Bidirectional Human–Robot Bimanual Handover of Big Planar Object With Vertical Posture

Abstract

Object handover is one of the basic abilities for the robot to interact with the human. Most of the previous works only focus on the limited handover scenarios where the robot uses one hand to give small objects to the human. In this article, we design a bidirectional bimanual handover system that enables the robot to both give and receive the big planar object with vertical grasp posture. In addition to the basic object handover function, the designed handover system also integrates a position adjustment mechanism to improve the human experience. According to different task states, the system is divided into four modes. In each mode, the robot performs a subtask and switches to the next mode at an appropriate time. We propose a two-finger grip force controller and a dual-arm admittance NN controller to control the robot to generate actual motions. By applying specific locating, trajectory planning, and signal identifying methods, we implement the designed handover system on a Baxter robot. The system is tested on two wooden plates with different widths, thicknesses, and weights. The results show that the robot can perform the handover task safely and effectively with the designed handover system. <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Note to Practitioners</i> —This article aims to solve the limitation that the robot can only hand over small objects with one hand in the human–robot handover systems. In daily life, especially in carrying tasks, many objects, such as windows, wooden boards, and big frames, may also be handed over to each other. These objects can be classified as big planar objects. To enable the robot to hand over this kind of object with the human, we design a bidirectional bimanual human–robot handover system. The designed system has three main functions. First, the robot can receive the big planar object from the human and hold the object safely with two hands, which is impossible in a single-hand handover system because the weight and size of the object are large. Then, the robot can help the human hold the object or transport it to other places. Second, the robot can adjust the object handover position according to the human’s intentions while holding the object. Because the size of objects and the height of humans may different, or some tasks require that the human position be higher or lower than the robot, the current object holding position may be hard for the current human operator to take over the object. With this function, the human can move the object to an appropriate position and then take it comfortably. Third, the robot releases the object only when it gets a clear signal. Before that, the robot always grasps the object safely, and the human can freely adjust his posture. With the designed handover system, the robot can cooperate with the human to complete more tasks indoors or in factories.