EECI09: Introduction to Networked Control Systems

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This lecture provides an introduction to networked control systems. Networked control systems are emerging as a common architecture for embedded and autonomous systems, especially in applications where higher levels of decision making are required. Unlike traditional control systems, where communication and computational aspects are often ignored, networked control systems require an integration of techniques from computer science, communications and controls. An architecture for such systems is beginning to emerge, in which issues such as optimization-based estimation and control, packet-based control theory, and asynchronous computational models play a more central role. Applications of this new architecture include manufacturing systems, robotics and autonomous systems, sensor networks, vehicle and transportation management systems, and other applications in which multiple-embedded processes are interconnected with sensors and actuation to provide robust, computer controlled systems. We describe one specific example, Alice, an autonomous vehicle built by Caltech undergraduates to participate in the 2005 and 2007 DARPA Grand Challenges. Starting with the high level architecture, we describe some of the design choices that were made in the networked control systems (NCS) architecture and was as summarize the basic operation of the major software modules that are used to implement Alice's autonomous control system.

Lecture Materials

• Lecture slides: Course overview, Introduction to NCS
• Lecture notes: NCS06, Chapter 1
• Alice movies: NQE clips, GCE clips

Further Reading

• Control in an Information Rich World, R. M. Murray (ed). SIAM, 2003. This book provides a high level description of some of the research challenges and opportunities in the field of control. The executive summary (Section 1) and the application sections on "Information and Networks" and "Robotics and Intelligent Machines" (Section 3.2 and 3.3) are particularly relevant.

• Design Patterns for Robust and Evolvable Networked Control, C. L. Robinson, G. Baliga, S. Graham, P.R. Kumar. Conference on Systems Engineering Research (CSER), 2005 . This paper provides a survey of the approach being developed at UIUC by P. R. Kumar. This paper gives an overview of recent work out of UIUC on networked control systems. Two intersting concepts are explored: local temporal autonomy (LTA) and "shock absorbers" (buffers). Both of these concepts are designed to allow operation in the presence of lost data or component failure (and restart).

• Issues in the convergence of control with communication and computing: Proliferation, architecture, design, services, and middleware, Scott Graham, Girish Baliga, and P.R. Kumar. Conference on Decision and Control, 2004. Another high level paper out of UIUC talking about some of the issues that arise in networked control systems. In addition to providing a good high level overview, it has references to specific work that will be studied in later lectures. Two new concepts that are summarized in this paper are reliability and time protocols.

• Alice: An Information-Rich Autonomous Vehicle for High-Speed Desert Navigation, Cremean et al. Journal of Field Robotics, 2006. This article provides an overview of Alice's architecture and operation.

• Sensing, Navigation and Reasoning Technologies for the DARPA Urban Challenge, DARPA final report, 2007. This is the final report that was submitted to DARPA, documenting the operation of Alice in the 2007 Urban Challenge.

There are also many earlier papers on networked control systems that focus on issues related to dropped data, scheduling, and time delays in networked systems. These papers are analyzed in more detail in the lectures specifically devoted to those topics.

Additional Information

• Google Scholar: Networked Control Systems
• Networked Control Systems Repository (M. Branicky and S. Phillipps)
• Center for Communicating and Networked Control Systems (UIUC)
• Team Caltech homepage - contains movies and other information about the project
• Team wiki - detailed information about Alice, including documentation on hardware and software (requires username and password)