Dual-Arm Control for Coordinated Fast Grabbing and Tossing of an Object: Proposing a New Approach

Picking up objects and tossing them on a conveyor belt are activities generated on a daily basis in industry. These tasks are still done largely by humans. This article proposes a unified motion generator for a bimanual robotic system that enables two seven-degree-of-freedom robotic arms to grab and toss an object in one swipe. Unlike classical approaches that grab the object with quasi-zero contact velocity, the proposed approach is able to grasp the object while in motion. We control the contact forces prior to and following impact so as to stabilize the robots’ grip on the object. We show that such swift grasping speeds up the pick-and-place process and reduces energy expenditure for tossing. Continuous control of the reach, grab, and toss motion is achieved by combining a sequence of time-invariant dynamical systems (DSs) in a single control framework. We introduce a state-dependent modulation function to control the generated velocity in different directions. The framework is validated in simulation and on a real dual-arm system. We show that we can precisely toss objects within a workspace of
${0.2}\,{\times}\,{0.4}{\text{m}}^{2}$
. Moreover, we show that the algorithm can adapt on-the-fly to changes in object location.