Network-based Multi-robot System Research

The development of Artificial Intelligent and robotics technology brings new hopes for task implementation in complex, uncertain and hazardous environment. Since the advent of distributed mobile robotics in the late 1980s, the research field of multi-robot system (MRS) has grown dramatically, with a much wider variety of topics being addressed. The great application prospect of MRS in military, space, industry manufacture, nature exploration, disaster prevention and recovery, and personal service fields has drawn many researchers' interest. However, because of the complexity of inter-robot relationship, the capacity and potential of MRS are associated with the conflict elimination and cooperation of inter-robot greatly. Shared information is a sufficient and necessary condition for cooperation. The efficiency and quality of communication influence the adaptation, flexibility, and reliability of multi-robot system.On the basis of physical, communication, and control network model building, the communication, information flow and distributed control methods have analyzed and designed in this thesis with some useful mathematic tools, such as algebraic graph theory, matrix theory, and distributed algorithm, and accordingly, a system was gotten with optimal communication architecture, information flow, and distributed control approaches. The main contributions of this thesis are as follows:(1) Information resource in MRS was analyzed, and multiple sensor information was fused with Support Vector Machine (SVM) method. The physical, communication and control network model in MRS were built also.(2) Under the characteristic of small-world network, a new method of small-world network evolution in terms of global and local efficiency evaluation index was proposed. Communication networks of MRS with different size were evolved, and optimal small-world network communication architecture was shaped correspondingly.(3) Information flow and consensus problems in MRS were researched with some mathematic tools, such as algebraic graph theory, matrix theory, and distributed algorithm. Consensus can be formed on the situational state or the coordination variable. In this thesis, consensus protocols of synchronous and partial synchronous networks in MRS were presented, whose convergence were proved and convergence rate were derived. The simulation results of synchronous, partial synchronous and small-world network verified further the convergence of presented consensus protocols.(4) Multi-robot formation system was studied. Under the communication and control network model, system's stability was analyzed in terms of algebraic graph theory.(5) An improved multi-object Particle Swarm Optimization (PSO) algorithm with external repository and mutation operator was presented, and used to solve multi-object optimization problem in multi-robot formation system on the basis of Pareto optimal concept.The aforementioned research results show that the network model of MRS makes it easier to analyze and design cooperation approaches. Consensus convergence study of information flow verifies the importance of communication in multi-robot cooperation. Evolution of small-world network constitutes optimal communication architecture of MRS. Successful application of multi-object PSO algorithm in multi-robot formation optimization problem show the efficiency of improved multi-object PSO algorithm. Therefore, MRS with optimal communication and control methods is gained.