A coordinated control system for dual-arm mobile manipulator balancing grasping and viewpoint selection

The mobile manipulators have been developed as a new robot platform due to its dexterity and mobility, and the motion planning coordinating manipulation and locomotion has been studied. In this paper, we deal with a mobile robot with dual-manipulators, where the one arm is equipped with a RGB-D camera to capture the image for the grasping targets with another arm with a gripper. A grasping task requires a cooperative control of dual-arms with the camera and gripper as well as positioning of the mobile base of the robot. An appropriate grasping posture has to be determined considering the robot's viewpoint selection such as frame-out avoidance of the visual target and self-occlusion of the arms avoidance, also the target distance has to be maintained in the measurable range from the depth sensor on the camera. We report the control system where request for the grasping posture such as joint limit avoidance of each arm and collision avoidance of the robot-base, in addition to viewpoint selection, are prioritized and coordinated by Projected Gradient control. The experiment results by consecutive pick and place tasks with the robot validate effectiveness of the proposed coordinated control.