Body attitude regulator applied to ground robots with active flippers

Abstract

At field missions, ground mobile robots may be requested to sustain a given body orientation while moving over uneven ground. Some robots have active locomotion mechanisms that allow body attitude reorientation. The present work implements a body leveler that takes as input the robot frame orientation and locomotion mechanisms' state. Based on quaternion algebra, the attitude error metric provides a single set of angle and axis vector which the body frame should rotate about to achieve the desired set-point. Locomotion mechanisms corrective action are considered system-specific and thus computed separately. The proposed method is applied to a skid-steer robot with four active tracked flippers. Simulated experiments allow evaluating the method performance over structured and representative rough terrain. The body leveler properly regulates the platform in static situations and when moving over uneven terrain with a slow-changing topography.