PROPRIOCEPTIVE SENSING OF TERRAIN FORCES BY COMPLIANT, FOUR-WHEELED ROVING MODULES

This paper presents a class of four-wheel drive autonomous robots designed to collaboratively traverse terrains with a deformable upper layer, where soil properties result in limited traction and have the potential to cause immobilization. The robots are designed to have front and rear axle yaw degrees of freedom, and front and rear axle roll degrees of freedom providing ground compliance and maneuverability on friable terrain. These degrees of freedom, along with four individually driven wheels and an actuated translational degree of freedom inside a mid-frame joint, enable poses and modes of mobility that differ significantly from a rigid vehicle. A primary goal of this work is to assess the capacity to use this vehicular form as a testbed that leverages these vehicle dynamics to assess mobility. Using a custom ROS-Gazebo simulation environment, a heterogenous driving surface is created and used to evaluate this capability. We show that the vehicle can sense imbalanced terrain resistances proprioceptively. Additionally, we show that rigidity of the vehicle can be controlled through a simple feedback control loop governing the robot’s unconstrained axles to maintain a proper heading angle and still can provide an avenue to monitor the dynamics related to full-vehicle immobilization.