Vehicle dynamic simulations form a significant part of the design and development process of vehicles. These simulations are used to study and improve the vehicle’s durability, ride comfort and handling capabilities. All forces acting on the vehicle are either generated in the tyre-road interface or are due to aerodynamic effects, where at low speeds the latter one can be ignored. The accuracy of the tyre model describing the forces on the tyre-road interface is thus of exceptional importance. It ensures that the simulation model is an accurate representation of the actual vehicle. Various approaches are adopted when developing mathematical tyre models. Many of these models are developed to study the handling capabilities of passenger cars over a smooth road. Passenger car tyres are the focal point as larger tyres introduce some difficulties due to their size and load rating. Off-road truck tyres also differ in their construction which will influence force and moment generation of the tyre. Research efforts are increasing to meet the need of tyre models that can describe the behaviour of the tyre over uneven terrain with sufficient accuracy. This thesis addresses the question of whether existing mathematical tyre models can accurately describe the forces and moments generated by a large off-road tyre while driving over rough terrain. The complexity of different mathematical tyre models varies greatly, as does the parameterisation efforts required to obtain the model parameters. The parameterization of most tyre models relies on some experimental test data that is used to extract the necessary information to fit model parameters. The selection of a suitable tyre model for a simulation is often dependent on the availability of such experimental data and the effort to identify the required parameters. In this study the parameterisation process for four different tyre models, are discussed in detail to highlight the difficulties in acquiring the test data and the effort to parameterize the model. The models considered are the One Point Contact, 3D Equivalent Volume contact, 3D Enveloping Contact and FTire model. Experimental measurements are conducted on a 16.00R20 Michelin XZL tyre. Laboratory tests, as well as field tests, over discrete obstacles and uneven hard surfaces are used for parameterisation and validation purposes. Simulation results are compared to experimental test data to determine whether the models could be used to describe the tyre road interactions with sufficient accuracy. Recommendations are made for tyre model selection and model accuracy for simulations over rough off-road surfaces. / Dissertation (MEng)--University of Pretoria, 2013. / gm2014 / Mechanical and Aeronautical Engineering / unrestricted

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Background. Games are becoming increasingly large, and that includes space games. They require new features to be developed and planets to be generated. Heightmap- and marching cubes-algorithms, allow for the generation of spherical objects and planets when adapted. With the help of noise and these algorithms,spherical terrains are created in this project the performance of the individual solutions is measured. Objectives. It is the scope of this project to implement two planet generators, one based on heightmap technology and another based on the marching cube algorithm.These are then compared in terms of performance to see the differences in memory consumption and which one is faster.  Methods. The two techniques, planetary marching cubes, and a planetary heightmap-based solution are implemented in the Unity Engine. These generators then generate a set of different sized terrains multiple times and then average the results to gather performance data. This data is then used to compare the two solutions. This yields a comparable result between the two techniques which can then be analysed.  Results. The resulting measurements show the Marching cubes implementation uses a higher consumption of both VRAM and RAM than the heightmap solution, which is very memory efficient. Furthermore, the generation time of the heightmap solution is significantly faster than the marching cubes implementation. Conclusions. It is concluded that the planetary marching cubes algorithm utilizes more resources, consumes time to generate and is slower than the heightmap-based solution. The planetary marching cubes algorithm does however support additional features.

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Interactive software applications which need to render large terrain meshes can suffer from slow frame rates if the geometry of the terrain is sufficiently dense. However, the viewing angle to many distant features of the terrain does not change rapidly with respect to time. If the movement of the viewing position is limited to continuous motion and restrained to a known speed, many terrain features may be rendered once in high detail and reused for several frames. This thesis proposes a method to increase the rendering speed of large complex terrains by splitting the terrain into contiguous chunks. If a given chunk is far enough away from the camera and its viewing angle will not change quickly, it is rendered into an image buffer. This buffer is then used to texture map a simplified version of the terrain mesh. The simplified and textured mesh is rendered in place of the original chunk of geometrically complex terrain. The simplified mesh is used to approximate parallax effects as the viewing angle changes in small increments. This technique is shown to as much as double the rendering speed of large terrain meshes without reducing the quality of the final image.

This thesis presents an approach to real-time image enhancement using texture synthesis. Traditional image enhancement techniques are typically time consuming, lack realistic detail, or do not scale well for large magnification factors.Real-time Enhancement using Texture Synthesis (RETS) combines interpolation, classification, and patch-based texture synthesis to enhance low-resolution imagery, particularly aerial imagery. RETS uses as input a low-resolution source image and several high-resolution sample textures. The output of RETS is a high-resolution image with the structure of the source image, but with detail consistent with the high-resolution sample textures. We show that RETS can enhance large amounts of imagery in real-time. Our implementation can produce over twenty-five million pixels per second on an average PC.

Procedural generation techniques are able to quickly and cheaply produce large areas of terrain. However, these techniques produce results that are not easily directable and often require artists to edit the results by hand to achieve the desired layout. This paper proposes a sketch-based system for controlling fractal terrain that allows for a wide variety of terrain feature types. Artists sketch features rather than constrained points or elevations. The system is interactive, provides quick on-demand previews of the terrain, and allows for iterative design modifications. Interaction between features is handled in a realistic fashion. An arbitrary vertex insertion order midpoint displacement algorithm is also described which provides the necessary flexibility and constraints for the terrain generation system.

Despite the first unmanned aerial vehicle (UAV) mission being flown on Aug 22 1849 to bomb Venice UAVs have only recently began to modernize into sophisticated tools beyond simple aerial vehicles. With an increasing number of potential applications, such as cargo delivery, communications, search and rescue, law enforcement, and homeland security, the need for appropriate UAV technology advancement also arose. Here, the development of a low-cost collision avoidance system is described. Hardware was tested and selected based on predetermined constraints and goals. Additionally, a variety of potential functions were explored and assessed at their effectiveness in preventing a collision of a UAV with mountainous terrain. Simulations were conducted using Cloud Cap’s Piccolo autopilot in conjunction with Matlab. Based on these simulations, a set of potential functions was selected to be used with the chosen hardware on subsequent UAV-development-related projects.

<p> The movement of diamond drills by tracked vehicles and drill trailers in south Central Keewatin was studied during the summer of 1980. Tests of the physical ground strength showed that the ability of the terrain to resist disturbance from tracked vehicle operations depended on two main physical factors: the type of surficial material and the presence of water. Moisture contents varied throughout the summer so that the response of till and peat to compression and shear was not constant. As the summer proqressed, the increasing depth of thaw and gradual surface drying caused strengthening of both major types of surficial material. As a result, vehicle trafficability gradually increased throughout the summer. While surface rutting increased the depth of thaw compared to an undisturbed site, especially in peat, after the first few weeks of the thaw this had little apparent effect on vehicle trafficability. In many cases the vehicle disturbance was largely aesthetic giving the impression that the terrain disturbance was much more serious than it actually was.</p> <p> Although the load distribution of the vehicle tracks concentrated much of the longitudinal stress directly beneath the bogie wheels, in most cases the performance of the tracked vehicle itself was adequate. However, problems caused by the drill trailer wheels resulted in unnecessary mechanical strain on the vehicles and created marked increases in terrain disturbance.</p> / Thesis / Bachelor of Arts (BA)