Two Arms are Better than One: A Behavior Based Control System for Assistive Bimanual Manipulation

Human environments present special challenges for robot manipulation, since they are complex, dynamic, uncontrolled, and difficult to perceive reliably. For tasks that involve two handheld objects, the use of two arms can help overcome these challenges. With bimanual manipulation, a robot can simultaneously control two handheld objects in order to better perceive key features, control the objects with respect to one another, and interact with the user. In this paper we present an approach to robot manipulation that emphasizes three design themes for robots that manipulate within human environments: cooperative manipulation, task relevant features, and let the body do the thinking. We have previously illustrated these themes with a behavior-based control system that enables a humanoid robot to help a person place everyday objects on a shelf. This system predominantly manipulates a single object at a time with a single arm. Within this paper, we present an extension to this control system that enables a robot to bimanually perform tasks that involve two handheld objects. In our tests, the robot successfully performs insertions that are akin to common activities such as pouring and stirring using a variety of objects, including a bottle, spoon, box, and cup. The success of this extended system suggests that our approach to robot manipulation can support a broad array of useful applications, and demonstrates several distinct advantages of using two arms. 1