The kinematic analysis of an articulated twin body, four-wheel, robotic vehicle is presented. Polaris, a research platform and contending robotic vehicle in the Intelligent Ground Vehicle Competition (IGVC) at Virginia Tech, was redesigned in 2006 to improve the mobility of the vehicle by incorporating an innovative four-bar linkage that connects the two bodies. The new linkage design minimizes vehicle off-tracking by allowing the rear wheels to closely track the path of the front wheels. This thesis will outline the theoretical kinematic model of the four-bar linkage as applied to a twin-bodied, differentially driven vehicle. The kinematic model is validated through computer simulation as well as experimentation on a fully operational robotic vehicle. The kinematic model presented here outlines the foundations for an autonomous, four-wheel drive, multi-body control system and opens avenues for dynamically controlling the tracking of the vehicle's rear body with an actuated linkage configuration. / Master of Science

Kinematic simulation (KS) is a means of generating a turbulent-like velocity field, in a manner that enforces an input Eulerian energy spectrum. Such models have also been applied in particle-laden flows, due to their ability to enforce spatial organization of the fluid velocity field when simulating the trajectories of individual particles. A critical evaluation of KS is presented; in particular, its ability to reproduce single-particle Lagrangian statistics is examined. Also the ability of KS to reproduce the preferential concentration of inertial particles is explored. Some numerical results are presented, in which fluid tracers and inertial particles are transported alternatively by (1) simulated turbulence generated by direct numerical simulation (DNS) of the incompressible Navier-Stokes equations, and (2) KS. The effect of unsteadiness formulation in particular is examined. It is found that even steady KS qualitatively reproduces the continuity effect, clustering of inertial particles, elevated dispersion of inertial particles and the intermittent turbulence velocity signal. A novel method is then motivated and formulated, in which, for input RANS parameters, a simulated spectrum is used to generate a KS field which enforces a target Lagrangian timescale. This method is then tested against an existing experimental benchmark, and good agreement is obtained. / Thesis / Doctor of Philosophy (PhD) / Turbulence arises in an immense variety of industrial and scientific applications; from weather to automotive design; from medicine to nuclear engineering. Because turbulence is chaotic, it is difficult to make accurate predictions of how a turbulent flow will behave in a given scenario. The objective of my research is to find easier ways of accurately modelling turbulence in a certain class of particle-laden flows.

The thesis has been done in collaboration with Kalmar Solutions AB and is a conceptual study that aims to design a hydraulic steering arrangement for the reachstacker DRG 450 where each wheel is steered independently of each other. This is done in order to reduce tire wear by achieving an Ackermann steering geometry; lesser tire wear reduces costs for customers. When steered independently of each other the same steering arrangement could be used on multiple different wheelbases while still achieving an Ackermann steering geometry. During the thesis, calculations for required steering angles and their required piston strokes has been done by creating a geometrical model of the steering arrangement. CAD-modeling and kinematic simulations of concepts has been conducted with CATIA R2024x where the concepts movement when turning could be simulated. Three main concepts of the steering arrangement were studied and developed during the thesis. Kinematic simulations concluded that by changing to two independent cylinders, along the same axis, and redesigning the steering knuckles could allow for the same steering arrangement to achieve an Ackermann steering geometry for multiple different wheelbases. This reduces tire wear and turning radius when compared to the current steering axle. Having the cylinders along the same axis proved to be best because less redesigns were needed and mainly no major redimensioning of the steering arrangement or chassis were needed.