Search and rescue mobile robots have shown great promise and have been under development by the robotics researchers for many years. They are many locomotion methods for different robotic platforms, including legged, wheeled, flying and hybrid. In general, the environment that these robots would operate in is very hazardous and complicated, where wheeled robots will have difficulty physically traversing and where legged robots would need to spend too much time planning their foot placement. Drawing inspiration from biology, we have noticed that the snake is an animal well-suited to complicated, rubble filled environments. A snake’s body has a very simple structure that nevertheless allows the snake to traverse very complex environments smoothly and flexibly using different locomotion modes. Many researchers have developed different kinds of snake robots, but there is still a big discrepancy between the capabilities of current snake robots and natural snakes. Two aspects of this discrepancy are the rigidity of current snake robots, which limit their physical flexibility, and the current techniques for control and motion planning, which are too complicated to apply to these snake robots without a tremendous amount of computation time and expensive hardware. In order to bridge the gap in flexibility, pneumatic soft robotics is a potential good solution. A soft body can absorb the impact forces during the collisions with obstacles, making soft snake robots suitable for unpredictable environments. However, the incorporation of autonomous control in soft mobile robotics has not been achieved yet. One reason for this is the lack of the embeddable flexible soft body sensor technology and portable power sources that would allow soft robotic systems to meet the essential hardware prerequisites of autonomous systems. The infinite degree of freedom and fluid-dynamic effects inherent of soft pneumatics make these systems difficult in terms of modeling, control, and motion planning: techniques generally required for autonomous systems. This dissertation addresses fundamental challenges of soft robotics modeling, control, and motion planning, as well as the challenge of making an effective soft pneumatic snake platform. In my 5 years of PhD work, I have developed four generations of pressure operated WPI soft robotics snakes (SRS), the fastest of which can travel about 220 mm/s, which is around one body per second. In order to make these soft robots autonomous, I first proposed a mathematical dynamical model for the WPI SRS and verified its accuracy through experimentation. Then I designed and fabricated a curvature sensor to be embedded inside each soft actuator to measure their bending angles. The latest WPI SRS is a modularized system which can be scaled up or down depending on the requirements of the task. I also developed and implemented an algorithm which allows this version of the WPI SRS to correct its own locomotion using iterative learning control. Finally, I developed and tested a motion planning and trajectory following algorithm, which allowed the latest WPI SRS to traverse an obstacle filled environment. Future research will focus on motion planning and control of the WPI SRS in outdoor environments utilizing the camera instead of the tracking system. In addition, it is important to investigate optimal control and motion planning strategies for mobile manipulation tasks where the SRS needs to move and manipulate its environment.. Finally, the future work will include the design, control, and motion planning for a soft snake robot where each segment has two degrees-of-freedom, allowing it to lift itself off the ground and traverse complex-real-world environments.

Το αντικείμενο της παρούσας διπλωματικής είναι η μοντελοποίηση, ο έλεγχος και η κατασκευή ενός επίπεδου ρομποτικού φιδιού βασισμένο σε υπολογιστικώς ανεξάρτητα μέρη τα οποία επικοινωνούν μέσω ασύρματου δικτύου \eng{Wifi} μεταξύ τους, καθώς και με εξωτερικές συσκευές για σκοπούς τηλεχειρισμού. Η κατασκευή βασίζεται στα ενσωματωμένα υπολογιστικά συστήματα \eng{Overo} της εταιρίας \eng{Gumstix}. Στόχος της διπλωματικής είναι η υλοποίηση της κίνησης του πλευρικού κυματισμού του φιδιού στο επίπεδο και η μελέτη της αποδοτικότητας του καθώς και η αντιμετώπιση του προβλήματος ελέγχου του. Στο πρώτο κεφάλαιο γίνεται μια αναφορά στην ανάγκη της ανάπτυξης ρομπότ εμπνευσμένα απο βιολογικούς οργανισμούς, συγκεκριμένα φιδιών, τις εφαρμογές τους στον πραγματικό κόσμο, την σχετική δουλειά καθώς και την συνεισφορά της παρούσας εργασίας. Στο δεύτερο κεφάλαιο παρουσιάζεται η ανάλυση της δυναμικής του επίπεδου φιδιού και επεξηγείται η σημαντική εξάρτηση από τα διάφορα μοντέλα τριβής για την κίνηση του ρομπότ στο επίπεδο. Στο τρίτο κεφάλαιο αναλύεται το πρόβλημα ελέγχου και παρουσιάζονται προτεινόμενοι ελεγκτές για την κίνηση της πλευρικής κυμάτωσης, επεκταμένοι για σύγκλισης τροχίας καθώς και τα αποτελέσματα της προσωμείωσης με βάση τους συγκεκριμένους νόμους ελέγχου. Στη συνέχεια στο τέταρτο κεφάλαιο παρουσιάζονται τα διάφορα στάδια κατασκευής του ρομπότ από τον σχεδιασμό του σκελετού, στη λογική των ανεξάρτητων μελών,τα κατασκευαστικά μέρη κάθε μέλους, μέχρι την αρχιτεκτονική του προγραμματισμού του και του χειρισμού του. Τέλος,στο πέμπτο κεφάλαιο παρατίθονται τα πειραματικά αποτελέσματα και σχολιάζεται η απόδοση της κατασκευής. / The subject of this thesis is the modelling, control and development of a planar snake-like robot based on modular links that communicate to each other via a Wifi network, as well as to other devices in order to remote control it. The links are based on the embedded computer-on-module Overo from the company Gumstix. The aim of this thesis is the implementation of the lateral undulation locomotion of snakes on a planar surface and the study of its efficiency as well as to present a control method for it. The first chapter points out the need of developing robots based on various existing biological organisms, specifically snakes ,their applications to real-world problems, the related work and the contribution of the current thesis. The second chapter contains the dynamic analysis of planar snake robots and explains the strong dependence on friction models for the movement of snakes on planar surfaces. In the third chapter, a control law is proposed to achieve lateral undulation as well as an extension of it to achieve trajectory tracking and the simulation results based on these control laws are presented. The fourth chapter contains the various stages of the development of the snake robot, from the design of its body, to the concept of modular links, to the programming architecture of them and their remote control. Finally, the fifth chapter presents the experimental results and comments on the efficiency of the developed robot.