Terramechanics-based wheel–terrain interaction model and its applications to off-road wheeled mobile robots

Abstract

SUMMARYThis paper presents a wheel–terrain interaction model, which enables efficient modeling of wheeled locomotion in soft soil and numerical simulations of off-road mobile robots. This modular model is derived based on wheel kinematics and terramechanics and the main focus is on describing the stress distributions along the wheel–terrain interface and the reaction forces exerted on the wheel by the soil. When the wheels are steered, the shear stresses underneath the wheel were modeled based on isotropic assumptions. The forces and torques contributed by the bulldozing effect of the side surfaces is also considered in the proposed model. Furthermore, the influence of grousers, commonly used on smaller mobile robots, was modeled by (1) averaging the normal pressures contributed by the grousers and the wheel concave portion, and (2) assuming that the shear phenomenon takes places along the grouser tips. By integrating the model with multibody system code for vehicle dynamics, simulation studies of various off-road conditions in three-dimensional environments can be conducted. The model was verified by using field experiment data, both for a single-wheel vehicle and a whole vehicle.

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“…1. Table 1 presents the results for the sinkage in CE-3, Luna 17 and Apollo 15 landing sites, using k = 861 kPa/m n and n = 1, as given by the Bekker pressure-sinkage model for FJS lunar simulant [33]. Notice even values are very close to the actual ones detected through image processing by [10], Apollo's LRV sinkage is overestimated due to the large D/b ratio.…”

An Approximated, Control Affine Model for a Strawberry Field Scouting Robot Considering Wheel–Terrain Interaction

“…The bulldozing forces are not needed for the torus-shaped wheels in contrast with the cylindrical-shaped wheels. 14,15 However, two extra coordinate transformations need to be included in the integrals when the terrain reaction forces are computed for torus-shaped wheels. This section focuses on the WTIM for an individual wheel.…”

“…The computation of these angles is based on ref. [14], as listed in Appendix A. An arbitrary point P on the torus surface can be expressed by the position vector r p from the wheel hub center 16 as…”

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“…Ishigami et al [9] incorporated this 2-D wheel-soil model into a multibody frame and generated a framework of vehiclewheel-terrain dynamics. Jia et al [10] rebuilt the model with an assumption of isotropic shear stress and took grousers into account. Iizuka et al [11], [12] noticed that the surface is probably rough and studied the influence of circular and pentagon wheels to the performance of a lunar rover running on a slope.…”