This paper describes an exercise in building a complete robot aimed at being as small as possible but using off-the-shelf components exclusively. The result is an autonomous mobile robot slightly larger than one cubic inch which incorporates sensing, actuation, onboard computation, and onboard power supplies. Nicknamed Squirt, this robot acts as a 'bug', hiding in dark corners and venturing out in the direction of last heard noises, only moving after the noises are long gone.

The development, implementation, and testing of a leader-follower based robust nonlinear formation controller is discussed in this thesis. This controller uses sliding mode control on the length and angle between the leader and follower vessels to produce the desired formation. A boat model, assuming planar motion (three degrees of freedom), is used as the bases for the controller. Open loop testing is performed to determine parameter values to match the simulation model to the physical one and, upon tuning of the controller to match, closed loop testing of the controller with a virtual leader is also performed. From these tests it is found that the controller is unstable, thus improvements to the controller, through changes made to the model and to the parameter identification process, are undertaken. Simulations comparing the initial and updated models of the vehicle to open loop data show an improvement in the new model.

An autonomous machine is a machine that can navigate through its environment without human interactions. These machines use sensors to sense the environment and have computing abilities for receiving and interpreting the sensory data as well as for controlling their displacement. At the University of Saskatchewan (Saskatoon, Canada), a low level autonomous machine was developed. This low level machine was the sensor system for an autonomous machine. The machine was capable of sensing the environment and carrying out actions based on commands sent to it. This machine provided a sensing and control layer, but the path planning (decision making) part of the autonomous machine was not developed.<p>This autonomous machine was developed on a Case IH DX 34H tractor with the purpose of providing a machine for testing software and sensors in a true agricultural environment. The tractor was equipped with sensors capable of sensing the speed and heading of the tractor. A control architecture was developed that received input commands from a human or computer in the form of a target heading and speed. The control architecture then adjusted controls on the tractor to make the tractor reach and maintain the target heading and speed until a new command was provided. The tractor was capable of being used in all kinds of weather, although some minor issues arose when testing in rain and snow. The sensor platform developed was found to be insufficient for proper control. The control structure appeared to work correctly, but was hindered by the poor sensor platform performance.

A web crawler provides an automated way to discover web events ? creation, deletion, or updates of web pages. Competition among web crawlers results in redundant crawling, wasted resources, and less-than-timely discovery of such events. This thesis presents a cooperative sharing crawler algorithm and sharing protocol. Without resorting to altruistic practices, competing (yet cooperative) web crawlers can mutually share discovered web events with one another to maintain a more accurate representation of the web than is currently achieved by traditional polling crawlers. The choice to share or merge is entirely up to an individual crawler: sharing is the act of allowing a crawler M to access another crawler's web-event data (call this crawler S), and merging occurs when crawler M requests web-event data from crawler S. Crawlers can choose to share with competing crawlers if it can help reduce contention between peers for resources associated with the act of crawling. Crawlers can choose to merge from competing peers if it helps them to maintain a more accurate representation of the web at less cost than directly polling web pages. Crawlers can control how often they choose to merge through the use of a parameter &#961;, which dictates the percentage of time spent either polling or merging with a peer. Depending on certain conditions, pathological behaviour can arise if polling or merging is the only form of data collection. Simulations of communities of simple cooperating web crawlers successfully show that a combination of polling and merging (0 < &#961; < 1) can allow an individual member of the cooperating community a higher degree of accuracy in their representation of the web as compared to a traditional polling crawler. Furthermore, if web crawlers are allowed to evaluate their own performance, they can dynamically switch between periods of polling and merging to still perform better than traditional crawlers. The mutual performance gain increases as more crawlers are added to the community.

A web crawler provides an automated way to discover web events ? creation, deletion, or updates of web pages. Competition among web crawlers results in redundant crawling, wasted resources, and less-than-timely discovery of such events. This thesis presents a cooperative sharing crawler algorithm and sharing protocol. Without resorting to altruistic practices, competing (yet cooperative) web crawlers can mutually share discovered web events with one another to maintain a more accurate representation of the web than is currently achieved by traditional polling crawlers. The choice to share or merge is entirely up to an individual crawler: sharing is the act of allowing a crawler M to access another crawler's web-event data (call this crawler S), and merging occurs when crawler M requests web-event data from crawler S. Crawlers can choose to share with competing crawlers if it can help reduce contention between peers for resources associated with the act of crawling. Crawlers can choose to merge from competing peers if it helps them to maintain a more accurate representation of the web at less cost than directly polling web pages. Crawlers can control how often they choose to merge through the use of a parameter &#961;, which dictates the percentage of time spent either polling or merging with a peer. Depending on certain conditions, pathological behaviour can arise if polling or merging is the only form of data collection. Simulations of communities of simple cooperating web crawlers successfully show that a combination of polling and merging (0 < &#961; < 1) can allow an individual member of the cooperating community a higher degree of accuracy in their representation of the web as compared to a traditional polling crawler. Furthermore, if web crawlers are allowed to evaluate their own performance, they can dynamically switch between periods of polling and merging to still perform better than traditional crawlers. The mutual performance gain increases as more crawlers are added to the community.

An autonomous machine is a machine that can navigate through its environment without human interactions. These machines use sensors to sense the environment and have computing abilities for receiving and interpreting the sensory data as well as for controlling their displacement. At the University of Saskatchewan (Saskatoon, Canada), a low level autonomous machine was developed. This low level machine was the sensor system for an autonomous machine. The machine was capable of sensing the environment and carrying out actions based on commands sent to it. This machine provided a sensing and control layer, but the path planning (decision making) part of the autonomous machine was not developed.<p>This autonomous machine was developed on a Case IH DX 34H tractor with the purpose of providing a machine for testing software and sensors in a true agricultural environment. The tractor was equipped with sensors capable of sensing the speed and heading of the tractor. A control architecture was developed that received input commands from a human or computer in the form of a target heading and speed. The control architecture then adjusted controls on the tractor to make the tractor reach and maintain the target heading and speed until a new command was provided. The tractor was capable of being used in all kinds of weather, although some minor issues arose when testing in rain and snow. The sensor platform developed was found to be insufficient for proper control. The control structure appeared to work correctly, but was hindered by the poor sensor platform performance.

It is known in the literature on Automated Highway Systems that information flow can significantly affect the propagation of errors in spacing in a collection of vehicles. This thesis investigates this issue further for a homogeneous collection of vehicles. Specifically, we consider the effect of information flow on the propagation of errors in spacing and velocity in a collection of vehicles trying to maintain a rigid formation. The motion of each vehicle is modeled using a Linear Time Invariant (LTI) system. We consider undirected and connected information flow graphs, and assume that that each vehicle can communicate with a maximum of q(n) vehicles, where q(n) may vary with the size n of the collection. The feedback controller of each vehicle takes into account the aggregate errors in position and velocity of the vehicles, with which it is in direct communication. The controller is chosen in such a way that the resulting closed loop system is a Type-2 system. This implies that the loop transfer function must have at least two poles at the origin. We then show that if the loop transfer function has three or more poles at the origin, and if the size of the formation is sufficiently large, then the motion of the collection is unstable. Suppose l is the number of poles of the transfer function relating the position of a vehicle with the control input at the origin of the complex plane, and if the number (q(n)l+1)/(nl) -> 0 as n -> (Infinity), then we show that there is a low frequency sinusoidal disturbance with unity maximum amplitude acting on each vehicle such that the maximum errors in spacing response increase at least as much as O (square_root(n^l/(q(n)^(l+1)) ) consequence of the results presented in this paper is that the maximum of the error in spacing and velocity of any vehicle can be made insensitive to the size of the collection only if there is at least one vehicle in the collection that communicates with at least O(square_root(n)) other vehicles in the collection.

This thesis presents a control algorithm to be used by a team of ECAVs (Electronic Combat Air Vehicle) to deceive a network of radars through the generation of a phantom track. Each ECAV has the electronic capability of intercepting and introducing an appropriate time delay to a transmitted pulse of a radar before transmitting it back to the radar, thereby deceiving the radar into seeing a phantom target at a range beyond that of the ECAV. A radar network correlates targets and target tracks to detect range delay based deception. A team of cooperating ECAVs, however, precisely plans their trajectories in a way all the radars in the radar network are deceived into seeing the same phantom. Since each radar in the network confirms the target track of the other, the phantom track is considered valid. An important feature of the algorithm achieving this is that it translates kinematic constraints on the ECAV dynamic system into constraints on the phantom point. The phantom track between two specified way points then evolves without violating any of the system constraints. The evolving phantom track in turn generates the actual controls on the ECAVs so that ECAVs have flyable trajectories. The algorithms give feasible but suboptimal solutions. The main objectives are algorithm development for phantom track generation through a team of cooperating ECAVs, development of the algorithms to be finite dimensional searches and determining necessary conditions for feasible solutions in the immediate horizon of the searches of the algorithm. Feasibility of the algorithm in deceiving a radar network through phantom track generation is demonstrated through simulation results.

This thesis describes the development of the Texas A&M University Autonomous Helicopter System and the integration of obstacle avoidance capabilities into that system. The helicopter system, composed of a Bergen Observer helicopter and a Rotomotion Autonomous Flight Control System (AFCS), was developed as a platform to support the development of the obstacle avoidance system through integration of sensors and onboard processing capabilities. The system has proven in various flight tests that it has the capability to autonomously hover and fly to user defined GPS waypoints. The obstacle avoidance algorithm has been proven in simulations involving an interface with the Rotomotion AFCS and the flight simulation software they created to facilitate the development of that system. The helicopter has also demonstrated appropriate responses to sensor input commensurate with the obstacle avoidance algorithm. Full avoidance tests were unable to be performed due to hardware malfunctions inherent in the obstacle avoidance sensors.

Thesis (M. Sc.)--University of Alberta, 2009. / Title from pdf file main screen (viewed on Dec. 23, 2009). "A thesis submitted to the Faculty of Graduate Studies and Research in partial fulfillment of the requirements for the degree of Master of Science, Department of Mechanical Engineering, University of Alberta." Includes bibliographical references.