Institute for Systems Research Technical Reports
Permanent URI for this collectionhttp://hdl.handle.net/1903/4376
This archive contains a collection of reports generated by the faculty and students of the Institute for Systems Research (ISR), a permanent, interdisciplinary research unit in the A. James Clark School of Engineering at the University of Maryland. ISR-based projects are conducted through partnerships with industry and government, bringing together faculty and students from multiple academic departments and colleges across the university.
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Item Optimal Output Feedback Control Using Two Remote Sensors over Erasure Channels(2007) Gupta, Vijay; Martins, Nuno C.; Baras, John S.; Martins, Nuno C.; ISRItem Lifetime Maximizing Adaptive Traffic Distribution and Power Control in Wireless Sensor Networks(2006) Sun, Fangting; Shayman, Mark; Shayman, Mark; ISRIn this paper we study how to maximize the lifetime of randomly deployed wireless sensor networks by applying adaptive traffic distribution and power control. We model this problem as a linear program by abstracting the network into multiple layers. First we focus on the scenario where transmission energy consumption plays the dominant role in overall energy consumption. After ignoring the processing energy consumption, we observe that: in order to maximally extend the lifetime, each node should split its traffic into two portions, and send one portion directly to the sink, and the other one to its neighbor in the next inner layer. Next we consider the effect of incorporating the processing energy consumption. In this case, we have similar observation: for each packet to be sent, the sender should either transmit it using the transmission range with the highest energy efficiency per bit per meter, or transmit it directly to the sink. Besides studying the upper bound of maximum achievable lifetime extension, we discuss some practical issues, such as how to handle the signal interference caused by adaptive power control. Finally, we propose a fully distributed algorithm to adaptively split traffic and adjust transmission power for randomly deployed wireless sensor networks. We also provide extensive simulation results which demonstrat that the network lifetime can be dramatically extended by applying the proposed approach in various scenarios.Item Packet based Inference and Control(2006) Rabi, Maben; Baras, John S.; ISR; SEILCommunication constraints in Networked Control systems are frequently limits on data packet rates. To efficiently use the available packet rate budgets, we have to resort to event-triggered packet transmission. We have to sample signal waveforms and transmit packets not at deterministic times but at random times adapted to the signals measured. This thesis poses and solves some basic design problems we face in reaching for the extra efficiency. We start with an estimation problem involving a single sensor. A sensor makes observations of a diffusion process, the state signal, and has to transmit samples of this process to a supervisor which maintains an estimate of the state. The objective of the sensor is to transmit samples strategically to the supervisor to minimize the distortion of the supervisor's estimate while respecting sampling rate constraints. We solve this problem over both finite and infinite horizons when the state is a scalar linear system. We describe the relative performances of the optimal sampling scheme, the best deterministic scheme and of the suboptimal but simple to implement level-triggered sampling scheme. Apart from the utility of finding the optimal sampling strategies and their performances, we also learnt of some interesting properties of the level-triggered sampling scheme. The control problem is harder to solve for the same setting with a single sensor. In the estimation problem for the linear state signal, the estimation error is also a linear diffusion and is reset to zero at sampling times. In the control problem, there is no equivalent to the error signal. We pay attention to an infinite horizon average cost problem where, the sampling strategy is chosen to be level-triggered. We design piece-wise constant controls by translating the problem to one for discrete-time Markov chain formed by the sampled state. Using results on the average cost control of Markov chains, we are able to derive optimality equations and iteratively compute solutions. The last chapter tackles a binary sequential hypothesis testing problem with two sensors. The special feature of the problem is the ability of each sensor to hear the transmissions of the other towards the supervisor. Each sensor is afforded on transmission of a sample of its likelihood ratio process. We restrict attention to level-triggered sampling. Although we are unable to demonstrate overall optimality of the asynchronous scheme we pursue, we are able to describe its advantages over other level-triggered schemes and of course the deterministic one. The chief merits of this thesis are the formulation and solution of some basic problems in multi-agent estimation and control. In the problems we have attacked, we have been able to deal with the differences in information patterns at sensors and supervisors. The main demerits are the ignoring of packet losses and of variable delays in packet transmissions. The situation of packet losses can however be handled at the expense of additional computations. To summarize, this thesis provides valuable generalizations of the works of Astrom and Bernhardsson and of Kushner on timing of Control actions and of Sampling observations respectively.Item Simulations of Robotic Pursuit Using Matlab and Simulink(2006) Lioi, Joshua; Krishnaprasad, P.S.; ISRA pursuit curve is the path one creature takes while following another, and these can be used to model predator/prey chases, missiles homing in on a target, or even robot movement during a rendezvous. This paper will focus on the mathematical modeling and subsequently the simulation of these curves in Matlab Simulink. Two other students who were working in the lab interacted directly with the robots, and in particular, they worked with experimental robotic pursuit. Using the Cricket system, which works like an indoor GPS, the robots in the Intelligent Servosystems Lab can communicate their locations to one another, and then run pursuit protocols. The Matlab programs, though idealized, are successfully able to simulate the realistic trials of robotic pursuit.Item Planetary Rover Hybrid Locomotion-System Design(2006) Morrow, Joseph M.; Akin, David L.; ISRHaving already proven their worth several times in extraterrestrial environments, rovers can be highly versatile and valuable machines. Previous rovers have been designed to transport astronauts and materials, perform strenuous tasks that an astronaut in a pressurized suit may be unable to do, analyze foreign substances, create virtual maps of regions, and serve as a life support platform to increase operational safety and chances of mission success. However, a successful rover design is often difficult to engineer and manufacture. Before a rover can be considered a valuable asset to mission success, it must be capable of operating in a variety of conditions and without requiring a great deal of human supervision. Specifically, it must be able to traverse irregular and treacherous terrain in a timely and efficient manner; it must be able to safely go where an astronaut can travel, and, in some cases, go and return from areas deemed too dangerous for human exploration. To do this, the rover needs an effective, yet simple locomotion system capable of crossing relatively flat terrain quickly and efficiently while also capable of adapting to rough terrain without undue difficulty. Inspired by the Jet Propulsion Laboratory (JPL) All-Terrain Hex-Legged Extra-Terrestrial Explorer (ATHLETE) and the University of Pennsylvania (UPenn) RHex, this paper proposes a simple experimental prototype locomotion system design that enables a rover to alternate between alkingand ollingmodes to successfully navigate variable and unpredictable terrain.Item Construction of a Hovercraft Model and Control of its Motion(2006) Schleigh, Jeffrey; Zhang, Guangming; ISRFor this research project, there are two basic requirements. The first requirement is to design and construct a physical model of a hovercraft prototype. The second requirement is to control the motion of the constructed hovercraft prototype, such as following a track, which consists of straight lines and curves. There are three software systems available in the completion of this research project. These systems are Pro/ENGINEER, SolidWorks and Robotics Invention System.Item Snake Inspired Robots with a Rectilinear Gait(2006) Brock, Garry; Gupta, S.K.; ISRThe problem that I was working on was trying to create a robot to successfully demonstrate rectilinear snake motion, try to create the quickest gait possible for the robot, and then work to create a modular robot. We were currently without a model that has no external constraints to test gaits on. Creation of the modular robot was being used to determine the effects of injection molding on robotic components and to see the effects that they would have on such parts. This would also help in the long term goal of creating a fully modular robotic snake. In accomplishing these goals I would need to create two separate robots. The first being a simple robot that would demonstrate rectilinear motion, the second robot would be modular and made from the injection molding. The two robots would have nothing to do with each other.Item On zero-one laws for connectivity in one-dimensional geometric random graphs(2006) Han, Guang; Makowski, Armand M.; Makowski; ISR; CSHCNWe consider the geometric random graph where n points are distributed uniformly and independently on the unit interval [0,1]. Using the method of first and second moments, we provide a simple proof of the "zero-one" law for the property of graph connectivity under the asymptotic regime created by having n become large and the transmission range scaled appropriately with n.Item Efficient sampling for keeping track of an Ornstein-Uhlenbeck process(2006) Rabi, Maben; Moustakides, George; Baras, John S.; Baras, John S.; ISR; SEILWe consider estimation and tracking problems in sensor networks with constraints in the hierarchy of inference making, on the sharing of data and inter-sensor communications. We identify as a typical representative for such problems tracking of a process when the number and type of measurements in constrained. As the simplest representative of such problems, which still encompasses all the key issues involved we analyze efficient sampling schemes for tracking an Ornstein-Uhlenbeck process. We considered sampling based on time, based on amplitude (event-triggered sampling) and optimal sampling (optimal stopping). We obtained the solution in each case as a constrained optimization problem. We compare the performance of the various sampling schemes and show that the event-triggered sampling performs close to optimal. Implications and extensions are discussed.Item Multiple Sampling for Estimation on a Finite Horizon(2006) Rabi, Maben; Baras, John S.; Moustakides, George; Baras, John S.; ISR; SEILWe discuss some multiple sampling problems that arise in real-time estimation problems with limits on the number of samples. The quality of estimation is measured by an aggregate squared error over a finite horizon. We compare the performances of the best detereministic, level-triggered and the optimal sampling schemes. We restrict the signal to be either a Wiener process or an Ornstein-Uhlenbeck process. For the Wiener process, we provide closed form expressions and series expansions. For the Ornstein Uhlenbeck process, we provide procedures for numerical computation. Our results show that level-triggered sampling is almost optimal when the signal is stable.