Nuno Martins - US grants

ECCS-0644764
PI: Martins


ABSTRACT

The interplay between control and communications is pervasive in most of today's large scale engineering enterprises, including the industrial and transportation sectors. This proposal puts forward a program, with tightly coupled research and educational components, centered on the design of distributed control systems with wireless communication capabilities. In contrast to wire-line networks, wireless communications allows mobility, streamlines re-configuration and reduces deployment costs. However, most mobile wireless communication technologies feature interference, fading and power constraints. These attributes make the analysis and the design of such networked control systems significantly more difficult. This proposal's research plan introduces two new paradigms. The first paradigm, denoted as networked preview control, specifies a framework consisting of a wireless network of spatially-distributed sensors and one controller. Given a disturbance field, networked preview control aims at using the remote sensors to provide the controller with disturbance preview information. The second paradigm concerns the design of cooperative control strategies for a mix of mobile and static agents, with the objective of attaining pre-specified communication objectives.

Intellectual merit: The overarching technical contribution is that of designing control systems with a communication component that features interference, fading and power constraints, requiring a deeper fusion of techniques from control theory, network information theory and networking.

Broader impacts: The PI intends to use this proposal's results in the design of more efficient transportation systems. This proposal includes a five year undergraduate internship program, aimed at increasing the number of domestic students who pursue careers in engineering at the industrial and academic levels, especially females and minorities.

This proposal outlines a two year research program for developing the first collection of methods, for designing controllers that achieve optimal reference tracking, for randomly time-varying systems. As a first step, the PI adopts a Markovian jump linear system formulation because it retains the tractability of the linear deterministic case, while featuring a stochastic variation of its underlying structure. Recent results provide solutions to the H2 and H_inf optimal regulator (no reference) problems, for Markovian jump linear systems. However, the paradigm described in this proposal, where a reference has to be tracked, has not been investigated and it cannot be addressed by methods based on classical adaptations of optimal regulation theory, such as the internal model principle. The PI expects that an efficient design methodology will rely on a new framework for the joint design of the state-estimator, the state-feedback controller and the feedforward terms, using linear matrix inequality techniques. The research outlined in this proposal will also unveil structural properties of servomechanisms that achieve optimal reference tracking, in the presence of random or intermittent failures.

Modern engineering systems are often made of a complex assemblage of mechanical components, electro-mechanical devices and sensors. Due to sudden fluctuations in the environment, component failure or assemblage interconnection disruptions, such systems may exhibit abrupt changes in their structure. Often, such variations are of an unpredictable, random or intermittent nature. Energy harvesting facilities, such as solar power plants, are examples of systems whose dynamic behavior depends directly on environmental parameters that may fluctuate randomly. Further examples abound, such as automobiles and manufacturing facilities, where actuator or sensor intermittent failures may occur. In this proposal, the PI plans to develop the first set of tools for the performance analysis, and the design of controllers that achieve optimal reference tracking in the presence of plants whose structure varies in a random and unpredictable way. The PI expects that the outcomes of the proposed research will enable the design of control systems that are safer and more efficient, in the presence of random and abrupt changes in the physical plant?s structure.

This proposal requests funds to support the fourth Northeast StudentWorkshop
on Systems and Control, to be held at The University of Maryland, College
Park, from Saturday, April 26, through Sunday April 27, 2008. The goal of the
workshop is to offer educational opportunities to graduate students, postdoctoral scholars, and junior researchers to learn about the latest developments in control systems research, particularly in emerging application areas; to present their research results; and to share and discuss ideas with their peers, as well as with faculty members from other universities. The proximity of the universities in the Northeast provides an excellent opportunity to realize this goal with minimal travel cost. In contrast to previous editions, this year the Northeast Student Workshop on Systems and Control will include panels on careers in industry and on funding opportunities. The former will give students and postdoctoral scholars the opportunity to interact with industry representatives and learn about research careers in industry. The panel on funding opportunities will give postdoctoral scholars and junior researchers a unique perspective on the funding opportunities at various funding agencies.

The intellectual merit of the proposed activity is that it will provide a stimulus for sustained research in control systems theory, as well as increased number of applications in other fields of science and engineering.

The broad impact resulting from the proposed workshop will be the encouragement of a broader and more diverse group of students (than those who are already able to attend major conferences in the field) to pursue research careers. A directed effort has been made to attract faculty and students from Historically Black Colleges and Universities to attend this workshop.

The objective of this research is to discover new fundamental principles, design methods, and technologies for realizing distributed networks of sub-cm3, ant-sized mobile micro-robots that self-organize into cooperative configurations. The approach is intrinsically interdisciplinary and organized along four main thrusts: (1) Algorithms for distributed coordination and control under severe power, communication, and mobility constraints. (2) Electronics for robot control using event-based communication and computation, ultra-low-power radio, and adaptive analog-digital integrated circuits. (3) Locomotion devices and efficient actuators using rapid-prototyping and MEMS technologies that can operate robustly under real-world conditions. (4) Integration of the algorithms, electronics, and actuators into a fleet of ant-size micro-robots.

No robots at the sub-cm3 scale exist because their development faces a number of open challenges. This research will identify and determine means for solving these challenges. In addition, it will provide new solutions to outstanding questions about resource-constrained algorithms, architectures, and actuators that can be widely leveraged in other applications. The PIs will adopt a co-design philosophy that promotes cross-disciplinary research and tight collaboration.

Networks of ant-sized robots are expected to be useful in disaster relief, manufacturing, warehouse management, and ecological monitoring, as well as in new unforeseen applications. In addition, the new methods and principles proposed here can be transitioned to other highly-distributed and resource-constrained engineering problems, such as air-traffic control systems. This research program will train Ph.D. students with unique skills in the design of hybrid distributed networks and it will involve undergraduate students, particularly underrepresented minorities and women.

This project will construct a wireless network of animal-borne embedded devices that will be deployed and tested in a biologically-relevant application. The networked devices will provide not only geo-location data, but also execute cooperative strategies that save battery-life by selectively recording bandwidth-intensive audio and high-definition video footage of occurrences of animal group behavior of interest, such as predation.
This project comprises three concurrent and interdependent research themes. The first is the investigation of methods to design and analyze the performance of distributed algorithms that implement autonomous decisions at the mobile agents, subject to communication and computational constraints. The second will pursue data-driven fundamental research on the modeling of animal group motion and will promote a formal understanding of the mechanisms of social interaction. The third is centered on the investigation of methods for hardware integration to build distributed networks of embedded devices that are capable of executing the newly developed algorithms, subject to power and weight constraints.
The results and experience gained in this project will guide the development of effective autonomous systems for the monitoring and protection of endangered species. This project will create undergraduate and graduate research opportunities at all participating institutions, expanding on an existing collaboration between the University of Maryland, Princeton University, and the National Geographic Society. There is the potential for using wide-reaching media resources to disseminate the results of this project to a broad audience. This may contribute to attracting more students to engineering and science.

Designing semi-autonomous networks of miniature robots for inspection of bridges and other large civil infrastructure

According to the U.S. Department of Transportation, the United States has 605102 bridges of which 64% are 30 years or older and 11% are structurally deficient. Visual inspection is a standard procedure to identify structural flaws and possibly predict the imminent collapse of a bridge and determine effective precautionary measures and repairs. Experts who carry out this difficult task must travel to the location of the bridge and spend many hours assessing the integrity of the structure.

The proposal is to establish (i) new design and performance analysis principles and (ii) technologies for creating a self-organizing network of small robots to aid visual inspection of bridges and other large civilian infrastructure. The main idea is to use such a network to aid the experts in remotely and routinely inspecting complex structures, such as the typical girder assemblage that supports the decks of a suspension bridge. The robots will use wireless information exchange to autonomously coordinate and cooperate in the inspection of pre-specified portions of a bridge. At the end of the task, or whenever possible, they will report images as well as other key measurements back to the experts for further evaluation.

Common systems to aid visual inspection rely either on stationary cameras with restricted field of view, or tethered ground vehicles. Unmanned aerial vehicles cannot access constricted spaces and must be tethered due to power requirements and the need for uninterrupted communication to support the continual safety critical supervision by one or more operators. In contrast, the system proposed here would be able to access tight spaces, operate under any weather, and execute tasks autonomously over long periods of time.

The fact that the proposed framework allows remote expert supervision will reduce cost and time between inspections. The added flexibility as well as the increased regularity and longevity of the deployments will improve the detection and diagnosis of problems, which will increase safety and support effective preventive maintenance.

This project will be carried out by a multidisciplinary team specialized in diverse areas of cyber-physical systems and robotics, such as locomotion, network science, modeling, control systems, hardware sensor design and optimization. It involves collaboration between faculty from the University of Maryland (UMD) and Resensys, which specializes in remote bridge monitoring. The proposed system will be tested in collaboration with the Maryland State Highway Administration, which will also provide feedback and expertise throughout the project.

This project includes concrete plans to involve undergraduate students throughout its duration. The investigators, who have an established record of STEM outreach and education, will also leverage on exiting programs and resources at the Maryland Robotics Center to support this initiative and carry out outreach activities. In order to make student participation more productive and educational, the structure of the proposed system conforms to a hardware architecture adopted at UMD and many other schools for the teaching of undergraduate courses relevant to cyber-physical systems and robotics.

This grant will support research on fundamental principles and design of robotic and cyber-physical systems. It will focus on algorithm design for control and coordination, network science, performance evaluation, microfabrication and system integration to address the following challenges: (i) Devise new locomotion and adhesion principles to support mobility within steel and concrete girder structures. (ii) Investigate the design of location estimators, omniscience and coordination algorithms that are provably optimal, subject to power and computational constraints. (iii) Methods to design and analyze the performance of energy-efficient communication protocols to support robot coordination and localization in the presence of the severe propagation barriers caused by metal and concrete structures of a bridge.

The proposal deals with innovative methods to analyze the performance and design optimal distributed estimation systems that operate over shared networks. The research plan adopts a configuration formed by multiple remote sensors, which assess potentially dissimilar information and are not allowed to communicate with each other, and one receiver that acts as fusion center. The role of the fusion center is to estimate a parameter or process of interest based on information that is transmitted to it through the network by the sensors. A central feature of the formulation is the constraint that the network is shared and can support only a finite number of simultaneous transmissions. In a multi-user wireless setting, such a limitation may be the result of interference that causes information loss whenever a receiver cannot discern simultaneous transmissions occurring in the same channel. In general, the number of simultaneous transmissions in a shared network, which can be wireless or wireline, may also be constrained due to security, regulatory considerations or power and bandwidth limitations. In general, it is not possible to estimate the process of interest with no error because it could require simultaneous transmissions by all sensors, which is not possible in the proposed formulation. A class of problems to design the processing at the fusion center is considered. Since there is no communication among the sensors, it can be shown that the resulting paradigm is a non-convex team problem with a non-classical information pattern.

A class of collision channels to model the effect of simultaneous transmissions is considered. In this approach, the problem, from the point of view of each sensor, is recast as one of designing an optimal remote estimation system across a new class of erasure links, and in the presence of communication costs. A connection to optimal quantization theory will be investigated to obtain effective numerical optimization algorithms. The proposed approach also leads to a new class of optimal quantization problems for which the cost is non-uniform across representation symbols. We explore how the ideas above can be used to find the optimal solution to particular cases of the problem. This includes the settings in which measurements are independent and dependent across sensors, and the one-step and sequential cases. The two-sensor framework that shows the optimality of asymmetric threshold policies at the sensors with Gaussian measurements, and extensions to multiple sensors in the presence of measurement noise will be investigated. In addition, efficient software tools to implement the algorithms for design and performance analysis will be developed. An important component of any networked monitoring or control layer, estimation algorithms executed at the sensors and fusion centers must be designed in unison to guarantee the performance of the overall system. The methods will allow implementation of optimal policies, and analyze the tradeoffs of performance for a range of applications for which the number of transmitting sensors exceeds what the underlying network can utilize. Examples include sensor networks in buildings, large renewable energy generation infrastructure and power distribution networks.

A sudden surge in demand in traffic networks disrupts the equilibrium conditions upon which these networks are planned and operated. Lack of understanding of the population's strategic choices under extreme demand may result in paradoxical outcomes, such as evacuations aiming to save lives instead resulting in mass casualties on the road or opening up of new roads increasing rather than decreasing travel time. This project will devise systems and procedures for managing the strategic choices of populations (e.g., whether to evacuate or shelter in place, which escape routes to take) and the actions of the authorities (e.g., which zones to evacuate and in which sequence, where to route the traffic, whether to close some roads or open extra lanes in a given direction). The tools resulting from this project will enable better response systems to assist local authorities in managing extreme demand, such as when entire counties have to be evacuated to protect the residents from a wildfire. The project will develop a modeling and simulation tool chain to predict traffic bottleneck locations and their severity together with expected travel times and delays, thus determining the spectrum of outcomes, identifying worst cases, and enabling the authorities to make informed decisions.

The technical approach is rooted in population games, which model the dynamics of strategic noncooperative interactions among large populations of agents competing for resources. The project, however, will depart from the equilibrium focus of the existing theory and will offer transient analysis tools that account for not only the strategy revisions of the agents, but also a host of cyber and physical dynamics, such as queueing dynamics in traffic flow, responsive signal control at intersections, information dissemination to agents, and evolution of hazards, such as fire propagation. The research tasks to enable the project's vision of a "cyber-physical population game theory" include characterizing transient behavior with system-theoretic methods, accounting for uncertainty in strategy revision models, extending the theory to a continuum of user preferences, rethinking the stochastic processes underlying the dynamical models, modifying the theory for short-term horizons for time-critical operations, learning dynamical models from data, and formulating extensive form games between a population and a single agent, motivated by the population response to evacuation orders. In addition, the project will identify control actions (such as responsive signal policies, road closures, disabling certain turns) to close the data-decision-action loop and steer the dynamics towards desirable outcomes and avoiding unsafe ones.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.