Building an efficient and robust robot that does not use appendages for locomotion requires inspiration and a thorough understanding of the working principles of limbless animals’ locomotion. In these animals, the passive properties of their morphology and material allow them to dwell in complex terrains at different animals’ scales by using only a simple mode of locomotion, i.e., undulatory locomotion. A better understanding of these animals can inspire efficient locomotion strategies and lead to multi-gait terrain adaptation that exploits their physical intelligence. This study endeavors to model undulatory locomotion in various environments and study the effect of endogenous and exogenous dynamics in limbless bodies. First, undulatory locomotion is modeled analytically using the Lagrangian mechanics approach in a dry frictional environment. A discrete multi-bar system is set to get the propulsive force through frictional anisotropy. The system is then non-dimensionalized to determine the factors representing material and environmental properties. The principal components of the model are body stiffness, internal damping, moment of inertia, and frictional anisotropy. Simulations showed the interdependence of these quantities to achieve the desired speed. The results also highlighted the interdependence of endogenous and exogenous dynamics to achieve different locomotion gaits. Swimming, crawling, and polychaete-like locomotion are characterized based on stiffness factor, frictional factor, and frictional coefficient ratio. The model is validated by inputting the required parameters of the corn snake from the literature. Then undulatory locomotion is modeled in a viscous environment, and the results are compared with the dry environment. It is found that the optimum weight of dry and viscous frictional factors can be found in a hybrid environment to achieve better speed performance. Finally, the experimental validation is carried out in a dry friction environment. The results from experimental and physical models are compared. The physical robot is a wheel-based modular system with flexible joints moving on different substrates. The influence of the spatial distribution of the body stiffness on the speed performance is also explored. Findings suggest that the environment affects the performance of undulatory locomotion based on the body stiffness distribution. Although quantitatively the stiffness varies with the environment, we obtained a qualitative constitutive law for all environments. Specifically, we expect the stiffness distribution to exhibit either an ascending-descending or an ascending-plateau pattern along the length of the object, from head to tail. Furthermore, undulatory locomotion showed sensitivity to contact mechanics: solid-solid or solid-viscoelastic contact produced different locomotion dynamics. Our findings elucidate how terrestrial limbless animals achieve undulatory locomotion performance by exploiting the passive properties of the environment and the body. Application of the obtained results can lead to better-performing long-segmented robots exploiting the aptness of passive body dynamics and the characteristics of the environment where they need to move.

Assuming that the emergence of inside-out positional tracking in commercially available VR systems indicate a future where room-scale VR is experienced more freely, there is a demand for adaptable and immersive VR locomotion techniques that while enabling real walking overcomes the physical restrictions of a play space without the use of additional hardware. Hence, the purpose of this study was to explore the hypothesis that a subtle situation-based rotation of the immersive virtual environment (IVE) around the user can free up physically restricted virtual space and enable extended real walking in room-scale VR, while a full sense of presence is maintained. Based on Findings of a literature study, a prototype of an adaptable and mobile locomotion technique manipulating the IVE was developed and tested using three different rotations; a baseline medium rotation, a fast and a slow, all defined through trial and error with the capacities of freeing up restricted virtual space, and of maintaining presence, in mind. The user tests were designed as a within-subject test, aiming to expose the limits in the prototype by putting pressure on two potentially critical factors: user velocity and the capacity of freeing up restricted virtual space in all directions. The results imply that the proposed locomotion technique has the potential of extending virtual walking while maintaining a full sense of presence and that there is an optimally balanced rotation between the medium and slow rotation used in the present study. However, since the participants were not redirected enough to be preserved within the physical play space, the prototype may be used as a tool rather than as a redirecting technique. / Om man antar att utvecklingen och appliceringen av ”inside-out” positionsspårning i kommersiellt tillgängliga VR-system pekar på̊ en framtid där room-scale VR upplevs mer fritt, så Finns det ett behov av anpassningsbara VR-rörelsetekniker som utan extra hårdvara möjliggör ett större spelutrymme än det fysiska spelrummet samtidigt som användaren kan förflytta sig virtuellt genom verkliga rörelser. Syftet med denna studie var att utforska hypotesen att en subtil situationsbaserad rotation av den virtuella miljön runt användaren kan frigöra fysiskt begränsat virtuellt utrymme och samtidigt upprätthålla en känsla av full närvaro.  Baserat på resultaten från en litteraturstudie utvecklades en prototyp som och testades med tre olika hastigheter; medel, snabb och långsam. Dessa var alla definierade genom ”trial and error” baserat på prototypens kapacitet att frigöra begränsat virtuellt utrymme och att bibehålla närvaro i åtanke. Användartesterna utformades som ”within-subject” tester med målet att exponera prototypens begränsningar genom att pressa två potentiellt kritiska faktorer: hastigheten användaren rörde sig i och prototypens kapacitet att frigöra begränsat virtuellt utrymme i alla riktningar.  Resultaten antyder att den föreslagna rörelsetekniken har potentialen att möjliggöra ett större spelutrymme än det fysiska spelrummet samtidigt som en känsla av full närvaro upprätthålls och att det Finns en optimal rotation emellan rotationerna medel och långsam. Däremot, eftersom deltagarna inte omdirigerades tillräckligt för att bevaras inom det fysiska spelrummet är det troligt att prototypen borde användas som ett verktyg snarare än som en omdirigeringsteknik.

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