A Novel Framework for Achieving Adaptation in Man- Made Systems Inspired by the Organisation of Living Systems
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This thesis presents a novel framework for adaptation to environmental fluctuations in man–made systems. The framework is inspired by adaptability of living systems. Emerged from the coevolution with the environment, living systems bear the traces of past environmental changes – they are endowed with inherent adaptive mechanisms which are employed upon the detection of environmental fluctuation thereby enabling the preservation of viability. The approach chosen in this thesis is based on the organisation of living systems because inherent adaptive mechanisms are possible thanks to the specificity of their organisation. The organisation of living systems is addressed at different hierarchical levels. For each considered level, a theory which assumes a mechanistic view on the living system is used as a basis for the proposed adaptive framework. At the biochemical level, a chemical automaton in a form of the Chemoton – a model of a minimal living system – is considered. At the system level, the framework of adaptive behaviour provided by a classic cybernetician, William Ross Ashby, is applied. In addition, the principles of hierarchies which emerge out of the dynamics of some basic units of the evolving system have been used for the increase in the robustness of the adaptation process. These principles account for the third level which arises during the adaptation process and which is hierarchically between the two mentioned levels. Man–made systems are designed to perform a function ascribed by a human designer. When affected by environmental variations, the functionality of a man–made system may deviate from the desired or it may be completely lost. In this thesis the loss of functionality of a man–made system is related to the loss of viability in a living system. The goal of the adaptation process is the preservation of system functionality. A model of a man–made system which accommodates for the proposed adaptive framework has been developed. The model assumes a modular system architecture which comprises of the cells whose architecture is inspired by the Chemoton. During the adaptation process, the control and communication between the cells is realised via signals resembling the operation of hormones in a living system. The dynamics of the hormone–like signals give rise to the formation of the higher hierarchical level which provides additional information for the control of the adaptation process. The system adapts according to the framework by W. Ross Ashby which is based on homeostatic principles. The results of computer simulations show that the strategy used by nature for building complex systems can improve the robustness of man–made systems to environmental fluctuations. As a proof of concept for the adaptive framework, an implementation in electronic hardware systems, a particular class of man–made systems, has been considered. Initial steps were made towards the implementation in silicon of an adaptive unit proposed within the framework.