| Vehicle Simulations have many practical applications ranging from leisure use, public safety, civilian training, and commercial design applications. Vehicle simulations are commonly designed to work with three-degree of freedom or six-degree of freedom motion bases. Each system has pros and cons, which make them more suitable for specific applications.;These two systems differ drastically when it comes to cost of hardware, software, and complexity. The three degree of freedom system is limited to rotation about the x, y, and z axes. This means this system is limited to causing the sensation of acceleration through rotation about these three axis and from maintaining a tilt angle and using gravity. The tilt in this system is limited typically to a 45 degree angle, which prevents the system from creating a sensation of acceleration over 0.707g's. The six-degree of freedom system not only has the ability to rotate about the three axes, but can move laterally along all three axes. The ability of this system to more accurately produce these forces would be a given, but is limited to the lateral distance available for movement about each of the three axes. This gives the system the ability to produce additional acceleration, which theoretically allows the system to change accelerations more freely.;Tuning of each system is accomplished by placing limits on the system's ability to rotate and move laterally to insure that the simulation does not request accelerations beyond the capabilities of the motion base. This will prevent the system from creating undesired sensations, which should not be present. These limits unfortunately will not prevent all undesired sensations. Altering control parameters contained in the washout algorithms is another method of tuning, which can attempt to prevent or limit the magnitude of these sensations.;The purpose of this study is to compare the two systems ability to replicate the forces or "feel" of actually riding in the vehicle. This comparison will show whether or not the extra cost and effort in designing a more complex system is warranted for the motion bases applications. |
