This paper starts with presenting a novel kinematics modelling approach for a snake-like robot travelling with concertina locomotion. The paper ends with confirmation studies using Webots simulation software. The significant advantage of the proposed kinematics model is in its flexibility to model natural snake robot concertina locomotion. Concertina locomotion refers to a type of motion where parts of the body contract, expand or do not change their shape. To simulate this, first we introduce a mathematical equation, called dynamic function, in which by varying a certain function parameter, body curve during motion is realized. To obtain concertina gait, the snake body is divided into three different modules, head module, tail module and main body module that connects the head to the tail module. Each module forms a specific curve which can be modelled using the proposed dynamic function. At each moment during snake locomotion, the kinematics of different links can be derived by fitting robot links to the body curve. Results indicate concertina locomotion is achieved. The proposed kinematics model represents a new approach to simulation of a snake-like mechanism in order to get basic characteristics of such locomotion and to enable our future research. Several ideas to further obtain natural snake locomotion is also presented.

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