Terrace climbing of the Alacrane mobile robot with cooperation of its onboard arm

Alacrane is a hydraulic mobile manipulator for search and rescue in disaster areas and natural environments, where surmounting elevations such as rubble mounds and terraces is usually required. The paper describes the autonomous terrace climbing maneuver of this mobile robot with the help of its powerful arm. During this operation, the arm is used both for levering, by pushing it against the ground, and for modifying the center of gravity of the entire robot. A 3D laser scanner, an IMU, and joint absolute encoders provide all the sensorial information required for this maneuver. Furthermore, fast 3D scan processing is proposed to estimate the pose, slope, and and height of the terrace. Experimental results in an outdoor environment demonstrate the utility of the proposed approach.