Gripper self-alignment for autonomous pole-grasping with a biped climbing robot

For biped climbing robots to climb poles, trusses or trees with dual grippers, it is required that the grippers are aligned with the target objects before they grasp for climbing or manipulating. However, this requirement is difficult to meet in practice with programming control, teaching-and-playback, or remote control with a joystick, due to the mobility of the base gripper, the manufacturing and control errors of the robot, and other uncertainty. It is hence necessary and significant for the grippers to be autonomously aligned with the target under utilization of sensors. In this paper, we develop a sensing system by integrating multiple sensors including a camera, a laser scanning range finder and two ultrasonic distance sensors to detect the relative configuration of a gripper with respect to the target to grasp, and then present an algorithm based on the sensor information to adjust the gripper configuration for alignment with the grasping target. In the experiments with our biped climbing robot Climbot, the gripper can grasp a static pole autonomously and can even follow a moving pole. The effectiveness and real-time of the sensing system and the self-alignment algorithm have been verified by the experiments.