervision of Prof. Chenyang Lu from the Department of Computer Science and Engineering at Washin ..."
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In response to your advertisement on your department website, I am offering myself as a candidate for the position of a tenure-track assistant professor. I am completing my PhD by May of 2013 under the supervision of Prof. Chenyang Lu from the Department of Computer Science and Engineering at Washington University in St Louis. My doctoral dissertation primarily concerns Cyber-Physical Systems (CPS), focusing on real-time scheduling for wireless control networks and parallel tasks on multi-core platforms. Driven by the grand challenges raised in emerging CPS, my research, in general, spans embedded systems, wireless sensor networks, real-time systems, and multi-core parallel computing. I approach research challenges through a blend of both theory and systems, with emphasis on analytical results. Addressing the critical demands on reliable and real-time communication in industrial CPS, my work established a real-time scheduling framework for wireless control networks by bridging real-time scheduling theory and wireless networks. I then developed a scheduling-control co-design approach to deal with the complex interactions between control performance and real-time communication in these systems. Considering the evolution of multi-core technology, I also researched on exploiting multi-core platforms through real-time parallel scheduling to address computation-intensive complex real-time applications. Furthermore, I built a wireless sensor network system for power monitoring and power capping
RESEARCH STATEMENT
"... My research primarily concerns Cyber-Physical Systems (CPS), focusing on real-time scheduling for wireless control networks and parallel tasks on multi-core platforms. CPS conjoin computing, communication, sensing, and control of physical processes. Deployment of these systems is widely seen in proc ..."
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My research primarily concerns Cyber-Physical Systems (CPS), focusing on real-time scheduling for wireless control networks and parallel tasks on multi-core platforms. CPS conjoin computing, communication, sensing, and control of physical processes. Deployment of these systems is widely seen in process control, smart manufacturing, smart grid, and avionics, where real-time performance guarantees are critical for correct operation [1]. Driven by this new frontier, my research, in general, spans a broad range of topics in embedded systems, wireless sensor networks, real-time systems, and multi-core parallel computing. In my thesis, I have developed a real-time scheduling framework and a scheduling-control co-design framework for wireless CPS through a novel approach that crosscuts the areas of wireless sensor networks, real-time systems, control, and optimization theory. I approach research challenges through a blend of both theory and systems, with emphasis on analytical results. CPS in Wireless Control Wireless control in process industries represents an important class of distributed CPS that involve realtime coordination among sensors, actuators, and controllers through a wireless network. These systems employ feedback control loops between the networked sensors and actuators. Sensors measure process variables, and deliver to a controller through the network. The controller sends the control commands to
A New Fixed-Priority Assignment Algorithm for Global Multiprocessor Scheduling
"... Abstract—Global fixed-priority scheduling of constrained-deadline sporadic tasks systems is important not only for CPU scheduling but also in other domains, for example, scheduling real-time flows in WirelessHART networks designed for industrial process control and monitoring. In this paper, we prop ..."
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Abstract—Global fixed-priority scheduling of constrained-deadline sporadic tasks systems is important not only for CPU scheduling but also in other domains, for example, scheduling real-time flows in WirelessHART networks designed for industrial process control and monitoring. In this paper, we propose a novel priority assignment scheme for scheduling such task systems on multiprocessors and demonstrate, using proof and simulation, that the scheme is superior to prior schemes. I.
Laboratório de Sistemas Informáticos de Grande-Escala (LaSIGE) Navigators Research Team
"... Networking communications play an important role to se-cure a dependable and timely operation of distributed and real-time embedded system applications; however, an effec-tive real-time support is not yet properly addressed in the wireless realm. This paper presents Wi-STARK, a novel architecture fo ..."
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Networking communications play an important role to se-cure a dependable and timely operation of distributed and real-time embedded system applications; however, an effec-tive real-time support is not yet properly addressed in the wireless realm. This paper presents Wi-STARK, a novel architecture for resilient and real-time wireless communi-cations within an one-hop communication domain. Low level reliable (frame) communications, node failure detec-tion, membership management, and networking partition control are provided; since these low level services extend and build upon the exposed interface offered by networking technologies, Wi-STARK is in strict compliance with wire-less communication standards, such as IEEE 802.15.4 and IEEE 802.11p. The Wi-STARK service interface is then offered as operating system primitives, helpful for building distributed control applications. The one-hop dependabil-ity and timeliness guarantees offered by Wi-STARK are a fundamental step towards an effective design of real-time wireless networks with multiple hops, including end-to-end schedulability analysis of networking operations.
Article Routing and Scheduling Algorithms for WirelessHART Networks: A Survey
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Real-Time Wireless Sensor-Actuator Networks for Cyber-Physical Systems
, 2013
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