The Vehicle Terrain Measurement System (VTMS) is a state-of-the-art test bed for integrating technologies from different disciplines, allowing researchers to validate their theoretical and computation work with experimental data. The system is capable of simultaneously scanning the complete topology of the terrain in 3-D; tracking the position, orientation, and speed of the vehicle; and measuring the wheel forces and torques. This data is simultaneously acquired allowing validation of vehicle and tire models, prediction of terramechanics, tuning of chassis components, and prediction of mobility and durability.
The Vehicle Terrain Performance Laboratory performs empirical and analytical modeling of the vehicle and tire. Nonlinear multi-body dynamic models are developed to understand the vehicle responses to the terrain. Tires are tested to determine nonlinear characteristics, such as the enveloping properties, and models are developed based on these empirical results. For example, characteristic constraint modes are used to capture tire deformations, then these modes are used in a nonlinear model to predict loading.
Stochastic models of terrain topology and terramechanics are being developed. These mathematical models are combined with dynamic models of the vehicle and tires to predict wheel loads. In this way, wheel loads for new vehicle concepts can be simulated under many terrain conditions. It is impractical to simulate a vehicle traveling hundreds of miles, but it is imperative to simulate terrain that represents the conditions that the vehicle will experience. Modeling techniques based on Markov Chains, Hidden Markov Models, Wavelets, Kriging, and Morphological filtering are being developed to characterize and model terrain. Using these stochastic models, reduced sections of terrain can be synthesized and simulated so that design decisions can be made in a timely manner, based on the most accurate information possible.
Complete understanding of interactions between vehicle systems and terrain is the founding research goal of the lab. It is critical to study these interactions as part of a system to understand vehicle performance. System analysis includes diverse areas such as prediction of chassis durability and development of durability testing schedules. Predicting soil properties and terramechanics improves the mobility of vehicles. Of course performance can also be subjective. Psychometric studies are performed to understand the subjective response and preferences that passengers have to a given vehicle and terrain, including the development of ride and handling metrics. These are a few examples of the many aspects of performance that the Vehicle Terrain Performance Laboratory is studying.