Real time rut profile measurement in varying terrain types using digital image correlation

An important parameter in terramechanics is the rut depth produced when a vehicle traverses deformable soil. The rut depth provides a measure of vehicle tractability as well as the impact on the environment. Rut depth is not uniform on natural terrain and typically only a few manual points are measured. Synchronizing rut depth with other measurements is also problematic. This paper investigates the feasibility of using cameras to measure 3D terrain profiles from which a single rut depth measurement is obtained. Tests were performed on different vehicles, for various dynamic vehicle manoeuvres, over varying terrains including sand, mud, grassland, snow and ice. Results were validated using the traditional stick ruler method. Measurement frequencies of 58 Hz were obtained using affordable commercially off the shelf computational hardware and dedicated software. Determining whether a vehicle can traverse a terrain can significantly improve the vehicle mobility. Therefore, real time measurements of rut depth can be used to determine the mobility of vehicles in off-road conditions that can change rapidly due to environmental conditions e.g. rain or snow. The techniques described can assist in gathering terrain and vehicle mobility data that can be used directly to assist the driver in making safety related decisions.http://www.elsevier.com/locate/jterra2020-04-01hj2019Mechanical and Aeronautical Engineerin

Finite element modeling of tire -terrain interaction.

Vehicle mobility on unpaved surfaces is important to military, agriculture, forestry, mining, construction, and recreation industries. Because of the complicated nature of vehicle-terrain interaction, comprehensive modeling of off-road mobility is often performed using empirical algorithms. When mechanical analyses have been applied, they are generally in two dimensions, sometimes with modifications to imply the effect of the third dimension. The desire to incorporate theoretical mechanics into performance models has generated great interest in applying numerical modeling techniques to simulate the full three-dimensional interaction of the deformable tire and terrain. To this end, a three-dimensional model simulating a tire rolling over snow or other terrain material was developed. Fresh snow and compacted sand terrain surfaces were modeled as inelastic materials using the Crushable Foam and Cap Drucker-Prager constitutive models of critical state and plasticity theory. The snow model was generated from experiments on the mechanical deformation of snow and was validated using plate sinkage test data. The soil model was constructed based on existing constitutive models from the literature for a soil similar to that used in vehicle mobility studies. Tires used during vehicle testing were simulated with (1) a rigid tire model, (2) the Shoop-Darnell tire model, which incorporates user-defined elements for the sidewalls, and (3) a modal analysis type of tire model. Comparisons of the tire models with measured deflection and contact stress indicate that both the Shoop-Darnell and modal analysis models yield accurate results, but the Shoop-Darnell model is much more computationally efficient. The combined tire-terrain model was validated for fresh snow using force measurements collected with an instrumented vehicle and measured snow deformation under the wheel; and it was compared to snow mobility predictions made using the NATO Reference Mobility Model (NRMM). These comparisons indicate excellent agreement between the finite element model and field measurements of forces resisting motion and snow deformation under the wheel. The model also illustrates the effect of slip on sinkage. Preliminary results of the modal analysis tire model on snow show very little deformation in the tire, as expected, indicating that the rigid wheel simplification may be more applicable for soft terrain.Ph.D.Applied SciencesCivil engineeringGeotechnologyUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/124024/2/3001048.pd

Assessing the Transfer of Simulator Trained Skills to Real Vehicle Control

The Army Cold Regions Research and Engineering Laboratory is conducting a project to investigate the value of a motion based simulator in teaching vehicle control for off-road driving conditions. A primary goal is to reduce accidents caused by the loss of control of high center-of-gravity military vehicles in situations normally not found in the civilian driving experience. This study presents data from a two year portion of our work to develop metrics to assess the effectiveness of simulator training for developing vehicle control skills. For the first year, 10 drivers were trained using a simulator in an accident avoidance (AA) maneuver. Their performance was compared against 10 untrained drivers in a real vehicle. The second year 5 trained drivers from the first study were given sparse sustainment training in the simulator and again compared against 5 untrained drivers in a real vehicle. We considered metrics specifically related to the vehicle control aspects of the training to determine if the trainee acquired the necessary muscle memory to correctly implement the various vehicle control steps involved in the maneuver. We also briefly describe the participant’s views on their training experience