While evolutionary computation is well suited for automatic discovery in engineering, it can also be used to gain insight into how humans and organizations could perform more effectively. Using a real-world problem of innovation search in organizations as the motivating example, this dissertation formalizes human creative problem solving as competitive multi-agent search. It differs from existing single-agent and team-search problems in that the agents interact through knowledge of other agents' searches and through the dynamic changes in the search landscape caused by these searches. The main hypothesis is that evolutionary computation can be used to discover effective strategies for competitive multi-agent search. This hypothesis is verified in experiments using an abstract domain based on the NK model, i.e. partially correlated and tunably rugged fitness landscapes, and a concrete domain in the form of a social innovation game. In both domains, different specialized strategies are evolved for each different competitive environment, and also strategies that generalize across environments. Strategies evolved in the abstract domain are more effective and more complex than hand-designed strategies and one based on traditional tree search. Using a novel spherical visualization of the fitness landscapes of the abstract domain, insight is gained about how successful strategies work, e.g. by tracking positive changes in the landscape. In the concrete game domain, human players were modeled using backpropagation, and used as opponents to create environments for evolution. Evolved strategies scored significantly higher than the human models by using a different proportion of actions, providing insights into how performance could be improved in social innovation domains. The work thus provides a possible framework for studying various human creative activities as competitive multi-agent search in the future. / text

This work addresses applications of search theory where a mobile search agent seeks to find an unknown number of stationary targets randomly distributed in a bounded search domain. We assume that the search mission is subject to a time or distance constraint, and that the local environmental conditions affect sensor performance. Because the environment varies by location, the effectiveness of the search sensor also varies by location. Our contribution to search theory includes new decision-theoretic approaches for generating optimal search plans in the presence of false alarms and uncertain environmental variability. We also formally define the value of environmental information for improving the effectiveness of a search mission, and we develop methods for optimal deployment of assets that can acquire environmental information in order to improve search effectiveness. Finally, we extend our research to the case of multiple cooperating search agents. For the case that inter-agent communication is severely bandwidth-limited, such as in subsea applications, we propose a method for assessing the expected value of inter-agent communication relative to joint search effectiveness. Our results lead to a method for determining when search agents should communicate. Our contributions to search theory address important applications that range from subsea mine-hunting to post-disaster search and rescue applications. / PHD / We address search applications where a mobile search agent seeks to find an unknown number of stationary targets randomly distributed in a bounded search domain. The search agent is equipped with a search sensor that detects the targets at a location. Sensor measurements are often imperfect due to possible missed detections and false alarms. We also consider that the local environmental conditions affect the quality of the data acquired from the search sensor. For instance, if we are searching for a target that has a rocky shape, we expect that it will be harder to find that target in a rocky environment. We consider that the search mission is subject to a time or distance constraint, and thus, search can be performed on only a subset of locations. Our goal in this study is to formally determine where to acquire the search measurements so that the search effectiveness can be maximized. We also formally define the value of acquiring environmental information for improving the effectiveness of a search mission, and we develop methods for optimal deployment of assets that can acquire environmental information in order to improve search effectiveness. Finally, we address the cases where multiple search assets collaboratively search the environment and they can communicate their local information with each other. We are particularly interested in determining when a vehicle should communicate with another vehicle so that the joint search effectiveness can be improved. Our contributions to search theory address important applications that range from subsea mine-hunting to post-disaster search and rescue applications.

This thesis addresses a multi-agent search problem where several agents, equipped with sensors and communication devices, search an unknown area. Lack of information about the search space is modeled as an uncertainty density distribution. A sequential deploy and search (SDS) strategy is formulated where the agents are first deployed to maximize single step search effectiveness. To achieve an optimal deployment, a multi-center objective function defined using the Voronoi cells and the uncertainty distribution is optimized. It is shown that the critical points of this objective function are the centroids of the Voronoi cells. A proportional control law is proposed that makes the agents move to their respective “centroids”. Assuming agents to be first order dynamical systems and using LaSalle's invariance principle, it is shown that the closed-loop system converges globally asymptotically to the critical points. It is also shown that the sequential deploy and search strategy is spatially distributed with respect to the Delaunay graph corresponding to any given agent configuration. Next, a combined deploy and search (CDS) strategy is proposed where, instead of first deploying agents and then performing the search, the agents engage in search operation as they move toward the centroids. This strategy gives rise to shorter agent trajectories compared to the SDS strategy. Then the problem is formulated with practical constraints such as sensor range limits and limit on maximum speed of the agents. A few issues relating to implementation of the proposed search strategies are also addressed. Finally, the assumption of homogeneous agents is relaxed and agents equipped with sensors with heterogeneous capabilities are considered. A generalized Voronoi partitioning scheme is proposed and used to formulate a heterogeneous locational optimization problem. In this problem the agents are deployed in the search space optimizing the sensor effectiveness. As earlier, the two search strategies are proposed. Simulation experiments are carried out to validate the performance of the proposed search strategies. The simulation results indicate that both the proposed search strategies perform quite well even when the conditions deviated from the nominal. It is also shown that the combined deploy and search strategy leads to shorter and smoother trajectories than those of the sequential deploy and search strategy with the same parameters.